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Unread 02-05-2006, 13:15
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Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
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Re: CMU Power & 7.2v Circuit

Quote:
Originally Posted by Keith Watson
After turning off the main 12v supply, the reset button will turn off the 7.2v supply. This is in the manual.
This is beyond the manual.
You seem to be thinking of how the reset button will turn off the RC when it's powered solely by the backup battery after you've cut the main power. The Master processor will also cut backup power after about 3 seconds. That's not the issue I'm bringing up here. I'll try to state the issue I'm warning about more clearly.

It's the interaction of the camera and the IFI backup circuit in particular that complicates matters in that when the main power is off, the circuit as designed (lacking a diode) allows power from the backup battery to bleed into the main breaker panel (there is no off-switch). From there it supplies power to the RC through the 12v terminals, bypassing the normal 7.2v power input.

At such low power the RC doesn't actually run (although you do get some faintly glowing status lights), but the trickle of power extends to the I/O pins.
This isn't an issue for most sensors, however, the camera receiving power from the RC pins seems to get just enough to prevent it from fully cycling the camera power. It's not usually noticeable and doesn't affect normal camera operation. I've only experienced it once in three competitions. It's only a problem if the camera doesn't power up the first time properly and requires a full power reset.

Most teams I've seen using the camera didn't incorporate a visible camera status indicator. We use a rapidly blinking light to indicate the camera is not working/communicating that goes solid when the camera is operational, so it was easy to see when the problem occurred and easy to diagnose.
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Last edited by Mark McLeod : 03-05-2006 at 08:32.