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Unread 17-02-2016, 18:16
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Poseidon5817 Poseidon5817 is offline
"Cool" Squad
AKA: Mitchel Stokes
FRC #5817 (Uni-Rex)
Team Role: Mentor
 
Join Date: Aug 2013
Rookie Year: 2014
Location: Clovis, CA
Posts: 360
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Re: Using the PCM to control a LED

Quote:
Originally Posted by cantdecide View Post
We're using a custom LED assembly for illuminating the retro-reflective tape and it needs ~300 milliamps at 12V, meaning we can't use DIO, and because it heats up so quickly, we can't directly hook it up to the VRM(having the LED be on during the whole match would probably destroy the LEDs). I would have traditionally done this with a boring transistor, but it was 4 am(when the best ideas are formed) in the morning, and we had no transistors. That's when it suddenly came to us: we already had a device that had regulated 12V outputs which can be controlled via code: the PCM! We hooked up the LED to one of the solenoid outputs on the PCM, and it worked just fine. We checked the manual to see whether doing that was legal or not, and according to Table 4-4 under R53, CUSTOM CIRCUITS(I assume that our LED assembly is considered a CUSTOM CIRCUIT) can be controlled using the PCM. However, I still have the urge to ask: is this legal? It just feels so odd and honestly, it's something I wouldn't have allowed if I wrote the rules.

Kinda off-topic: third party fans for ESCs aren't allowed but wiring lights to solenoid slots is. Rules are weird.
We used this last year in week 2 and it wasn't an issue.
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My FRC History:

2014 - Team 1671: Central Valley Regional Finalist and Chairman's Award Winner, Sacramento Regional Finalist, Archimedes Quarterfinalist
2015 - Team 1671: Central Valley Regional Semifinalist, Sacramento Regional Semifinalist and Chairman's Award Winner, Newton Winner, Einstein Winner
2016 - Team 5817: Central Valley Regional Finalist and Rookie All-Star, Orange County Regional Quarterfinalist and Rookie All-Star, Newton Division
2017 - Team 5817: Return of the bench grinder