Introduction

This is a MOSFET based speed controller for DC motors. Motors with 12 Volt are suitable for this application. MOSFET is a voltage controlled device. So, when we vary the 10 kΩ potentiometer the voltage at the Source terminal of MOSFET vary with respect to ground. As a result the input voltage to the motor is varied. Therefore a variable controlled speed is achieved. It provides us a very smooth controlling action.

Components required

1kΩ

10 kΩ potentiometer

470 Ω

1M Ω

IRF 540

DC Motor

12 V DC supply

LED

IRF540 MOSFET

IRF540 is a power MOSFET. It is designed to drive high current loads. It can handle a maximum load upto 23A and the maximum load voltage is  100V DC. It is using trench technology which makes it capable of reaching high level of drivingcapability.

Circuit diagram

Working

A heat sink is compulsory to protect the MOSFET from thermal break down. The brightness of LED with a series resistor across the motor is proportional to the motor speed. As shown in the image, the measured maximum voltage across the motor is 7.85 Volt when the input voltage to controller circuit is 12 Volt.