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Matrix Medallion

Electronic parts are getting smaller and smaller. In fact some parts are not even available as through-hole components. I’d read several articles detailing how to effectively solder surface mounted components and wanted to give it a try. Here’s a little SMD practice project I put together to experiment with various SMD soldering techniques. Since it’s a practice kit, I thought it should be something flashy but not critical. Hence the Matrix Medallion was born.

Completely assembled Matrix Medallion board

Completely assembled Matrix Medallion board

Note – The beading is just shown as an example of what you can do. The kit/assembled unit only includes 2 split rings and hemp cord.

It’s a little bit of electronic jewelry you can build while practicing your SMD soldering techniques. The project consists of a circuit board with 49 SMD LED’s (1.6mm X 0.8mm x 0.75mm), one SOIC ATTiny26L processor, a 20mm battery holder clip (for a CR2032 battery) and some interface pins. Throw in some software, a couple of beads, and a piece of chain or cord and you’ve got a neat piece of programmable jewelry!

Order kits and assembled units here.

The LED’s in the 7 x 7 matrix are individually controllable and there are three sample programs available to control the LED’s. The first sample program allows you to scrolls a text string across the matrix. The second program, implements Conway’s “game of life”. The third program, implements 4 bouncing balls. You can see videos of each below. You can of course write your own program, or modify one of the sample programs. Just remember that the device is limited by the 3V battery as the 3V level is pretty close to even the Tiny26 ‘L’ variant’s drop-out power level, so be careful how much current your program draws at one time. You’ll notice that the sample programs don’t just scan the LED row’s, but scans each LED so that only one LED is ever on at a time. This substantially reduces the peak current draw. If the peak current is too high, the Vcc voltage will sag and the processor will reset. Keep this in mind if you decide to write your own software.

Scrolling Text String

Conway’s Game of Life

Bouncing Balls


Hand Soldering Reflow Skillet Ah, the fun stuff. The reason you purchased the kit. To try your hand at SMD soldering. Yes you can do it! I personally have used two different techniques with this board. Let’s call the one technique the “Reflow Skillet” technique and the other the “heat and slide” (hand soldering) technique. …

Circuit Diagram and Source Code

I use a USBTinyISP from It works just fine, however you need an adapter to connect the 6×1 connector on the Matrix Medallion to the 3×2 pin connector on the USBTinyISP. The pin-out on the Matrix Medallion is (from the middle to the edge) Gnd, Reset, MOSI, SCK, Vdd, MISO. All source code is …