[Alan Anderson]

What do you mean by "does not recognize start"?

The compressor should be connected to the M+ and M- on a Spike relay module. The fuse in the Spike should be replaced with a 20A snap-action circuit breaker. The Spike's three-wire control cable (it's the same as a PWM cable, but it isn't actually carrying PWM signals in this case) should be connected to one of the relay outputs of the Digital Sidecar.

The pressure switch should be connected to the white (SIG) and black (-) wires of another PWM-style cable, with the red center wire (+5v) taped off and not connected to anything. The other end of the cable should be connected to one of the DIO inputs of the Digital Sidecar.

The compressor object should be initialized with two numbers, telling it which Relay port and which DIO port you have wired things to. When you call the Start() method (and enable the robot), the compressor should run when the pressure switch indicates that the pressure has fallen below 90 PSI and has not yet reached 115 PSI.