High-Power LED Ring for Vision Tracking

Our team (Pigmice 2733) is hoping to make ~35 feet shots using a JeVois for vision tracking, and to do so you need a pretty bright LED ring. We’ve been working on a ring similar to the superbrightleds.com and Andymark ones, but much brighter.

Our current design is 58mm OD, 42mm ID and uses 24x 3.2v @ 30mA LEDs. It draws about 2.81 W and produces approximately 160 lumens of luminous flux. By comparison, the 60mm green LED ring from superbrightleds.com daws 1.2 W and produces 69 lumens (with the same apex angle of 120deg).

LEDs: https://www.digikey.com/short/zc2432

It runs off 12v which means it’s trivial to use a Spike relay connected to the PDP to only turn on LED ring when we’re vision tracking (see R8 m.), and if it’s still too bright we can easily swap out the resistors.

You can find the KiCAD files, BOM, and Gerber files (under releases) here: https://github.com/Pigmice2733/led-ring (DISCLAIMER: we have yet to test this design. I’ll update the thread in ~5 days with whether it’s confirmed functional).

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For comparison, the limelight is 400 lumens.

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then LLV2+ is 460 lumens? It says a 15% increase from V2.

I’m sure @EricH will warn you of some stuff soon. Let us all wait in anticipation.

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I would be curious what the apex angle of their setup is.

LimeLight is twice as powerful and is widely used. I don’t get the naysayers who bring up so much stuff around a team’s invention.

I’d also add: it would be pretty easy for us to develop a solution using a higher power LED. We could throw 12 of these in a ring and have something over 1000 lumens. If this gets the job done though, what’s the point? We wanted something that’s brighter than the superbrightleds or Andymark rings (and this is, more than 2x), not something that washes the entire field in green light.

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They’re already aware of it. I wish more Limelight users were.

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Just for fun: 31 W, 1416 lm, I call it the “Military-Grade Self-Defense Re-Inspectinator”

https://www.digikey.com/product-detail/en/cree-inc/XPCGRN-L1-0000-00501/XPCGRN-L1-0000-00501TR-ND/2209536

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When can I buy 3?

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Note that powering the ring directly off of 12v battery will dim when motors pull current, and overvolt at other times, so you might want to use a 12v boost/buck to get a stable voltage.

I would also like to point out that retroreflective tape doesn’t need that much illumination, as it is very efficient at reflecting light back to its source. In fact, too much light can blow out the image (saturating the camera image sensor), making filtering less effective. The key is to have enough brightness but not too much, and pick a unique color so HSV filtering is effective against other field and background elements.

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We were discussing this, we’re hoping it’s not going to be enough of an issue to seriously affect vision, but we’ll definitely consider adding some voltage regulation depending on what we see during testing.

By that much illumination are you referring to the amount of illumination in this design, or that it just doesn’t need much illumination in general? It might be pretty efficient at reflecting light back, but we were definitely running into issues with the superbrightleds LED ring at 35 feet.

Yeah, we tried to pick an LED with a pretty pure green.

Thank you for the advice.

The vision targets are not simple reflective tape. It is really conspicuity tape (think that is the right word). The surface is made of micro-prisms. Bottom line - huge amounts of light are reflected (mostly directly back at you no matter your angle) and you’ll need less light than you think. You can see this stuff from many hundreds of yards away, using a flashlight to red tape on a parked semi at night for example. It is almost unbelievable.

Did I say they were? We’re aware the vision targets are retro-reflective, and of it’s properties. Bottom line: the rings we used weren’t enough. There’s a reason (as someone pointed out) the limelight is 400lm.

It is common misconception - just trying to offer extra information. I didn’t say you were doing anything wrong. Take a pill!

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The limelight interface has a mode where it only turns on when necessary. Teams rarely use that mode and I agree - its a little annoying.

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For teams considering the DIY camera/LED ring approach, our team used these back in 2017 with great success:

SparkFun PicoBuck LED Driver

SparkFun LED 3W Aluminum PCB - 5 pack, Green

Pixy2 CMUcam5 (exact model we used is obsolete, so linking the latest version)

Arduino Uno R3

The assembly was a bit tedious, but the end result was excellent. We never saw a drop in our LED brightness due to the constant current being provided by the LED driver. We also used a Spike relay to control when the LED driver was supplied with power so we didn’t leave it on all the time.

Additionally, the team found a way to use the LED lights as a visual indicator when the robot was across the field picking up game pieces. The code would monitor the current draw of the intake motor and blink the LEDs when a current spike was identified, indicating that a game piece was successfully captured.

(apologies, I have not yet found a picture of the front of the setup)

Edit: Found the picture!

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The original Pixy is still available if you find interchangeable lenses to be useful. We spun our own light source with 12 piranha LEDs that fits the Pixy.

It doesn’t fit the Pixy 2, however.

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Alright, here’s a version that utilizes a Lightline RCD-24 LED driver. This is better for a couple reasons:

  • Constant current, meaning the LEDs will remain a constant brightness regardless of battery load (mentioned by @Peter_Johnson)
  • Can be controlled via PWM (on/off/dim) so there’s no need for a Spike relay (I doubt we’ll use dimming, but not having to use a Spike is really nice)

This version also has:

  • M2 mounting holes (since it was gonna be larger anyways)
  • A powerpole connector & PWM connector going out the back (45A powerpole is overkill but we pretty much standardize on it)
  • A more compact LED layout

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