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BobL
9th Aug 2019, 08:34 PM
I have what used to be a fancy Italian espresso machine that still makes a decent espresso even though I've had it for just over 15 years. One thing that annoys me is the noise made by the vibe (electromagnetic) pump which can almost drown out any nearby conversation. I've replaced the pump but it did not make much difference.

Around at my mates place (his coffee machine is newer and fancier and makes anything I do coffee wise pale into insignificance) a few months ago and noticed his machines (yes he has more than one!) are really quiet. Turns out they use a outboard pump with a centrifugal type water pump so I thought I'd have a crack at putting one on my machine. At the same time I thought, why not make it a 3 phase motor and add small VFD to get a bit more control over the flow rate through the ground coffee. As it so happens, - as you do, I already had a suitable 1/5HP motor and a 1/2HP VFD on hand.

Turns out said mate also has discount access to an Italian coffee machine spare parts mob in Milano and my mate was about to place an order so I jumped on board. As well as a bunch of other parts I ordered a beaut SS pump and the standard pump/motor coupler/connections.

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So the first task at hand was to mate Motor (M) to Pump (P)
C are the component parts of the coupler.
F and F2 are two nice bits of 6 and 10 mm SS that I decided would hake good flanges.

Here is what the back and fronts of the couplers look like. The 3 pins on each plug into the holes in the rubber ring to smooth out the power transfer.
I bought two sets of each as they were less than 2 euros for each set!
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You can see the pump side of the coupler has a slot - no problem so does the pump - the problem is the other side of the coupler which is designed to suit a shaft with a flat spot or D shaped shaft while the motor has an 11mm shaft and a 4mm keyway. It turns out the D shaped hole is also 11mm - no worries I thought, I will place the coupler in the lathe, bore away the flat and cut a keyway in the hole and all will be honky-dory.
Well I have no idea what those couplers are made of but the TC tipped boring bar was having a very hard time so I stopped as I was worried about the 4mm Keyway broach I had not being able to cut the keyway. When I tried to scratch the coupler with the keyway broach it barely scratched the surface.

So plan B - make up a new 3 pin coupler with built in keyway hole/slot and the same 3 pin arrangement on the other side.

First problem with that was my keyway broach bush set only goes down to suit 12 mm holes/shafts = so let's make an 11mm one.
Vey soon I found out why the set stops at 12 mm - the spine of the broach is ~6.5mm wide (presumably to give it some strength) but this means the size of the accommodating slot in the smaller bush leaves very little metal left to hold the whole bush together.
Here on the left you can see the 11mm bush whereas the 12 mm bush is on the right.
You can see how little metal is left area the corners where the broach spine slides.
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This also made it difficult to cut the 6.5mm slot because any vice hold would just crush the bush.
In the end I made the bush out of some 16 mm stock with ~30mm of excess length to hold, both while turning and then cutting the slot, where I held the 30 mm of extra length in a collet held in a collet block in a vice, with the bush/slot section just hanging out in the breeze and just took fine cuts.
It's not absolutely symmetrical but the proof is in the fact that the bush works and together with the broach has cut two 4mm slots (first one was a cockup!) that neatly fit the motor shaft and keyway.

K below shows the finished piece with the 3, 6mm pins in place.
The other 3 holes were my first attempt at holes for the pins but due to poor marking out the holes were not symmetrically located and BOY - did this create some vibe.
Some of this was due to the pins not being of equal length/weight so I subsequently ground them to equal length/weight
I am much happier with the current pin locations but I think the old hole locations maybe still are throwing the thing out of kilter.
I will try filling the holes with short stubs of equal weight threaded rod to see if that makes a difference.
381188
And here it is assembled and on the motor.
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So now I have to make up a flange arrangement that couples the whole lot together. IT Hs to be pretty sturdy because the pump just hangs off the end of the motor.
Basically I'm going to use the two round plates of SS shown in the first picture bound together by some lengths of 8mm SS all-thread.
Getting everything aligned could be tricky.

simonl
9th Aug 2019, 08:50 PM
Keep it coming this is really interesting.

Being a keen coffee drinker I appreciate the effort you are going to. Also given that (if your like me) you have several coffees a day, you will really appreciate this little mod!

Simon

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BobL
9th Aug 2019, 09:44 PM
Keep it coming this is really interesting.

Being a keen coffee drinker I appreciate the effort you are going to. Also given that (if your like me) you have several coffees a day, you will really appreciate this little mod!

Thanks Simon, yes I do like my coffee and have 4 - 6 double shot coffees most days.
I have cut back from a true double shot (14g basket) to a reduced double shot (12 g basket)
Usually start the day with a double short espresso and the either long blacks or milk based coffees. In summer I extract the shots over ice and then add full cream milk, in winter I usually go with steamed milk. Some 3 months ago I weaned myself off milk completely and over to a shot of thickened cream topped up with hot water as this combo has less sugar in it and being diabetic means I am trying minimise surge. It doesn't work over ice unfortunately so I don't know what I'll do this summer.

The excuse of the quieter pump is just to placate SWMBO - I have something much nerdier in mind but won't spill the beans on it util I get the new motor and pump working.

simonl
9th Aug 2019, 09:54 PM
Hi Bob. Have you tried other "milks"?

I used to drink nearly 1 L of cows milk a day, have all my life but I recently gave up cows milk and reduced my dairy. I feel much better for it too.

I now use almond milk in my coffee. Took me a bit of getting used to but I like it now.

I also used to have 2 sugars in coffee, eliminated sugar in coffee too. Never thought I could do that but it's just a matter of training your taste buds.

Still love ice cream though. I'll never give that up!

Simon

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BobL
9th Aug 2019, 10:09 PM
Hi Bob. Have you tried other "milks"?
I used to drink nearly 1 L of cows milk a day, have all my life but I recently gave up cows milk and reduced my dairy. I feel much better for it too.
I now use almond milk in my coffee. Took me a bit of getting used to but I like it now.
I also used to have 2 sugars in coffee, eliminated sugar in coffee too. Never thought I could do that but it's just a matter of training your taste buds.
Still love ice cream though. I'll never give that up!
Simon


Yes have tried them all but don't like any of them - I can tolerate the taste of almond milk but I find the texture, I dunno - sort of rubbery? I love coconut and make my own coconut yoghurt using coconut milk but I don't like the taste in coffee.

I haven't had sugar in coffee since my early 20's but what I do like is a double espresso with a shot of grappa followed by the rinse, the dregs of the previous plus another shot of grappa. Unfortunately my diabetes limits these to special occasions only.

tony_A
9th Aug 2019, 10:26 PM
What model espresso machine are you running Bob

Good coffee is worth being obsessive about

Tony

BobL
9th Aug 2019, 10:49 PM
What model espresso machine are you running Bob

Good coffee is worth being obsessive about

Tony

It's a La Cimbali Junior.
The only thing I have modified is the water handling system.
It came standard with water tanks for input and output water but I removed these and plumbed it in on both the inlet and the outlet.
The inlet water is sediment (1) and charcoal (2) filtered followed by a reverse osmosis filter (3).
The water is forced through the reverse osmosis filter by a pump (4) and the impurities (basically salty water) pass away from the reverse osmosis filter through the red tube to a drain point D.

Water comes out of the reverse osmosis filter very slowly so it is stored in a pressurised 8L tank (T)
From there the water goes up to a pressure reception valve and control solenoid to CM where it heads off to the coffee machine.

M is a meter that monitors total dissolved solids after the reverse osmosis filter.

Filter 5 is not part of the coffee water system but a lab grade deioniser that I use to produce clean water for fume bluing. Its slow - about 2L/hour but it produces VERY clean water which I run into 20 carboys.

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The water filtration system alone cost more than a budget end espresso machine.

Here's a photo of my "shrine" taken some 12 years ago.
The left hand grinder is for SWMBO's decaf.
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Michael G
10th Aug 2019, 08:09 AM
You know, most people use that drain outlet on the sink S bend for a dishwasher. I guess that means the coffee machine is the more important appliance.

Michael

tony_A
10th Aug 2019, 09:09 AM
Having drunk WA's salty water I can understand you going to a bit of trouble to get pure water, but definitely obsessive. Tas has some of the best drinking water in Oz so no such treatment required here.
Will watch with curiosity to see if this gives you any improvement in control over the coffee shot compared to the regulator valve and standard pump.

Tony

BobL
10th Aug 2019, 09:49 AM
You know, most people use that drain outlet on the sink S bend for a dishwasher. I guess that means the coffee machine is the more important appliance.

Michael

The grey corrugated hose is the dishwasher waste drain (DWW).
The Reverse Osmosis drain (D) is the red line.
The brack 1/2' PE pipe (CMW) is the coffee machine waste drain pipe.
ALL three connect to the same spigot on the sink waste drain.
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Which brings me to something that happened about a decade ago.

Just before bed one night I stacked and set the dishwasher going.
At around midnight I got up to get a drink and went into the kitchen in the dark and felt my feet getting wet.
Turn on kitchen light to see brown dirty water coming out of the base of the coffee machine dribbling down the cupboards and covering most of the floor. For a moment I thought the machine had somehow turned itself on but there was no filter handle on the machine and then it dawned on me the water was soapy so it must have been coming from the dishwasher and back up to the coffee machine.

What had happened was the end of the dishwasher drain where it entered the sink waste line had become blocked and when the dishwasher had gone to discharge its waste the waster had nowhere else to go except back up through the coffee machine drain line. What had blocked the spigot into the sink waste line was a single olive pit. The plumber who had installed the dishwasher had used a 1/4" drill bit to break open the connection of the drain spigot to the waste line. So I drilled it out using a 1/2" bit and all was good.

After a few months another problem arose because the coffee machine drain line slope was too shallow, coffee grounds were over time blocking the coffee machine drain line. To counteract this I subsequently moved the coffee machine drain line straight down from the coffee machine through the cupboards and kitchen floor, to under the house where I connected it to the PVC sink waste PIPE.

