The point source pixel design I came up with last fall has a lot of advantages: Small size, low power & good color mixing in a 10mm package. The hardest part was finding a way to chain multiple boards together. I’d done lots of tests by hand and found that building the wiring harness often took much, much longer than the actual board assembly.
Life’s too short to spend days and days building a wiring harness.
So I redid the design… It ended up costing a few pennies more in components, but the time saved making wiring harnesses more than compensates.
Since each pixel has an on-board voltage regulator – and since the LED is driven from the processor directly – voltage drop within the cable is less of an issue than otherwise expected.
It’s based on a ‘backplane’ of 10-conductor ribbon cable. 4 conductors each for power and ground, plus a pair for DMX data.
It’s easy to lay out the cable, mark it every 6″ or 12″ and install IDC female headers as needed.
Since I was concerned that the high-speed data would be corrupted over long lengths of flat cable, I also designed a tiny DMX repeater / splitter board. It has connections for DMX in & through, plus an RS-485 receiver. Then, two RS-485 transmitters feed data to two separate 10-pin headers.
Each header connects to a female ribbon cable jack. So in essence, a string of lights can be driven from the center.
I expect to drive 16-18 pixels on each side of the ‘T,’ with each arm being 8-10 feet long.
Each splitter board will be connected to the control equipment two cables: a shielded, twisted pair for data and a heavy gauge pair for power.
~600 of these are being assembled by a shop here in town… Will post some video clips when it’s all installed.
After taking the picture of the board + heat shrink tubing, I used a razor blade to trim the tubing back to the junction between the LED’s wider ‘neck’ and main bulb. This way most of the 10mm bulb is visible but the water resistant seal remains reasonably sound.
These are being mounted in the eaves, under the raingutter and near the soffit. It’s not designed to be fully submersible, just resistant to the occasional sideways-blowing blizzard.
Haven’t had time to test it fully yet, but these boards arrived early this morning.
UPDATE: These work wonderfully well. I’m using two (one for each universe) in my display this year.
It’s an 8-way somewhat-isolated DMX splitter.
DMX in & through on XLR-5 jacks. DMX in section is fully isolated from the rest of the world.
8 RS-485 drivers in parallel with pinheader (.1″) outputs. These outputs are *not* isolated from each other, but each does contain a discrete driver chip. A proper opto-splitter design would have each output powered by it’s own DC power supply and isolated from its neighbors with an optocoupler. To get an isolated DC power supply, use a small DC-DC converter per channel or a small AC transformer + regulator per channel.
Expensive and complicated, but very safe.
I skipped the added isolation because my rig was all being powered from a single power supply and all gear was connected to a single AC outlet. Your mileage may vary, of course.
I’m using these to route my rooftop data lines, but ran about 20 extra boards in case anyone else was interested. $5 each, and I’ll send you the full schematic and parts list.
There was some decent interest in a completely through-hole design. Some folks wanted to build their own pixels but weren’t comfortable with surface mount components.
This board receives DMX through a pair of RJ45 connectors in parallel. A SN75176 translates the differential data into a single-ended signal that the PIC can process. 5 x 2N3904 transistors drive 5 banks of LEDs. The intention was to drive red, green, blue, amber and white LEDs.
The LEDs are arrayed as follows:
R G B W A R
G B W A R G
B W A R G B
W A R G B W
A R G B W A
Grab the PDF copies of the schematic and board layout here:
Tried to post this on YouTube, but their video compressor kept dropping the frame rate – the clips looked horribly jumpy, no matter how nice my input file looked. I tried a few different versions of the export, with no luck.
So here it is in QuickTime instead. 25 pixels sitting in a grid, controlled by DMX-512. Runs fine in Firefox under OS X. Let me know if you can’t view the file.
Since I had a stack of pixel circuit boards from the factory, I decided to make some Halloween lights for the trick-or-treaters.
Solar powered garden lights are nothing new. Contrary to the marketing copy on the box, they cast their pale yellow or blue glow mere inches across the yard. It was time for a change.
I chose 16 of these lanterns, which complemented the lighting package on the rest of the house. They’re spaced about four feet apart along the sidewalk and driveway in front of the house.
I inserted an RGB lighting engine into each chassis, connected them together with CAT-5 cable, ziptied the cables to the lantern stand, and voila:
YouTube Video Clip:
Warning: My camera isn’t so great. For some reason, the brightness levels have been heavily quantized. In real life, the fades are very smooth and clean. The flickering amber flames, in particular, are very realistic.
My wife and I were cleaning the garage this morning when a shiny yellow DHL truck pulled in the driveway. I was delighted to receive about 5 Kg of new circuit boards. Among them were…
A new version of the Point Source RGB Pixel design. It’s based on a 10mm RGB LED, a PIC 16F688 microcontroller and an RS-485 receiver. With the exception of the LED itself, all parts on the this board are now surface mount.
No changes here, but I’ve added silkscreen and soldermask. This is a great way to combine power and data into a single Cat5 cable for powering strings of large DMX pixels. The board has a footprint for a Neutrik NC5MAH 5-pin male connector, an RJ45 ‘pixel drive’ jack, an RJ45 ‘DMX IN’ jack (pinout matches the USITT standard) and large solder points for power and ground.
New revision of the ‘Mini Pixel’ design. All components are surface mount except for the LEDs. Contains a 16F688 processor, an RS-485 receiver and a programming header for your hacking pleasure.