We’re planning to use LEDs on our robot for amplification strategy. Today, we started experimenting with the ThriftyBot 12V Individually Addressable LEDs, trying to test the controller triggering different colors. I don’t think the code is the issue for reasons that I will explain in this post, but here is our repo anyway: GitHub - FRC1884/season2024 at testing-1884
The code we wrote under AddressableLEDLights (ignore PWMLEDLights for now) followed the example code on the user manual quite closely. Note that we named our LED strip m_blinkin in code, but we are NOT utilizing a Blinkin and are connecting via the 10A-fused VRM with a PWM cable going back into port 0 on our roboRIO, as shown here:
Printing the first LED’s color periodically did return the value it should have been set to (blue, white, and red corresponding to the right buttons pressed when running the program). However, none of the LEDs actually turned on despite the buffer length being 5 LEDs as it should be. Using a multimeter, we measured continuity and nonzero current across the strip, but when double-checking this, we connected the wrong ends together and shorted the diode we were testing on, causing the GND pin on that diode to smoke up.
We understand that this is likely a blown capacitor, so will we still be able to continue using this strip apart from that one diode? Also, what might our next steps be to get that working?
You say the lights are plugged into port 0, and your code has BLINKIN_PWM_PORT = 1.
Those should match.
As far as the magic smoke goes, you could cut a new strip of 5 LEDs and try again being extra mindful of wiring, but I would keep trying with this setup for the time being. If the only damage is the first diode, the rest should still light up, if there’s damage to the first data chip, you might struggle longer than you’d like.
Thank you! I’d forgotten to mention that we had changed the port in code to 0. After some more code tweaking, we will solder the same wires to the section of the strip we cut off. Will post an update soon.
Is the strip connected in the correct orientation? Addressable strips are directional—there is an input side and an output side. There should be an arrow or other indicator on the strip to determine which is which.
Yep, the connection is in the direction of the arrow (connected on the left side of it, away from the arrowhead). We took a short break on LEDs but I will be back tomorrow with more information!
Are you sure you are wired up to the correct pads? Your red wire from your VRM looks like it is going to the DATA line on the LED strip (next to the GND pad) instead of to the 12V pad on the far side. There is a disconnected red wire that looks like it wants to be your power lead, connected to the VRM.
If you find upon inspection that this is not wired correctly, you might want to replace the strip with a new segment to rule out any permanent electrical damage.
My bad, I had completely forgotten to post an update! So far, we have tested a bunch of things, such as connecting the strip to a Blinkin and swapping around the red and black cables @veg for the PWM connection. (For this, I had assumed that the disconnected red wire would have connected to the red wire on the PWM, with the dark red and black were the leads that attached back to the VRM 12V/2A channel.)
However, this also did not result in the LEDs turning on. No matter what we tried, including a soldered connection onto another strip of 10 LEDs in the same configuration as the end of the TTB strip (red-red on 12v, black-black on GND), the LEDs would not turn on any color. So far, we have tried tweaking code a lot to output a PWM signal, switching around the power cables between PWM and the VRM and trying some more configurations with the Blinkin. Nothing we’ve tried has worked so far, even though the Blinkin is receiving a valid signal, indicated by the solid blue status LED, so does anyone know of any other fixes, or whether the TTB LEDs are even compatible with the Blinkin?
How are you powering the Blinkin? One quick test would be powering the LEDs with the VRM and running the PWM to the strip directly from the RIO, that would isolate the problem to the strip or the driver.
That VRM setup was one of the things we’d been trying so far. The Blinkin was being powered through a 10A breaker on the PDH and a PWM connection back to the code-matching port on the roboRIO. Should the LEDs be lighting up the instant they receive power from the VRM (as they do on the Blinkin), or do they indeed need a PWM signal?
Alright, apologies for the delay here, I have done some testing with the Blinkin -
The Blinkin 12V strip mode is set up for common anode. What this means is it is not designed for a serially addressable LED strip like the TTB LED Strip. That’s the bad news.
The good news is that in 5V mode, the strip will in fact work. Also, if the strip was once in 12V mode and is switched, it will not kill the strip. I just swapped between 5V and 12V on my end and the LEDs seemed fine. I am planning on leaving these LEDs on at my desk for the next few days to verify running the strip at 5V long term does no damage to the LEDs themselves, but that is out of precaution and I see that as highly unlikely. I will be updating the guide after that test with a wiring setup using the Blinkin.
For now, since you have the Blinkin, I would advise starting with about 5 LEDs and carefully wiring signal (either of the two or both of the middle wires), ground, and power back to the Blinkin. This should turn on the LEDs as soon as the Blinkin receives power. I would power the Blinkin from a switchable port on the PDH or from a VRM, whichever is more accessible, since there is an on board regulator in the Blinkin.
I’m sorry for the delay! CS haven’t had as much time as we might have hoped with the robot these last few days, but hopefully we can try this tomorrow!
Despite our best efforts, we were not able to get the Blinkin to work with TTB strips (same issue as before: nothing turned on, despite having a valid PWM).
On a happier note, we did manage to get the VRM/MPM setup working in time! I couldn’t figure out how to reproduce the issue because I pretty much redid the entire setup, starting on a clean slate including on code. Here’s a video of it working:
Thank you so, so much everyone (especially you, Sam!) for all your help! I will push for getting the Blinkin working with other strips as a post-season project, but I’m afraid we have run out of time on it before competition this week.
