12 LED Charlieplexed Snowfall with AtTiny85

Strykeroz, I know this thread is sorta old-ish but I wanted to thank you for your Larson code. I borrowed it and modified it for a 40-led circuit. The 40 leds are my cars 3rd taillight. I will program this to be a normal brakelight but when the car is stopped, they will start scanning back and forth.

Here's a video of my circuit in action. http://www.youtube.com/watch?v=c_tHc5Vl_Gw


Thanks for sharing Mike - that looks great. Love the soundtrack too. I’m pretty sure that high level tail light wouldn’t pass a roadworthy here - but VERY pleased it’s okay somewhere!

I’m overdue for an update here too I guess. Since last posting I’ve had two versions of the circuitboard made up at Seeed. The first was to prove that my new EagleCAD skills actually translated okay to the real world. When it came back fine I’ve moved to the smaller 50x31mm board in the DP sick-of-beige PCB size which is far more compact, and I added a footprint for a 2.1mm DC jack sharing the space of one of the two screw terminals.

The idea is these boards will daisy-chain together for power with the end board in a chain having a wall wart plugged in via the 2.1mm jack. Each is standalone with a diode for polarity protection. At the bottom are two groups of 0.1mm spaced terminals for the string of LEDs to connect to, via a row of holes for strain relief. The larger hole at the top centre takes a curtain hook or ring, to hold it to a curtain rail on the inside of a window.

In the attached photos you’ll see two of the boards populated along with the front and back view. In the group shot the board at the upper right is the v0.1 first attempt for scale.

In coming weeks I’m going to make up these first 10 to get a look at how the massed effect appears. Once that’s done I’ll be ordering a batch of 50 more in black to complete the job. I’m not looking forward too much to soldering 1200 white LEDs…but it appears we do suffer for our art XD

Will post a video of the effect when done,

Are the PCBs holes for the barrel jack the correct size? They look huge. Did you use the Adafruit Eagle library?

[quote author=Coding Badly link=topic=135596.msg1268000#msg1268000 date=1370480096]
Are the PCBs holes for the barrel jack the correct size? They look huge. Did you use the Adafruit Eagle library?
[/quote]They are huge. That’s one of the libraries I have installed so it’s quite possible that’s where the part came from. I suspect from your observation that’s a known issue?

It did work out okay though.

I suspect from your observation that’s a known issue?

Well, it’s known to me. I have not found anyone else who has had problems. I did create an issue for it on Github/adafruit.

It did work out okay though.

Yeah but having it the correct size (probably #) works so much better. If you want, I can dig up my version which (hopefully #) is correct.

# I have not yet made up boards since correcting the footprint.

[quote author=Coding Badly link=topic=135596.msg1268005#msg1268005 date=1370480671]
If you want, I can dig up my version which (hopefully #) is correct.

# I have not yet made up boards since correcting the footprint.
[/quote]That would be great - thanks. And happy to be the lab rat for sure.

Cheers ! Geoff

I have no idea how to extract the one part so I’m attaching the entire library.

PJ-102A is the part number. It’s the Eagle Package for this…

I believe it is the same or very similar to the one you are using.

adafruit.7z (206 KB)

Time flies…

I should have posted my version long time ago…
So I will do it right now :wink:

Ik looks great Strykeroz! You did a great job.

Here are mine:

Measurements: 1x29 Cm
Used components:
• 1 ATTiny 45 @ 8Mhz (SMD SOIC)
• 1 100 nF capacitor (SMD 0805)
• 5 100 Ohm restistors (SMD 0805)
• 20 diffuse cold white LEDs 3mm

I’d just took one that wasn’t cleaned up…
You can see the flux around the solder… :wink:

Here an other picture:

I just read this entire thread. I'm impressed, you guys do awesome work.

How can I get the pcb files to have my own made?


Thanks for your interest. I've not actually gone back to this project for several months - time flies - have a big box of LEDs sitting beside me here that needs to be assembled before December though :)

Traxxtar: How can I get the pcb files to have my own made?

I've just updated github with the EagleCAD schematic and board as well as a zip file that can be sent to Seeed Studios (that's where I had mine made) without any further work. Note this is still with the bigger pad Adafruit 2.1mm component discussed above and produces a board in the sick-of-beige 50x31mm shape.

Not sure if Dave has published his somewhere as yet...

Cheers ! Geoff

Hi all,

Funny, here just the same, only finished 5 of them and still need something to weatherproof it. ;)

But I did posted my layout on the Fritzing site: http://fritzing.org/projects/charlieplex-snowfallshooting-star-20-leds

Take a look at it and have fun with it!


daaf1984: ...and still need something to weatherproof it. ;)

Hi Dave

I've had some success with some test circuits embedding them in casting resin (here's a link to the brand I bought but you're sure to have an equivalent local to you). After several months the resin remains clear, and the circuit protected. I can see some of the circuitry has changed colour due, I presume, to corrosion where I didn't get all the flux off.

Overall I think that's a method I'll continue to use for weatherproofing LED circuits, and my results can only improve.

Cheers ! Geoff


That's a good idea!! I have clear resin here, so I will do a test run. :D

Did you made a mold or brushed it over?


Hi Dave, for my tests I actually used small circuits which fit nicely into icecube trays...so I had a mold that did the job just great. Maybe you could form a mold out of Sugru or similar for yours?


After some considerations, I decided to use clear tubing for weatherproofing. Just seal the bottom and top with acrylic rod.

If something occurs, it's easier to re-solder, than using resin.