pic: How we cool our compressor

[eshteyn]

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[eshteyn]

This is not a joke this is really the configuration of our compressor.

[Xenozero]

Wow, that looks "cool" lol. quick question, today after my team was doing some neat re-wiring our compressor would not go on, after rigorous checking with the multimeter, the pwm cable leading to the compressor practacly exploaded, and the black cable was the only one that melted like crazy, do you think it happend because of how hot the compressor gets, or of some other reason.

[Alan Anderson]

Originally Posted by Xenozero

...the pwm cable leading to the compressor practacly exploaded, and the black cable was the only one that melted like crazy,...

That might happen if the connector got plugged in wrong on the RC. If you are off by a pin, the black can might be connected to +5 on one end and ground on the other.

[eshteyn]

Thanks for the cool comment, lol. The first thing i would say is that the compressor should be hooked up with at least 18 guage wire, i used 14 to wire our compressor. Also electricity is the flow of electrons, which are negatively charged. They flow from positive to negative, and since the black wire is the negative thats why it melts. Also if you wire your compressor and it doesn't turn on but just melts the wire then you probably have a bad compressor or something has jammed in the motor causing the charge to build up and melt the wire. If you have more questions im me at etakto738

[Xenozero]

cool, thanks everyone

[Doug G]

Originally Posted by eshteyn

Also electricity is the flow of electrons, which are negatively charged. They flow from positive to negative, and since the black wire is the negative thats why it melts.

I can't help myself... There's a couple of things about this statement that bothers me and so I felt a teaching moment coming on ...

1) Electrons absolutely flow; but from negative to positive. Unfortunately the definition of "current" is the flow of positive charge (even though no positive charge carriers are flowing in these circuits, thank those dudes from the 1800's for defining current before they knew the existance of electrons), and thus we say current flows from positive to negative. This is a commonly misused/misunderstood concept. 2) The current in the black wire is no different than the current in the red wire and no different than the current in the motor windings inside the compressor. It is a series circuit (red wire --> Compressor --> black wire) and thus the current flow must be the same everywhere (conservation of charge). Perhaps the black wire melts first because it's insulation can't stand the heat and/or it is a higher AWG than the red wire resulting in more heating (I^2*R)?

[Adam Y.]

Originally Posted by Doug G

I can't help myself... There's a couple of things about this statement that bothers me and so I felt a teaching moment coming on ...

1) Electrons absolutely flow; but from negative to positive. Unfortunately the definition of "current" is the flow of positive charge (even though no positive charge carriers are flowing in these circuits, thank those dudes from the 1800's for defining current before they knew the existance of electrons), and thus we say current flows from positive to negative. This is a commonly misused/misunderstood concept.

This isn't entirly correct either. You have a positive charge flowing in a circuit. The correct term to describe this is holes. Holes move from positive to negative in a circuit. In reality it doesn't really affect anything in this example but once you get into semiconductors you get devices in which depending on how they made primairly move one type of charge (Holes or Electrons).

[billbo911]

Originally Posted by Xenozero

Wow, that looks "cool" lol. quick question, today after my team was doing some neat re-wiring our compressor would not go on, after rigorous checking with the multimeter, the pwm cable leading to the compressor practacly exploaded, and the black cable was the only one that melted like crazy, do you think it happened because of how hot the compressor gets, or of some other reason.

Last night we melted down a PWM cable. It had backed out of the connector on the Victor it was attached to. Then the ground (Black) pin slipped into the lug on the +12 volts feeding the Victor. POOF!!! +12 volts to ground made a LOT of smoke!!!
We were so glad that we had not fried the RC nor anything else for that matter.

[Andrew Blair]

Originally Posted by billbo911

Last night we melted down a PWM cable. It had backed out of the connector on the Victor it was attached to. Then the ground (Black) pin slipped into the lug on the +12 volts feeding the Victor. POOF!!! +12 volts to ground made a LOT of smoke!!!
We were so glad that we had not fried the RC nor anything else for that matter.

It seems like those cables are magnetically attracted to the Victor power leads. Last year I did the same thing, and I seem to remember another team telling me they did it as well. Scary stuff.

Make sure all cables and power leads are hooked up correctly polarity wise, and when they are right, make sure they're tight! It'll save you alot of headaches later.

[woody]

Originally Posted by Andrew Blair

It seems like those cables are magnetically attracted to the Victor power leads. Last year I did the same thing, and I seem to remember another team telling me they did it as well. Scary stuff.

Make sure all cables and power leads are hooked up correctly polarity wise, and when they are right, make sure they're tight! It'll save you alot of headaches later.

On the subject of PWM's coming loose, it is a good idea to put a blob of RTV silicone sealant (only a couple bucks at just about any hardware store) on all PWM connections. It holds them in place, but if you really need to get it off it can be peeled off with relative ease.

[eshteyn]

Originally Posted by woody

On the subject of PWM's coming loose, it is a good idea to put a blob of RTV silicone sealant (only a couple bucks at just about any hardware store) on all PWM connections. It holds them in place, but if you really need to get it off it can be peeled off with relative ease.

We use hot glue, works perfectly

[Alex Minot]

to be honest with you....that is really not necessary. The compresssor is built to perform.....so it is inevitably going to get hot...but it is supposed to do that. We run our test board with the compressor and we push that little thing pretty hard, it gets so hot you cant touch the top but its fine. And the match is very short, only a few minutes, so the compressor will only be on a max time of the match time, which is pretty brief, but still very demanding of the compressor. If weight is an issue for you guys, i would consider removing that.

[Mike Hendricks]

Originally Posted by Alex Minot

to be honest with you....that is really not necessary. The compresssor is built to perform.....so it is inevitably going to get hot...but it is supposed to do that. We run our test board with the compressor and we push that little thing pretty hard, it gets so hot you cant touch the top but its fine. And the match is very short, only a few minutes, so the compressor will only be on a max time of the match time, which is pretty brief, but still very demanding of the compressor. If weight is an issue for you guys, i would consider removing that.

I'm going to agree with that. Just seems like a waste.

On a side note (in the past) COTS fans have been considered motors and are illegal. I looked around the Q&A and didn't find anything, so you might be okay, but don't be surprised if you fail inspection at your event(s) and have to remove it.

If your compressor gets too hot to the point of where you need a heatsink after running it for 2 minutes (or less) then something is probably wrong with your compressor. Our pneumatics demonstration board has ran for several hours straight before when the programmers were working with it .. and the compressor got warm/semi hot to the touch, but nothing worth being concerned over, and nothing that could cause any burns or raise any safety concerns (although common sense is a different story)

JMHO

[sanddrag]

if the compressor is running in reverse, it will still work but not as well and it will get very hot very quickly. you might want to check that it is running the right way.