Tuesday, September 4, 2007

Using Wheelchair Motors

Here is the post which I originally posted it in Society of Robots Forum. My ID there is airman00

A lot of people have been asking questions about wheelchair motors lately so I will just list some of the ideas behind using a wheelchair motors.

Note: I am assuming that you are buying the wheelchair motors along with the gearbox attached.
Why choose a wheelchair motor?
Wheelchair motors are very powerful and can handle 300+ lbs. They are relatively cheap for their size(~$75 ebay) and are very easily found online or in repair stores. Try to buy a motor with the wheels still attached.

Controlling Wheelchair Motors
When using wheelchair motors I would recommend having differential drive( two motorized wheels and one caster in front). This makes controlling the drive system easy and it allows for on the spot turning. To control the motors you can either use relays or a motor driver. Im also sure that an electric wheelchair includes a controller with joystick, so just hack that. But for most of us who are buying the motors separate from the wheelchair , make sure that your relays or motor drivers can handle at least 5 amps more than the motors draw( better safe than sorry). I personally used automotive relays bought from All Electronics Corp to control my wheelchair motors.

Mounting the Wheelchair
This varies by motor but most have mounting holes on the gearbox so all you would do is drill through the base material( i recommend wood) and stick a bolt in through the wood into the motor.

Miscellaneous Advice

Even if your motors are rated for 24V they will run on 12Volts except theyll be slower.

Install a Kill Switch : And also remember wheelchair motors are powerful machines. They are meant to carry 300 pound people @ 5 mph. Thats really strong so be careful! My biggest mistake with using wheelchair motors was too not install a kill switch. The robot just kept moving forward on a test run and I was not able to hold it down( luckily I pulled out the wires in time) Now I have one R/C kill switch and another tactile kill switch. The button should be really big so you can hit it while the robot is moving. Also it should be a direct kill switch, meaning not a switch that goes through the micro controller, but a switch that separates the motors from the batteries directly.

If the robot does not stop it will either damage itself, your belongings, your house, or you!

There is a copy of this on my blog.(http://erobots.blogspot.com) That will be the more update version if I forgot something

Any questions?
Feel free to email me - airman00@gmail.com


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