pic: ummm......what?

[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 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.

[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.

[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.

[Cory]

Originally Posted by EricH

Unplugging the battery when the circuit is on carries a risk of sparks, guys. I would not suggest trying that--ANYWHERE. That's why I asked.

Don't be overly dramatic. I've seen this done hundreds of times. No problem.

The simplest way of doing things is usually the best. No need to concoct some scheme when you can just do this.

[kiettyyyy]

Originally Posted by Cory

Don't be overly dramatic. I've seen this done hundreds of times. No problem.

The simplest way of doing things is usually the best. No need to concoct some scheme when you can just do this.

There's little to no current being sourced while the bot is still booting up... There should also be little to no current if you're some how up close to the bot without it running around.

Those "sparks" really only fly when you're dealing with MUCH higher potentials(200 VDC++).

It's no big deal.

[Bill_B]

You won't have to go very far into Electrical Engineering before you find out that sparks at disconnection are largely due to inductive loads, viz. motors and transformers. Inductors try to maintain current in their circuits. To do that voltage will increase across a switch as it opens and increases resistance. Eventually the switch "wins" and makes a very high resistance in the air gap, but not before a large inductor load tried to jack the voltage very much higher than usual. Sometimes the voltage spike will actually get high enough to cause current to jump the minuscule air gap as a switch opens. Result? Sparks. Not usually a good thing, so quite a bit of E.E. talent has been devoted to this solving problem.

As it applies here, if motors weren't running when you pulled the battery plug, there is very little chance of noticeable sparking. Voltages in FRC robot-land are usually quite low, so bare-skin contact is not a great danger. However, if the hand in contact has metal jewelry or tools in it, the danger of high current short circuit should not be ignored. I sometimes think that a you tube video of egregious electrician's behavior should be made to convince "kids" how easy and calamitous such short circuit "welding" can be.

[Andrew Y.]

Originally Posted by Alex Cormier

Unplug the battery?

Originally Posted by Bill_B

You won't have to go very far into Electrical Engineering before you find out that sparks at disconnection are largely due to inductive loads, viz. motors and transformers. Inductors try to maintain current in their circuits. To do that voltage will increase across a switch as it opens and increases resistance. Eventually the switch "wins" and makes a very high resistance in the air gap, but not before a large inductor load tried to jack the voltage very much higher than usual. Sometimes the voltage spike will actually get high enough to cause current to jump the minuscule air gap as a switch opens. Result? Sparks. Not usually a good thing, so quite a bit of E.E. talent has been devoted to this solving problem.

As it applies here, if motors weren't running when you pulled the battery plug, there is very little chance of noticeable sparking. Voltages in FRC robot-land are usually quite low, so bare-skin contact is not a great danger. However, if the hand in contact has metal jewelry or tools in it, the danger of high current short circuit should not be ignored. I sometimes think that a you tube video of egregious electrician's behavior should be made to convince "kids" how easy and calamitous such short circuit "welding" can be.

a little late, but i will comment...

I agree that there is little load when disconnecting the battery. Connecting the battery has a greater chance due to the capacitors charging the instant they are connected. soo basically we are not supposed to plug our batteries in because of spark.

@Santosh....ill see you thursday night...and we can duke it out. Selling tickets to see the fight for $450 a seat.