Motor Circuit DiagramsOscillators Circuit Diagrams

PWM governor

The governor described in this article is intended primarily for small 12 V motors that draw a current of not more than 2 A. Many governors limits the current through the motor, which also reduces the torque. Since it is controlled by pulse-width modulation (PWM), the present governor preserves most of the torque. The control is based on a sextuple CMOS inverter, IC1 (Type 40106). Three motors are driven via a discrete Darlington, T1-T2.

Inverter IC1a function as an oscillator, whose on time (time T2 conducts so that the motor is provided with power) is determined by R2-C9-D3. The off time of the oscillator (when T2 is also off) is determined by R3-P1-C2-D4, and may thus be varied with P1.

Parallel-connected inverters IC1b and IC1c, form a buffer between the oscillator and the power Darlington.

The motor is connected to the + and 0 terminals in the diagram.

Power for the governor and the motor provided by a mains transformer, whose secondary voltage is single-phase rectified by D1 and D2).

An indicator LED with current limiting resistors is connected to the motor terminals.

Network R1-C1 smooths the supply voltage to IC1.

Finally, T2 must be fitted with a suitable heat sink.

PWM governor Schematic diagram

PWM governor Schematic diagram

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