SWMBO is constantly amused and my "playing around with the coffee machine" but does not comment too critically as she really likes her coffee.

steamingbill
10th Aug 2019, 11:37 AM
Y
I haven't had sugar in coffee since my early 20's but what I do like is a double espresso with a shot of grappa followed by the rinse, the dregs of the previous plus another shot of grappa. Unfortunately my diabetes limits these to special occasions only.

Hey Bob,

My favourite tipple very similar, only the added liquor is anise (sweet not dry) somehow the coffee and aniseed tastes go well together.

Bill

simonl
10th Aug 2019, 12:19 PM
Holy Bob!

That's quite a rig you got worked out there!

I feel so inadequate (more inadequate) now.

I've got myself a Jura but I do like it. Not in the same league as yours!

Simonhttps://uploads.tapatalk-cdn.com/20190810/b1f33445e2b5967ffdba3f98c4abea86.jpg

Sent from my SM-G970F using Tapatalk

RustyArc
10th Aug 2019, 01:21 PM
Back in the early 90's when I got my first machine (a Saeco "Magic" from memory) I had to replace the pump - it was a little Ulka vibrating positive displacement pump, and I suspect the same pump is used in pretty much all small domestic machines.

I'm relieved to see Bob has found another thing to stick a VFD on, but a little disappointed his machine doesn't appear to have a PID temperature controller on it???

Hopefully he'll at least add a pressure transducer and run the VFD in a closed-loop constant pressure mode.

BobL
10th Aug 2019, 01:49 PM
Simon, nothing wrong with Juras. We had one at work and with good beans it made many dozens of good coffees each day. When I think about it, It got flogged mercilessly and when the dude who normally serviced and clean it went on LSL it died from misuse.

When I visit my coffee nerd mate I'm the one feeling completely inadequate.He used to work in the coffee machine maintenance and the coffee roasting business during which time he acquired and disposed of various machines. He also owned a water purification business for about 5 years which is what enabled me to get my water setup otherwise it would have been out of my price range. Currently I think he has 3 machines, two of which are "multiple group head", 3 phase machines and he's in the process of converting one of these to single phase. His regular single group head home machine is fairly tricked out with dual boilers with PIDs, various gauges, coffee cam, and coloured LEDs that display a raft of machine conditions. It has an outboard pump but it's only single phase so no VFD. He has a number of pro grinders including a monstrous 3 Phase Mazzer with a VFD on it, and another one that cost more than my coffee machine.

About 12 years ago we both qualified as barista competition judges but only judged a couple of comps because keeping up the qualification required judging at a certain minimum of competitions each year but that was out of my financial bracket - you had to pay for your own travel and accomodation to attend events. Anyway it was a bit of fun and I learned heaps about coffee.


Back in the early 90's when I got my first machine (a Saeco "Magic" from memory) I had to replace the pump - it was a little Ulka vibrating positive displacement pump, and I suspect the same pump is used in pretty much all small domestic machines.
Yep these Ulka pumps are the standard pump - as I said, over time mine seemed to get a bit noisy so I replaced it but it didn't make much difference.


I'm relieved to see Bob has found another thing to stick a VFD on, but a little disappointed his machine doesn't appear to have a PID temperature controller on it???
Even without a PID the Cimbali is pretty good at temp control but PID IS on the "upgrade plan" :)


Hopefully he'll at least add a pressure transducer and run the VFD in a closed-loop constant pressure mode.
Close, pressure will be monitored so as not to go outside set limits but rather the pressure the aim is controlled extraction flow by varying the pressure.

KBs PensNmore
10th Aug 2019, 02:37 PM
Having drunk WA's salty water I can understand you going to a bit of trouble to get pure water, but definitely obsessive. Tas has some of the best drinking water in Oz so no such treatment required here.
Will watch with curiosity to see if this gives you any improvement in control over the coffee shot compared to the regulator valve and standard pump.

Tony

You might have Australia's best water, and Bob the saltiest, but Adelaides water is so bad, it's been re-evaluated from H2O to a new Chemical Symbol, K9P
Kryn

BobL
10th Aug 2019, 03:59 PM
You might have Australia's best water, and Bob the saltiest, but Adelaides water is so bad, it's been re-evaluated from H2O to a new Chemical Syymbol, K9P
Kryn

Nah its not that good. Back in the 1970's our suburb used to get all dam/rainwater which was not too bad but now it's mainly groundwater or desal so our tap water is "ordinary"


According to World Health Organization, total dissolved solids (TDS) levels less than 300 mg/litre is considered as excellent, between 300 and 600 mg/liter is good, 600-900 is fair, 900 – 1200 is poor and TDS level more than 1200 mg/liter is unacceptable.

Water can also have low TDs but still smell and taste poor. Some folks are more sensitive to this than others.

Perth Water's TDS is between about 100 and 600 mg/L depending on the amount of Dam/Ground/desal you get in your suburb. Where we live the typical value is around 390 mg/L and my Reverse Osmosis (RO) system pulls that down to under 10, the lowest I have seen it is around 3 mg/L. Although it does help the taste, the main reason I do it is not for taste but to protect the coffee machine boiler. To give you an idea how helpful the system is for the coffee machine, in 15 years I have only had to descale the machine 3 times. Whereas with my previous coffee machine without the RO I had to descale it very 6 months.

We don't cook or recharge our drinking water containers with RO water, we just draw water after the sediment and charcoal filters which is more than enough to improve the taste.

The deioniser cartridge reduces the TDS so much my TDS meter cannot even read the TDS remaining in the water. You cannot really drink this water without medical supervision as you can injure yourself from drinking water that is too pure. Also it seems to suck the life out of the water so it does not seem to make as good a coffee as the RO filter water.

Flo
10th Aug 2019, 07:17 PM
Good to see another coffee nerd on here.. nice setup you have there Bob.. I have a Giotto and Mazzer Mini which has served me well for almost 13 years.. I have been toying with the idea of doing a rotary pump conversion on it to quieten things down although the missus doesn't want me cutting holes in her benchtop so that I can plumb it in.. mind you the Giotto is quieter than the Mazzer..

I also roasted my own coffee for a number of years, but due to study and the fact that my green bean supplier sold his business, I started buying roasted coffee.

I drink milky coffees but my daughter got me to try Oat Milk. Its not too bad and doesn't alter the taste of the coffee too much unlike soy or almond milk.. It also stretches pretty well and is not unlike cow's milk.

Flo

RustyArc
10th Aug 2019, 07:33 PM
Even without a PID the Cimbali is pretty good at temp control but PID IS on the "upgrade plan" :)

I added one to my Rancilio Silvia about 10 years ago - it has a considerably smaller boiler I think. Made a pretty big improvement, and added shot timing with pre-infusion, all of which helps with consistency. The other more recent improvement is a (relatively) cheap Breville grinder has a grind timer and numerical grind-fineness display, which helps with tweaking the grind as the beans age.


Close, pressure will be monitored so as not to go outside set limits but rather the pressure the aim is controlled extraction flow by varying the pressure.

So you're going to sense the flow rate?

RustyArc
10th Aug 2019, 07:37 PM
I also roasted my own coffee for a number of years, but due to study and the fact that my green bean supplier sold his business, I started buying roasted coffee.

I bought a Behmor 1600 roaster, which is sitting in my workshop next to my welding table, having been used maybe 6 times. I discovered that I actually kind of preferred buying a consistently-roasted blend, provided I could get them within a few days of roasting.

Flo
10th Aug 2019, 08:04 PM
I bought a Behmor 1600 roaster, which is sitting in my workshop next to my welding table, having been used maybe 6 times. I discovered that I actually kind of preferred buying a consistently-roasted blend, provided I could get them within a few days of roasting.

I used a breadmaker and a heatgun and had a thermocouple to monitor bean temps.. One of my future projects is to build a little 1- 2kg drum roaster although I can comfortably roast 500g in the breadmaker..

I guess the key to buying decent beans is having access to a good roaster who will tell you when the beans were roasted..

BobL
10th Aug 2019, 08:09 PM
Good to see another coffee nerd on here.. nice setup you have there Bob.. I have a Giotto and Mazzer Mini which has served me well for almost 13 years.. I have been toying with the idea of doing a rotary pump conversion on it to quieten things down although the missus doesn't want me cutting holes in her benchtop so that I can plumb it in.. mind you the Giotto is quieter than the Mazzer.
Thanks FLo. The Giotto is a nice machine, one of my other coffee news mates has one and he has made some excellent shots with that.

Cutting holes in bench top started with the plumbed in CO2 bottle under the house for the soda water maker and as that was desired by SWMBO it was then an easy step for the coffee machine. SWMBO though it was a good idea because the drain pan always seemed to overflow when she was using it.


I also roasted my own coffee for a number of years, but due to study and the fact that my green bean supplier sold his business, I started buying roasted coffee.
I've dabbled a bit and was co-owner of a baby popcorn style roaster for a while but we were never consistent enough for my liking. Then my mate got a job as a coffee roaster although I did not get much from him. On and off I have been buying my beans from FiveSenses Coffee and am one of their oldest domestic customers and get their VIP discount - we used to go through 3kg a month but have cut that back to 2 in the last few years.


I drink milky coffees but my daughter got me to try Oat Milk. Its not too bad and doesn't alter the taste of the coffee too much unlike soy or almond milk.. It also stretches pretty well and is not unlike cow's milk

I can drink oat milk and have it sometimes on cereal, not that I eat cereal all that often as I am on a low carb diet. I'm mainly a block coffee drinker and just have milky coffees to break thinks up a bit. For me the milk has to have a decent fat component to complement the texture of the black coffee. That's why I like cream in coffee although I can understand why the oil spots might put some folks off. I don't worry about the calories as I only eat one meal a day anyway and my cholesterol is OK.

BobL
10th Aug 2019, 08:23 PM
I added one to my Rancilio Silvia about 10 years ago - it has a considerably smaller boiler I think. Made a pretty big improvement, and added shot timing with pre-infusion, all of which helps with consistency.
The Cimbali is a small machine but as it weighs 33kg it has a decent thermal inertia so the temp does not very much between heating cycles. It's built like a brick outhouse although mine does have a few rust spots on some of the non-SS or brass components. Earlier this year the stop start button failed but I tracked that to a connection where some steam had surface corroded a couple of ribbon contacts, a bit of wet and dry, and a dab of vaseline fixed that.


