Outroot and things

Electronics, programming, computers, and geek stuff by Kevin Darlington

8x8 Heart

I decided this year to make a 8x8 RGB LED device to give to my girl­friend for Valentine’s Day. I had made her a heart of red LEDs two years ago and I decided to step it up a lit­tle. No, this was not a cheap solu­tion (it cost around $100 in mate­ri­als, includ­ing all the stuff I bought that I ended up not using). I spent more time on this thing than any­thing I have made before.

I knew what I wanted to make, but wasn’t sure what I was going to do to make it. Ini­tially I was think­ing I would buy the 8x8 RGB LED from Seeed­stu­dio and then build my own LED dri­ver board to run it. After some research, it seemed that this would take a much longer time than I had to com­plete this. Some exten­sive google search­ing yielded the 64-pixel RGB LED matrix kit from the 2uF blog. The cre­ator of the kit was very prompt in send­ing me the device and it wasn’t long before I sol­dered every­thing together and had it running.

I spent sev­eral weeks slowly pro­gram­ming the ani­ma­tions into the device. I sort of knew what I was doing but I had never done any ani­ma­tions before. The most dif­fi­cult part was opti­miz­ing parts of the code to pre­vent flick­er­ing. Also, I ran into RAM limit prob­lems since the kit is based on the atmega168 and not the atmega328p.

After I had pro­grammed the basic ani­ma­tions, now comes the task on how to power this thing. I could either go the cheap/easy way of just get­ting a wall adapter and hook­ing it up to the device, or I could make it cooler by mak­ing it bat­tery pow­ered and portable.

The cir­cuit I chose to use was the one based on the Minty Boost from adafruit. There are plenty of cir­cuits out there involv­ing the LT1302 that I could use, but I fig­ured if it’s good enough to be charg­ing iphones, ipods, etc.. it’d be good enough to run my device. The only thing I cut out of that design were the 100K charg­ing resis­tors. I also used a 22uH induc­tor as rec­om­mended by the design process.

Back of device

Orig­i­nally I was going to make the step-up con­verter be on a board that cov­ered the whole back of the device, then put the bat­ter­ies on the board with it, but then I would have to add extra but­tons as it would cover the but­tons already on the board. The deci­sion to put the bat­ter­ies on the side came about because they would not fit on the back prop­erly. It just looked weird. What I did here had a nice side-effect of giv­ing it han­dles to hold on like a hand-held game.

Step-up con­verter board

I had to use some hot glue on the head­ers and the switch to keep them from moving.

Bot­tom of step-up converter

Was it worth it? It sure was. My girl appre­ci­ates this a lot more than if I were to buy her jew­elry (she has enough of it anyways).

Red heart

Source code

The code is a bit of a mess and uncom­mented for the most part.

outroot_gf8x8.pde

This entry was posted on Wednesday, February 17th, 2010 at 2:57 pm and is filed under Arduino, Electronics, Microcontrollers. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.