If a customer must use a single ended Step/Direction signal to control the drives, we recommend the GC-SDA as the interface between their control signals and the drive I/O connector. It plugs right onto the Drive I/O (50 pin) connector and provides screw terminals for their connections from the single ended signals. The GC-SDA provides optical isolation to help with noise issues.
Note that our recommendation is to always use a differential signal. The inputs are designed as differential. They are very susceptible to noise when they are NOT differential.
However, the GC-SDA will provide a solution for those customers that can't use a differential signal. Using the GC-SDA does not provide a way for the cable shielding to be continuous all the way up to the drive, nor will it allow them shield to be bonded to the drive's connector shell. It will be more susceptible to noise than our high end CE cables because of that. The optical isolation will make it better than the GC-50 though.
Also note that not every signal input or output available on the Gemini's drive I/O connector is available on the GC-SDA. It was primarily designed for use with the GT (stepper drive only, as compared to the programmable GT6 or GT6K).
The GC-SDA was obsoleted Nov 1, 2013 and is no longer available.
Related FAQ: GC-SDA Fault output is not really the fault output
Wiring Gemini with Single Ended signals (without the GC-SDA):
Do not connect anything to ground. Connect the OV or GND side of the input to Digital Ground. Connect the Step signal to the Step+ of the Gemini.
If you measure across the Step+ and Step- with nothing connected, you will measure a 2.5V difference. When wiring it with a single-ended input, the Step will go above 2.5V and this will be a 5V (high) signal out of the comparator. When it goes below 2.5V, this is a 0V (low) signal out of the comparator.
Note, the GC-50 had been discontinued but we did a last time buy and now have them for a limited time (until that inventory runs out).
Long term after that, we also offer a 50pin screw terminal breakout that can be mounted on din-rail that includes a 2-foot cable to connect to the Gemini:
We also offer 50 pin to flying lead cables, to run the cable back to the controller/PLC:
Gemini Cable Part Numbers & Descriptions
Or if you wanted to source your own, the Drive IO connector manufacturer part number for it and the mating connector is listed in the GT Hardware Installation Guide:
71-018850-01 was the printed circuit board part number on the GC-SDA. Adding this number as reference. The entire assembly with the connectors was GC-SDA and was the part number when ordering.