I finally have all the components to test the complete electronics board with all 7 stepper motors. And they work!

The top 6 of motors did not have a connector for it, so I had to solder it with a cable I purchased from RepRapWorld (4-wire cable 24AWG, Red Blue Green Black (1m)). But I had to make sure that red and blue should be swapped for these motors from StepperOnline.

Those 6 motors needs 0.4 A so the DRV8825 is overkill, but the motor in the middle right has to rotate the complete base and that one will draw 2A and needs a DRV8825. This DRV8825 heats up a lot and probably needs a fan to actively cool it.

The decision of using DRV8825 is purely based on having swapable modules because they are all the same. And for future projects that can have bigger stepper-motors.

The DVR8825 I purchased from RepRapWorld (€12 no heat sink) but also from Xcsource (10 for €22 includes a heat sink) and they both appear to function very well. But from Xcsource it took 3 weeks to deliver. I was convinced that they would never arrive, that was why I ordered 3 more from RepRapWorld

Next step is the most challenging part. I want all 7 motors to work fluent and fast. I have doubt that the Arduino language is powerful enough. Here I will deviate from the Thor and Danny's project and design my own version.