The other more recent improvement is a (relatively) cheap Breville grinder has a grind timer and numerical grind-fineness display, which helps with tweaking the grind as the beans age.
Grinders are indeed often underestimated in the search for good coffee. Last year I finally replaced the burrs on my Mazzer, ~3kg/month, 36kg a year x 15 years = 540 kg, recommended replacement is 4-500kgs on those little grinders. The replacement Burrs were eye watering expensive ($100) bit it was interesting to see how sharp the new ones were compared to the old ones.


So you're going to sense the flow rate?
Yep - well that's the plan. It's apparently very tricky to do at the ml/s rate but that's the plan and I like a challenge.

Flo
10th Aug 2019, 08:29 PM
Thanks FLo. The Giotto is a nice machine, one of my other coffee news mates has one and he has made some excellent shots with that.

I've been happy with mine.. and it as certainly paid for itself over the years..


Cutting holes in bench top started with the plumbed in CO2 bottle under the house for the soda water maker and as that was desired by SWMBO it was then an easy step for the coffee machine. SWMBO though it was a good idea because the drain pan always seemed to overflow when she was using it.

Yeah that's not going to happen for me.. my daughter and I are the only ones who use the machine even though my wife enjoys a coffee made with the machine!



I've dabbled a bit and was co-owner of a baby popcorn style roaster for a while but we were never consistent enough for my liking. Then my mate got a job as a coffee roaster although I did not get much from him. On and off I have been buying my beans from FiveSenses Coffee and am one of their oldest domestic customers and get their VIP discount - we used to go through 3kg a month but have cut that back to 2 in the last few years.

Yeah Popcorn poppers lack control and capacity.. They are basically on or off. With the breadmaker and heatgun I can can control the roast better. I reckon we'd go through 1.5kg a month..


I can drink oat milk and have it sometimes on cereal, not that I eat cereal all that often as I am on a low carb diet. I'm mainly a block coffee drinker and just have milky coffees to break thinks up a bit. For me the milk has to have a decent fat component to complement the texture of the black coffee. That's why I like cream in coffee although I can understand why the oil spots might put some folks off. I don't worry about the calories as I only eat one meal a day anyway and my cholesterol is OK.

I prefer cow's milk in my espresso.. If I drink french press/plunger coffee then I like it black.. When I make myself coffee I always use a 20g basket and pull 2 shots.. one becomes a piccolo and the other a flat white..

I have a mate who has thickened cream in his piccolo's.. the thickened cream has less carbs than full cream milk apparently. Who knew? :wink:

BobL
10th Aug 2019, 10:02 PM
I have a mate who has thickened cream in his piccolo's.. the thickened cream has less carbs than full cream milk apparently. Who knew? :wink:

Cream has 14 calories per gram whereas full cream milk has about 3, but cream has half the sugar per gram compared to milk. Usually one uses a lot more milk in a full stretched latte than in a drink with a shot of cream plus hot water so calorie wise it works out about the same.


When I make myself coffee I always use a 20g basket and pull 2 shots.. one becomes a piccolo and the other a flat white..

I usually use a 12g basket and extract everything a touch short ie ristretto. If I'm making for a crowd I will use the the 21g basket with 22g of ground coffee in it to make two coffees at a time

As far as mounting the new rotary pump to the motor is concerned, today I attacked the two flanges and bored them out with a TC boring bar (one at 25mm and the other at 53mm). They are both stainless. One I'm pretty sure is 316 but I'm not sure about the other as I got that from the scrap bin at a steel merchant. They are both pretty hard but the TC tipped cutter got me though easily enough. I now need to align them which is not going to be easy.

RustyArc
10th Aug 2019, 10:38 PM
I guess the key to buying decent beans is having access to a good roaster who will tell you when the beans were roasted..

Yep, it does vary. I'm fortunate to live about 5 minute's drive from an industrial precinct where there's 3 roasters, and there's 2 more 10 to 15 minutes away. I don't drink that much coffee per day - a kilo of beans will last me about a month, which is getting a bit past their prime, so getting beans that are just a few days old, i.e. degassed and right to go, is the goal, but has proven a challenge. That said, the 3rd, most recent roaster is totally cool about going out the back and getting a newly-roasted bag, so good times.

BobL
11th Aug 2019, 09:48 AM
One issue I have with roasters is consistency. You just get to like a particular bean and the way they roast it and they change things, no its "no longer available" or "we're now buying these beans" or... or... etc.
We have several roasters that are local that I can buy from in an emergency but the one I buy from are 40 km, or depending on traffic between 40 and 70 minutes minutes, away, but they deliver my 3kg monthly order for a whole $4. They roast stuff daily and deliver within 2 days which makes them expensive but they are highly consistent. I have been buying from them since 1995 and have not been disappointed with anything I have bought from the.

Recently the a young close friend of ours set up a commercial roaster just 10 minutes away and I have bought some beans from him. He's very keen and enthusiastic but only just getting sorted and only roasts stuff that I like about once a week. However, he does seem to be able to get a consistent roast - whether he is able to refrain from extensive "experimentation" or even survives in the cut throat business of coffee roasting is another matter.

RustyArc
11th Aug 2019, 10:34 AM
Yep, the barrier to entry for commercial coffee roasting seems to be getting ever lower, given how many roasters pop up.

I tend to go for the house espresso blend, as it tends to be the most consistent, since they make heaps of it for supply to cafes.

BobL
12th Aug 2019, 05:51 PM
Found some time to get back to the motor pump couple/flanger this morning and just assembled and tested it and I am pretty happy with the way it runs.

The hard connect and some alignment adjustment is done via the SS all-thread rods.
I will be rotating the motor side flange by 90º CCW so the pump I/O's are pointing upwards.
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Heres a close up of the coupler - on the above photo it's just possible to see the 5mm grub screw on the motor side of the coupler just to stop it siding on the motor shaft.
381247

Initially I used 6mm all thread because there were already 6mm threaded holes in the pump side of the flange plate but I tapped the holes on the motor side flange plate just so slightly non-perpendicular and this then threw the whole shebang out of alignment and there was too much vibe for my liking.

So I swapped the 6mm for 8 mm and this time I used my home made centre finder in the drill press to hold the back of the tap vertical like this.
Being able to minutely control the height of the table with my auto table riser really came into its own in this situation.
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381249
The holes in the flange plates are now vertical but there was still a slight mismatch between the opposite hole positions on each flange plate which is why the all thread doesn't look that straight in the photo but it seems to work fine. I had the pump running up to 75Hz without any appreciable vibe and I reckon I can reduce the vibe even further by improving the alignment a bit more if I need to.

BaronJ
12th Aug 2019, 06:09 PM
Hi Bob,

I would have trapped a piece of plastic tube, either inside or outside the spacer bolts, just to help alignment and to keep the drive clean.

But we wouldn't have been able to see it then :no:

Nice job anyway :2tsup:

BobL
12th Aug 2019, 06:57 PM
Hi Bob,

I would have trapped a piece of plastic tube, either inside or outside the spacer bolts, just to help alignment and to keep the drive clean.

But we wouldn't have been able to see it then :no:

Nice job anyway :2tsup:

Thanks.

RE: Plastic tube
Great idea.
I can still do that and it might be worth doing for safety sake.
You will still be able to see the coupler because I will probably do it with clear tubing OR I can make a tube with some 1mm Polycarbonate.

The final location of the pump and motor will hopefully be in a cupboard where SWMBO keeps her serving ware, glass platters and trays, and ceramic and metal serving dishes etc so the cupboard itself is pretty clean.

BaronJ
13th Aug 2019, 12:52 AM
I know Bob, use some translucent tube and put some coloured LEDs in the bottom, a few strips of reflective tape on the spindle and you have a light show. Should look good in a dark cupboard... :cool::cool::cool:

BobL
14th Aug 2019, 08:03 PM
As suggested by BJ.

from a piece of olycarbonate 1mm thick scrap sheet.
381286

I also found some beaut 10mm ID, 1mm wall, SS tube and turned the bits all to the same length and used it as a more accurate way of aligning the pump and motor and this helped reduced the vibe a bit more.
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BaronJ
14th Aug 2019, 10:46 PM
Hi Bob,

I like that clear 1 mm sheet tube that you have made ! Much better than leaving it open and exposed, dropping a cloth or something on that rotating shaft could cause problems. Those tubular spacers are a much better way of lining the two surfaces up as well. You now can guarantee that the plates are parallel to each other.

Nice to know that the vibration has reduced. What little is left could be the coupler itself.

PS. You know that my suggestion about the LED's was not a serious one :no:

BobL
19th Aug 2019, 07:31 PM
I finally got back to this project and was for a few days stuck on why nothing was working.

I hooked up the VFD and a water supply to the motor/pump and the first obvious thing is that water flows straight through this pump but of course it's a pressure addition pump.

Then, changing the speed of the motor didn't change the pressure much, and hardly changed the flow rate at all.
Varying the VFD from 30 to 70 Hz only changed the pump pressure by ~15% and the flow rate changed by <5%

After wondering what was going on, it struck me that of course, this is EXACTLY how these pumps are supposed to work so that if someone flushes the loo or turns on a HWS etc which can change the incoming water pressure which will throw the pump pressure out as it's a P-adder pump. But I don't need this as I already have a highly regulated water supply - what I want to be able to do is control P&F with the VFD.

Opening up the press regulation mechanism I could see how it worked.
Plunger P sits in a passage connecting the pump outlet back to inlet.
Spring Sp supplies a back pressure to seal P inside the passage at the outlet end with the tension of the spring determined by screw S position.
As the pump pressure builds up, once the pressure starts to overcome the spring tension this opens up the passage from the outlet water back to the inlet.
Final flow is limited by any pump outlet restriction but if that is fixed it will maintain a fixed flow at a fixed pressure.
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To get around this I replaced the 7mm diameter x 19 mm long spring with turned brass cylinder C, the length of C is adjustable by a short brassscrew on the end.

