# Question on Electric Motors?

1. Nov 27, 2006

### zekester

I am trying to implement an electric motor as a generator at the end of a steering wheel shaft. The motor would be used to apply a resistance torque to the shaft. What type of motor would you recommend?

2. Nov 27, 2006

### Danger

This sounds like a rather odd project. Is the purpose of the motor specifically to generate electricity, or to dampen the motion of the shaft, or what?

3. Nov 28, 2006

### zekester

the purpose of the motor is to apply a small resistance (4-7 N*m) to the steering wheel shaft. The shaft itself will be turned by a steering wheel. this should allow the motor to run as a generator creating a voltage.

4. Nov 28, 2006

### marcusl

Why not use friction? Wrap the shaft with a piece of leather and put a clamp around the whole thing...

5. Nov 28, 2006

### zekester

sorry, i should have said this before, but the resistance needs to be able to vary from no resistance to around 7 N*m

6. Nov 28, 2006

### marcusl

tighten the clamp to vary the torque...

Seriously, a generator is complicated. Doesn't the torque depend on the speed? Also athe armature poles in a generator will give you funky results if you turn your steering wheel only a little (like 30 degrees). Mechanical systems are easy. Look at the simple brake on an exercise bike--you turn a screw that squeezes two pads onto the turning wheel. The knob has a pointer that indicates the relative drag. Once you calibrate the torque or drag (which you'd have to do your way too), you're done.

7. Nov 28, 2006

### Danger

And if you have to have something that varies on the fly, without manual input, you might look into using the motor as a motor, instead of a generator. Check into how force-feedback joysticks work.

8. Nov 28, 2006

### KleptoPanda

A generator wouldn't be that hard to do. You would just use an MCU controlled digital potentiometer to apply resistance to the motor windings. Then it is just a matter of measuring the change in voltage to determine speed. Make sure you have a set of diodes in place at least equal to the sample rate of you MCU to prevent any damage in case Vin Diesel gets in your car.