Newb advice: drive a motor with a flex sensor

[Reacharound]

Hi. I'm new at this and looking for advice or pointers to resources.

I'd like to drive a 3V DC motor in response to a flex sensor (its just a variable resistor/voltage divider set-up, but it won't handle very much current). Bend the arm, more power to the motor, robot rolls forward faster. This is just an analog voltage divider thing; I don't need digitizing.

I know the flex sensor can't handle enough current to drive a motor, so I need some sort of separate amplifier. I know how voltage dividers work. Should I use an op-amp, or do you not drive motors with an op-amp? Should I use a PWM chip and a MOSFET? Will either of these work at very low voltages, so that I can get motor response anywhere from 0.1V to 3V? Do I need some sort of diode or resistors in the path to prevent back currents or something? What about resistors in the path to the MOSFET gate?

This is, I think, the basic concept:

3Vin ---> flex sensor ---> PWM chip ---> MOSFET ---> motor

Is this an obvious thing? Are there schematics for this anywhere? What can I read or do to get started? Any friendly advice is appreciated!

 

[ronv]

Hmmm. The answer needs a couple of questions. How much current is needed to drive the motor. If it is real low an op amp could maybe do it. Can you measure the resistance of the motor so we will know the maximum current?

Do you know the resistace range of the flex sensor?

If it needs what you pointed out flex - pwm - FET - motor it might be an easier implentation to use 4.5 volts as opposed to 3 volts. Might that be ok? If need be we could limit the PWM voltage to 3 volts.