Then here is the testing setup
I = incoming water
WR - water pressure regulator set at 4bar
IWP = gauge shows input water pressure
P = pump
OWP = gauge showing putt water pressure
NV = Needle valve to supply a back pressure
V = VFD

All I did was set the motor speed and record the OWP and measured the amount of water delivered by the pump by catching the water stream into a container for a set time period.

381392

Replacing the the spring with the brass cylinder effectively removes/decouples automatic pump pressure/flow control enabling these now to be controlled by the VFD.

Below you can see with the VFD ranging from 30 to 70 Hz the pump output pressure more than doubles (+122%) while flow increases by ~70%

This means a barista can now control P & F even during a shot/extraction depending on their specific requirements.
381394

Some more testing to do to determine the optimum position of the length screw on the brass cylinder.

I have spoken to SWMBO about giving up some valuable kitchen cupboard space to accomodate said pump and she was surprisingly positive about it!

BobL
23rd Aug 2019, 01:48 PM
Started prepping the machine and under cupboard plumbing for the new pump.

One major issue while doing all this is to keep coffee machine in action - ie coffee has to be available at all times

I moved the solenoid and filtered water pressure regulator from under the sink to the cupboard immediately under the machine. The benefit of this so I can see what happens at the machine while adjusting the filtered water pressure. Otherwise I'm going back and forth all the time.

Thought I had everything done up tight ie could see no leaks, so went down shed for a bit and came back up later (for a coffee) and found the inside of the cupboard full of water!
DANG - had to completely empty the cupboard and then mop up and let it dry out - ie crockery everywhere.

Then I needed to par-strip down the machine to see what additional internal plumbing and electrical fittings would be needed to attach the new pump. Turns out its not going to be too hard.
I will have to bypass the old pump over pressure valve which is separate from the old pump but that should not be too hard.

To see where the pump was going to be connected required 4 panels on the machine be removed but while I was doing this I looked for a placed to attach a thermocouple so ended up stripping it down this far - Even this far stripped down, apart from the milk steaming wand, the machine still works

381469

To attach a thermocouple I needed a flat bit of machine close to the water chamber just before the water goes onto the coffee and that I could easily drill and tap to attach a bolt or screw through which thermocouple wires could be run. I fully envisaged removing the "group head" (Big fat brass chamber that forces the hot water onto the ground coffee) and putting it on the mill but I quickly spied a screw that didn't seem to be doing anything.

I checked the screw on the machine schematic in the manual and it turns out to be a test point that goes all the way into the inside of the group head. ie perfect
381470

Running a couple of fine wires though the middle of that screw was not going to work and using a standard hex bolt head was not going to be any better because with all the panels back on I would not be able to get a spanner in there to tighten it and there is no room for a socket either.

So this is what I did using an M6 capscrew. Where the wires come out they sit just below the bottom of the key.

The long hole down the middle was done in the lathe and the side hole on a drill press.
The 2 mm bit snapped just as it broke though from the side hole into the long hole but I was able to get the broken bit out, resharpened the bit and carried on.
Now the holes get filled with epoxy for a 10+ bar pressure seal.
381471

RustyArc
23rd Aug 2019, 02:32 PM
The PID conversion kit for my Silvia came with a screw-in RTD temp sensor that screwed into a spare hole in the top of the boiler. The setpoint of the unit is 107 degrees, which corresponds to some lower temp at the face of the group head - when I first got it, I put a thermocouple on top of the packed coffee before locking it into the head, so I could see the temperature of the water as it met the coffee grounds, and adjusted the setpoint to suit. Your sensing point looks pretty much ideal - much closer than mine to the actual coffee grounds.

BobL
23rd Aug 2019, 05:15 PM
The PID conversion kit for my Silvia came with a screw-in RTD temp sensor that screwed into a spare hole in the top of the boiler. The setpoint of the unit is 107 degrees, which corresponds to some lower temp at the face of the group head - when I first got it, I put a thermocouple on top of the packed coffee before locking it into the head, so I could see the temperature of the water as it met the coffee grounds, and adjusted the setpoint to suit. Your sensing point looks pretty much ideal - much closer than mine to the actual coffee grounds.

thanks RC. I wasn't thinking PID just yet but it looks like it's getting closer to to fruition.

RustyArc
23rd Aug 2019, 07:47 PM
thanks RC. I wasn't thinking PID just yet but it looks like it's getting closer to to fruition.

It may well not be needed - I think your machine probably has a greater boiler volume and overall thermal mass which means it's able to maintain a more stable temperature, whereas the Silvia suffered the hysteresis and overshoot you get from a simple thermostat, relatively large heating element and relatively low thermal mass. I guess being able to monitor the temp during the shot will give you some idea of how stable it really is.

BobL
23rd Aug 2019, 08:22 PM
It may well not be needed - I think your machine probably has a greater boiler volume and overall thermal mass which means it's able to maintain a more stable temperature, whereas the Silvia suffered the hysteresis and overshoot you get from a simple thermostat, relatively large heating element and relatively low thermal mass. I guess being able to monitor the temp during the shot will give you some idea of how stable it really is.

Yeah we'll see soon enough.

The Cimbali Junior has a 2.5L boiler and even with a 2000W element it still takes ~ 8 minutes to warm up before the ready light comes on, but the brew head is still not hot so the first shot or two are underdone. Things improve markedly If I flush the head for 30s before pulling the first shot.

For comparison purposes I looked up the Silvia and it said it had a 300ml Boiler, 1100W heating element and a machine weights of 14 kg, versus 33 kg for the Jnr.

I'm now going to do a basic hook up of the pump to the machine so that the pump is turned on/off by the existing electrics. The pump speed will be done manually by simple analog pot, and pressure/temp monitoring done via an Arduino. That way I can get a feel for what it's doing before attempting a more automated setup.

Also while all this is happening I have to keep the machine functional.

RustyArc
23rd Aug 2019, 09:17 PM
Gosh - the difference in volume and element size was considerably greater than I assumed.

I have a bit of a routine - I turn on my machine at least 1/2 an hour or more before I get up in the morning, then once up, turn on the steam stetting and give it another 10-15 minutes to build up the heat. Then steam the milk, run the head into the cups to drop the boiler temp and heat the cups, then pull a double shot.

My lunchtime routine is to just let the machine come up to temp for at least 15 minutes, then pull a double shot. The temp is probably more stable for the lunchtime coffee, but there's no milk, so a bit more critical, although if it's looking a little over extracted, I add a dash of milk.

BobL
23rd Aug 2019, 09:58 PM
We use the larger boiler quite a bit to make tea or soups or for cooking etc.


I have a bit of a routine - I turn on my machine at least 1/2 an hour or more before I get up in the morning, then once up, turn on the steam stetting and give it another 10-15 minutes to build up the heat. Then steam the milk, run the head into the cups to drop the boiler temp and heat the cups, then pull a double shot

My lunchtime routine is to just let the machine come up to temp for at least 15 minutes, then pull a double shot. The temp is probably more stable for the lunchtime coffee, but there's no milk, so a bit more critical, although if it's looking a little over extracted, I add a dash of milk.

Your routine sounds like my routine when I was employed and we had the machine on a timer to come on 1/2 an hour before we got up.
My first coffee was always a double espresso and I wanted it just so and then usually followed it with another.
I used to drink 90% espresso (at work we had a Jura), with the odd iced milky coffee in summer, but have now substituted cream for milk - doesn't work with ice unfortunately.
Still make a lot of steamed milk coffees for SWMBO and guests etc.

These days I get up anywhere between 5 and 7 am so the timer has be decommissioned and my first coffee is a double shot with a slug of with cream, topped up with hot water.
I have another one of these after walking the dogs and another one after dinner
The rest of the day I have a variety of coffees; usually espresso, but also long blacks and machiattos using cream.

And as far a cream and body weight are concerned, even though I have been going through a lot of cream, my weight since April has gone down by 7 kg.

BobL
2nd Sep 2019, 10:12 AM
Still waiting for the pressure sensor to turn up.

In the meantime I started on the micro controller- a $10 Arduino Uno clone.
Initially its just going to monitor a few machine parameters an I will control the pump speed manually via the VFD.

Here is the prototype MC/monitor hanging off the side of the machine.
The two pots on the RHS of the MC box are the pots fro controlling the VFD
381730

The power for the MC/monitor and the VFD come from a double GPO wired via the coffee machine mains switch so that the MC and VFD are switched on/off when the machine is switched on/off.
The MC draws about 35mA while the VFD/Motor draws about 1/2A so it should not over tax the coffee machine electrics.
Also the 3P motor only runs for no more than 30s at a time while the coffee is being extracted.

The only sensor currently connected is the Brewhead temperature (BT) thermocouple - see below.
The LHS number is the instantaneous temp, the other is an average of 20 readings over one second.

PP: will be pump pressure in bars
ET is elapsed time or extraction time (the shot clock) from when the pump is turned on to off.
MF is the VFD/motor frequency
Both ET and MF are working on the test bench with dummy inputs but as I don't yet have the new pump connected they are not working on the machine

381731

Wasted a lot of time getting the thermocouple to work properly.
It was working fine on the bench, even when using boiling water, but when connected to the coffee machine the TC output temp was all over the shop (25 - 140ºC).

At first I thought it was a noisy PS (I'm using an old Telstra 9V AC/DC adapter to power the MC) because the MC ran fine on the coffee machine a 9V battery.

What eventually tipped me off was I saw a tiny spark between the TC tip and the coffee machine, just when I was for the umpteenth time removing the TC from the coffee machine.

It turned out the voltage between the coffee machine and the MC grounds was 105V AC !!.
As soon as I connected the MC signal ground to mains earth the problem virtually disappeared.
There’s still something small and funny going on - might need to put a filter on the TC input.

Now I have to recalibrate the TC and it should be good to go.

lamestllama
2nd Sep 2019, 01:23 PM
A fantastic amount of intellect being applied to this. Looking forward to seeing the finished result.

BobL
2nd Sep 2019, 02:19 PM
A fantastic amount of intellect being applied to this. Looking forward to seeing the finished result.

Well I would not put it like that, lots of going around in circles trying to remember stuff I should know but have most inconveniently forgot.

