Re: Keeping the main breaker from tripping
 

To clarify, I don't think anyone cools their breaker to keep alive...they (or at least we) just do so in order to not start with an elevated temperature due to short match turnaround. An elevated temperature means your breaker will trip under lower current draw than a room temperature breaker.

Re: Keeping the main breaker from tripping
 

I doubt FIRST would rule it's use illegal because it modifies performance of the item being sprayed.
That said, I definately believe they might ban it's use for health reasons.

Dust Off is difluoroethane, a refrigerant.

Here is the "Safety" text from Wikipedia on difluoroethane.

Re: Keeping the main breaker from tripping
 

It keeps the 40 amp breakers from tripping. By switching from 4 to 6 cims with a single speed the current gets divided through 6 40 amp breakers instead of 4 40 amp breakers. Thus you can push with a higher gear ratio and have decent enough speed to move around the field.

Re: Keeping the main breaker from tripping
 

Shouldint we be trying not to draw more current than the system is supposed to handle rather than stop a safety mechanism from activating? Like turning of a smoke alarm rather than putting out the fire?

Re: Keeping the main breaker from tripping
 

On this note, when I went in to buy some compressed air recently to use on our robot between matches, I needed to show my ID upon purchase. When I asked the clerk why out of curiosity, she replied that "people must be huffing it or something like that."

Re: Keeping the main breaker from tripping
 

I had to show ID to purchase a can of air (to be relabeled as "magic smoke" as a gift for a mentor) as well at a store that will not be named but whose logo is a bullseye. I wasn't yet 18 at the time so they wouldn't let me buy it after seeing my ID. I explained to my dad that canned air "used to be the way teenagers would get high" and then made him go to T**g** and buy it for me.

Re: Keeping the main breaker from tripping
 

But if you gear for like 12 fps anyway, why not just shift down? The 40 amp breakers autoreset, right?

Re: Keeping the main breaker from tripping
 

No teams that I know of used canned air to allow them to draw more current. They use it to cool down the main breaker during quick match turnarounds (such as during the finals) so that they can still draw as much current as they would be able to if the breaker was at room temperature. Running quick match turnarounds without cooling the main breaker off can result in tripping the breaker while not pulling more current then the breaker should be able to handle.

Re: Keeping the main breaker from tripping
 

I agree that this is likely the usual case for cooling breakers and I am generally doubtful that FIRST would call that illegal for the listed reasons.

Maybe a better question would be is the breaker thermally triggered because that is simply one of the many ways the creator decided to implement it, or is the "left over" heat from previous operation indicative of actual risk?

The question would be, what is the case where the breaker trips meant to prevent?

• Is it to protect the breaker itself from damage?
• Is it to protect the motors from excessive currents over time?
• Is it to protect the motors from excessive heat.

I can't find any documentation stating which is true, but I would guess that it is a combination of all of the above.

If so then in the last case (protecting motors and components from excessive heat), then cooling the breaker DOES circumvent the system and add risk. Risk of overheating a motor, controller, etc. because the breaker "thought" that the system was much cooler than it was.

Any thoughts?

Re: Keeping the main breaker from tripping
 

I also see small gains in acceleration and top speed in my model for conservatively geared robots. Some reasons I'd still consider 6 cims over 4 on a single speed bot geared at 12 ft/sec:

1. 6 cim is more efficient than 4 cim during high loads like pushing and turning (less motor heating, less speed drop under load, robot seems a little stronger)
2. Distribute load between motors to reduce heating for back to back matches
3. Redundancy, we lost a talon last year, robot was still very much driveable other than not driving straight

Re: Keeping the main breaker from tripping
 

Yes, they auto-reset. The datasheet is on AndyMark's site here.

Essentially the goal is to have a high speed which is great for getting across long distances fast and a low speed which is good for fine maneuvering/pushing.

If you are having your high speed at 12fps (I think that's what you're saying?) there really isn't much incentive to use shifters anyway.

When robots use shifters, its usually because they want to have a really fast gearing that would stall the motors if you tried to push at that gearing. Therefore, its best to be able to downshift so you can hold your own if you get into a confrontation. 12fps isn't much for a high gear, that's usually what people do in single speed setups.

Re: Keeping the main breaker from tripping
 

It is to protect from uncontrolled discharge of the battery. The breaker protects whatever the branch circuit is, so essentially the main breaker is protecting the wiring from battery-main breaker-PDB.

Re: Keeping the main breaker from tripping
 

So I'm guessing the reason it trips based on heat and not some sort of chip detecting high current is for lower price or some other manufacturing reason? In which case the residual heat is nothing more than a side effect. Well jeez, I'm surprised FIRST doesn't recommend cooling it down if what you say is true :D

Re: Keeping the main breaker from tripping
 

I can see it now - FIRST bans using canned air to cool parts. Teams then begin keeping multiple spare main breakers in a cooler on ice and swap them between elimination matches.

Re: Keeping the main breaker from tripping
 

Generally breakers have 2 methods of protection. If you have a slow increase of current until you get to a continuous amount that will trip the breaker, the trip occurs via a piece of metal bending as it heats up until it no longer makes contact with the circuit.

If you were to have a short you'd see a huge sudden surge of current, which would cause a solenoid to pull the contacts apart.

I assume the one we use features both methods, but I've never looked inside one before.