Motor controller project help

Discussion in 'General Electronics Chat' started by keaster, Jul 11, 2013.

  1. keaster

    Thread Starter New Member

    Apr 28, 2013
    11
    0
    I need a bit of help with a project I'm working on. I've been looking for a good simple high amp pwm motor driver circuit and found this
    [​IMG]
    It is suppose to handle 24v 60a. I want to use it for a kids ride on Power Wheels toy from what I've read is that the motors should not draw more then 30a. I made some small changes to the circuit like removing 1 mosfet because I know I would never reach 60a the other thing is I',m using a PIC micro PWM to control the motor because I use a hall sensor for the throttle and also added a 1k between the pic i/o and base of the totem pole circuit.
    I hope I can explain this problem, because its for a childs ride on I wanted to be able to run 12 and 24v I have 2 positive wires into the circuit. The first is for the 12v replays that control forward and reverse and also the digital circuit that is dropped to 5v using a lm7805. The second is just for the motors positive side so if I want to run 12v connect both to 1 12v battery if I want 24 I leave the first 12v wire on the first battery and then add a second 12v battery and connect the motor positive to the second battery in series. 12v mode works good its the 24v that kills the mosfets. I cannot figure out why. Also I have a 50v cap on the 12v only side that blew as well. Is there some how running 2 different voltages that 24v is getting to the 12v or 5v somehow?

    please help I hope I didn't make your head explode
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Don't know what you're saying here. A drawing of exactly what you want to do would help trememdously. If you want to run on different voltages, you'll need to do some redesign. Easiest thing would be to run the circuit as it is shown.
     
    Last edited: Jul 11, 2013
  3. keaster

    Thread Starter New Member

    Apr 28, 2013
    11
    0
    This is quick drawing showing the mods I made, using the original circuit wont work because I use a hall sensor plus there's other stuff that the PIC is needed for. Its just the basic motor control I need to get working
    https://www.dropbox.com/s/7wihnsswadp15nr/cache.php.png
    [​IMG]
     
  4. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Electrically speaking, the main difference between the original and modified circuits is the drive voltage to the FET's. That alone doesn't seem to be enough to cause the failures. I don't see a good reason why the FET's are blowing. That is, assuming the circuit you built is EXACTLY the same as the drawing, except for your designated mods.
     
  5. Mick4358

    New Member

    May 4, 2014
    2
    0
    Have programmed the PIC properly?
    When you connect the batteries in 24V series, do you take a 12 Volt tap of ONE battery for the circuits?
    Check or put new 7812 & 7805's in.
    Can you alter the Vr somehow to stop it going all the way up and giving full power?
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    1) Is that the manufacturer's info, or something vague on the web?
    2) Is 30A the running current or the stall current (which would be much greater)?
     
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