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.

Thursday, August 04, 2005

Progress and Setbacks

Yay for finally getting some more work done.

Microcontroller Board
I started off on Monday by baking (with my wonderful new toaster oven) one of the boards and ~8 components. I baked them for 7 hours at 150F on Monday, ~1-2 hours on Tuesday, and 5 more hours on Wednesday. After Wednesday's baking session, I pulled them out of the oven and set out to soldering the components to the board. All the components were for the voltage regulator portion of the board and could be easily tested once they were soldered in place.

The first thing I noticed was that I hadn't planned on knowing what orientation the diodes and polarized capacitors needed to be in. A little bit of checking of my schematics and a quick refresher course on what pin was referred to by the small band on the diodes (band = cathode), I was able to orient the diodes properly.

The next thing I noticed was that the diodes were huge compared to the pads they were supposed to be soldered to. Like, I couldn't see either pad when the diode was placed symmetrically on them. Luckily, with some flux on the diode contacts and a bunch of solder, I was able to flow enough solder under the contacts to solder them to their respective pads. For rev 4b (if needed), I will be enlarging the diode pads considerably.

After that, the soldering was pretty much smooth sailing. I grabbed my small 4.5V 3-AA voltage source for a quick test, hooked it up with a switch (so I don't bounce the hell out of the voltage source by trying to connect a wire directly to the board), and turned it on. I had my voltmeter hooked up to the ground and voltage out of the regulator and it started freaking out claiming that the voltage across the pins was well over 1000V (NOT possible), so I unhooked everything just in case. After smelling for burnt components, I hooked it all back up, threw the switch, and then put the voltmeter across the same contact points. This time, I got a wonderful 3.496V output on the voltmeter. Huzzah! It's slightly larger than the 3.3V I wanted, but oh well. I really don't think any of the components will freak out about it.

After this initial success, I decided to solder a few more testable components to the board. I grabbed one decoupling cap, a resistor, and a surface-mount LED (for power status) and soldered them all in place. I also noticed that one of my previously-soldered caps was basically shattered on one of the leads, so I had to scrape it off and re-solder a replacement. I'm gonna end up burning through a lot more 0.1uF caps than I had anticipated. They're so large and so brittle; the ceramic cracks off very easily. Anyway, I fired it all back up again and got a wonderful amber glow out of the LED, so yet more success.

Distance Sensors
And now, the setbacks. Before, I was looking at ordering up a few more distance sensors to use and checked DigiKey for price and availability.
For part number 425-1161-ND, I saw this:

Quantity Available 0

Price Break

Bad News Bears. Ruh Roh Rorge!

I have yet to call them (I will when I am ready to order some more stuff... it may be a while). I checked the manufacturer's website (Sharp Microelectronics) and found that there are 2 other resellers of the part (Future Electronics and Jaco Electronics).
Future has them in stock, but they only sell in quantities of 100. At $8.625 each, that would lead to quite a hefty investment; one I'm not willing to take at this time.
Jaco has it listed as 400 in stock, but they don't have any online ordering mechanism. They have a Minnesota contact number, so I might call it to find out, but my guess is that they only deal in 100-count quantities as well.
DigiKey has the 4-30cm (~1.5"-~11.8") version available and is the same price, but I don't really want that range. That's getting too close to the wall itself. I also found that they had an unlisted version (425-2046-ND) that appears to be approximately the same thing (it's also analog with 10-80cm of resolution), but the availability for 25 of them is Nov 1st. Ye-ouch... not cool.

So I may not be using the distance sensors at all. Harumph is what I say to that. We'll see, but the prospects are not that great.

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