Stepper Motor Driver Using MOSFET

This stepper motor driver uses four identical n-channel MOSFETs. You could use something like a HEXFET from the IRFxxxN series, which also has built-in protection diodes. The centre tap of each coil connects to the +12 V rail, whilst each MOSFET simply provides a path to ground for each half of the coil. This circuit has four individual inputs that will require the correct switching logic circuitry.

Each MOSFET has a 100 kΩ resistor between the gate and ground thereby keeping it pulled LOW. A positive voltage at the gate from logic circuitry causes the MOSFET to conduct, producing a flow of current through one-half of the coil.

The value of resistor R in the diagram depends upon on the load handling specification of the motor. You will need to refer to the documentation of your component to determine the best value.

This driver part will also require the logic circuit to generate the correct sequence of coil energising, and in addition, a square wave generator for the logic circuitry. All of these circuits are in the following pages of this multipage article.

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Stepper Motor Driver Using MOSFET
Stepper Motor Logic Circuit
555 Variable Oscillator Circuit