Pwm Schematic

Tachogenerator help control system?

How would the Schematics for a simple speed controled D/C motor look like by using a tachometer.? I have a rough idea but ament quite sure of the control system which gives the negative feedback and how it would transfere to the motor – diference setup shoudl be used for the op.amp to cut down on lag.

PWM can be used but would rather there was an easier way

Cheers
Blair

You have the basic idea – a simple differencing controller that compares your speed setting to the tachometer feedback.

The tach signal can come from a pulse sensor on the motor shaft and be converted from frequency to voltage for the comparison loop. If the motor always spins the same direction this works fine; if it’s reversible then you’ll need to encode direction too (use a quadrature encoder for this.)

The control signal can come from a DAC, potentiometer or other DC source.

As far as the loop details, the best-known type of motor control is called PID (proportional integrator-differentiator.) Link below explains this in detail, other links in the same page have supplemental info. The wiki page (second link) has lots of useful info and external links .

The drive style is up to you. PWM is more efficient (it’s popular with fan speed controls for example) but for a small, lightly loaded motor a linear signal is adequate.

Arduino Microcontroller H Bridge PWM Serial LCD Schematic and Sketch