I breadboarded a new design for the OnStep design. It will have all the functions of the MaxSTM but no stepper drivers and using a standard wall 5VDC adapter.
When you start looking at the prices for the 3D printer drivers it becomes apparent (example TMC5160 @ $50 each) that there are alot more options that I am familar with that are indeed cheaper and can do the same if not better.
Standard Stepper drivers and closed loop stepper drivers that i am used to using in building cnc equipment are cheaper, and include microstepping. You actually have more options for price and functionallity there. A big bonus if you have a large telescope or heavy telescope and mount it will allow the OnStep that Howard Dutton designed to continue to be used by the ATM guys at reduced cost compared to the other system out there.
Anyway here are some pics of the simple layout and parts on a breadboard. I will use terminal blocks for stepper driver connections. it works like a charm. Howard has done a great job with OnStep. I just need to modify some more code that allows other stepper drivers and a different or additional way to calculate gear ratio or type of drive with ratio inputs.
Thanks Howard for putting the design out there. My MaxSTM works great.
San Jose, CA