I've a Proxxon Micromot drill. I'm planning to attach it to the plotter as replacement to the pen, to be able to do some light cuts.

For this I don't want to use it's original power supply unit. As the speed control is located in the power supply I wanted to know it's properties:

• How the motor driven? Pure PWM or filtered to DC?
• What is the PWM frequency?

To measure this without disassembling, not looked like an easy task. The reason is that Proxxon uses a proprietary connector, what is not available on the market. So I measured the diameter of the pins and looks like with two 2.3mm drill bit I made it:

The measurements:

Without load:

At minimum speed:

At maximum speed:

It is a bit noisy to my taste and figured out that it runs at 100Hz and not really filtered.

Based on this I can design the new electronics into the plotter.