Burned out 2 5V regulators on Power Distribution boards

[jskene]

We have burned out 2 5-volt regulators on different Power Distribution Boards. Has anyone else had this problem?

The only thing the 5-volt connector was powering was our camera. We double checked our wiring and it was correct. The camera is electrically insulated from the frame, as required by rule R41.

The specifications on this regulator indicate that it has a 3 amp capability and it that it has over-current protection. In spite of this, on two separate boards we experienced a strong burning smell, followed by a loss of our 5-volt supply.

In the interim we wired up a simple 7805 5-volt regulator, connected to an unused 12 volt circuit breaker, and this works just fine, except that it contradicts rule R43.

[Al Skierkiewicz]

JS,
That really sounds like a wiring problem, maybe a pinched wire somewhere, or a wayward strand. Does the camera power from the wall wart OK or does that supply get hot?

[jskene]

The camera powers up properly from a wall wart or the 7805. Power surges at ~ 1 amp for under a second, then holds steady at ~ 300 ma.

[EricVanWyk]

All of the reports I've received of damaged 5V regulators on the PD were caused by a lack of isolation between the camera and the chassis. The failure mode is that a trace on the underside of the board acts as a one-time-fuse.

The only other failure mode that that supply has reported is that it smokes when reverse biased on the Analog breakout.

I did see one failure in which the robot did pass R43. The camera was somehow shorted to the output of a victor. Once the victor was turned on, it completed the circuit and released the doom.

If you are using the kit metal pan/tilt unit that you will have a dynamic short that only occurs when the robot is accelerating.

Please check to see if you are encountering a similar situation.

[Mike Betts]

Jerry,

I strongly urge you to post your issue on the FIRST forum here (http://forums.usfirst.org/forumdisplay.php?f=745) which is regularly visited by the engineers who designed the circuit you are having problems with.

Regards,

Mike

[Russ Beavis]

It's important to remember that, assuming Eric is right about the shorted camera chassis in your system, there is at least 1 other failure in your wiring. Something else must also be touching your robot frame/pan-tilt system. You should definitely probe around your robot and find shorts from the battery terminals to various metal parts on your robot.

Russ