View Full Version : Using wheelchair motors: Is there a solenoid???

07-25-2009, 05:21 PM
Hi Group,

Very excited that for the first time got my humongous motors with gear heads and wheels attached. Obviously, this was only possible thanks to the fact that old wheelchairs are pretty much ready to go robot platforms. There is still one question I hope somebody in here knows the answer for:

After tons of reverse engineering the chair, it is obvious that each motor has four wires. Two power wires for the DC motor winding and two smaller wires for what appear to be a solenoid of some kind (or maybe a relay?). All I have done is look at the chair using the controller. So when I command the motor, I hear a click and then the motor starts. If I stop the motor, the motor stops and then a click comes up again. I eventually measured the voltage going to this solenoid/relay mechanism and as it turns out, there are 24V when the first click is heard and then as soon as the other click is heard, the 24V goes off.

What I would like to know if this is a relay to allow power to go into the motor, or if this is a solenoid or some sort of brake mechanism, for safety purposes. I am inclining for the second, as when I took the cover apart, there was this humongous thing that looked more like a brake than a relay, but I could be wrong.

In essence, the previous question is for information purposes only. What I really wonder if there is a way around this extra security measure. In other words, what is the best way to disable it, without having to apply 24V at all times to make it go. Is there an easy fix out there that any of you have tried? Thanks for your input!

07-25-2009, 06:20 PM
I think, and I say this not really knowing...but I think that the solinoid is more of a breaking mechanism...as in no power and its breaked...not positive on that one though.

07-25-2009, 06:31 PM
Seems like a reasonable theory. You wouldn't want a wheelchair to go haywire downhill when you're out of batteries.

If you can post some pictures maybe we can help out in how to disable it.

07-25-2009, 09:06 PM
I've not seen a wheel chair motor where it wasn't the brake.

07-26-2009, 12:41 AM
Yes, it is a brake. Take off the cap in the back of the gearmotor. The brake can be taken off by unscrewing a few long screws that hold the coil and plate. Be carefull because there will be a spring that will shoot the plate at you. DO NOT THROW THEM AWAY. If you every want to build a arm using this type of gearmotor, the brake is a good way of keeping the arm where you stop it without using any power.


07-26-2009, 01:48 AM
A big +rep! Thanks Al!

07-26-2009, 08:20 AM

Thank all for your replies! I wish I had waited for them, but instead decided to risk my ignorance and play with the motor. I was able to remove the brake, but to do this I literally had to drill the screws out. This brake will no longer work as at some points in time I had to use a chisel to remove the darn thing in pieces! Not very scientific or practical, but I really needed the thing out.

I concluded, same as some of you, that the brake was for allowing the chair to remain still on slopes. But I do not need this feature, and I really do not want to apply 24V at all times, not even having to control them on and off every now and then.

However, the idea of using these motors for an arm and needing the brake is pretty good! I would not have thought about that. Luckily, wheel chairs are starting to be pretty easy to find at ridiculous prices, so in the event that I go for the arm, I'll look for another chair.