BobL
12th Sep 2019, 08:37 PM
Finally got my pressure sensors so I could finish up this project.
Lucky I bought two because in between calibration and the prototyping I buggered one - that will teach me for buying cheapies.
Once this all gets sorted I will buy a decent one for long term use.

Decided to do the prototyping outside - just as well as I had two leaks - water pissing out everywhere. That's also why I had everything sort of spaced apart.
The prototyping set up is shown below.
PR is the mains water coming in via a garden hose and a pressure regulator (drops the mains pressure to about 3 bar) - on the coffee machine a solenoid completely shuts this down to zero in case there's leaking in the system - especially when no one is around. The solenoid only opens when water is needed.
PS is the new 20 bar pressure sensor.
The typical pressures used will be between about 7.5 and 12.5 bar.
There are auto pressure relief valves on the motor and another on the machine that will open at ~14 and ~15 bar respectively.
V is the VFD, A is Arduino box.
N is a needle valve that was used to simulate the back pressure generated by a coffee puck.

382036

The aim of this prototyping was to make sure the Arduino was measuring the pump pressure and reading the VFD frequency.
And here it is - The temp reading (BT) is meaning less as the temp sensor has been disconnected for this testing - it's screwed in back at the machine.
382037
The pots on the side of the ARDUINO box control the motor speed so the operator will be able to force more or less water though the coffee.

The values shown are averages of 10 readings per second. The number of readings per second being limited by the time needed for the pressure sensor and associated analog port to settle between changes (~70ms).

Maybe - tomorrow I will try it all on the machine.

BobL
13th Sep 2019, 07:03 PM
We have coffee!

Today I assembled everything inside the cupboard under the coffee machine and connected the stuff inside the cupboard through the 50 mm hole in the bench top to the machine.
There are 6 connections
Input water from pump to machine
Output waste water from machine to drain
Solenoid control
VFD power
VFD control
Pump pressure sensor

Had to drill out and seal/paint a 24mm hole in the base of the machine so the woven SS water cable end fittings could get water into the machine itself
No leaks - that was good.
And it all worked as it should!
30s later a connection on the thermocouple broke - repeated overhanding most likely.

Here's what it looks like inside the cupboard.
You can just see the front of the the coffee machine on the bench above e (green light)
You can see it does not take up a lot of space
Still have to try up the cables etc.
382052

Close up
S = Solenoid that opens only when the pump activates
PRV is the pressure reducing valve - dropping the pressure gives the pump better control at low speed.
The gauge on the PVR tells me what I have dropped the pressure to
V = VFD - its a little Telemechanique 1/2HP - I got it for the price of postatge from a Woodie forum member
PS is the Pressure sensor.
That power plug in the picture has nothing to do with the pump gear - its for the dishwasher in an adjacent cupboard.
382053

Best thing is it's very quiet.
With ambient noise levels @ about 40dB, with the pump running it was about 55 dB versus >85dB for the vibe pump.
Now I need to do something about coffee grinder noise and fix that thermocouple!

RustyArc
13th Sep 2019, 08:10 PM
Very cool. Curious to see your flow sensing solution and how that works out in terms of closed-loop operation.

BobL
13th Sep 2019, 09:10 PM
Thanks. No flow sensing happening yet it’s just pump substitution at this stage. The strain gauge to sense fluid mass arrived but I managed to break off one of the fine wires and had a devil of a time reattaching it. I managed also to get hold of an actual flow sensor but I think it will be too coarse for what I need.

RustyArc
14th Sep 2019, 10:14 AM
Measuring the very low flow of a coffee shot at decent sample rate sounds tricky. I have collection of paddle wheel and axial impeller flow sensors from 1/2" to 2" and even with decent flows, they're tricky to get repeatable readings from, particularly when you start to factor in turbulent flow whose effect on readings changes with flow rate. Filtering helps, but you sacrifice responsiveness.

That said, I'll have to go Google fluid mass sensing. Sounds like it might be more appropriate for the application

BobL
14th Sep 2019, 12:26 PM
Measuring the very low flow of a coffee shot at decent sample rate sounds tricky. I have collection of paddle wheel and axial impeller flow sensors from 1/2" to 2" and even with decent flows, they're tricky to get repeatable readings from, particularly when you start to factor in turbulent flow whose effect on readings changes with flow rate. Filtering helps, but you sacrifice responsiveness.

That said, I'll have to go Google fluid mass sensing. Sounds like it might be more appropriate for the application

I agree, I doubt a conventional impeller or paddle wheel sensor will be sensitive enough. The best tech for low flow is ultrasonics as used in medical devices but these are out of my price range. I've been looking on eBay but they typically start at US$500 for used gear and over a grand US for new stuff. That's why I'm looking at using mass rather than volume.

Meanwhile it turns out the thermocouple was not broken. Like my dust collector pressure/temp sensors the Thermocouple is upset by the VFD, there's noise from the VFD sneaking through somewhere. I thought it was via the PS but there's a bunch of other ways it could be sneaking in. For example the speed controller is connected to Arduino analog and earth ports.

I suspect it might be radiated noise. With a right PITA. Gunna have to get out my filtering hat.

BaronJ
14th Sep 2019, 06:56 PM
Hi Bob,

Sounds like you need some ferrite rings or beads. If its any help the lump in a cable near the end is a ferrite tube and they are easily salvageable. If you want any I've got hundreds of various ones. From 3 mm diameter with a 1.5 mm bore right up to 3" inches and a 2" bore.

Stustoys
16th Sep 2019, 12:20 PM
Hi Bob,

Wow what people will do for the perfect brew! Good job and it's "cheaper than golf" lol

How are you getting the frequency from the VSD? an RS-485 port?

BobL
16th Sep 2019, 04:56 PM
Hi Bob,

Wow what people will do for the perfect brew! Good job and it's "cheaper than golf" lol

I know it sounds ridiculous, but it really has cost me very little in hard $ and providers hours of fun and many hours of frustration


How are you getting the frequency from the VSD? an RS-485 port?

I have no idea,

There's only a problem when the VFD is switched on ie motor not even running, with motor on problem is worse.

Some possibilities
The VFD control lines are connected to the Microcontroller through an unshielded Cat5 cable - need to move to earthed shielded cable (eg cat 6)
I have put a ferrite ring on this cable but it makes no difference

The TC is connected to the coffee machine through a twisted teflon insulated wired pair. This thing seems to act like an aerial - move it away from the machine and it works OK, the closer I move the wire to the machine the weirder the temps become. when the insulated wire itself touches any metal part of the machine that's when its at its worst. I need to use a shield cable here too

The Press sensor is also connected between the pump and microcontroller - this works fine and I doubt is a source of the problem.

The 240V mains into the VFD has a Ferrite core on it - no difference. I need to put a ferrite on the VFD output.

The main issue seems to be around the presence of AC on the output of the TC op amp.

Theres <0.01mA of AC on the TC input signal going into the op amp (DC is ~1mV)
Out of the OP amp is ~1.5V DC BUT between 500 and 200 mV AC!

Interestingly my meter says this AC is 100Hz.
Have tried various input and output filters with no luck.
When I remove the TC from the coffee machine back to a position on the bench where it was reading normally and turn off the VFD the temp reading is not back to normal until I turn the microcontroller off and then back on.

BaronJ
16th Sep 2019, 06:01 PM
Hi Bob,

I would check the power supply to the micro. 100 Hz suspiciously like line hum !

BobL
16th Sep 2019, 08:25 PM
OK - we have significant progress.

Firstly I put a large ferrite ring on the VFD output phases to the motor.
382139
WHALLA!
This immediately dropped the AC on the TC Opamp output from ~500mV to <5 mV.
In terms of what it did to the temperature reading by the TC was it moved it from a constant -13ºC to something between ~8ºC when the motor is off and +4 ºC when the motor is on.

Next I added a snap on ferrite ring to the TC lead.
One loop made only a marginal difference but the more I looped it the lower the AC volts on the OPamp

382141
5 turns of the TC lead around the ferrite dropped the Opamp AC out to <0.01mV with the VFD on and motor of , and a transient of max ~ 0.5mV AC when the motor starts dropping to ~0.02mV.
The reading of the TC with the VFD and motor running is nominally now within 2º of what it should be.
I could just recalibrate the TC to take this difference into account but now I have a lead I will chase this further ie try more winds onto the ferrite, more/different size ferrite rings etc.
Also try shielding.

Interestingly just after I did all this I found an excellent practical website on reducing EMI from VFDs (https://kebblog.com/7-steps-to-reducing-emi-with-vfds/) and it said


A relatively inexpensive option to reduce common mode noise is to install correctly sized ferrite rings at the output of the VFD. Common mode noise is a result of the interaction of pulse width modulation and parasitic capacitances of the cable and motor. Common mode noise produced by PWM travels throughout the motor to ground.

So I reckon this has been a very useful pursuit of a tricky problem. Thanks to BaronJ for the tip on the Ferrites - just needed to work out how and where to place them

BobL
16th Sep 2019, 08:45 PM
Hi Bob,
I would check the power supply to the micro. 100 Hz suspiciously like line hum !

Thanks I thought that too and have spent a lot of time looking at power supplies.
If it was this then it shouldshould show up all the time but there was only a problem when the VFD was on and worse still with the motor running.
The AC on the 5V DC out of the Arduino is <0.01mV.
As I described above the noise seems to be the VFD-motor-ground and anything else that connects with ground..

Michael G
16th Sep 2019, 08:59 PM
I was always told that the VFD output should be shielded cable to reduce noise. Is yours?

Michael

BobL
16th Sep 2019, 09:59 PM
I was always told that the VFD output should be shielded cable to reduce noise. Is yours?

Michael

Nope - but it soon will be.

Stustoys
16th Sep 2019, 10:11 PM
I have no idea,
Oops sorry. I saw your display, then read "MF is the VFD/motor frequency " in your post, but missed the very next line "Both ET and MF are working on the test bench with dummy inputs but as I don't yet have the new pump connected they are not working on the machine"
I was asking as I'm working on a project that will use an Arduino to control fan speed via a VSD, but I wont mess up your thread further with that.

