Tech Question of the Week:

Q: I have spent a few days trying to get my G201X up and running. I can successfully drive it directly from Smoothstepper (ESS) however not via a few breakout boards.

I have now tried three break out boards that use the Sharp EL/PC817 opto-isolators. After finding out these were possibly not fast enough, I tested a small breakout board that uses the TLP281 without success.

Finally, I built a test board with 6N137 still without success.

Could you recommend a correct/proven circuit to opto-isolate the ESS to the G201X? If you could include the correct input and output waveform/level that would be even better.

A: The G201X is internally opto-isolated on the step and direction inputs (HCPL-2531 hi-speed dual opto) and must NOT be driven by an external opto-isolators.

The step and direction inputs expect 5V logic that can supply 16mA of drive current, Identify the step and direction driver on your breakout board and see if it's 74AC or 74ACT series logic which can provide the necessary drive current, (74LS, 74HC or 74HCT is inadequate for this purpose).

If your step / direction driver is 74AC/74ACT then drive the G201X step / direction terminals directly from the driver IC output pins (bypass any optos that may be connected to those pins). The reason the SmoothStepper worked is because it uses 74AC/74ACT ICs and has no optos on its outputs.

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