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Unread 12-02-2009, 09:32
EricVanWyk EricVanWyk is offline
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Re: Solving static electricity problems by grounding the frame

A drag chain is a good idea.

ErichKeane -

As several others have pointed out, connecting the battery's return to the chassis is a bad thing that is illegal for very good reasons. This has examined and agreed on by many EE and safety experts, including our friends at UL.

I've gathered a few quips from this thread:

AdamHeard - and don't forget that a grounded frame allows a single wire failure to short the battery (a single positively charged wire coming loose).

RyanCahoon - Not really, it's more a convenience incentive, that way only one power wire (positive) has to be run to devices, leading to less cable runs.

Al Skierkiewicz - The robot frame is insulated from the control and electrical system for one very important reason, we want you to be able to play.

And I'll add a slightly less elegant one:
Quote:
The battery short issue is easily solved by using fuses and circuit breakers.
This is not true. In order to do this, all of the smaller paths need positive AND negative breakers. If a 5A return is sourced by a 40A source, the 5A return will fail. The converse is also true.

"One Breaker per Path" is only viable if your topology is a star. If the ground is already shorted, you are one mistake away from breaking that assumption.