Compressor blowing spike fuses or melting spikes

[de_]

We are running our compressor hard (ie pretty well continously during a 2 minute game). We blew 2 - 20 amp fuses in the spike, melted a connection terminal off a spike pcb and I believe killed a spike outright over the weekend.

The compressor is rated at ~10 amps. I could not find its rated duty cycle but I would hope it is good for 2 minutes. We will change to a breaker but we are concerned it is apparently drawing so much more current than its rated 10 amps. We do realize starting currents with a 100psi back pressure may be significant. We did increase the supply wire size to 12g to reduce voltage loss.

Anyone know of
1) compressor infant mortality failures ?
2) any material benefit to add a cooling fan (its got one built in side I believe)
3) what its duty cycle rating is ?
4) what could its startup current be when it restarts at 100psi (as opposed to starting with no back pressure) ?

[EricH]

Originally Posted by de_

We are running our compressor hard (ie pretty well continously during a 2 minute game). We blew 2 - 20 amp fuses in the spike, melted a connection terminal off a spike pcb and I believe killed a spike outright over the weekend.

The compressor is rated at ~10 amps. I could not find its rated duty cycle but I would hope it is good for 2 minutes. We will change to a breaker but we are concerned it is apparently drawing so much more current than its rated 10 amps. We do realize starting currents with a 100psi back pressure may be significant. We did increase the supply wire size to 12g to reduce voltage loss.

Anyone know of
1) compressor infant mortality failures ?
2) any material benefit to add a cooling fan (its got one built in side I believe)
3) what its duty cycle rating is ?
4) what could its startup current be when it restarts at 100psi (as opposed to starting with no back pressure) ?

Have you replaced the Spike's fuse (yellow) with a 20A breaker (black box marked with "20A")? If not, that may be the problem. Startup current is, I believe, 25A, which would blow a Spike fuse pretty quickly. NOTE: Only do this on the compressor Spike, where is is explicitly permitted.

[TubaMorg]

Also make sure you are absolutely certain you aren't running your compressor backwards.

[falconmaster]

I know is sounds funny, but try a different brand of yellow fuse. We kept blowing them too. We switched brands and it stopped.

[Racer26]

The compressor can and will blow the 20A ATO fuses. Many teams have experienced this, including since this season, my own. Also, when under strenuous operation the compressor CAN get VERY hot. Be sure to remember this when working on your robot in the pits, burns are no fun.

I haven't however, heard of the compressor killing spikes.

[Joe Ross]

Originally Posted by falconmaster

I know is sounds funny, but try a different brand of yellow fuse. We kept blowing them too. We switched brands and it stopped.

<R67> disallows modifying the spike relay modules in any way, except for replacing the fuse with a snap action circuit breaker. I think your different fuses are illegal, but it should be easy to swap with a 20A circuit breaker.

[Aces]

my team blew 3 or 4 of the supplied fuses, so we bought a pack of identical 20Amp automotive fuses from Pepboys, haven't blown one of them yet.

[Daniel_LaFleur]

Originally Posted by de_

We are running our compressor hard (ie pretty well continously during a 2 minute game). We blew 2 - 20 amp fuses in the spike, melted a connection terminal off a spike pcb and I believe killed a spike outright over the weekend.

The compressor is rated at ~10 amps. I could not find its rated duty cycle but I would hope it is good for 2 minutes. We will change to a breaker but we are concerned it is apparently drawing so much more current than its rated 10 amps. We do realize starting currents with a 100psi back pressure may be significant. We did increase the supply wire size to 12g to reduce voltage loss.

Anyone know of
1) compressor infant mortality failures ?
2) any material benefit to add a cooling fan (its got one built in side I believe)
3) what its duty cycle rating is ?
4) what could its startup current be when it restarts at 100psi (as opposed to starting with no back pressure) ?

In answer to your 4 direct questions:
1> I haven't heard of any failures, and compressor technology hasn't changed much in the last 10 years so it should not happen.
2> Adding a cooling fan will do little for the compressor in a FIRST type enviroment.
3> 100% duty cycle.
4> Startup current can exceed 25 Amps.

The rules specifically allow you to change out the fuse for a 20 amp snap action breaker (for the compressor spike only!), and I suggest all teams do this.

I have not heard of a compressor damaging a spike, are you sure that the spike was not wired incorrectly? Wiring the spike backwards (battery to motor side) will kill a spike.

