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Unread 12-05-2016, 22:06
Peter Johnson Peter Johnson is offline
WPILib Developer
FRC #0294 (Beach Cities Robotics)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2008
Location: Redondo Beach, CA
Posts: 247
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Re: What COTS parts would you like to see?

Quote:
Originally Posted by JesseK View Post
I would like to see a better solution for using LED's. Right now LED's paralyze my team with how many choices / setups there are, so usually there's a mediocre attempt at them but never a finished product.
- How do we connect power to the LED's?
- Which LED brand, model, and length do we use?
- Do we really have to care that each light is addressable, seriously?
- To control them do we use an offboard processor, use a Spike, or is there a better way?

Would love to have something simpler that doesn't depend on in-house custom circuitry or an arduino. Plug this 12" LED strip into this device, then plug this device into the PDB and into the RoboRIO using these connectors. Then use this sample code to get going with writing different colors/brightnesses or blinking lights to the LED's.

FWIW, introductory courses in embedded electronics in college were all about blinking LED's, and connection of those circuits to the corresponding code was way more straightforward than the FRC LED situation.
We've used standard cut-to-length non-addressable 12V LED strips (Amazon sells lots of these in various colors) and this tiny board from pololu to control them: https://www.pololu.com/product/2802

Basically the polulu board is a simple digital switch (think of it like a spike without the ability to reverse the voltage polarity), controlled by a PWM signal. The linked one above is 3A but they also have higher current ones. The wiring diagram shows how to wire it up. Load is LED strip, source is either 5V or 12V (depending on LED strip voltage) from VRM. The PWM comes from a PWM output on the roborio. You do need 5V in from somewhere too; if you're using 5V LEDs or a PWM from a MXP board you can get 5V from that connection, or you can get it from the VRM or RoboRIO DIO. I think we used the Talon class in software to control the PWM output--set(0) turned the LEDs off, set(1) turned them on. Easy enough to do das blinkenlights from there with software timing.
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Author of cscore - WPILib CameraServer for 2017+
Author of ntcore - WPILib NetworkTables for 2016+
Creator of RobotPy - Python for FRC

2010 FRC World Champions (294, 67, 177)
2007 FTC World Champions (30, 74, 23)
2001 FRC National Champions (71, 294, 125, 365, 279)

Last edited by Peter Johnson : 12-05-2016 at 22:13.
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