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Topic: Overcurrent protection (Read 1 time) previous topic - next topic

jims

Mar 13, 2007, 08:45 pm Last Edit: Mar 13, 2007, 08:49 pm by jims Reason: 1
I slipped with a probe, shorted a power to ground, and burned a trace off my protoshield (sparkfun variant) today. Seems the first 7mm or so of trace from the +5v pin is the fusible link in the design.

I'm a bit surprised. I was running on USB power and I thought those were limited to 500mA. Perhaps PCB traces don't handle as much current as I thought.

So, for people making protoshields, I'm glad the shield failed before the Arduino, but...

It would be nice to have a resettable fuse to limit the current to something under the trace failure current. I looked at polyfuses but wasn't able to find one of an appropriate current limit that didn't have an unacceptably high resistance.

An alternative would be to beef up the +5 traces so they could handle the 1 amp or so that the onboard regulator makes, and hope the USB won't make more. It is currently a very narrow trace so it can sneak through the hole field. A wider trace would have to go around, but could be serveral times wider... heck, have both.

Daniel

hi

fyi the Arduino regulator is a 78M05, good for 500ma. It does have short circuit protection/current limiting. but that won't help with burnt traces...
But hey, what would building things in electronics be without the occasional smell of burnt PCB? :)

D

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