Talon SRX LED Control

Technical Technical Discussion
1

Seen on Cross the Road Electronic’s Facebook page

FRC Teams, Does your robot have a Talon SRX with a spare feedback port? Find out how to quickly add LED Strip Control to your robot using Talon SRX at our booth (St Louis FRC World Championship).

Anyone get there to ask about this? I had planned on it, but was too busy watching matches :smiley: and cannot find anything about it on their site or in their example code (but ask my wife, I have been known to not see things right in front of me on more than one occasion).

2

The demo was basically one of these…
http://www.ctr-electronics.com/gadgeteer-driver-module.html
… plugged into a Talon SRX Gadgeteer Feedback port.

Then in HERO you can call something similar to …
aTalon.SetOutputPin(pinIndex, dutyCycleMs, periodMs)
… and therefore control a common-anode LED-strip.

Same routine will be available for the FRC languages; we are in the middle of redesigning our HERO/FRC library build system, so it hasn’t been released yet.

So if you want to add an LED strip to your robot and there is a Talon on your bus with no sensor, you can install this inexpensive low-side driver module, and then in software control color and brightness.

Maybe we should post some videos of it. :slight_smile:

3

Thanks for the quick reply. Looks very useful. A couple more questions:

  1. If we are have one or more Talons in follow mode, can they also be used for this?
  2. The power supply for the LEDs comes out of the Talon?
  3. What is the max power/number of LEDs that would be supported?

Thanks again,

p.s. Love the talon so much :]

4

This has a lot of interesting implications outside of LEDs… :slight_smile:

5

Heard you talking about this on the plane, pretty cool stuff.

I don’t think this would be able to trigger any LEDs while in disabled though, would it?

Please do!

Already thinking of some “neat” things we could use this for outside of LEDs :stuck_out_tongue:

6

The Talon’s motor output is unaffected. So it can be in follow mode, or PercentVoltage, or VoltageComp, or similar.

The LED strip is common-anode. So +12V goes to the LED strip’s anode, and the R,G, and B cathode-ends go to the driver module, which switches low side.

Looking at the specs, each channel can sink 5A. (http://www.ctr-electronics.com/gadgeteer-driver-module.html)

I leave it to you…

I don’t believe there are any rules this season requiring turning off LEDs in disabled mode that would have prevented this use.
You can do this now with other submodules like Arduino in both disabled and enabled loops (please correct me if I’m wrong).
So likewise there isn’t anything in the Talon firmware that would prevent updating your LED strip.

7

I saw the demo in St. Louis. We might look into these.