BobL
16th Sep 2019, 11:04 PM
Oops sorry. I saw your display, then read "MF is the VFD/motor frequency " in your post, but missed the very next line "Both ET and MF are working on the test bench with dummy inputs but as I don't yet have the new pump connected they are not working on the machine"
I was asking as I'm working on a project that will use an Arduino to control fan speed via a VSD, but I wont mess up your thread further with that.

Sorry, I misread your post. I thought you were asking about noise.

The VFD speed is set on the Arduino box using an external potentiometer.
I'm adjusting the speed using a pair of pots [one for coarse and one for fine adjustment) in what is known as an H-pattern but that's not part of your question.

The connection to the Arduino itself is as follows.
1) Ardunio Ground to the VFD Analog COM or ground.
2) Since the the max V of the pot wiper is 10V and the max analog input of the Arduino is 5V I've set up a simple Voltage divider using a pair of 100k resistors between the pot wiper and ground, an Arduino analog port is connected to the midpoint of the divider so the analog port never sees more than 5V.

I'm using a max VFD frequency of 100Hz and the Ardunio analog port has a max ADC value of 1024 bits, if I divide just divide any ADC value by 10.24 and that gives me Hz.

Depending on the VFD you can get the frequency from the VFD in other ways - I just thought of doing it this way as I already have the speed control lines for the external speed pots in the arduino box.

The VFD and the Arduino display the same frequency to within 0.1Hz.

Stustoys
16th Sep 2019, 11:54 PM
Sorry, I misread your post.
Well thats easy enough to do. Sadly, more than once I've looked at one of my own posts a few years on and thought "how did anyone even understand what I was asking?" :no:

Ok I see what you are doing now. Thank you.

I'll start a new thread over in electricals some time soon.

BobL
17th Sep 2019, 12:19 AM
Well thats easy enough to do. Sadly, more than once I've looked at one of my own posts a few years on and thought "how did anyone even understand what I was asking?" :no:

Ok I see what you are doing now. Thank you.

I'll start a new thread over in electricals some time soon.

This thread should probably be moved over there as well.

BaronJ
17th Sep 2019, 01:27 AM
I was always told that the VFD output should be shielded cable to reduce noise. Is yours?

Michael

Hi Michael, Bob, Guys,

My only concern about using shielded cable for the VFD output is obtaining a cable with sufficient voltage rated insulation along with the current carrying capability you need.

Also the connectors for shielded multicore cable are expensive and not that easy to obtain.

BobL
17th Sep 2019, 06:54 AM
Hi Michael, Bob, Guys,

My only concern about using shielded cable for the VFD output is obtaining a cable with sufficient voltage rated insulation along with the current carrying capability you need.

Also the connectors for shielded multicore cable are expensive and not that easy to obtain.

One of the most useful things I picked up when scavenging stuff from the hospital demolition site was a roll of 6 core shielded cable. I think the cores are 1mm which is more than enough for the 1/2A total current draw by this small (1/5 HP) motor and the insulation tests better than 100MΩ so it should be fine for 240V.

Connector wise, the Arduino enclosure is plastic so even though I have some fully metal enclosed connectors/feedthroughs they are not going to do much.

Now I need to get that roll of 6 core wire back from Anorak Bob!

russ57
17th Sep 2019, 01:18 PM
You could also consider differential mode adc - eg ADS1115.

This should help with sensors like the thermocouple and flow.



Russ

BobL
17th Sep 2019, 08:06 PM
I was always told that the VFD output should be shielded cable to reduce noise. Is yours?

Michael

I replace the VFD to motor cable with a shielded cable and It had about the same effect as the large ferrite ring on the output ie it helps but does by itself not solve the problem.

BaronJ
17th Sep 2019, 09:08 PM
Hi Bob,

Try adding a couple of turns through the ferrite ring, and if you now have shielded cable only earth or ground the cable at the VFD end.

Ferrite beads are useful on individual wires close to the ends of ones carrying signals.

Good luck ! I've spent many happy hours chasing RF leakage down only to find that its coming from the most unexpected place.

BobL
17th Sep 2019, 11:19 PM
Hi Bob,

Try adding a couple of turns through the ferrite ring, and if you now have shielded cable only earth or ground the cable at the VFD end.
That is whatI have done.


Ferrite beads are useful on individual wires close to the ends of ones carrying signals.
Good luck ! I've spent many happy hours chasing RF leakage down only to find that its coming from the most unexpected place.

I've done the same but I wouldn't necessarily call them "happy"

BobL
18th Sep 2019, 09:26 AM
I found another issue contributing to the noisy TC problem.

So that I don't have to turn on 3 mains switches (coffee machine, VFD/Motor, Micro-controller[MC]) just to have a coffee, I wired the mains for the VFD/Motor and the MC via the coffee machine. This meant the coffee machine mains switch powers up all 3 system components. However this means the earths for the VFD/Motor and MC are all going through the Coffee machine.

When I run these direct from the same GPO as the coffee machine (ie NOT through the coffee machine) there is a further small reduction in TC noise.

So although its more work I will connect the VFD/Motor and MC direct to the mains, but switched via a relay powered via the coffee machine.

Yeah I know - what a load of palaver.

BobL
19th Sep 2019, 06:49 PM
Set up the mains power supply to the VFD and Microcontroller (MC) so they are powered from the same outlet as the coffee machine
Remember I want to turn on the VFD / MC and coffee machine from the one switch.

Outlets
The 5 way GPO.
1: Electric kettle power
2: Ginder 1 power
3: Coffee machine power
4: Grinder 2 power
5: Power redirect to double GPO above the 5 way outlet.

R: Relay - Switched by coffee machine power - Connects power from outlet 5 to the double GPO above.
6: VFD power
7: MC power

Messy cables I know!
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Getting closer
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With regards the thermocouple noise I tried a couple of other things.

I tried shielding the TC cable between the machine and MC with shielding grounded to Earth - Didn't do much.

Tried locating a "snap on ferrite" just on the TC signal line, and then just on the ground, no good - have to wrap both ground and signal line around the ferrite core.

I want to wind more of the TC lead around the "snap on ferrite" but the TC lead is not long enough so will be making a new one.

BaronJ
19th Sep 2019, 07:21 PM
Hi Bob,

You have to determine which of the items is creating the hash, then the ferrite filter bead needs to be as close to the source of interference as possible. With those multitude of wires the interference can wonder from wire to wire at will and will also vary as the wires are moved around, particularly when coiled up together.

One source of interference that you may have overlooked is the Ardino itself. The clock can radiate a modulated signal that will escape down any wire and interfere with its self.

One piece of equipment that I used to use was a small insulated two turn loop diode probe and an oscilloscope set on its most sensitive range. You could get away with a high impedance multimeter but you would have to make the probe as an adaptor to get rid of the meter leads. At one time I had an op amp in a die cast box to amplify the diode output to a 25 ua meter. That worked quite well when I made it into a variable tuned one.

Interference is a most difficult thing to pin down, nowadays manufactures spend thousands to make sure that their equipment meets interference standards.

BobL
19th Sep 2019, 08:11 PM
Hi Bob,
You have to determine which of the items is creating the hash, then the ferrite filter bead needs to be as close to the source of interference as possible. With those multitude of wires the interference can wonder from wire to wire at will and will also vary as the wires are moved around, particularly when coiled up together.
Yes it is a bit of a dog's breakfast so it does not surprise me there are probs.


One source of interference that you may have overlooked is the Ardino itself. The clock can radiate a modulated signal that will escape down any wire and interfere with its self.
Yep, I am ware of this, same with the PS. However these should show up as problems even on the bench when not attached to the coffee machine. All through the bench testing and calibration (sans VFD) there was no problem.

It's definitely the VFD generating the noise as only when I turn on the VFD (not even motor running) do things go pear shaped, when the motor runs things get slightly worse.


One piece of equipment that I used to use was a small insulated two turn loop diode probe and an oscilloscope set on its most sensitive range. You could get away with a high impedance multimeter but you would have to make the probe as an adaptor to get rid of the meter leads. At one time I had an op amp in a die cast box to amplify the diode output to a 25 ua meter. That worked quite well when I made it into a variable tuned one. Interference is a most difficult thing to pin down, nowadays manufactures spend thousands to make sure that their equipment meets interference standards.

Thanks for the tips. Die cast box might be on the cards for prototype two.

All during today I've been comparing the Arduino temps with two other battery powered TCs. On the bench away from the machine/VFD they agree to with a degree but due to working positions problems in situ comparisons are difficult as the working position of the Arduino TC is deep inside the machine and I cannot locate the other two TCs in the same location at the same time. I can get one of the battery powered TCs within about 15 mm of the Arduino but that's about it - the other one is about 30mm away.

After waiting for the machine temp to stabilise (tricky because the boiler thermostat is either on or off ie either heating or cooling) I can then turn the VFD on/off (takes about 15 seconds to stabilise between switching) and compare the temps. The latest round of testing suggests the temps now agree most of the time to within less than one degree.

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However I cannot compare the displayed temps with and without the VFD while running the pump as the VFD is needed to run the pump. Also while the pump is running the water temp change significantly as the pump flushes out overheated water that has been sitting in the heat exchanger and replaces it with fresh cool water. To do this I need to compare temp profiles with the old pump but I will be blowed if I'm reinstalling it.

Despite all this I feel I'm getting closer - how close is enough is yet to be determined

BaronJ
20th Sep 2019, 01:13 AM
Hi Bob,

OK, based on what you have told me, you are sure that its the VFD, can you put the VFD into a tin box with a ferrite ring on both the inside and outside on the output wiring and put a ferrite ring on the mains input lead on the inside as close to the tin box wall as you can get it. That should Knock anything coming from the VFD out completely.

It should kill anything going back up the mains lead and anything coming down the output leads. The tin box will stop any radiated interference getting out.

You should now have a quiet system.

HTH.

BobL
20th Sep 2019, 09:05 AM
Hi Bob,

OK, based on what you have told me, you are sure that its the VFD, can you put the VFD into a tin box with a ferrite ring on both the inside and outside on the output wiring and put a ferrite ring on the mains input lead on the inside as close to the tin box wall as you can get it. That should Knock anything coming from the VFD out completely.
.

