I am trying to figure out how the control for the motors on a Jazzy powerchair works. The P/N on the motor is CM808-075B. I haven't got the uppert half of the chair with the control stick so I have no clue where to start on getting it to move. The motors have 4 wires running to them and judging from the wire thickness it seems to be a hot and common alongf with 2 control wires.
That link is basically right. However you need to know several things.
The motor is a DC brushed motor rated at 24V and 75A max. A serious PWM motor-controller is needed to drive these... Expect the no-load current to be several amps. The continuous power rating will be a lot less than 24x75 as these motors don't have the cooling fans for sustained high-power use.
Secondly the electromagnetic clutch brake (the two smaller wires) is likely to be rated at 24V and an amp or two, and to be an EXTREMELY inductive load. You must use a free-wheel diode in the circuit controlling this otherwise it will generate possibly thousands of volts and destroy the circuit. It may be able to give a lethal shock in this situation should you be foolish enough to touch the wires at the time. The motor is held locked until the clutch is activated. The clutch can probably be unbolted from the motor and removed if not needed - its a safety feature for the wheelchair.
I like the idea of removing the clutch. I can do all the starting and stopping manually.
The clutch is only useful for something like a chair or scooter where you want things to stop quickly if anything fails. Unless you're making something like that remove it (it should just be
bolted on the end of what is basically a standard DC motor)
MarkT:
The clutch is only useful for something like a chair or scooter where you want things to stop quickly if anything fails. Unless you're making something like that remove it (it should just be
bolted on the end of what is basically a standard DC motor)
I would think that any device based on motorized chair platform (even if it is just the platform, motors, and batteries - your talking around 100 lbs) would want to keep (and use) all safety systems and mechanisms in-place. Should you have a runaway robot, 100+ lbs of metal and batteries -will- do some damage. It would be best in this kind of a situation to take -all- possible precautions. In fact, any of your software on the Arduino or otherwise, which controls the robot, should be designed from the ground up to include watchdogs and other mechanisms to detect failures, and drop into an "all power off" mode on failure, to prevent as much as possible, such a situation. You should also install some kind of manual all-stop switch that is tied directly to the power system in such a manner so when it is tripped, all power is shut off - it should be clearly labeled and easily accessible and used; a pull-type switch, kinda like that used for jetski riders, with an easy-grab handle or such, is ideal. You should also include a remote-controlled shutdown system as well, that is separate from any software system. Plan for any and all failure modes; give it a -lot- of thought, of what could possibly go wrong, then design your system (before -any- actual building is done) to take into account such a failure.
If you do it right, you'll end up with a robust system that will have a much smaller chance at causing harm to property or limb; you won't ever get to "zero-harm", but you can mitigate it drastically.
Finally - something else to keep in mind - when testing your motor controls and such in your work area, do so with "wheels off the ground"; I've read more than a few stories about people testing such chairs (or similar large-scale autonomous platforms), only to have the device zoom off, and not come to a stop until impacting a wall and causing other damage.
Now, granted, a powerchair isn't all that fast - but it's fast enough, and if you have a later goal of using a larger or faster platform in the future, your security precautions taken now at the design phase can translate over, without you needing to patch or bandaid in a solution to similar issues (which at best is a foolhardy and generally error-prone approach).
