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  1. #1
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    Default RS485 VSD Control

    Hi,
    I'm working on ventilation fan* that will use an Arduino/VSD setup to control the outlet temperature. I was planning on using the Arduino PWM output to control the VSD speed but came across the page below that uses RS485 to control the VSD, this maybe a better way to go. Now I think I understand the comms side of things but I'm struggling with what he is doing with the HEX to change the speed. Now I might be able to nut it out but I thought I would ask if there was anyone that knew more than I and could give me a quick run through.
    VFD control with Arduino using RS485 link
    https://pastebin.com/QpmDDHsD

    T IA


    *Its going to draw air from the roof cavity as make up air for the fire and also increase speed if the temp in the cavity goes above 20C or so. As an example, its currently 13C outside and 26C in the roof cavity, so I figure that's worth having.

  2. #2
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    Default

    To answer my own question lol
    Tried some different search terms and came up with this

    https://www.woodworkforums.com/f170/...fd-users-96380

    Haven't read it all yet, but going by the quick skim I have had the answers are in there.

  3. #3
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    Default

    Just to clarify what you're after, do you want to know what hex values are sent to the VSD to change the speed, or more after some explanation of what is actually happening in the code itself?

    Steve

  4. #4
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    Quote Originally Posted by OxxAndBert View Post
    Just to clarify what you're after, do you want to know what hex values are sent to the VSD to change the speed, or more after some explanation of what is actually happening in the code itself?

    Steve
    Hi Steve
    Well it was both really.
    But as I understand it now. After telling the VSD to start, the number you need to send to the VSD is just the FEQ you want minus the decimal point. So 10Hz becomes 1000. Then converted to HEX. Then you just have to add the check digits, which I think I know where it is in the code but haven't had a chance to work it out yet.
    If I'm not mistaken(likely) the code is trying to read the return from the VSD, but I don't need that (unless the VSD requires it?)
    Does that sound about right?

    I have little Arduino experience but long along did some Basic, G code and a few others. So I sort of know whats going on, just the format is just taking some getting used to. But then I'm old and grumpy, calling programs "sketches" is taking some getting used to lol

  5. #5
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    Default

    Hi Stuart, Guys,

    Quote Originally Posted by Stustoys View Post
    Hi,
    *Its going to draw air from the roof cavity as make up air for the fire and also increase speed if the temp in the cavity goes above 20C or so. As an example, its currently 13C outside and 26C in the roof cavity, so I figure that's worth having.
    Interesting concept ! At the moment our roof cavity temperature and the outside temperature are almost the same value, 42 F (6 C) whilst the room temperature is around 72 F (22C).

    Are you using the lost heat in the roof space to add to the room heat ?
    Best Regards:
    Baron J.

  6. #6
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    Hi Baron

    Quote Originally Posted by BaronJ View Post
    Are you using the lost heat in the roof space to add to the room heat ?
    Yes + a bit lol There a few parts to my plan. Lost heat and solar
    This house is not exactly normal in its layout, it has large cast iron fireplace near the center of the house built into a cavity in the corner where two internal brick walls meet. While there is a steel flue the brickwork extends through the ceiling(fiberglass bat insulation) then tapers to the chimney size then exits the roof(colorbond with foil insulation). So when the fire is on this all heats up. There is also a duct from the top of the cavity to run air to the other end of the house about 20m, that's losing heat as well.
    So
    Part A. As the air temp in the roof cavity will (almost*) always be warmer than the outside air when the fire is on, draw enough air(+ a bit) from there to make up for the air going up the chimney and duct it as close to the fire as possible. That way in a perfect world warm air will be flowing away from the heater to the rest of the house to flow out all the leaks rather than cold air being drawn through all the leaks flowing towards the heater.(wind can mess this up, but I cant do much about that)

    Part B Whenever the roof cavity temp goes above say 20C increase fan speed in steps until the temp drops or the fan hits Max. This of course will mostly happen during the day. The temp I choose will depend on a few things, but if the central brick work can be heated during the day and it doesn't get to cold at night there will be days that don't need a fire. But then firewood is free(well apart from the whole cutting it, splitting it, loading it, carting it, staking it thing lol) and I have to pay to run the fan.

    This is for winter. I haven't given much thought as yet to want I might do for summer.

    *ok 99.999% of the time

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Stustoys View Post
    But then firewood is free(well apart from the whole cutting it, splitting it, loading it, carting it, staking it thing lol) and I have to pay to run the fan.
    I guess the exercise may help counteract the excess PM2.5 particulate generation by the fireplace?

  8. #8
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    Quote Originally Posted by BobL View Post
    I guess the exercise may help counteract the excess PM2.5 particulate generation by the fireplace?
    Maybe lol
    I have a thermocouple coming that I can mount in the chimney. I have no idea why I would need to know that but hey measuring stuff can be fun.

    For another data point its currently 21.5C outside, 17.8C inside. So opening windows etc would have little effect. Its a toasty 38C in the roof. Now just how much air you can move before that drops to say 30C I don't know.

  9. #9
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    Hi Stuart, Guys,

    I've nothing like that ! I live in an all electric bungalow. Basically a stone built box with studding walls and tiled roof. Electric storage heating, cavity wall insulation and a foot of glass fibre roof insulation. Nice when its cold outside, but like an oven in summer when we have to shut the curtains at the front or back to keep the sun out. The windows face east - west, so we get the sun all year round, that is when it shines ! At the moment we are close to getting drowned, its done little but rain for days now.
    Best Regards:
    Baron J.

