Jurek and the Amazing Techno, Colored DreamWall

Jurek and the Amazing Techno, Colored DreamWall

The title is mostly a placeholder, as I haven't really figured out a name for it yet. This project is a wall hanging that consists of semi-large triangular pixels using discrete RGB LED's and PWM to control intensity levels of each LED, resulting in a 4096-color display.

Wednesday, May 18, 2005

Holy soldering Batman!

Wow. Trying to solder a QSOP chip with a 50-mil tip is really, really hard. Like, "Don't try this at home, kids" hard.

I used a flux pen on the contacts of the QSOP/DIP adapter chip, tinned the contacts, re-fluxed the contacts, and fluxed the leads on the chip. After a couple attempts at tacking one of the corner pins to the adapter, I finally succeeded and moved onto the opposite corner. I was able to align the chip on the adapter, despite my wildly-shaking hand. I'm really going to have to do something about that if I'm going to be soldering dozens--nay, hundreds--of components.
I had to fudge around with the chip a little bit, because after tacking opposite corners, I realized that the chip was pitched up on one end, so as to not make good contact with the contacts. Using my trusty scalpel, I had to free the chip and re-mash it down on the right pins; this time, correctly-aligning it parallel to the adapter.

The soldering really wasn't much of anything except me trying to hold the iron on top of a pad (this generally resulted in the tip on top of 2 contacts at once) and then pushing the solder into the area next to the contact of the chip. I made a very concerted effort to not touch the iron to the chip leads, mainly out of fear of frying the chip. After my first attempt at soldering all 24 pins, I checked the solders using a continuity tester and found that about... 8 of the pins were actually soldered correctly. Wow...
It took me 3 more attempts at soldering the remaining pins before I finally got them all soldered to the pads. Thankfully, I had some wick around, as I needed it on at least 4 separate occasions. Solder spread across 4 pins at once is not a good thing.
Now that I had them all soldered and continuity was good, I had one last test to do: make sure none of the pins were shorted. I thought for sure that I would have shorted at least one set of pins, but a quick check showed that none of them were shorted. Yay flux! Yay me!

At this point, the only thing I was worried about was whether or not I fried the chip with heat. 700F for more than a few seconds probably doesn't feel to good to those chips. I know I wouldn't last nearly that long.

I pulled out my previous hack job (see Success!) and put this one in its place. A quick test showed that it worked great (Yippie!), and then I decided that it would be a great idea to use Monday's test along with this. So I grabbed my little makeshift pixel and hooked it up to the uC test board and... viola... instant 12-bit RGB color pixels.

Here's a couple videos (.mov) of it all in action. On the right is obviously the pixel. In the middle is the 3 LEDs I tested with in "Success!", and on the far left is the uC board with the test status LEDs.

video 1 (4.2MB)
video 2 (4.2MB)



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