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Unread 12-02-2007, 02:10
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Dave K. Dave K. is offline
Engineer/Mentor
FRC #0930
Team Role: Mentor
 
Join Date: Jan 2007
Rookie Year: 2005
Location: WI
Posts: 91
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Re: light up buttons

Quote:
Originally Posted by Al Skierkiewicz View Post
Dave,
This is a difference and not fuly documented since the OI manual you linked to, on page 7 "Notes:" states "[2] LED drivers provide 5V at 10mA". There are several other places in the manual where this is repeated. This is the criteria teams have used as far back as I can remember. If the LED outputs are indeed the raw input voltage, there will be times when the LEDs will extinguish due to low current. In the past we were told they were part of the 5 volt rail held up by the backup battery. I will pass this on to my software team.

Thanks,
Hi Al,

Good catch, they clearly missed editing the note on pages 7-9, and I'll pass that along.

I originally noted the discrepency after being forced to reverse engineer the interface to design some interface electronics and was looking into a source of power other than the +5VAux pin.

As it is unregulated, it then became important to understand more about the power that is supplied via the (undocumented) competition port, so I also pressed for answers on that and got a reasonably detailed description of that as well... and that's where the information on the 9.9V supply voltage comes from. The undocumented power pin, is parallelled with the coaxial power connection.

It appears to be fine to use as intended, except for the possibility of a situation requiring a higher voltage LED such as white, or blue.
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--Dave