Wheelchair motors not moving with joystick - please help
Hey,
I purchased an old electric wheelchair a little while back for a project. I ended up removing the motors, and the electromagnetic brake attached to it so I only had +and - wires coming from the motors. I basically removed everything from the chair including the joystick controls and motors. Now Ive decided to put it back together in its most basic form, ie frame, wheels, motors and joystick. The chair is an old merits, with a penny and giles joystick/computer unit as pictured here: http://www.esolutionsusa.com/ebay/Travi ... 29_4_2.JPG
I can get the unit to turn on, but the battery meter is flashing 3 bars which means left motor wiring fault. I had connected the motors the way they came off before with the wires the right way around, yet I cant get them move with the joystick. The only thing different is that there are 4 wires (2 for each motor) that used to run the electromagnetic brakes. I think it thinks theres an error because they are not connected to anything. I have also tried applying voltage to them and also connecting them together to make it think the brakes off. The motors work perfect when connected directly to 24v supply.
The chair worked fine before I dismantled it, the only thing different is the brake wires from the control unit are not connected because I removed the brakes on the motors for something else. I hope someone can help me in some way. I'm sure its something easy that ive just missed, I hope!
Cheers!
Tim
I purchased an old electric wheelchair a little while back for a project. I ended up removing the motors, and the electromagnetic brake attached to it so I only had +and - wires coming from the motors. I basically removed everything from the chair including the joystick controls and motors. Now Ive decided to put it back together in its most basic form, ie frame, wheels, motors and joystick. The chair is an old merits, with a penny and giles joystick/computer unit as pictured here: http://www.esolutionsusa.com/ebay/Travi ... 29_4_2.JPG
I can get the unit to turn on, but the battery meter is flashing 3 bars which means left motor wiring fault. I had connected the motors the way they came off before with the wires the right way around, yet I cant get them move with the joystick. The only thing different is that there are 4 wires (2 for each motor) that used to run the electromagnetic brakes. I think it thinks theres an error because they are not connected to anything. I have also tried applying voltage to them and also connecting them together to make it think the brakes off. The motors work perfect when connected directly to 24v supply.
The chair worked fine before I dismantled it, the only thing different is the brake wires from the control unit are not connected because I removed the brakes on the motors for something else. I hope someone can help me in some way. I'm sure its something easy that ive just missed, I hope!
Cheers!
Tim
Comments
Welcome to the forum... If you want to run the motors from the controller, without the brake attached, you have to put a resistor between the two wires that were previously attached.
You need low ohm large current capacity resistors. I can't give you exact numbers because the brake systems on the various Merits floating around vary a little. You can figure it out if you
measure the resistance across the brake or you could then use a resistor that limits the current to about an amp at 24volts? or two or three? don't remember exactly:)
I do remember that I found my resistors at Radio Shack.
It is late and I am going to bed... Sorry to be somewhat obtuse.
Rich
Thanks heaps for your answer, someone else on another forum thought it would be a resistance problem too. I'll look into putting a resistor in place of the wires. Im from Australia so dont have radio shack down here, but I'll find some anyway. Lucky I thought it was going to be a hard fix.
Cheers!
They have to be pretty beefy. I looked around and I think I found the one I used, which was 100 Ohm 10 Watts. I had to remove the brake because that is where I decided to put my diy quadrature encoders, which are based on optical switches. You can also just put the brakes back into the circuit but attach them elsewhere, which is what I did initially to get the battery charger to work right.
If you look around on the forum you will find some really great guys here from Australia.
Rich
Rich, PLEASE tell me you don't mean these guys.
The resistors other people have recommended were 120ohm 5w, I will have a play around with it. I did try to connect up the brake wires from the motor to see if it worked but it didn't unfortunately. Maybe because I removed the mechanical brake part inside (unscrewing the cap and removing the round plates) but left the end housing on with the brake wires attached. Would this make a difference in resistance than having the complete brake system hooked up normally? I know the computer can be picky with this thing as its all to do with safety. I spose if its not a certain resistance then its not going to move.
ROFL... very much.
Rich
Cheers
If (stress on the if) the brakes were in series with the motor a 120 ohm resistor will likely limit the current to a value too low to turn the motor. Time for a little detective work.
What was the voltage of the battery in the wheel chair?
Is there a voltage rating on the motor?
Does one of the wires that was connected to the brake have voltage on it with the joystick moving?
Can you measure the resistance of the brakes?
value in its place to be sure. You might get away with a higher value resistor, but that's trial and
error. Expect the brake to take of the order of an amp or two, so 12 to 30 ohms is the sort of value
I'd expect (although this is from knowledge of re-purposing old mobility scooters). The brake
solenoid is a massive great high-force actuator that operates against a sprung clutch.