DC motor voltage supply

[Guest]

Hello,
My question is that when I apply the voltage to my DC motor, before applying it I change the analog voltage into digital to make changes on the speed with PWm. However, I wonder after changing the digital from of the voltage, doe the pic device change it again into the analog from before suppyling it to the motor ?

[SherpaDoug]

Only the tiniest motors will actually be driven by the PIC itself. Almost always the PIC PWM will drive a switching transistor which produces a digital high power output. Usually this digital signal is applied to the motor windings. In higher power applications there may be some filtering of the higher harmonics of the PWM signal to prevent EMI (electromagnetic interference) or audible noise.

Since the motor winding is by definition an inductor, it inherently low pass filters the voltage applied to it. It is actually the current through the motor winding that does the work, and the current is the integral of the voltage.

In some low power applications the output of the processor is a D/A instead of PWM. Then a power op-amp can be used to drive the motor with an analog signal. This is very precise and quiet, but leads to poor efficiency and heat problems at any but the lowest power levels.
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