Although the main circuit breaker is rated for 60 Amps, we suspect that we can run our robot at a higher current draw without popping the breaker.
Does anyone have practical experience with exactly how much? 80 amps? 100 amps?
How many total sustained amps do you think we can safely run our robot at?
Since we have a bunch of really powerful motors this year, it seems to me that we really have to watch what we ask of that breaker.
Any help would be appreciated!
at kickoff, woody stated that the breaker will run for about 8 seconds at 200 amps (short circuit current of the batter) and almost two minutes at 100 amps.
Like he said, you have just enough rope to hang yourselves.
Hi Joe,
Thanks for the information, that should help us figure out how hard we can run the robot.
By the way, how about the 30 amp speed controller circuit breaker. Do these trip at 30 amps?
I think robot’s should use just enough juice to totally discharge the battery after a match :). If you’re not using that much, you’re not using enough. Short circuit the battery if you must. I mean you wouldn’t have to worry about recharge memory problems this way. On a more serious note using that much juice that quickly may cause the battery to get rather warm.
Short circuit the battery if you must
For all those rookie teams out there, Patrik was kidding about shorting the battery. Don’t do this! It’s a bad bad bad thing (smoke, fire, burning flesh, ruined battery, etc.).
Whew … 
I appoligize for my team mate’s suggestion. I’ll try to keep him in line in the future. 
~Tom Fairchild~, who personally saw one of our other programmers short out a battery which turned into a smoke bomb. Stupid, stupid, stupid…
Sorry I had thought I made it clear it was a joke.
*Originally posted by Anne Lam *
**By the way, how about the 30 amp speed controller circuit breaker. Do these trip at 30 amps? **
The 30 amp breakers will take considerably more than 30 amps for short periods of time, but will heat up and trip much more quickly than the 60 amp breaker if run at, say, 2x its rating. Of course, tripping the 30 amp breakers occasionally is not the “big deal” that tripping the 60 would be, since the 30’s reset when they cool down.
If you trip the 30’s very often your robot is telling you that something is geared too high.
Check the data sheets that come as an appendix to the robot rules.
All circuit breakers (and fuses for that matter) have an “inverse time” curve. They have an extremely small but accurate internal resistance which heats up via the power dissipated in this small resistance (P=IIR). The actual trip mechanism is thermal.
Be warned that the internal heat does not dissipate quickly. If you run at 200A for 6 seconds and then try running at 100A, you will trip in a lot less time than the quoted 120 seconds (more like 20-30).
This warning also applies to self resetting 20 and 30A circuit breakers. Once they start tripping, they will re-trip in a very short time at the same amperage.
Lastly, these are not “precision” devices. Variations of +/- 30% are not uncommon. Plan accordingly.
Mike
We always seem to trip breakers from gearing things badly every couple of years.
So this year we are going to have a “breaker clip” for some of our heavier draw breakers. The custom circuit board will detect the open/close condition of the breakers by measuring the voltage drop across it. When a breaker is found to be open, the board tells the controller to change out the open breaker with one from the breaker clip. As of now, the process is a tad slow with the breaker change rate at about 3 breakers per minute. We’re trying to up the rate to about 6 breakers per minute.
Maybe we can get the electrical team to come up with a sound effects generator to make the breaker change sound cooler.
Lastly, what’s wrong with smoke! We’ve smoked plenty of components before.
-smokescreen
The batteries used for the competition do not have a memory problem like NiCad batteries. These batteries do not like to be fully discharged either.:eek: :eek: :eek: