The first version of my stepper motor controller could only handle current up to 2A per motor coil. The motors i used can drain up to 4A depending on the voltage given to the motors. The first version of my stepper motor controller thus just burned Frown .

I decided to build a more powerful version using MOS-FETs. Those small parts can handle enormous current but need a driver (see also the h-bridge section).

The idea was to build a MOS-FET output stage which is compatible to the output stage from the 1st version.  Unfortunately this couldn't be achieved. Due to space limitations i could only get one stepper motor, which consists of two separated h-bridge, on one board.

The eight N-channel MOS-FETs are mounted from the lower side to be able to mount them on a heat sink. There are also two fan connector to be able to  add fans for cooling the heat sink. Both shouldn't be necessary for N-channel MOS-FETs with small RDs_on. I will first take irfz34n (RDs_on = 40mΩ) for testing but maybe later switch to irfs44n (RDs_on = 17.5mΩ)

The current through each coil is measured using an op-amp and is then fed to the microcontroller board.

The controller board is shown in the next image

I will post the schematic and the source code as soon as i did some further tests.