We’re trying to build an RGB LED matrix (about 2.5ft by 2.5ft) with a resolution of at least 64x64. We want it to go on a robot and be visible from the bleachers during competition. What kind of LEDs, if any, would work for something like this?
Lotta work. And, it can draw a fair bit of current.
Easier to get two of these: https://www.adafruit.com/product/2277
Agreed. It’s going to be a lot of work. The panel here is only 12.5 inches on a side (if you chain two together) so it won’t be nearly big enough. I think it would make sense to try to chain lengths of LED strips together, such as [Adafruit NeoPixel Digital RGB LED Strip - White 60 LED [WHITE] : ID 1138 : $99.80 : Adafruit Industries, Unique & fun DIY electronics and kits](this one). It’s 60 LEDs per meter which is a bit too sparse I guess. You probably want to look for either 70-80 LED/meter strip, or ~15mm pitch panel. Can’t look too hard right now as I’m on mobile but hopefully that helps.
We did this type of display on our 2015 “Hollywood” Robot
Some photos and a GitHub code link are located at:
https://www.chiefdelphi.com/forums/showthread.php?t=135874&h
This whole system weighed at least 12 pounds or more (electronics and screen supports), so you will need to have considerable weight margin.
Within the large lifting tower support “boxes”; we had all our normal FRC electronics mounted on a pullout board in one cabinet (behind the Plexiglas panel). The other side contained all the display electronics on a separate pullout board.
Here’s one live match video to see how it appears.
That is really cool! About how expensive was that system?
According to the BOM listed in that post*:
9x LED matrix @$44.95/pc
2x 9A power regulators @$27.95/pc
1x BeagleBone Black @$55.00/pc
1x OctoScroller Shield @$30.50/pc
1x 2A power regulator @$10.95/pc
For a grand total of $501.90 before shipping and taxes.
*Some of the parts might not be exactly what they used, just what some quick googling turned up.
Note that LED matrixes “strobe” – they light up one column, turn that off, light up the next, turn that off, light up the next, etc… Do it fast enough and they all appear to be on at the same time. But, since they’re not actually all on at the same time, you end up using a fraction of the current that you’d need if you were trying to light them all at once. If you do LED strips, especially the ones that are individually addressable, then you might actually be lighting them all at once.
Are those dimensions / resolution hard requirements? We used three 8x8 NeoPixel matrices to show our team number on the front of the robot, and you could see it clearly from across the field.
Hey, thanks for putting that all in one place. I’m the mentor behind speccing our display out. We acquired our panels from AliExpress which puts them in ~$20 per panel range, so looking at around $300 for the whole display.