Simplest DC motor controller with E-MOSFET

DC motors are widely used in various applications, including toys, appliances, and robots. Controlling the speed and direction of DC motors is crucial in many applications, and one of the simplest ways to achieve this is by using a DC motor controller. In this article, we will explain how to build a simple DC motor controller using an E-MOSFET.

What is an E-MOSFET? An E-MOSFET (Enhancement mode MOSFET) is a type of metal-oxide-semiconductor field-effect transistor (MOSFET) that operates in the enhancement mode. In this mode, the MOSFET is off when no voltage is applied to its gate, and it turns on when a voltage is applied. This makes the E-MOSFET ideal for use as a switch to control DC motors.

Circuit Diagram

The simplest DC motor controller circuit using an E-MOSFET is shown below. The circuit consists of an IRF540N N-channel E-MOSFET (Q1), a power supply (Vcc) of 12V, and a DC motor (M1). The E-MOSFET is connected to the power supply and the motor as shown. The gate of the E-MOSFET is connected to the middle pin of a 100KOhm resistor. One end of the potentiometer is connected to the drain and the other end of the potentiometer is connected to common ground which is the negative terminal of the battery. The drain is connected to the positive terminal of the battery or power supply via a switch.

Simplest DC motor controller with E-MOSFET circuit diagram

How the circuit works

Assuming that the 100KOhm potentiometer is set such that the voltage at the gate is higher than the E-MOSFET gate to source threshold voltage, when the switch is closed, voltage at the gate causes the current to flow from the drain to the source. This current flows through the motor and the motor starts to rotate. The amount of current flowing to the motor can be adjusted by adjusting the potentiomter which then changes the voltage applied to the gate of the MOSFET. By controlling the gate voltage, we can control the speed of the DC motor. For example, to increase the speed of the motor, we can increase the voltage applied to the gate of the MOSFET. 

The circuit is biased using voltage divider biasing method. To learn more about this see Enhancement MOSFET Voltage Divider Biasing.

Video demonstration

The following video demonstrates how this simple DC motor controller with IRF540N power E-MOSFET works.


In conclusion, here a an N-channel IRF540N based simple DC motor controller was illustrated. Using an E-MOSFET is a simple and effective way to control the speed of DC motors. The circuit is easy to build requiring only a MOSFET and a potentiomter and can be implemented in a variety of applications. By controlling the voltage applied to the gate of the MOSFET, we can control the speed and direction of the DC motor, making this circuit ideal for a wide range of applications.


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