old wheelchair speed control unit help.

Discussion in 'The Projects Forum' started by remorsan, Aug 26, 2013.

  1. remorsan

    Thread Starter New Member

    Aug 26, 2013

    I am new to this forum and this is my first post, it is by my experience generally on forums such as theese, a bad idea to come with a huge question/problem right off the bat, but here goes. Also as i'm more than a little interesten in this subject I will most likely at the very least be an avid lurker on this forum until i actually know what i'm talking about and then i'll most likely end up posting comments/suggestions etc in other threads.

    But enough about that, and more about my project.

    You see, a few years ago, I was given a really old electric weelchair. It was all fun and games until it broke down and i didnt have room to store it. (later found out it was a broken electromagnet for the brakes) So i dismantled the thing, took care of the motors and electronics and gave away the frame to my nephew so that he could make a gravity racer.

    Eitherway, i've always planned to actually use the motors for something else, something that i could control remotely with my rc transmitter, or via wifi and an arduino.

    So i'm stuck with three options:

    i can buy an appropriate speed controller for the motors that gives me serial or pwm control over the motors; which is expensive and not all that challenging.
    I can assemble the complete electronics for the wheelchair and try to make it work; which is pretty much like option one but minus the expensive part and add bulky and ugly
    I can actually try to learn something about a subject i'm interested in and somehow "reverse engineer"/repurpose the circuit boards of the wheelchair, making it more compact; which is what i hope to be able to do.

    I really dont know enough about electronics to know where to start exactly. There are two boards on this thing; one mainboard and what i guess is some sort of speed controller. And a set of contactors.

    What my intentions are, is to remove the mainboard completely; or if need be, scavenge some components from it to make it work with the suspected speed controller and an arduino. And for this i need at the very least some input and help.

    Contacted the maker of this wheelchair, and since ancient they didnt have much information on it, but they did have a flow-chart.
    So i made an album containing pictures of the two boards, the small one is the "power unit" or speed controller, and the large one is the mainboard by my guess.

    Album url is:http://img.im/a/h1p3sl

    So if anyone have any suggestions on how to attack this problem, or any "do this, this and that to make it work like you think it should"-comments i would be gratefull either way. Any comments on this project task is greatly appreciated.

  2. wayneh


    Sep 9, 2010
    I may be mistaken, but your option 1 is likely the cheapest, fastest and easiest way to a working solution. You can find surprisingly inexpensive PWM controllers.

    Do the existing boards work?

    I guess I'm a little confused about what your goal is.
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Hi and welcome to the forum! :)

    And thank you for posting comprehensive information AND a good informative thread title. That makes it easier for everyone.

    My suggestion since you want to use the motors etc for another project, would be to google for "DC motor driver module" and/or check out the "robot combat suppliers" who sell DC motor drivers. That will give you tested and working motor drivers so you can get the project up and running more quickly.

    However if the budget is really tight or you want the experience you could try to re-use some or all of the original motor driver circuitry. Just keep in mind that might not be easy, and might result in burining up the electronics if you do something wrong as wheelchair motors are pretty beefy. :)
  4. remorsan

    Thread Starter New Member

    Aug 26, 2013
    Thanks for replies.

    Yes the boards work, or they did before i disassembled the wheelchair, though i'm not exactly sure if the motherboard will work without all the peripherals the wheelchair is supposed to have. But i've kept all the electronics on the weelchair for eventual testing purpouses.

    What i'm thinking is if there is a way of logging the signal cable from the mainboard to the speed control unit, then use an arduino to emulate those signals?

    I've done a few searches on robot sites and such to find a suitable controllerboard for them, and since the flow-sheet shows 80a fuse on each of the motors, i figuered i would have to have atleast an 80a speed controller, which is in the 500$ range, which is kinda steep for a project thats basically only on the drawing board as of yet.
    I also found another esc unit yesterday after a few hours of looking, not sure if its crap or actually something usable though: http://www.ebay.com/itm/High-Voltag...adio_Control_Control_Line&hash=item231b27ca15

    What i'm going to make with the motors, is one of two possible porjects.
    Either a small electric car for my daughter to play with, or an rc-lawnmower.

    I'm probably going to go for the electric car.

    I'm hoping to use an arduino mega or leonardo as the control unit, since I have few of those lying around, and since they are somewhat easy to program.

    Also since it would fit within the enclosure for the speed control unit and not take up much room.
  5. wayneh


    Sep 9, 2010
    It's hard to offer suggestions from afar, but it seems to me the shortest path to success would be to rebuild the original functions into the electric car, using as much of the old electronics as possible. Using anything else will require reverse engineering what the original part was doing, and then substituting a new solution. That can be a lot of work. Somebody did all of that work once already to produce the system you have.

    Just my 2¢.

    If you just want to harvest the motor and build your own control system for it, you'll need more details about the motor so you can design around it.
  6. remorsan

    Thread Starter New Member

    Aug 26, 2013
    So a quick question, If I retrace every connection on the power unit board (halfway there already), identify every component and make a schematic of it, would it plausibly easy to determine what it does and how to get it to work without the motherboard?

    Yes i know it would be easier to use the motherboard, but 90% of the reason why i'm doing this, is to try to learn something in the process.
  7. wayneh


    Sep 9, 2010
    In a broad sense, yes, I suppose so. It's "just" a motor controller and there is plenty of knowledge out there about how to control a motor.

    The mother board might also have battery monitoring circuitry, to control charging and prevent excessive discharge?