This may (or may not) be the source of the problem.wapcaplet wrote:As far as I can see, it's equivalent to your schematic,
The difference is your schematic has a length of wire common to the motor & sensor circuit.
This is the stretch of wire from where the batt (-) connects to GND and the FET source connects to GND.
I had to think about this for a minute.wapcaplet wrote:measured about 0.1V when Pin8 was off.
With the gate of the FET @ 0-v, the resistance from S to D should be many Meg-ohm. If your meter
has an input resistance of 10M-ohm (typical) then you have a voltage divider with the FET being 1,000M-ohm.
Just to check, put a 100K or 1M resistor across your multi-meter leads and see if the voltage indicated by the meter drops.
You are correct. We just do not want current to the motor be be in the GND ckt wiring to the sensors.wapcaplet wrote:I understand (correctly, I hope) that they need a common ground so that (a) the Gate voltage is relative to Source (to turn on the FET)
I see your photo and will check out the 'Wing Shield' that you are using and see if I can spot a possible issue.
Later, John