pic: ummm......what?

[David Dawson]

Originally Posted by EricH

I would suggest a non-conductive poke stick to separate the contacts on the main breaker. Normally, that non-conductive poke stick is the red button. Separate the contacts, then yank the battery, then pull and replace the breaker. In this case, poke on that upper tab-type thing to break connection is where I'd go for first.

I've seen the sparks that can fly when there's marginal contact on a battery to some other connection (charger, bolt, other battery). They may look pretty, but you don't want to see them because they mean something's wrong.

I have never seen sparks emit from a live Anderson connector. And Ive seen them used to jump start cars. Safety doesn't mean find the hardest way to do something.

[EricH]

Originally Posted by David Dawson

I have never seen sparks emit from a live Anderson connector. And Ive seen them used to jump start cars. Safety doesn't mean find the hardest way to do something.

I've seen a plugged-in FRC battery spark. I forget whether it was the Anderson or the terminals, but I seem to recall that the area around the Anderson fused (read: welded) to something else before someone could get in there and separate the battery from whatever it was connected to (thankfully, not a robot in that case).


Chris, the thing about using a non-conductive poke stick on the connector is that 1) you only get one place for a spark (the breaker, which in this case is already broken) as opposed to 2 (each side of the Anderson) and 2) your hands are not right there to risk getting zapped.

I don't know about you guys, but I'm not sure I'd want my hands right next to a fully-live FRC battery's current and voltage if I had to unplug it, even with an Anderson connector between my hands and the wires. (By fully-live, I mean current is flowing actively, not current can flow if the connection is made.)

[David Dawson]

Originally Posted by EricH

I've seen a plugged-in FRC battery spark. I forget whether it was the Anderson or the terminals, but I seem to recall that the area around the Anderson fused (read: welded) to something else before someone could get in there and separate the battery from whatever it was connected to (thankfully, not a robot in that case).

What you just described wasn't a Anderson short circuit. If two power poles fused together a wire had a short or the system drew too much current. Anderson terminals are designed for safety and useability which is why they have shielded contacts. If you really want to get technical even if there was a slight spark between the power poles it would take the path of least resistance (i.e not your hand) for the milliseconds it would have before the connectors were far enough apart. I would take my chances with this before touching a broken exposed circuit breaker.

[Andy A.]

Under the circumstances, disconnecting the battery would have been the safest thing. The priority should be to depower the robot, and the very busted up breaker, ASAP.

While not good practice, breaking the connection at the Anderson while the robot is 'live' isn't particularly hazardous to operator or robot. By design, any arcing will occur while the Anderson is still enclosed. So while it may score the contacts a bit, that's the worse case scenario. As long as it's not an every day occurrence you won't notice.

[EricH]

David, IIRC, it was some form of short circuit. It's been a few years, but it was in a row of batteries that were charging. I looked around to see several people rush over to try to figure out how to disconnect the battery that was throwing sparks. Like I said, it's been a few years, so I forget the details like what exactly fused to what.

Also, I never said to touch the circuit breaker with your hand. I said to use an insulated poke stick. That way, there is zero chance that electricity goes to your hand.

[Andrew Y.]

eric, thanks for your point of view...but my professional experience and my advisors at work all agree my kids took the correct action by unplugging the battery...even the OSHA dude at work agrees...and him and i NEVER agree.

[Bill_B]

How does the replacement look now? Look carefully for cracks and feel the smoothness of the new breaker in the places the other one failed. Not sure about your situation, but I have seen Bakelite body terminal strips give out because the mounting holes were ever-so slightly misaligned. Tightening the mounting screws for the terminal strip didn't break the strip but it did stress it so that normal usage eventually caused failure. If the mounting hardware didn't slide into place easily or wasn't perpendicular to the mounting plate, then tightening the mounting nuts may have set up internal stresses that were later released by your collision. It would be harder to develop that stress in a more flexible or more compliant base, like wood or lexan.

[Hawiian Cadder]

This, is why all of our electronics are secured via Zip Tie, and not solid mounting hard-wear, its faster, easier, as secure.

[santosh]

Originally Posted by Hawiian Cadder

This, is why all of our electronics are secured via Zip Tie, and not solid mounting hard-wear, its faster, easier, as secure.

The breaker and the cRIO are the only things that we dont have ziptied down. Im still not 100% sure it was because we got hit hard a few times. But it is definitely a possibility

[Billfred]

First it was the digital sidecar at Peachtree, now a main breaker in North Carolina.

If you guys make Einstein, I'm bringing a fire extinguisher.

[santosh]

Originally Posted by Andrew Y.

eric, thanks for your point of view...but my professional experience and my advisors at work all agree my kids took the correct action by unplugging the battery...even the OSHA dude at work agrees...and him and i NEVER agree.

I dont understand the smileys. there is nothing fun or happy about safety issues such as these.

[MishraArtificer]

Originally Posted by santosh

I dont understand the smileys. there is nothing fun or happy about safety issues such as these.

...I believe the smileys were directed at the incredible circumstance of him and the Occupational Safety and Health Administration guy actually agreeing on something.