Re: Started new OnStep hardware design


Yes external drivers, no not like the one you linked. That is a servo driver, anything servo either ac or dc servo is a bit more expensive.

LV8729 -  Amazon $7, Ebay $8. Limited to 0.8 amps cont, peak 1.5ams
TMC2130 - Amazon only listing 2208 and Ebay $11 each  Limited to 1.4amps cont, peak 2amps

TB6600 stepper driver Amazon  $11, It will run Nema 17 and 23 Stepper Motors, 9 to 40VDC and 3.5amps cont 4amps Max  Amazon

Here is a stepper driver combo, 4amp driver and nema 17 motor $20 Amazon driver and motor

If you shop around even better deals to be had on ebay or ali express.

I have used steppers both open and closed loop on cnc machines from vertical mills, router tables, lathes and plasma cutters. I can get them within .001 repeatable accuracy. Perfect smooth lines and cuts. Accuracy and smoothness that the telescope mount will need in tracking and goto. Micro steps from 1/4 all the way down to at least 32 is available on most drivers. The ones I have about about $22 apiece and go all the way down to 256 micro steps.

You save time soldering and cost of components with board made for running external drivers. Using my MaxSTM is overkill. Realistically almost half of the board and components are used with just picking up the 3 pins for each driver. I know i will only save about $20 on single electrical components, but as far as drivers and steppers it breaks even.

The biggest saving is in time. Probably at my speed I will save about 4 to 6 hours in setup and soldering time not having to install about half of the sockets, caps, resistors and sockets that are not going to be used by using external steppers.

When I am done with the new board and have one sitting here. I will post real time assembly and list the total cost and BOM for a direct comparison.

David Mikesell
San Jose, CA

Join to automatically receive all group messages.