PDA

View Full Version : Future Project - Speed Indicator for MIll



bwal74
19th Apr 2019, 11:15 AM
Hi Blokes,

I want to attache a speed indicator to my mill. But I have little experience with electrical work so I'm asking what I need and how to go about it.

I'd probably get my materials for Jay Car.

If anyone has done it and has a build log or knows of a U tube series that would be really helpful.

Regards Ben.

Com_VC
19th Apr 2019, 12:17 PM
Something like this is probably what you are after I think. You can set it up to run from a plug pack type power supply.

https://www.ebay.com.au/itm/4-Digital-LED-Tachometer-RPM-Speed-Meter-NPN-Hall-Proximity-Switch-Sensor-AULE/123686264870?epid=24024032314&hash=item1ccc46a026:g:T24AAOSwXaxasfBe

LexD
19th Apr 2019, 08:15 PM
The unit shown by ComVC would be a good choice. I set up something similar on my milling machine as shown in this thread starting at post #134:
http://metalworkforums.com/f65/t159263-mars-lathe-dc-motor-conversion/page-9?highlight=tacho+milling+machine

warrick
20th Apr 2019, 12:13 AM
Then unit shown by ComVC would be a good choice. I set up something similar on my milling machine as shown in this thread starting at post #134:
http://metalworkforums.com/f65/t159263-mars-lathe-dc-motor-conversion/page-9?highlight=tacho+milling+machine

I used almost exactly the same unit as sugested by ComVC on my two wood lathes. One thing I did find with those units was that when i mounted the sensor in a metal bracket it gave irratic readings but as soon as made plastic brackets for them the readings were solid

Rick

simonl
20th Apr 2019, 07:53 AM
Same, I have used similar setups on two machines although I sourced the components individually on ebay rather than as a kit.

They work very well and cheap as chips. I did however have an issue initially with the one mounted on my mill. It picked up noise from the VFD and gave erratic readings. It was a simple fix of using a 0.1uF MKT capacitor as a basic low pass filter by connecting it across the signal in and ground.

Simon

Michael G
20th Apr 2019, 11:16 AM
You can't just use an optical tacho from ebay? Cheap, self contained and no working out why the electrons won't behave.

Michael

Com_VC
20th Apr 2019, 11:22 AM
One of these? https://www.ebay.com.au/itm/Mini-Pro-Wide-Range-RPM-Measurers-LCD-Display-Digital-Laser-Optical-Tachometer/312487884609?hash=item48c1bab741:g:FDgAAOSwFstcbLhq&frcectupt=true

I have one of those, but fixed permanent display is a much better option.

bwal74
20th Apr 2019, 12:20 PM
One of these? https://www.ebay.com.au/itm/Mini-Pro-Wide-Range-RPM-Measurers-LCD-Display-Digital-Laser-Optical-Tachometer/312487884609?hash=item48c1bab741:g:FDgAAOSwFstcbLhq&frcectupt=true

I have one of those, but fixed permanent display is a much better option.

I like this, much more suited to my electrical abilities.

BobL
20th Apr 2019, 02:12 PM
Something like this is probably what you are after I think. You can set it up to run from a plug pack type power supply.

https://www.ebay.com.au/itm/4-Digital-LED-Tachometer-RPM-Speed-Meter-NPN-Hall-Proximity-Switch-Sensor-AULE/123686264870?epid=24024032314&hash=item1ccc46a026:g:T24AAOSwXaxasfBe

How well do those things work at slow speeds. I seem to recall that type struggled below 100 rpm?

LexD
20th Apr 2019, 05:20 PM
How well do those things work at slow speeds. I seem to recall that type struggled below 100 rpm?

No problem at all at low speed with mine using an Inductive Sensor.

