Weird fuse issues

[Wildcats1378]

So we were having some trouble with pnematics and such and I noticed that the fuse for the digital sidecar was not Plugged in. I plugged it in, and the signal light (which had not been working) immeditatrly lite up, but the spike relay gave up working. Now, we have the compressor working fine, but only if the digital sidecar does not have a fuse on the powerboard. It wouldnt really pose of a problem except i believe you have to have a signal light during competition.

Anybody have any clues what could be the cause of this anomoly? No one understands why this would happen haha.

[Tom Line]

Can you please explain what you mean by it 'works'?

Does it pressurize and shut off at the correct pressure (around 125), or does it simply keep running? Does it start again when the pressure drops below 80?

The pressure switch should be feeding back to your digital I/O on your digital side car, and the spike that powers the compressor should be fed from one of the relay connectors on the sidecar.

You absolutely need to power your digital sidecar.

[Kevin Sevcik]

Are you certain it's that the Spike isn't working? If you've only tried it using the compressor class, that depends on the Spike and your normally closed pressure switch. It might be your pressure switch doing something funny. Does the compressor ever stop running when it "works" without the fuse in? It should stop when the pressure hits around 110, and it should be electrically "open". It should also be "closed" atpressures below 110.

Since I can't think of a reason the spike would stop working with power, I'm grasping at this straw of the pressure switch, which I vaguely think might read closed by default on an unpower sidecar.

[Cecil]

I am thinking your pressure switch is backwards. One side needs to be hooked to a signal wire, and the other to ground. When the PD board is unpowered, I would guess that the cRIO would read a closed switch.

[Wildcats1378]

Well, what i mean is when the sidecar is NOT powered, the spike works as it should (Compressor starts right away, keeps pumping until whatever pressure ect). But when we plug the fuse in to the sidecar, it no longer pumps at all. Its not full, it should pump up, but it does not.

[Cecil]

The pressure switch is hooked into the digital side car. When the sidecar gets power, all of the inputs are pulled high (getting a positive reading). When the pressure switch hits 120 psi, it opens, and should make contact between a ground pin and a signal pin. When your sidecar is unpowered, it sees this ground anyway, thinking that the system is at 120 psi.

[Al Skierkiewicz]

Wild,
I am guessing that you have the pressure switch wired incorrectly. If you are using a PWM cable (almost everyone does), the switch should be connected to the white and black wire. The red wire (the center of the three) should be cut back and insulated.

[Alan Anderson]

Measure the voltage on the power input connector to the Digital Sidecar. Perhaps you have it wired backwards.

[DavidGitz]

Originally Posted by Cecil

I am thinking your pressure switch is backwards. One side needs to be hooked to a signal wire, and the other to ground. When the PD board is unpowered, I would guess that the cRIO would read a closed switch.

I think the word "backwards" is open for interpretation here. To me it implies that your suggested fix would be to switch the wires from one side of the switch to the other and that would fix it, which is not true as it is a switch.

Wild,
I am guessing that you have the pressure switch wired incorrectly. If you are using a PWM cable (almost everyone does), the switch should be connected to the white and black wire. The red wire (the center of the three) should be cut back and insulated.

Al's wording is much more accurate.

[FrankJ]

Is your pressure switch wired to a digital input on the side car (correct) or in series with the command on the spike (wrong).

The + 12 should go through the spike to the compressor. The negative from the compressor should go directly to the PD board or to the spike. Since the spike connects both outputs to 0V (negative), it is possible to use it as a normally closed relay if it is not wired according to the rules.

[Wildcats1378]

I am not sure I follow. Our pressure switch doesnt have a pwm cord going to DIO.
Now it does not work no matter where the fuse is. And yes, the pressure switch did work in the previous arrangement. It would reach about 120 and then shut off.
Even though it does not work now, if I unplug the fuse while the bot is running the spike will flash green for half a second.

[DavidGitz]

Originally Posted by Wildcats1378

I am not sure I follow. Our pressure switch doesnt have a pwm cord going to DIO.

It should. See R76.

Originally Posted by Wildcats1378

Now it does not work no matter where the fuse is.

You should be using a 20A Circuit Breaker in the Spike for the Compressor.
See R43-D

[Al Skierkiewicz]

Originally Posted by Wildcats1378

I am not sure I follow. Our pressure switch doesnt have a pwm cord going to DIO.
Now it does not work no matter where the fuse is. And yes, the pressure switch did work in the previous arrangement. It would reach about 120 and then shut off.
Even though it does not work now, if I unplug the fuse while the bot is running the spike will flash green for half a second.

I am going to guess from this description that you wired the switch in series with the compressor. The switch is not capable of passing the current needed to run the compressor. It will work for a while but eventually will burn open inside. The switch must be wired to the Digital Side Car so that the compressor will run only under Crio control. You don't have to use a PWM cable but it must be wired to the DSC. Most teams simply use a PWM cable since it is so convenient.