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Soldered Board

A project log for DMX-84: Calculator-Controlled Lights

Control DMX equipment, such as lights, from a TI-84

Alex Cordonnier 08/09/2014 at 19:070 Comments

(This log details work from January 2014)

While I was still on winter break, I needed to verify that my breadboarded circuit actually worked before I went ahead and soldered the board. Luckily, I was able to test it in the school theater after training some students on the lights. It worked, but only after running some bare-minimum firmware instead of the full version I had written. I also had to remove the optocoupler I was originally planning to use. The important part is that the hardware worked, so I could solder the board.

I had to solder it the next evening because the evening after that, I would be in the theater again to train students and would be able to test the soldered board. This was my only time to test it before going back to college.

I tried to lay out the board in Eagle, but I didn't get very far without experience using it. I ended up using GIMP to make sure I had everything in reasonable positions.

I had only soldered three times before. For Electronics merit badge, I had to solder 12 LEDs and a few resistors onto a board that was already mostly populated. Another time was when I made a wireless Wii sensor bar with a 9V battery, some IR LEDs, a green indicator LED, and a switch. Lastly, I had to solder the headers onto the Arduino back in September so it was breadboard-compatible. Clearly I had a bit of experience, but not making a full board.

First, I soldered the Arduino's male headers onto the protoboard. I wanted to use female headers so I could detach the Arduino later, but that would make it too tall for the enclosure. Then I tried soldering wires to the relevant pins, but doing so proved difficult. I had to wrap the wires around the headers and solder that connection, which meant that I had to skip every other pin to have enough space. I also made some solder messes on the board, which left some of the pads unusable. Eventually, I got it done and put back in the enclosure.

When I tested it the next day, it failed. Turns out I had forgotten to change the pin numbers in the code. Changing those numbers fixed the problem, so I was good to go.

Another issue cropped up that I didn't fix until I was back at college: how could I push the LED into its holder when it was soldered to the board? First I had tried putting it in the holder and then soldering it with the board in place, but I couldn't get the pins lined up just right with the protoboard holes. Then I tried soldering it to the board and just pushing it into the holder, but the legs weren't strong enough and kept bending.

I gave up for a while, but then I thought about using female headers soldered onto the board and putting the leads into that. When I tried it, I ran into the same issue where I couldn't line them up with the headers.

Next, I tried using some male-to-female jumper cables with the LED leads going in the female ends and the male ends plugging into the female headers on the board. This approach was good because the jumper cables were flexible enough for me to plug the LED in before closing the enclosure. The problem was that the male + female headers on the board were too tall for the enclosure, so I snipped off the male ends and plugged the bare wires in the female headers on the board. Success!

After opening and closing the enclosure so many times, I had to replace the screws that came with the enclosure because they were getting stripped. In any case, with the LED issue fixed, I finally had the hardware finished.

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