BaronJ
20th Apr 2019, 08:37 PM
Hi Guys,

I have one of these, they do work very well. They come with some self adhesive reflector strips which you apply to to item you want to measure the speed of.

https://www.ebay.com.au/itm/Mini-Pro...frcectupt=true (http://metalworkforums.com/redirect-to/?redirect=https%3A%2F%2Fwww.ebay.com.au%2Fitm%2FMini-Pro-Wide-Range-RPM-Measurers-LCD-Display-Digital-Laser-Optical-Tachometer%2F312487884609%3Fhash%3Ditem48c1bab741%3Ag%3AFDgAAOSwFstcbLhq%26frcectupt%3Dtrue)

However I did find that mine also picked up electrical noise from the motor brushes arcing as the motor turned. easily recognised by the erratic readings. Moving further away from the source of the interference solved the problem.

bollie7
20th Apr 2019, 11:26 PM
Something like this is probably what you are after I think. You can set it up to run from a plug pack type power supply.

https://www.ebay.com.au/itm/4-Digital-LED-Tachometer-RPM-Speed-Meter-NPN-Hall-Proximity-Switch-Sensor-AULE/123686264870?epid=24024032314&hash=item1ccc46a026:g:T24AAOSwXaxasfBe

I recently bought one of this type from Banggood. I think it was about $12.00. When it arrived I tried to get it working but it constantly showed 5990 RPM. Even the electronics techos at work couldn't get it working. So I contacted Banggood and told them the story. No problems, they are sending me another one. Hopefully it will work a bit better than the first one.
For some reason I didn't even look on ebay at the time. :doh:
If I had I would have paid the extra $4 to get one that was already here in Aus.
peter

Michael G
21st Apr 2019, 09:12 AM
I guess the relevant question is whether your mill has a fixed speed gear box (or belts) and you just want to check the speed occasionally, or whether it is variable speed and needs near constant checking.

Michael

BobL
21st Apr 2019, 09:27 AM
I have an optical tacho purchased more than 12 years ago - I've used it a lot on motor HP measurements where it stays on for 1/2hr periods or so at a time - its still running from the same battery it came with. The optical ones can suffer from false readings if a second or high reflectivity patch is picked up. This can be checked by placing a second reflective patch on the rotating object and the readout should double - if not you have a reflective patches involved. Running or painting a dark non reflective stripe around shafts etc and placing the reflective patch on the dark stripe is a way around it.

I'm also after something a little more permanent. Will give one of those inductive ones a go.

bollie7
3rd May 2019, 03:46 PM
Well my replacement Tacho arrived from Banggood recently. Just got to try it out. Wired it up how I believe to be the correct way and got exactly the same result as the first one.
So that means I'm either wiring it up incorrectly or by some massive fluke I have been sent two faulty ones.
So can someone tell me the correct way to wire these please? The directions are, typically for China origin stuff, not very clear.

This pic is what I got directly from the Banggood listing.

379261

This one is the new one (replacement) I have on the bench

379261

So I have 12V + going to terminal no 1
12V- _ to terminal no 2

Sensor Brown going to term no 1
Blue going to term no 3
Black going to term no 5

Terminal 4 is not used

The red LED at the back of the sensor lights up but the readout immediately goes to around 5997 RPM.
With the magnet attached to my drill chuck and the drill running the readout fluctuates all over the place.

Any help would be greatly appreciated.
thanks
Peter

warrick
3rd May 2019, 03:52 PM
379262

Is this how you wired it ?

Rick

bollie7
3rd May 2019, 04:02 PM
Rick
yes thats it
peter

Com_VC
3rd May 2019, 04:52 PM
I have the same Tacho and mine is wired the same way. Led on the sensor is on and the Tacho display reads 0000 without machine running. Not sure what is going on with yours. It is unusual with two giving you the same result.

I am powering mine with a 9V plug pack from an old cordless phone. Have you checked what voltage yours is putting out with a multimeter?

Com_VC
3rd May 2019, 04:55 PM
I just disconnected the sensor and it still will read 0000, does yours do the same or will it still display 5997 RPM?

bollie7
3rd May 2019, 05:48 PM
I have the same Tacho and mine is wired the same way. Led on the sensor is on and the Tacho display reads 0000 without machine running. Not sure what is going on with yours. It is unusual with two giving you the same result.

I am powering mine with a 9V plug pack from an old cordless phone. Have you checked what voltage yours is putting out with a multimeter?

My power supply is putting out 14V. I think I have a couple of 12v plug packs which I'll dig out tomorrow although as the Tacho is supposed to run on 8-24V I cant see how that would be a factor. However desperate men etc.:)

When I disconnect the sensor the readout displays 0000

I've just gone and checked both, they are almost exactly the same. I have also swapped the sensors with no difference.
I wish I could get the same sort of odds buying a lottery ticket.

