G540 Input/s Resistance Threshold

[CL_MotoTech]

What resistance threshold disqualifies a closed circuit on an input? As I understand it the inputs only measure an open or closed state.

The reason I ask is because I was using a solid state relay as a trigger across an input and even in it's closed state it seemingly had too much resistance to trigger an input in Mach3.

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[john-100]

what solid state relay did you use ?

some are designed to switch DC and others AC

the G540 input terminal is connected a LED ( within a ILQ74 optoisolator ) and a series connected 2200 ohm resistor
the resistor limits the current the LED takes from a 12V supply when the input is grounded

I expect the voltdrop across a SSR designed to switch AC mains voltages will be too large and limits the G540's input current

John