How to wire pneumatics

[ZInventor]

remember to swap the 20 amp fuse for a 20 amp breaker, otherwise, you'll find yourselves running through fuses like popcorn...

that's what happens then FIRST requires you to run a 40amp compressor through a 20amp fuse...

it's not a problem during competition matches, but if you ever have the compressor running more than once in a period of five to ten minutes, it'll pop the fuse... however, oddly enough, the breakers don't seem to have the same problem...

remember, the pressure switch is on-off, and does NOT tell you the pressure in PSI...

the way we (mechanical pandas) explained it to the control team is that, if poer can flow through the pressure switch, turn on the compressor, if power can't flow, turn it off...

i know, you're probably asking "why dont we just run the compressor directly through the pressure switch" well, it's because FIRST says so...

Originally Posted by FIRST Pneumatics Manual Rev B Page 3

Do NOT put the pressure switch in series with the power supply to
the compressor.

I added the emphasis...

Originally Posted by FIRST Competition Manual, The Robot Rev H, Page 29, <R77>

The Nason pressure switch must be connected to the high-pressure side of the pneumatic circuit (i.e. prior to the pressure regulator) to sense the “stored” pressure of the circuit. The two wires from the pressure switch must be connected directly to a digital input and ground port on the Digital Sidecar, and the cRIO Mobile Device Controller must be programmed to sense the state of the switch and operate the relay module that powers the compressor to prevent over-pressuring the system.

-Z

[Al Skierkiewicz]

Originally Posted by ZInventor

remember to swap the 20 amp fuse for a 20 amp breaker, otherwise, you'll find yourselves running through fuses like popcorn...

that's what happens then FIRST requires you to run a 40amp compressor through a 20amp fuse...-Z

Z,
The compressor has a start current of 25 amps and run current of 12 max.

[ZInventor]

Originally Posted by Al Skierkiewicz

Z,
The compressor has a start current of 25 amps and run current of 12 max.

really? we measured it at 40 when it was getting close to 110 psi... or if it had to run for more then 30 seconds at a time...

also, we popped several 20 amp fuses, which shouldn't have popped if it only went to 25 at start-up.

-Z

[Alan Anderson]

Originally Posted by ZInventor

also, we popped several 20 amp fuses, which shouldn't have popped if it only went to 25 at start-up.

Um...25 is greater than 20. A 20 amp fuse is supposed to blow in that case.

[ZInventor]

[Q

Originally Posted by Alan Anderson

Um...25 is greater than 20. A 20 amp fuse is supposed to blow in that case.

usually, it'll take a second or two of high amperage for these fuses to blow...

we checked everything, and it's fine, the compressors we've used for the past 3 years have all done it too...

i don't know why, and we've never had any issues...

-Z

[Vikesrock]

Originally Posted by ZInventor

Usually, it'll take a second or two of high amperage for these fuses to blow...

This is about right, at 25A a 20A fuse will likely take a second or two to blow. The Snap-Action breakers on the other hand take a minimum of 6 seconds and potentially much, much longer to trip at that level. The testing spec for the breakers is to trip in under ten minutes at 135% of rated current.

If your compressor was actually drawing 40A your 20A breaker should have lasted about 2.5-6 seconds before tripping.

[Al Skierkiewicz]

Originally Posted by ZInventor

really? we measured it at 40 when it was getting close to 110 psi... or if it had to run for more then 30 seconds at a time...
-Z

What did you use to measure that current? It sounds like something was wrong with your compressor. A rising current with heat could be an indication of damaged internal wiring. Also, this pump does get hot when running in the wrong direction and it does build pressure but very ineffeciently.