to make or adapt, pwm 100v 30a motor controller

Discussion in 'The Projects Forum' started by daveyjones97, Dec 29, 2011.

  1. daveyjones97

    Thread Starter Active Member

    Oct 21, 2011
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    i want to make myself an ebike but kids, mortgage and pay freezes mean i have to do it the hard way. i have no technical background apart from a bit of automotive and fabrication (precision) engineering.
    the motor i stumbled across is a 240/50hz plated universal brushed motor which i think is rated at 2000w, but as yet unknown speed.
    the controller wish list is 100v 30a and maybe current limit holding feature, so when the load reaches 30a it will hold that but not exceed it, and a simple thermal cut out. i dont need regen braking motor reverse or anything flash.
    im after informed opinons on wether
    a: i should attempt a scratch build and reccomendations on schematics and parts,
    b: my favorite concept, adapt something, but what and with what parts?
    c: cry at the realisation a pwm controller is not a suitable first major electronics project and save for the forseeable.
    i have spent all the limited spare time i have looking into this since i priced up a proper ebike setup a month ago and tbh have no idea what route a,b,c to take.
    any help gratefully appreciated thanks
     
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
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    While this post may be closed for violating the TOS (no vehicle circuits) I'll sneak in a head start for you, before it is.

    This circuit is a very easy and able to be modified for almost any DC voltage and amperage motor, by just changing the out put mosfets to suit your needs. To better understand the main IC("brain") of the circuit Google for the data sheets and application notes to go along with SG3525. To help pick the mosfet check out -
    http://mcmanis.com/chuck/robotics/projects/esc2/FET-power.html

    Here is the link to the control circuit - http://wzmicro.virtualave.net/3525.htm

    One thing with the motor you've found, how are you going to get 100V DC in a light package? Although it is marked for 240VAC since its a universal motor it will work with DC. At the lower voltage it won't give near as much power or speed.

    To avoid being closed down, this circuit could also just be a PWM motor controller. Wink, wink, nudge, nudge. :)
     
    daveyjones97 likes this.
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Shortbus,
    Why did you recommend that particular circuit?

    Did you read the part where our OP wants to control 100V, 30A?

    The circuit you linked to would get fried immediately with 100v being fed to it. The SG3525 isn't rated for that much voltage.

    I do NOT like the MOSFET gate drive. It should at least have a fast turn-off; 220 Ohms to ground will be rather slow.

    A single MOSFET won't handle the load.

    Along with multiple MOSFETs, a gate driver will be required.

    Board layout will be pretty critical.

    At these voltage and power levels, it's not really something for a beginner to take on. One should start with much less complex projects, and see how they go first.

    Troubleshooting the SG3525 circuit without a 'scope would be problematic.
     
  4. daveyjones97

    Thread Starter Active Member

    Oct 21, 2011
    46
    1
    thanks, what about using some sort of power tool speed controller as the basis for the circuit?
    i was wondering just how many parts i would need to change other than the capacitor, fets and shunt circuitry? if i tried to adapt something.
    or if not, which parts of the pwm controller schematics on aac can be changed for higher voltage and current?
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    I suggested it because I have used it and it worked OK, after reading the data sheet and app notes. I also thought since I was able to get it to work almost anyone can. I showed the circuit because I've learned so much here and got help from you and many others that I feel like I should return the favor to others that ask questions that I can answer.

    Its not real elegant or maybe as good a circuit as you or some of the others on the forum would design, but like I said in the original reply it will give him a head start and he could ask questions from there.

    By changing the mosfet to a part that will match his needs or for that matter anyone else's needs, it makes an easy PWM in a chip. After all thats what the chip is made to do. Even though the original use was for a SMPS, in this configuration it will drive a motor in a single direction fine.

    No offense meant but I think some of you guys have been doing this for a living for so long that you forget what its like to be just starting out and needing something to just work without all the bells and whistles. Some things just take something simple.

    If I should keep out of answering questions just say so, no problem. I'll just go back to asking questions. I know that I'll never have the knowledge of electronics that you or many others on the site do.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Speed is limited mechanically. meaning, it will spin faster and faster, approaching infinity, until air resistance & the resistance of the bearings/brushes makes it plateau or it spins into a thousand bits in your face. Don't test it unloaded.
     
  7. daveyjones97

    Thread Starter Active Member

    Oct 21, 2011
    46
    1
    ok, what would be a safe max voltage and current for shortbus' reccomendations? i think starting with less lethal voltages and currents is the responsible thing to do. a nice simple easy build is easily as important as any other aspect, hence considering modifying something.
    i would like to make the first circuit one i could use to aid r&d and because i dont get much free time at home. (can post at work). im itching to waste solder and components but have had a nightmare choosing which circuit to make / adapt.
    i respect everyones opinions as you all know more than me thanks for your patience.
     
  8. daveyjones97

    Thread Starter Active Member

    Oct 21, 2011
    46
    1
    luckily i have learnt about universal motors and will not be connecting it to anything without a load. some say im ugly enough...
     
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