Com_VC
3rd May 2019, 06:12 PM
Is your sensor an NJK-5002C?

https://www.ebay.com.au/itm/NJK-5002C-Proximity-Switch-Hall-Effect-Sensor-NPN-3-Wires-Normally-Open-Magne/282611698315?hash=item41ccf84a8b:g:9zcAAOSwHQdcY5XW&frcectupt=true

warrick
3rd May 2019, 06:28 PM
The red LED at the back of the sensor lights up but the readout immediately goes to around 5997 RPM.

Is the light and get brighter when the magnet gets closer ?

Do you have a photo of your wiring just in case you missed something, not that I doubt you but stranger things have happened

Rick

bollie7
3rd May 2019, 06:42 PM
Is your sensor an NJK-5002C?

https://www.ebay.com.au/itm/NJK-5002C-Proximity-Switch-Hall-Effect-Sensor-NPN-3-Wires-Normally-Open-Magne/282611698315?hash=item41ccf84a8b:g:9zcAAOSwHQdcY5XW&frcectupt=true

The number on both the sensors is SJA12-10N1

bollie7
3rd May 2019, 06:44 PM
Is the light and get brighter when the magnet gets closer ? Not that I have noticed

Do you have a photo of your wiring just in case you missed something, not that I doubt you but stranger things have happened

Rick[/QUOTE] Better than that. This link is to the short video I made of the first tacho to send to Banggood.

https://youtu.be/X1iziOhrMK4

I think i have the wiring correct but I'm certainly open to be corrected if I havent.

warrick
3rd May 2019, 07:09 PM
Not that I have noticed

I think i have the wiring correct but I'm certainly open to be corrected if I havent.

Peter,
If you have the wiring correct then there should be the LED on and it gets brighter when the magnet is in close proximity, I also think that it is pole sensitive (i.e. it likes one side of the magnet to the other)
It is very hard to see the wiring as it is twisted and the camera is moving so a photo would be better, also a photo of the sensor showing the diagram on it


Rick

bollie7
3rd May 2019, 09:00 PM
Rick.
The orientation of the magnet doesnt change anything. I have just tried it from both sides.

Yes the LED does get brighter when the sensor is closer to the magnet. Changes approx 6 or 7 mm from the magnet.

Whe the sensor is not close to the magnet the readout shows this.

379270


Closer than 6 or 7 mm the LED is brighter and the read out shows this

379271

Wiring pic

379272

sensor
label

379273 379274 379275

thanks
Peter

russ57
3rd May 2019, 11:50 PM
I'd try a different power supply. Yours may not be filtered well enough. Even a battery - say cordless drill battery.



Russ

warrick
4th May 2019, 12:35 AM
I'd try a different power supply. Yours may not be filtered well enough. Even a battery - say cordless drill battery.



Russ

If I remember correctly I had problems when I first tried hooking one up and realised I had a AC powerpack so using another source would be a good suggestion.
I went out to my shed and checked the wiring on mine and it is exactly the same as yours Peter so the power supply look to be the only thing to change now

Rick

BobL
4th May 2019, 09:41 AM
My power supply is putting out 14V. I think I have a couple of 12v plug packs which I'll dig out tomorrow although as the Tacho is supposed to run on 8-24V I cant see how that would be a factor. However desperate men etc.:).

My experience is that just using a multimeter to measure the output of a PS often misses most of the story. Some are super noisy and/or show a fair bit of residual AC - try measuring its AC output.

bollie7
4th May 2019, 11:34 AM
so the power supply look to be the only thing to change now Rick

I tried a 9V plug pack supply just now and the results look very encouraging. Learn something new everyday. It gives a read out that is very close to what I'm getting from the hand held optical one I have here. Next step is to see if it works with the 12V supply I have on the mill for running the lights and the fans in the VFD enclosure.

Thanks so much to all who have offered suggestions. I really appreciate the help.
Peter

bollie7
4th May 2019, 11:37 AM
My experience is that just using a multimeter to measure the output of a PS often misses most of the story. Some are super noisy and/or show a fair bit of residual AC - try measuring its AC output.
Bob - I have heard of this stuff before but with me just being a dumb fitter, its all a bit of a black art. I've had some of the electrical/electronic people at work try to explain this to me on a couple of occasions but I struggle (and usually fail) to get my head around it.
Thanks for you input
peter