I'm using Mach3 to bypass the onboard RS232 controller in a chinese router. I hoping to use the existing opto interrupter home switches (as well as the XY drivers, XY steppers etc). The breakout board I have has 10k pullup resistors on the inputs which are wired straight to the port pins.

If I wire up one of the opto interrupters like this:



I can see it working in Mach. But that seems way too simple. Am I going to fry anything if I run it like this?

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Jon

Hi, Jon

Should work fine, Printer Port/Mach3 is looking for the 0 or 5 volt's,  Over 5 volt's can damage the p/port.

Chip

Yoiu may find the 5 volt pull up resistor on the input is too much. Most ports already have 5 volt internal pull up resistors.

I use much the same circuit for my rev counter but it didn't work at first. I soon found the input was never pulling down to zero (or close enough for the computer to register it). I removed the external pull up resistor (the opto does not need it) and it works fine.

In this case perhaps, miss out the breakout board and wire the input straight to the computer.