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What's the difference controlling a 180v PMDC motor to controlling a 12v PMDC motor?

Discussion in 'General Electronics Chat' started by bigal_scorpio, Feb 3, 2015.

  1. bigal_scorpio

    bigal_scorpio Active Member

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    Hi to Eric, Nigel and all,

    Before anyone gets the wrong idea about the post I don't mean the need for components that can handle the larger voltage. ;)

    What I can't understand is that I have used PWM to control small low voltage motors before and now that I come to need to make a controller for a larger PMDC motor I wondered if it would be cheaper just to buy a ready made unit, but to my surprise they don't seem to be easy to come by.

    OK thinks me, they must not be very common these PMDC motors but I was wrong. Many things use them especially in industry and other things especially tread mills (which is where this motor comes from).

    I then decided to check for any help in google to give me the confidence to build one myself. Again I seem to be having difficulty finding anything that applies to motors over about 90v.

    Can I just make a controller as for a 12v motor and uprate the components as necessary? Is there something different in the way higher voltage controllers work? All I want to do is get this motor working as a variable speed for my Wood Lathe, which would mean I didn't have to keep changing the belt all the time. I have seen others who have done this on the web but they either don't mention how they control the motor or they get a commercial unit from ebay or somewhere.

    So any help or suggestions would be welcome. Thanks, Al

    Edit: The motor is a PMDC 180v 1.25Hp motor from a treadmill that was working ok but the frame was broken so scrapped.
     
  2. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Do you already have the DC voltage available and need to use it? If you want to control a 180V PMDC with a commercial controller plugged into AC, check out KB Electronics (http://www.kbelectronics.com/data_sheets/kbic.pdf). Even their new stuff is reasonably priced on eBay. I have several of their "chassis" controllers built into machines. KB also has controllers in consumer boxes.

    John
     
  3. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Google 180 volt DC motor controller and you will get hundreds of hits.
    It is common as it is double the voltage of the very common 90 volt DC motor.
     
  4. dave

    Dave New Member

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  5. bigal_scorpio

    bigal_scorpio Active Member

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    Hi John and 4pyros,

    I agree there are some on the web and indeed the Kbics look just the part but both of you have something in common in that you are in the states. The import duties and postage costs to the UK make the items about double the cost! If the cost is that much I will need to start from scratch and build one.

    I don't know why I can't find any in the UK? Its as if we don't know about PMDC motors or are keeping their existance secret for some reason? Or maybe its just my regular paranoia surfacing? ;~)

    Any UK suggestions or even better a build I could follow? I really don't want much spec wise like over current or speed under load regulation, just a softish start and full range of speed regulation. Any ideas guys?

    Al
     
  6. ronv

    ronv Well-Known Member Most Helpful Member

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    Seems like it should be easy enough. It only turns in one direction... right?

    edit:

    Was it running on 230 volts before?
     
    Last edited: Feb 3, 2015
  7. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Where is the controler from the treadmill?
     
  8. bigal_scorpio

    bigal_scorpio Active Member

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    Hi 4pyros,

    I still have all the treadmill, its not even stripped yet.

    It does have a tin box that I think may have the controller inside and a larger separate board for the actual control of all the programs etc.

    It never occurred to me to use the original controller! I will have to investigate how it works signal wise etc.

    Thanks, Al
     
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Open it up and send us pictures.
     
  10. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Ron,

    Yes Ron it will probably only turn in one direction on the lathe, I can't see a need for reverse on a wood lathe, unlike the metal ones where it is quite normal to have reverse. Got me thinking though! Wonder if there is a use for reverse on a wood lathe?

    Edit: Yes it is 230v mains here.

    Al
     
    Last edited: Feb 4, 2015
  11. bigal_scorpio

    bigal_scorpio Active Member

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    Here are some pics, the tin box is an EMI filter, I didn't notice it said that at first.

    Al
     

    Attached Files:

  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Are the controls on the treadmill itself suitable for your needs?
    Can you take all the electronics off and use the hole setup.
    If not we need some close ups of the controller itself, the red board.
     
  13. bigal_scorpio

    bigal_scorpio Active Member

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    Hi 4pyros,

    No the controls sadly are not suitable, the main problem being the slow startup which is a safety feature for the user, it is way too slow to get up to speed and to slow down.

    The actual speed setting is done by either 3,6,9 or 12 buttons or simply pressing up or down to get to any speed desired, again this is a fairly slow process for safety's sake but too slow for my liking I think a simple pot would be much better for my needs.

    There is also a really good set of 7 seg leds to give read outs of the speed, time and calories as well as blood pressure. The speed readout would be handy i suppose but the others aren't needed (except maybe the blood pressure one for when a tenon splits or something ;) ).

    I will take out the board and get some pics shortly.

    Thanks, Al
     
  14. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Make sure you mark all the wires and remember whats connected to what. You may want to make a diagram.
     
  15. bigal_scorpio

    bigal_scorpio Active Member

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    Hi 4pyros, here are some pics, left as big as possible for clarity.

    Al
     

    Attached Files:

  16. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    looks like a standard off the shelf motor controller.
    Are there any other markings on it, part numbers or manufacturer?
     
  17. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Mate, do you mean on the board or the machine itself?

    The machine is dynamix but it seems like a generic model just badged for them to me. Probably loads more with the same innards.

    Al
     
  18. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Either on the board or the metal around it. Its called an open frame motor controller.
     
  19. bigal_scorpio

    bigal_scorpio Active Member

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    I've been searching for numbers and only found the actual model of the treadmill - YT-3134 on the main body tag. The board only has the legend E323292 YQ-005 in the corner above the standard 94V-0.

    On looking for clues from the components I see what appears to be an 18pin Soic that I assume to be a Microcontroller of some kind running at 16Mh, maybe a PIC, it has a regular old memory chip connected to it (24lc02b). The u-controller itself has absolutely no numbers on it as I have seen in other commercial designs just to make the design a little safer.

    It seems to me that there is a whole lot of components on the board for the relatively small number of things it does but then again I have little to no experience of these large motor drive circuits so I could be way wrong in my thinking.

    I can't find anything on the web about the board or the treadmill (other than ones on ebay) so I am stuck now. Does anyone think it feasible to use this controller for my project? BTW I have tried moving the trimpots full scale and they have an effect on the soft start and stop, to a small degree, but not enough to make any difference to my needs especially since the mill has a 3 second countdown even before the start or stop process begins so the possibility of using the board unchanged seems very unlikely to me.

    PS I looked at the IGBT that drives the motor and it is a 40N60A rated at 600v 75A and 3v vce(sat) so it seems that it would be the ideal thing to drive from microcontroller voltages. I could understand a couple of opto isolators and the odd components needed for the micro but the many components on board baffle me somewhat.

    Any further thoughts please, Al
     
  20. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes use the board. the pots should be acceleration and deceleration. thats what you want.
    You will need to experiment with them.
    Can you tell from the existing wiring how the speed control pot was hooked up?
     
  21. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Mate, I have played with the trimpots and got the softstart a bit quicker but even then there is the 3 second run up and run down times that I can't change.

    As for the speed control, maybe I didn't realise I didn't mention that there is no pot but only buttons to change the speed or select 3, 6, 9 or 12 kph so I cant really use them for a lathe. Something else I forgot is that I would also like an emergency stop that braked the motor if possible? You never know if something is going to get caught or even start a massive wobble with an uneven blank!

    Al
     

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