Funny you mention "tin boxes" I was just 5 minutes ago eyeing one of SWMBO cake/biscuit tins :D

BobL
20th Sep 2019, 12:25 PM
Funny you mention "tin boxes" I was just 5 minutes ago eyeing one of SWMBO cake/biscuit tins :D

Said cake tin turns out not to be quite large enough bit according to SWMBO her Mum's place (40km away) has a stash of square cake tins that are about to be thrown out.

To test the effect of enclosing the VFD I wrapped it in Al foil.
Not a very good job of wrapping but it looks like it makes a significant difference.
The first thing one notices is the transient changes in the temperatures are much larger and longer when switching the VFD ON/OFF.
Immediately following switching the VFD On/Off the temp jumps by as much as 2º then settles back down over about 10s .
The temperature difference between on an off are now down to about 0.3º which is about the same as the second to second variation in readings anyway.

Anyway I have seen enough to warrant pursuing an enclosure.

BaronJ
20th Sep 2019, 06:11 PM
Hi Bob,

A case of de ja vu ?

I sense success here :;

Seriously though those all metal confectionery tins if deep enough would be perfect. A couple of small self threading screws will ensure electrical continuity between the box and lid.

BobL
22nd Sep 2019, 11:39 PM
Now that the noise problem has been been reduced to something manageable Ive been playing around with various temps and pressures.
The setup is a magnet for testing and experimentation - I'll be spending many days futzing around with it if I'm not careful.

One issue I've uncovered is the usual 10s water flush before pulling the shot is WAAAAY too long and drains too much heat from the heat exchanger.
This is because the NEW pump has a nominal flow rate of ~10x more than the original pump! In practice it turns out to be about 6x more than the original pump but it means only really short (2s) flushes are all that is required.

The Graphs shows the temperature following 3, 5, 10, 15 and 20s flushes.
The green line is for a 20s flush after a coffee has been extracted.
Flushes longer than 5s take many minute to recover anything close to the starting temps (ie >90ºC)


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The next issue is - despite the supposed ideal placement of the Thermocouple, - it may still not be in the optimum place.
Below is a cross section schematic of the machine
The TC is inserted as shown by the red arrow an lays along somewhere along the red line - if its too far back from junction "2" it may be sitting in a dead zone and not really measuring the actual water temp.
I will need to remove the TC (for the ump-teenth time) and do some probing with a fine wire.
382296

BobL
25th Sep 2019, 10:53 AM
I probed the depth of the hole where the TC sits with a piece fo wire and was able to determine the TC was about 10 mm back from junction "2" in the schematic above so then made a new TC that sits just inside the junction and tested it out A small consistent difference was observed for a 10s flush but not enough to explain the "over cooling" of the group head reported by the probe.


I then measured the flow during a flush which for 10s was ~250 mL which is about 6X more that the original ULKA vibe pump.
This is equivalent to flushing the entire water content of the heat exchange finger ~1.7 x so the fact that this volume overcools the whole head doesn't surprise me.
I could stick to 3s flushes, that’s about 1/2 the volume of the heat exchange finger which should be more than enough but really wanted to understand why this was happening.


Then I checked this flushing flow rates against the flushing flow rates of machines that use external pumps and found out that such machines use a flow restrictor with a 0.5 - 0.6mm diameter to the group head to reduce the flow by, guess what ? - ~6X!
Just a reminder that this is not a problem when extracting coffee as the coffee grounds generate a back pressure which restricts the flow to expected flow rates, it's only a problem when flushing.
I could turn the flow down using the VFD but that would mean running the motor at ~8Hz which I don't really want to do because that would mean making continual adjustments to the pump speed in between shots.
The high normal flow of the pump also has a valuable use in rapidly refilling the boiler when water is withdrawn from it.

To investigate this I made a pseudo restrictor with a brass disc and fitted it to a portafilter and the following temp profile was observed.
The short term temp drop during the 10s flush time is dramatically reduced - the longer term temp drop of 2ºC is probably more related to the TC placement still being an issue.

382337

The flow restrictor needs to be further back in the system, somewhere between where the water is diverted to the boiler and before it enters the group head. Looks like I'll be taking the machine again for the umpteenth time.

Michael G
25th Sep 2019, 08:07 PM
Not sure how you would do it in this situation, but once I had to measure pipe temperature with a thermo couple and the suggested method was to mount a small piece of tube to form an oil pocket and then put the TC in the oil. Theory being that the heat transfers better with the liquid interface.

As for the flushing, have you considered a diverter valve so that you get say 2 seconds of flush and then the rest of the water is diverted back into the tank - heat up the pipework without losing so much hot water.

Michael

BobL
25th Sep 2019, 09:20 PM
Not sure how you would do it in this situation, but once I had to measure pipe temperature with a thermo couple and the suggested method was to mount a small piece of tube to form an oil pocket and then put the TC in the oil. Theory being that the heat transfers better with the liquid interface. l
Thanks Michael. I've also seen that method in use.
However, now that over flushing has reared its head for the moment I'm not too concerned about the TC placement although I might come back to it later..


As for the flushing, have you considered a diverter valve so that you get say 2 seconds of flush and then the rest of the water is diverted back into the tank - heat up the pipework without losing so much hot water. l

2 seconds of flush wouldn't lose much heat and I could probably do that consistently enough. Over flushing is more problem when it comes to other people (eg SWMBO) use the machine, eg I have seen SWMBO start a flush and then walk away and do something else and come back 10-20-30s later. Another reason this undesirable is that this unrestricted amount of water flows overwhelms the draining capability of this machine and can end up flooding the bench top!

Another approach I have thought of is via the micro controller using a a pot (to set a flush time eg between 0.5 and say 4 secs) and a button that activates the flushing.

However this afternoon I found a readily accessible and suitable spot on the machine (where the fresh water copper pipe/brass flange enters the heat exchanger) where I could easily insert a restrictor

I turn up an 1.0mm thick x 11.1 mm diameter disc from some phosphor bronze (PB).
It’s beautiful stuff to turn but is still considered quite hard and has better corrosion resIstance than brass.
Even though it was easy to turn II could tell it was much harder than brass because I broke 3 drill 0.5 mm bits drilling the orifice.

Unrestricted flow rate with the PB restrictor is now ~19 L/Hour - was aiming for 18 L/hr but is MUCH better than the 90+ L/Hr without the restrictor.

The other thing I have noticed is the temp of the head at the TC is significant effected by whether the machine is fully assembled or not. ie its SS panels enclosing the machine are in place.
With the top and side panels off the head temp only gets to 85ºC as measured by the TC in the new position.
Putting the panels back in place increases the TC temp to 92º
Am toying with the idea of adding some insulation between the brew head where the TC is located and the SS cup rack tray on top of the machine.
The insulation cannot be any more than about 5mm thick and nothing exposed that frays or releases fibres it needs to be able to cope with about 100º.
Anyone have ay ideas?

Michael G
25th Sep 2019, 09:53 PM
How about some self adhesive EVA foam sheet from Clark rubber? I bought some recently for a project at work and for a 3mm thick piece I think 500mm sqr was around $10. Other thicknesses are available (4.5mm, 6mm, ...)

Michael

BobL
26th Sep 2019, 12:33 AM
How about some self adhesive EVA foam sheet from Clark rubber? I bought some recently for a project at work and for a 3mm thick piece I think 500mm sqr was around $10. Other thicknesses are available (4.5mm, 6mm, ...)

Michael

Thank Michael.

I got excited when I read this as somewhere I have a roll of EVA I purchased a few years back for some reason I cannot remember.
Then I looked up the max temp EVA can handle and it appears most types of EVA can only cope with 70ºC with some special ones going to 80 and I really need something that can cope with at least 100º.
However the mention of Clarke Rubber has got me looking on their website and one option would be strips of neoprene rubber which can handle 100ªc
Even better would be Silicone rubber as this can handle more than 200ºC
A couple of issues I can see with this are - it usually comes as a very thin (~1mm) sheet - which would be better than nothing - maybe join a couple of sheets
Chinese Ebay vendors sell 5mm thick 500x500mm sheet but it costs $50!
AND
how to stick it to the SS panels - maybe with something like HT silicone?

BaronJ
26th Sep 2019, 12:43 AM
Hi Bob,

Silicone baking sheet from Ikia !

382481382482

Lovely colour :o:U:q

Michael G
26th Sep 2019, 08:27 AM
You may have trouble sticking silicone sheets in place. Sealant may do it, but I don't know how good the bond will be.

Neoprene will stick with a contact adhesive, but the nice thing about the EVA foam was the foam part. I'm wondering whether you get a sheet and put it in, and perhaps put some foil tape over the places in close contact. You might find that it works well enough - after, what you have works without insulation so even if the insulation is not 100% successful, you still gain.

Another thought (although more complicated) is to get some thin sheet metal (Al, SS?) and using double sided tape, add a layer inside the housing. It will give you an air gap that should provide some insulation.

Michael

BobL
26th Sep 2019, 09:37 AM
You may have trouble sticking silicone sheets in place. Sealant may do it, but I don't know how good the bond will be.

Neoprene will stick with a contact adhesive, but the nice thing about the EVA foam was the foam part. I'm wondering whether you get a sheet and put it in, and perhaps put some foil tape over the places in close contact. You might find that it works well enough - after, what you have works without insulation so even if the insulation is not 100% successful, you still gain.

Another thought (although more complicated) is to get some thin sheet metal (Al, SS?) and using double sided tape, add a layer inside the housing. It will give you an air gap that should provide some insulation.

Michael

Thanks, some good ideas there.

I have just found one of SWMBO's silicone baking sheets - it's <1mm thick but it fits the inside top of the machine near perfectly so I can try it out as insulation (at least for the top part) without cutting and sticking it on. I will just lay it on top of the inside of machine and see what happens. This will also form a small air gap in between the Silicone sheet and the the SS top.

BaronJ
26th Sep 2019, 10:19 PM
Hi Bob,

Further to Michael's suggestion, thin perforated alloy sheet could be used to hold the silicone sheet, forming a sandwich.

