Read -5V Signal with Microcontroller
You can use this circuit to change the level of your -5V signal to something that can be read by the micro controller.

This circuit will give a logic high (+5V) output when the input is not connected or a small negative voltage.

If the input is -3V or more the output will be a logic low.

kevin







simulate this circuit &ndash; Schematic created using CircuitLab