Good motor for providing bike resistance?

I would like to use a motor to provide a variable bike resistance.  The bike will be turning the motor, and the motor will provide a physical resistance, making it easier or harder to pedal.  My ultimate goal is to make a microprocessor-controlled stationary bike, where the micro can both set the physical resistance of the motor and detect the speed of the motor.  My intention is to use a variable electrical resistance to make the motor harder or easier to turn.  However, I don't know much about motors, so my question is: what kind of motor will work for this?  Any comments welcome.

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Re-design7 years ago
Find a good working treadmill motor.  Then chuck a rubber wheel to it and mount it against the rear tire.  Find the right sized wheel so that minimum resistance is very slight.  Not hook up your variable resistance source.  Lights or rheostat which ever way you want.

THat should work pretty well.  It's basically a copy of the production resistance machines available for about $125 iIrc.
FazJaxton (author)  Re-design7 years ago
This sounds like a good idea.  Are treadmill motors usually DC?

Now to find a treadmill to scavenge for cheap...
The two that I've taken apart were.  I think dc motors are way easier to speed control.
FazJaxton (author)  Re-design7 years ago
A friend also recommended a starter motor from a car.  I think I will start with this, as I don't have any treadmills lying around, and there are car salvage places in my area.  I still think the treadmill is the best choice, though.
rickharris7 years ago
Go with a car alternator and head light bulbs.
FazJaxton (author)  rickharris7 years ago
The lights are a good idea, thanks!  I understand from other instructables that alternators don't have a permanent magnet, and instead either need a minimum speed or some kind of priming circuit to build up a field.  Is this correct?
An alternator needs to run at about 3000 RPM to produce meaningful output. It should be self energising as it is in a car.
lemonie7 years ago
Hook the bike up to a generator/motor.
Rick' and Steve' are offering good advice, have a series of loads (e.g. lights) that you can switch on/off for your physical resistances, you do it that way not by fiddling with the motor it's self.

I'd use a DC motor for preference, the size you need depends on the maximum power you expect to extract from the rider.