Guide for DC motor Control

DC Motor Speed Control Circuit using a Phototransistor Optical Interrupter Switch
These controls may be of the open loop type, where light just provides a no-contact, non-wearing circuit input from a person or machine which monitors the output of the motor, or a closed loop type, where the light monitors motor speed as a tachometer and maintains a fixed, selected, speed over a range of load and line conditions.
  Closed loop, tachometer feedback control systems utilizing the MOC70P3 or any other optical Interrupter Switch for which the gap and the depth of the ā€œUā€ is mechanically compatible with the chopper wheel, provide superior speed regulation when the dynamic characteristics of the motor system and the feedback system are matched to provide stability. The tachometer feedback systems illustrated in Figure 1 were designed around specific motor/load combinations and may require modification to prevent hunting or oscillation with other combinations. This dc motor control utilizes an opto-tachometer circuit to control a P.U.T. pulse generator which drives the D44E1darlington transistor which powers the motor.

Schematics tachometer low res
                                                                            Fig.1- DC motor, tachometer feedback, PWM, speed control

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