We are a new team and we are concerned about being able to purchase certain COTS items this year, in particular anything to process vision, so we’ve been looking at Photonvision a little bit and it looks really good. The shape detection in the beta download worked really well on one the the Steamworks fuel balls (we only have any old game pieces to play with because AndyMark is still using them for packing materials. Thanks, AndyMark!)
We are using a Pi 3B+ with a Pi camera.
However, thinking forward, we want to test it out with the usual retroreflective material with green LEDs. It looks like the limelight 2+ has 400 lumens brightness and there is a cone structure that probably directs the light on the 8 LEDs. These LED rings are a little over 100 lumens with a 120 degree cone so we’d need 4 of those to match the output of one limelight, right?
(honestly, we’ll might just buy a limelight if they end up being available, but this is a nice preseason exercise for the programmers and electronics folks and we’d definitely use something they build themselves if it works).
Power over ethernet is also desirable, but it looks like the Raspberry Pi POE hat runs at 48V and not the 12V that is available on the robot so I’m not sure that will work (anyone use a Pi with the REV PEO injector cable?
One of the kids can CAD up a case and we can 3D print that once we figure out what we need to make a functional system. (And I’m hoping we can find a local team with some retroreflective tape that they are willing to part with so we don’t have to pay $50 for a roll - ouch).
Anyway, if anyone has thoughts on greed LED solutions and POE solutions then I’d love to hear them.
You can get some reto reflective tape at a hardware store near the mailboxes. It is not the exact same as what is used on the field, but works well and is much cheaper.
I think this is the best option right now with the pi 3b+.
I’d probably just go with the standard (green leds) even though I have the red. I think the v1.3 pi camera is preferred, which I think does work with the mounting holes, but I’ve been using the v2 as the board recommends. There is some differences in the FoV and the 1.3 is better for photonvision.
I used the PoE to power it. I ended up splicing a longer power cable of a REV PoE cable.
You do have to solder on the headers onto the board. So that is something to consider. For the standard 3d printable case it does work okay. I soldered the 2 wire weidmueller connector on the top of the board which is the wrong place. I’d probably just leave that off and use PoE.
Here was the github markdown doc for the case which notes which fan goes with it (recommended) and hardware.
There is more in the installation in the case like partially folding the camera flat cable to fit better.
As far as Photonvision, it is pretty easy to get up and going. There is a hardware config on the github for snakeeyes that is added to let you control the LED brightness in the Photonvision dash.
edit: I forget to add. The PoE power cable was connected directly to the PDP with a 5A snap action. And also the PoE male connector went to the rPi and the female connector had an ethernet cable attached that went to a 5-port switch, so you’ll want to also have a switch.
People are still using those LED rings with success. Here is an example of using concentric 60mm and 100mm rings from superbrightleds as linked above. Great performance at long range in bright venue lighting. You don’t need to turn the whole alliance wall green with full power Limelight LEDs to get very solid vision targets.
I’ve been working up a case to integrate numerous off-the-shelf components into a usable vision module for PhotonVision for teams to make use of. It’s slightly larger than a Gloworm or LimeLight but not overly so (that’s what the price of using off the shelf modules is).
I’m working on the assembly notes as I assemble the first batch of 4 “final” versions but the CAD is available at Onshape
There are reasonably complete BOM notes for non-obvious components.
It uses 4 1W green LEDs (typical eBay and Amazon stuff) similar to the Gloworm configuration.
I have a lot of the assembly notes written up and if I get a chance, I’ll make them available as well - probably via a github repo.
I was planning a more public release but got sidetracked building a new 3D printer - a 350^3mm Voron 2.4 - that is a cool deal.
Oh yeah - it’s PWM’d. WIth a user-accessible trimmer for modest +/- mechanical adjustment brightness adjustment - figuring it’s easy to get someone, just about anyone, to make a minor brightness adjustment in <5 seconds as opposed to making a Photonvision dashboard adjustment (which likely can be done only by a more specific subset of team members).
I consider the LEDs to be 1 “eBay watt” - which in my experience is quite different (but still bright).
I think there might be an update to the final doc regarding PoE support
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