Today at our warmup day for one of the MAR FRC competitions, we ran into a major issue; our compressor won’t turn on.
While this may seem like something simple at first, we are having massive troubles being able to get it back on. When we left our shop, our robot worked flawlessly, compressor and all. When we get to the competition, suddenly whenever we enable the robot, the compressor won’t turn on. Literally nothing has changed on the robot.
We narrowed it down to the fact that the spike relay wasn’t receiving any signal to turn on, but from there we are stuck. The code worked previously and hasn’t been modified, we swapped out the ribbon cable, spike relay, cRIO cartridge, and digital sidecar, but nothing can seem to get it to turn on, with the exception of the extremely brief moment when you plug the ribbon cable into the digital sidecar while enabled. Does anyone have any advice or input? We all would really appreciate it.
Which compressor are you using? If you are using the small compressor (the one without casing), check the resistance between the leads and the casing (power to casing and ground to casing) against one fresh out of the box. I don’t remember the specific value, but if it’s significantly lower than your compressor has gone bad. We had the same problem yesterday.
Start with the relay light on the digital side car where your PWM is connected. Is it showing either side on?
If it is, then you have a problem downstream of the digital side car. Because the compressor blips when you plug it in, that would suggest that it’s not the breaker or the spike itself. Which leads you to the PWM. To further isolate the issue, is the light on the spike changing? What is its status?
Since we’re 8 posts in and everyone has missed this obvious bit:
Have you tested your pressure switch and the cable coming from your pressure switch? The compressor won’t run without a closed contact on the digital input for the pressure switch. So do this:
Make certain the cable for the pressure switch is plugged into the correct digital IO AND the correct way.
Short out the terminals on your pressure switch with a screwdriver or something. If the compressor runs, your switch is bad.
If 2 doesn’t work, find a known good PWM cable, plug it into the pressure switch digital IO, and short the white and black pins together. If the compressor runs, either your pressure switch cable is bad, or the connection from the cable to the pressure switch terminals.