powerchairs...

[DarkPenguin]

I just found an old power chair that was stripped of everything except the motor, motor conrtoller and the speed controller.
I would like to hook this up to a pic or an RC receiver circuit.
Problem is, the speed controller is a potentiometer. How would I hook it up/program the pic?
I would rather not use a servo to control the pot.

[HarryBotter]

If the motor controller has an H-bridge circuit on it you should be able to feed a PWM signal generated by a PIC or similar chip to control speed. Look for a PIC that has onboard PWM.

Harry

[DarkPenguin]

I am pretty sure the motor controller uses an H-bridge (when I opened it up, there are a bunch of large transistors bolted to a heat sink) and I read somewhere it uses PWM. Where would I feed in the PWM signal? I could post a picture of the controller if it would help. I already have a basic stamp, but I will eventually move on to something else (to add more sensors)

[HarryBotter]

Here are a couple of good explanations.

http://www.bobblick.com/techref/projects/hbridge/hbridge.html
http://www.mcmanis.com/chuck/Robotics/tutorial/h-bridge/bjt-circuit.html

Harry

[DarkPenguin]

I understand how H-bridges work, I am just wondering how I would mod the controller to interface it with a pic/basic stamp

Picture of the motor controller:

http://www.jneumann.com/images/robot/DSC02309edited.jpg

Edit: I just talked to a friend who brought up the idea of using a series of transistors and resistors (eg. 1/3 speed, 2/3 speed, full speed, 1/3 reverse, 2/3 reverse, full reverse) to emulate the potentiometer at different resistances. Good idea/bad idea?

[HarryBotter]

If I remember correctly the PWM signal is usually connected to the enable pin on the controller. I'm not sure why you would want to replace a pot with a bunch of resistors.

[DarkPenguin]

Well, I would like to thank you for the help, but the motor controller is now toast thanks to a nut coming loose and falling onto the circuit board while I was testing it. :mad:

Anyways, I now plan on building my own H-bridge, so I was wondering which would work better - build a new H-bridge out of the transistors from the now toast motor controller, or get some H-bridge IC's and just hook them up in parallel?
It needs to be able to draw ~8-10A avg, and 15-20A max

[HarryBotter]

I've never put together an H-bridge and have only piggy backed a couple of ICs to give me a 2 Amp draw and even they got pretty hot.. Paralleling a bunch of ICs to cover up to 20 Amps seems iffy.

Anyone else out there with experience in this?

[DarkPenguin]

Bump!

anyone?

[alain]

Hi,
I am in the process of building a new robot mower, using parts of 2 powerchairs. I built my CPU with a PIC 16F877, it controles Hbridges of one of the powerchairs (Invacare electronics).
You need to identify the Hbridge itself, as well as the IC which is controlling it. Then find the right place to cut of the PCB, I would say that's the real trick.
Just in case, you can have a look to my webpage. Don't be too disturbed, it's in French, but you can get it translated by openning it with some web translating tools.

http://greenbot.over-blog.com/

Have fun.
Alain