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projects icon Lo and Behold, 64 Pixels are Enough

I was enamoured with Alex Weber’s 64 Pixels project from the moment I saw it. When I happened across it (via Make:blog, I think), I was just starting the design process for my new satchel. I was thinking about making something similar, but no coherent vision had actually formed in my mind. Once I saw 64 Pixels, I knew it had, nay, must be affixed to my new bag.

Unfortunately, Futurlec jacked up my order, and recieved a trio of green led matrices. Not only do they require a higher voltage to drive them, they’re common cathode, as opposed to Alex’s common anode. That meant I had to do a little more legwork in order to make these buggers work. Fortunately, Alex was kind enough to preemptively include a section of code that handled a common cathode matrix. So that meant I all I had to do was hook up a bigger battery :)

Not so easy. If I added an extra battery (4.5V) or two (6V), random LEDs would flicker, making the entire thing a seizure-inducing mess. Alex was a great help in troubleshooting the problem, though we didn’t come up with a solution right away (I was busy, and I assume he was too; I don’t blame him for not flying across the Pond to solve my problem. (Though it would have been cool.)). Ultimately, I decided to actually READ the specs on the ATTiny, and found that it has a max voltage of 5.5V, and I was pushing 6V into it. The lowest resistor I had was 100 Ohms, and that wouldn’t even let the bugger turn on. So, thinking back to my friend Dan’s incessant reminders, I added a decoupling cap with an arbitrary value (read as: I grabbed whatever was handy), and lo and behold, it worked! So now, I have a wonderfully green and geeky Badge of Honor on my satchel, that (sort of) turns on when I throw the strap over my shoulders.

Here’s a few final pics, showing how it’s all wired up inside.

And, of course, for those of you who are curious, here are the quotes I decided to use:

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Posted on 2009-07-06 15:57:09 -0700

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