routercnc_MK3

[HankMcSpank]

Checked the black wire without resistor and it was 12V (running from 12V supply for now) which means there is a resistor in the sensor and I can't wire it as a simple switch. Used method Clive posted and worked out the value as around 5k ohm

So I can work out the other resistor required to complete the divider except I need to factor in the Bob resistor

Tried to check Bob resistance across pins with multimeter (board was off) and got no reading at all. What is the method to determine this resistance

As mentioned, the BOB input resistance will likely be high ...there's nothing special involved with the measuring method - just check for resistance between the BOB input pin & BOB ground ...powered off is fine. (if you get too high a reading for your meter to detect, then to all intents & purposes the BOB input resistance can be disregarded for the purposes of your 'to be deployed' voltage divider)

What supply voltage do you eventually intend running your sensor with?