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Re: Are motor speeds proportional to PWM value?
If you search the forums (or is it "fora"?), you should find a few whitepapers and threads that describe the operation of DC brush motors. I'll give you a super-high-altitude summary.
With no frictional load attached to (or inside) the motor, a perfect power supply and a motor drive that efficiently and linearly converts PWM command into voltage, the motor speed will indeed be proportional to the PWM value. That's a whole lot of IFs...
In general, approximating speed with PWM value is often good enough. But only you can know what's "good enough" for your application. Deviations from that ideal can be due to nonlinear or inefficient motor drives, power supply sagging or frictional loads. There are also transient effects due to rotational inertia to consider.
It's actually a really fun system to model. Do a search through CD and you'll find some good resources if you'd like to learn more.
Russ
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