awkwardbunny / stepper

Driving a stepper motor with an arduino and MOSFETs

stepper

Driving a stepper motor with an arduino and MOSFETs

Quick story time! (skip to next section if not interested)

Before I had to do my last few assignments as a senior in college, I was procrastinating and wanted to do a random project. I had an idea, which involved pulling out the read assembly that slides back and forth.

So I took some old drives and stripped out a few.

To move the read assembly, the stepper motor needs to be driven. However, I had no stepper motor driver nor H-bridges ready. So I built some and wrote this code to drive it.

The motor has four connections and is two-phase bipolar, meaning two coils and per wires per coil.

Circuit & Connections

AA, AB, AC, AD goes to the first H-bridge that controls one coil inside the motor. BA, BB, BC, BD goes to the second H-bridge that controls the other coil inside the motor.

AA and AB are the high side, AC and AD are the low. For example, to set output of the H-bridge one way, A and D should be on, B and C for the other way.

The circuit just has 4 MOSFETs in the most basic H-bridge configuration. This is probably not as good though(?) FET A and B are PMOS FETs (I used IRF9450)
FET C and D are NMOD FETs (I used IRF450)

One phase of the stepper motor is connected to the two outputs of the H-bridge.

This was repeated for the other coil/phase of the mototr.

Code?

The transistors are switched on and off to run the stepper (obviously).
I drew a similar table:
A B C D 1 0 0 0 0 0 1 0 0 1 0 0 0 0 0 1

Turning those on at that sequence should turn it one way, reverse the order and it should turn the other way.

Also, the A B FETs are PMOSs, so the logical trigger level should be opposite the trigger voltage level. For example, I want to turn A on, then I should output LOW. But if I want to turn C on, I should output HIGH.

Ya so that worked.