DC Motor Controller for PCB Drill

This is a simple circuit that can be use to vary the speed of a DC motor. It is very useful for controlling a PCB drill, but it can be used for whatever applications you want. The speed can vary from full to complete stop. The circuit is versatile and can be used with motors of different currents and voltages.

This circuit is widespread on the internet. Here is an example. The PWM signal is generated by a 555 chip. The chip drives a MOS-FET transistor that will switch the motor on and off. The 555 is powered from a 7805 regulator. Therefore, the motor DC voltage can be between 8 and 35 V (the circuit can be powered by AC 7...26 V). The maximum current is limited by MOS-FET.
The circuit shown here is designed to be AC powered by a mains transformer. But you can power it from a DC adapter, battery or even a computer power supply if you remove the diode bridge and connect the power lines straight to ground and positive pads, where the output pins of the bridge would otherwise fit.

Read more »