Re: No auto-resetting fuses on Spikes?
 

In this case I think it's more analogous to our spike scenario to say that we shouldn't bypass/decrease the over temp protection on the jaguar since the fuse seems to be for internal protection of the spike.

I agree with that but unfortunately the rules are the rules. I'm also curious to know how those 20A snap actions typically behave above 20A. The data sheet gives a huge range...

Re: No auto-resetting fuses on Spikes?
 

the robot moves with the safety enabled. And when the joystick moves forward and back one light is green the other red. When turning left both lights are red and when turning right both lights are green. They were a solid Orange when enabled but not moving. The lights still flash orange when not enabled. Is that okay?
Otherwise I would like to thank everyone for there help in fixing the problem!

Re: No auto-resetting fuses on Spikes?
 

That's perfect. I think you might be in the wrong thread, though.

Re: No auto-resetting fuses on Spikes?
 

I, too, have always been puzzled by why the auto-resetting circuit breakers are permitted in the PDB, but not in the Spike. In all honesty, I don't recall ever hearing an explanation that satisfied my curiosity.

Does anybody really *know* why the rule is there, rather than just speculating as to why they think it is there?

I've heard all kinds of rumors, but still don't feel that I've really heard *why* from somebody who had inside knowledge of the reasoning used by the authors of the rule.

One "rumor" I have heard is that snap-action auto-reset breakers are not allowed in the Spike as the wider terminals of the auto-reset breaker (as compared to a standard automotive fuse) bend the Spike terminals out slightly, leading to problems when a standard automotive fuse is later used.

I do understand the difference in the two above cases. Clearly, the "single trip" breaker provides better protection.

However, if better protection is the goal, why are auto-reset breakers allowed in the PDB? Does the PDB respond to the presence of an auto-reset breaker differently than the Spike does?

I am particularly seeking to understand why it is okay to use auto-reset breakers in the PDB but not in the Spike.

Re: No auto-resetting fuses on Spikes?
 

Not really, the self resetting circuit breaker in effect becomes a current limiting device.

Helping other teams troubleshoot problems I've seen circuits that were shorted and were causing rapid cycling of the breaker and I've not seen damage to the wire, which is the purpose of a circuit protection device.

On automobiles self resetting circuit breakers are often used for items that are considered mission critical like headlights and wipers. While I've seen shorts in those circuits and people driving them for extended periods of time with the breaker cycling I've not seen damage to the wire other than what was causing the short.

Re: No auto-resetting fuses on Spikes?
 

The idea that the fuse is there to protect the wire is really a building code & utility wiring kind of thing. On the equipment level (robot) your fuses or other current protection should be there to protect the equipment in addition to the wiring.

Current rating of relays have two components. 1) How much current can you have & reliably open the contact. 2) The need to have a very high number cycles until failure.

Re: No auto-resetting fuses on Spikes?
 

Everyone,
R65
E. If powering the compressor, the fuse on a Spike H-Bridge Relay may be replaced with a 20A Snap-Action circuit breaker.

No other provision is stated.

The Spike can handle short high current loads but as pointed out, the contacts in the relays will be damaged above the design currents particularly with the inductive loads provided my motors. The arcing that takes place can (and often does) welds the contacts together making it impossible to disable motors from the field when commanded. The Spike contains a fuse to protect the contacts, the resetting breaker can easily pass damaging current before trip and will immediately reset.
The compressor presents a 25+ amp load during start but rapidly returns to about 12 amps max run current. If you use the supplied fuse on a compressor it is only a matter of time before the fuse will open. I predict it will occur in your last match in the finals when you need the most. (Al's Fuse addendum to Championship Murphy's Law.)
The FETs in the Victors are rated for 40 amps each provided the junction temperature remains in a specified range. There are three in parallel for a total of 120 amps. This is a conservative rating so under the right conditions, they are easily capable of short currents well above that. They cannot reduce the junction temperature with the fans supplied so eventually a stalled CIM will damage them.
The FETs in the Jaguars and the Talons are different and have different ratings and operating parameters. In the Jaguar, the internal fault checking will shut down the output of the Jag for low input voltage, high internal temperature or currents above 100 amps that last longer than 0.2 sec. In general the internal fault checking is to try to prevent damage before it occurs. Mike can relate the parameters for the Talon. Soon we will all see for ourselves how these new devices act in the harsh FRC environment.
The breaker current rating is indeed tied to the current rating for the wire size. The wire table and breaker size are taken from the NEC for open frame, non-bundled DC wiring, used in intermittent duty (based on 2.5 minute, non-continuous operation). If smaller wire is used with a given breaker, overheating of the wire may result, causing melted insulation, the possibility of shorted conductors and therefore smoke or worse. While the rules are meant to prevent this activity, we still see it occur from time to time.