PWM Power Control
SCR Power Control
CRO Display of Waveforms
4-Digit Speed Display in rpm
Contactless Eddy Current Braking

Closed loop speed control of dc motor is a common experiment for studying various features of automatic control systems like control, regulation and disturbance rejection. The present unit is designed to demonstrate the working of PWM and SCR based controllers and show the resulting waveforms of the voltage supplied to the motor. Measurement of the timings on the waveforms under various conditions has been suggested to get a good insight into the operation of the system. The experiment is complete with all the sub-systems and a detailed operating literature is included which introduces the basic theory, suggested experiments and an interpretation of the results. An external CRO is all that is needed to view the waveforms and measure the timings.


• Open loop speed control for PWM Controller, with and without load
• Open loop speed control for SCR Controller, with and without load
• Closed loop speed control for PWM Controller with load
• Closed loop speed control for SCR Controller with load
• Observation and measurements on the voltage waveforms

Features and Specifications
• Speed control of a 12V, 4W permanent magnet d.c. motor
• Speed range: 0 to 2000 rpm (typical)
• Opto-interrupter based speed sensing
• 4-digit speed display in rpm
• Electronic tachogenerator for feedback
• Separate unit for motor in a see-through cabinet
• Smooth, non-contact eddy current brake
• 220V±10%, 50Hz mains operation
• Supporting literature and patch cords included
• Essential accessory – a CRO


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