  10. #10
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    Quote Originally Posted by BaronJ View Post
    Hi Stuart, Guys,

    I've nothing like that ! I live in an all electric bungalow. Basically a stone built box with studding walls and tiled roof. Electric storage heating, cavity wall insulation and a foot of glass fibre roof insulation. Nice when its cold outside, but like an oven in summer when we have to shut the curtains at the front or back to keep the sun out. The windows face east - west, so we get the sun all year round, that is when it shines ! At the moment we are close to getting drowned, its done little but rain for days now.
    Hi Baron

    We are more in the 5" of insulation area.
    Is your heat storage slab heating or one of those cast iron block things?(or something else?)
    Uncontrolled storage heating isnt that great here as you can never be sure what tomorrow will be like, so you might "heat up the slab" only to find you have to open the windows the next day to cool the house down. For the same reason the fire place setup here isnt particularly well suited to the climate. Much better suited to places where you know you're going to need it for the next three months, not the next 12 hours

  11. #11
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    Hi Stuart, Guys,

    Quote Originally Posted by Stustoys View Post
    Hi Baron

    We are more in the 5" of insulation area.
    Is your heat storage slab heating or one of those cast iron block things?(or something else?)
    Uncontrolled storage heating isn’t that great here as you can never be sure what tomorrow will be like, so you might "heat up the slab" only to find you have to open the windows the next day to cool the house down. For the same reason the fire place setup here isn’t particularly well suited to the climate. Much better suited to places where you know you're going to need it for the next three months, not the next 12 hours
    Yes it is the slab type ! We get seven hours of what used to be half price electricity during the night, now we are paying about 80% of the daytime rate.

    The thieves are using the old our prices haven't gone up this year, but the standing charges have doubled, so you look around and switch supplier just like the Government says we should, only to find that it doesn't really matter who you switch to, the overall price is the same. Having solar panels gets you little benefit because they charge you a premium for having them.

    If I could I would go off grid, but even if you did they still want their standing charges, meter rent and service fees. I've kept usage records for the past ten or so years and our average electricity consumption has hardly changed in all that time, but the cost has more than doubled.

    Sorry for the rant, electricity costs get my goat.
    Best Regards:
    Baron J.

  12. #12
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    Quote Originally Posted by BaronJ View Post
    Sorry for the rant, electricity costs get my goat.
    Hi Baron

    Things are much the same here. Or perhaps a little worse our first world grid is so reliable there are now TV adds telling you how to prepare for when the power goes off. I have a selection of generators. (just to poke at your goat) I am currently running them in when the sun is shining as I get $0.60kWh infeed tariff on my solar so that helps pay for the fuel

  13. #13
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    Hi Stuart, Guys,

    The in-feed tariff here is now 15p not worth having since they get that back and more with the unit costs.
    My Daughter in the Midlands, is paying much less per unit than I am, but she also gets gas from them as well. So I suppose she gets a dual fuel discount.

    OK Goat poked.

    As far as generators go I went to test mine because it hasn't been run for a while. I put some fuel in and found that it just coughed a couple of times and that was it. I thought that I had oiled the plug, so I took it out and found that it was dry, so I checked for a spark... Nothing, zilch, not even a tickle. Seems that the ignition coil has died.

    It doesn't quite measure an open circuit its about 8K. There is no voltage reading on a meter when you wave a magnet at it. Time to get a new one from China ! Honda want £35 for a new one, Banggood has them for £5 complete with a new plug and leads. So you know where I will be getting a new one from.
    Best Regards:
    Baron J.

  14. #14
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Stustoys View Post
    Hi Baron

    Things are much the same here. Or perhaps a little worse our first world grid is so reliable there are now TV adds telling you how to prepare for when the power goes off. I have a selection of generators. (just to poke at your goat) I am currently running them in when the sun is shining as I get $0.60kWh infeed tariff on my solar so that helps pay for the fuel
    CRIKEY, IC powered generator by day and and open fire at night, sounds like continuous PM2.5 contamination 24/7 for both you and your neighbours.
    I read recently than an open fire place produces as much PM2.5 as a medium size diesel truck engine.

  15. #15
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    Quote Originally Posted by BaronJ View Post
    Hi Stuart, Guys,

    The in-feed tariff here is now 15p not worth having since they get that back and more with the unit costs.
    My Daughter in the Midlands, is paying much less per unit than I am, but she also gets gas from them as well. So I suppose she gets a dual fuel discount.

    OK Goat poked.

    As far as generators go I went to test mine because it hasn't been run for a while. I put some fuel in and found that it just coughed a couple of times and that was it. I thought that I had oiled the plug, so I took it out and found that it was dry, so I checked for a spark... Nothing, zilch, not even a tickle. Seems that the ignition coil has died.
    Hi Baron,
    Yeah most peoples infeed tariff here make it pretty useless to export any power. I think it's about $0.12(about 1/4 the price of grid power) it was as low as $0.06. The $0.60 infeed was a deal early on. I have no idea who is paying for it but it makes me laugh.

    "not starting" is part of the reason I have two generators(well ok three but one of them is only 1700w). Another reason is the electric start gen has a 150cc engine v the pull start one being 212cc for the same output. The pull start one also has a tank twice the size. But, I dont think SWMBO could start the pull start one, so something with a key was in order even if it only gets used when I'm not here to start the other one.


    Quote Originally Posted by BobL View Post
    CRIKEY, IC powered generator by day and and open fire at night, sounds like continuous PM2.5 contamination 24/7 for both you and your neighbours.
    I read recently than an open fire place produces as much PM2.5 as a medium size diesel truck engine.
    Hi Bob,
    Well only for the 20 hour run in. Also it isn't an open fire if that helps, on the down side I have two small diesel trucks...... but I only use one at a time


    On the code side of things I'm about 80% confident I'm good to go, just waiting on the RS-485 Module. Just ordered another one from an(fingers crossed) Aus supplier, as the ones I ordered China over a week ago don't seem to have moved.

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