@ Aces,

Make sure it's the EXACT same fuse, not just any old 20 amp automotive fuse, as you will be in violation of <R67> if it's not exact.

[Al Skierkiewicz]

If you are running a compressor and still have fuses in the Spike, they will blow, guaranteed. Start current on the compressor is 25 amps and run current somewhere between 10 and 12 amps. Change to a 20 amp circuit breaker. The fuse will fail and Murphy's Law states that it will occur in a finals match.

Running continuous for a two minute match will get the compressor hot but not enough to cause any harm or damage. Remember that the compressor end is getting hot from compressing air. Make sure that you have the compressor connected properly. It will still work going backwards but will not be as efficient.

The damage to the Spike terminal was likely caused long before you applied power to the compressor. These terminals are press fit into the circuit board and then soldered. They are not designed for significant stresses (up and down is very bad) when inserting or removing the Faston crimp connectors. A bad joint at high current will cause local heating which raises the temperature of the joint and makes the contact even higher resistance.

Just to be sure, is the compressor running continuous by design? (i.e.multiple large cylinders) Is it under RC control and does it shut off at 125 PSI or less when you are not running the robot?

[IndySam]

We were having a lot of trouble with ours. We replaced 3 20a breakers on the spike.

We decided to replace the spike and in examination we found that the power connection on the spike had come loose.

Since replacement we have not had another failure.

[MegaSparks]

We had the same issue and we measured the current draw of the compressor during normal use and found that at 0 psi it drew 5-6 amps going to 11-12 amps at 100 psi. The inrush current when the compressor starts at 95 psi to recharge the system is between 23 and 26 amps. The interesting thing is we are blowing fuses when the system is starting at 0 psi where the inrush or stall motor current is less than 20 amps. We will be running the compressor with a 20 amp resetable breaker in place of the 20 amps fuse in the spike relay for all competitions, just because of Murphy. I have taken measurements on last years compressor as well and have found the two to be very similar, but not identical. This may be just variances during the manufacturing process. The fuses used last year are the same as this year as well.
I would advise everyone to replace the fuse in the spike running the pneumatic compressor with a 20 resetable breaker, it is the only way to fix this issue and stay compliant to the rules.

[ayeckley]

My strong recommendation is to use the breaker rather than the fuse. As many others have stated, this is permitted by the rules. There is no down-side to it. It's a no-brainer, which is a rare treat in FRC world.

We didn't find out this was legal until the Championship event last year. I wonder how well we would have done if we'd realized it sooner .

Our plan is to track down all of the rookie teams at our regional events and make sure they understand the importance of doing this, as an illustration of GP.

[de_]

Thanks Everyone.

I sounds like FRC should just make it a rule that the compressor has to use a breaker and that 12 gauge, not 18 guage wire should be used.

I'm still somewhat concerned that in one case the case of the spike melted where the output terminal goes into it and the output terminal was desoldered from the spike pcb. One possible explaination is that high (excessive) currents led to heating in the push-on terminal that led to the metal softing reducing the contact pressure leading to increased resistance leading to more heat...
But the plastic insulation showed no heat damage so it sounds more like a weak solder joint on the pcb.

Out of spec excessively tight clearance between the compressor piston and cylinder wall could increase current draw but since nobody else has seen this and since the compressor seems to be starting and running fine, that doesn't look likely.
I will measure the current the next time I see the robot. I just ran out of time. Thanks again everyone.

[R.C.]

just replace the fuse with a 30 amp one and that will do the trick, we had the same problem

[Ricky Q.]

Originally Posted by rc_cola1323

just replace the fuse with a 30 amp one and that will do the trick, we had the same problem

Sorry, that would be illegal.

The only allowed modification is to replace that fuse with a 20A Snap-Action breaker, and it is highly suggested to do so.

From <R67>: The control system is provided to allow wireless control of the ROBOTS. The Operator Interface, Robot Controller, speed controllers, relay modules, radio modems, batteries, battery charger, AC adapter, and 9-pin cables shall not be tampered with, modified, or adjusted in any way (tampering includes drilling, cutting, machining, gluing, rewiring, etc.),
with the following exceptions:

...The fuse on the Spike relay for the air compressor may be replaced with a 20 Amp Snap-Action circuit breaker...