BobL
26th Sep 2019, 11:52 PM
I've been using it all day with the thin silicone sheet.
Best estimate is the silicone sheet increases the temp at the TC measuring point by about 0.7ºC and it appears to help stabilise temps during flushing a little better

Hard to say exactly how much as the pulsing of the boiler element on and off contributes varies the temperature by about +/- 0.5ºC over a period of a few minutes minutes.
When I get round to it I will add another One or two sheets and see what that does.

The in line restrictor is the main improver in stabilising temps and appears to have reduced temp variations especially during flushing.
I'm now pretty happy with where it's at - Now I have to practice my coffee making.

benhoskin
28th Sep 2019, 12:07 AM
Bob i can drop off some high temp rated neoprene. It is in the form of pipe insulation, approx 80mm od 20 id. You will just need to trim it up to what you need.

BobL
28th Sep 2019, 08:58 AM
Bob i can drop off some high temp rated neoprene. It is in the form of pipe insulation, approx 80mm od 20 id. You will just need to trim it up to what you need.

Thanks Ben, the space I need to fill/cover is 350 x 270 x 5 mm. How hard will it be to cut into 5mm thin strips?

BaronJ
28th Sep 2019, 02:01 PM
Hi Bob,

Have you thought about the insulation that is used on the walls of camper vans ?

Its a 5 mm thick synthetic foam rubber that is self-adhesive on one side and a 2 mm thick metallised plastic bubble bonded onto the other. Its rated to 150 C. I've loads of it from when I did my van, I'll take a picture later.

One thing that I will say is that once you have stuck it on it doesn't come off easily, even with the heat of direct sunlight on the van walls.

BobL
28th Sep 2019, 03:34 PM
Hi Bob,

Have you thought about the insulation that is used on the walls of camper vans ?

Its a 5 mm thick synthetic foam rubber that is self-adhesive on one side and a 2 mm thick metallised plastic bubble bonded onto the other. Its rated to 150 C. I've loads of it from when I did my van, I'll take a picture later.

One thing that I will say is that once you have stuck it on it doesn't come off easily, even with the heat of direct sunlight on the van walls.

Thanks.

BaronJ
1st Oct 2019, 01:09 AM
Hi Bob,

Some pictures of the insulation I referred to earlier.

I used this stuff on all the walls, roof and floor of the van and then did the lining out with plywood and wool carpet. It really keeps the heat out and suppresses the noise from outside. Net result is a cool van when its hot outside and nice and cosy when it gets cold.

382606 382607 382605
It is 8 mm thick overall, with a strong adhesive on one side that grabs on contact, so you do have to be careful when applying it. The other side is a layer of nitrogen filled plastic bubbles with a metallised plastic film glued on top. The idea is that it reflects the heat or cold back into the van. Its rated to withstand 150 C.

BobL
1st Oct 2019, 12:35 PM
Thanks for the info. It looks like the van insulation would be perfect for the sides but I am less concerned about the sides as I am about the top which unfortunately has a much smaller gap. Some of the gaps at the top are 5mm or even less so I would have to cut around these spots. This is why I went for the thin (~1mm) silicone sheet. So far it seems to be doing its thing and has stabilised the temp enough for my liking for the moment. There are still the odd temperatures fluctuationsthat cannot be explained by the usual boiler cycling but I have moved onto another coffee related project which I will post about as soon as I have something to show.

BobL
9th Oct 2019, 08:52 PM
Coffee machine is going well but here I'm reporting on a coffee related experience that coffee nerds may be interested in.

Today my uber coffee nerd mate arranged for us to get access to a "coffee lab" containing a wide range of coffee making equipment and testing gear to test out some of our ideas. The lab is owned by a major roaster that my mate used to work for. To give you an idea of the gear involved the coffee machine we were using was a 3 group head Synesso ( $20k+) the grinder was an automated Mazzer Robur Electronic (~$3), and the auto tamper was was about $2k. With all this gear being able to be automated we could consistently fix some variables to be automatically reproduced and could then test, for example, the overall extraction using a Coffee specific Total Dissolved Solids (TDS) meter ($1.5k).

We were given a bag of fresh coffee and spent over 2 hours making about 2 dozen coffees. The coffee was all ground the same way and weighed into the portafilter using digital scales. The coffees all looked amazing to me but all bar 2 coffees ended up down the sink as I had already had 3 double shots before arriving and we were served a different coffee on arrival.

Today was just a play around day to get a handle on the gear for future testing of some other ideas. One thing we check out was how the extraction (amount of coffee extracted) depended on tamper force and it turns out it is not dependent on tamping pressure at all. In fact "no tamping at all" and just a level filter basket produces the same extraction as coffee tamped with 30kg force. We also checked out the reproducibility of the TDS meter - it reads to 0.01% but the reproducibility is something like about 0.3% extraction for typical extractions of 20%. Not as good as we hoped for but it should be enough for what we want to do.

Taste interpretations are of course a a different matter but we don't get too much into that. It's basically good, so-so or not good.

We are going back again in a couple of weeks once we decide what else we are going to test. I will try to remember to takes some photos next time

BobL
15th Oct 2019, 12:20 PM
More coffee nerdy frippery. . . . . stop here if you are not into "frippery" - go and find something more useful to do with your time :D

One of the aspects of making espresso that seems to get a lot of attention is the tamping of freshly ground coffee into the portafilter/ basket. In my previous post I suggested that tamping was not necessary in terms of % coffee extraction, although taste is possibly another matter . What is desirable is an even distribution of the ground coffee in the basket otherwise the water will not pass evenly through the same distance/volume of coffee leading to "over extraction" of some of the coffee and "under extraction" of other. To this effect some baristas tap the portafilter with the tamper or onto a table while others use a highly over priced "distributor" to sweep the coffee grounds out to fill the basket evenly. Auto tamping is carried out with various manual and (semi) automated devices some of which cost more than $1k!

While watching a vid of all this it got me thinking about using vibration to more evenly dIstribute and pack the coffee into the filter basket. I have a mind the time when I used to work at a concrete slab factory and later as a high rise form work labourer when we used vibe to settle wet concrete inside form work. It's very quick and produces a very compact layer of settled material.

By way of a pre-test I got out one of my old 1/3rd sheet vibration sander, tipped it upside down and put a portafilter filled with coffee on the pad and turned it on. The coffee just went everywhere so I tried it again this time with the tamper just sitting on top and it distributed and tamped the coffee to as firm as hand tamping in less than a second. Of course being untouched by human hand the process is quite reproducible.

To further explore this possibility I have made the following apparatus.
Remember this apparatus is for testing, any working product would need to be much more compact and possibly even built into the coffee grinder.

It's basically a sprung table that firmly holds a portafilter handle and basket. A tamper is just paced on top to prevent the coffee flying off everywhere and to provide a counter weight. Two small vibrators (DC motors that rotate small offset weights) will be attached to the underside of the top and connected to a micro controller to switch the motors on and off so control length of time of vibration. An on board accelerometer connected to the MC will measure the g-forces. Other variables examined will be vibe frequency (motor RPM), motor directions, amplitude of vibe etc.

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Underside.
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The whole thing is made from 4 and 5mm ally plate and SS screws (because that is what I had in the desired sizes), a real working product would need to be all in SS. The bayonet plate that enables the portafilter (PF) to clip onto the underside of the table and apply firm pressure to the 5mm thick rubber gasket is so that it can be held firmly while being vibrated. The current bayonet plate suits my coffee machine but as we will be taking this into the roasters coffee lab I will need to make another plate to suit their machine's PF..

This approach is unlikely to be the way any final product will be made/used. Once the optimum vibe parameters are determines I envisage setting up a shallow rubber covered vibrating plate onto which the coffee filled PF with tamper on top is just placed/held on top which automatically switches on a vibration source.

I wanted to call this "vibrotamp" but my colleague prefers "vibroset" as in "vibe settling".

I am leaving this in the electronics section because I have prototyped the micro controller and its now working - just need to get it into a suitable box for working with. I will post about this soon. I am also making the MC setup into a generic vibe measuring device so that I can use it on machinery and don't have to risk constantly using my mobile phone or iPad as a vibe measuring devices.

I told you it was going to be nerdy frippery - and it is only going to get worse.



.

BaronJ
15th Oct 2019, 06:14 PM
Hi Bob,

That's why we are called "Experimental Engineers" :)

RustyArc
15th Oct 2019, 07:57 PM
I wonder if an adequate effect could be achieved by just holding the portafilter down on a vibrating rubber pad, or rubber-covered forks?

BobL
15th Oct 2019, 08:48 PM
I wonder if an adequate effect could be achieved by just holding the portafilter down on a vibrating rubber pad, or rubber-covered forks?
That’s exactly where I’m eventually headed but I’m doing the above to test things out first.

BaronJ
15th Oct 2019, 09:02 PM
Hi Bob,

If you want small vibrators, grab a defunct Sony game controller ! There's usually two different size ones in them. They run at 5 to 8 volts. I've tried one at 12 volts and had to disconnect the supply voltage to catch it ! It bounced all over the bench. Also some mobile phones have them as well, but they are very small. You can alter the frequency by adjusting the voltage.

HTH.

BobL
15th Oct 2019, 09:27 PM
Thanks BJ. I’ve researched vibe motors and played with some small one used for haptic feedback such as are used in mobile phones and various game controllers. Some of these are very powerful but I have a feeling they will still be too small for this purpose. I’ve played around with a 12V motor from a cordless drill but it drew between 5 and 17A (@ full rpm) from a 12V car battery. I’ve ordered some cheap ($5) vibe motors on line that nominally operate between 6 and 12V but given I’m only running them for about 3 s at a time I’m hoping to run them over a wider range than this. These draw between 250 & 500 mA so this is up to 1A for 2 motors. The mains V sheet sander I was using was rated @ 140W but it was not transferring much vibe onto the PF. It will be a suck it and see experiment.

Have also experimented with a loudspeaker and square wave as a vibe source. It also sort of works ( between 6 and 30 Hz ie good motor speeds) but appears quite inefficient