Wednesday, November 27, 2013

The ugliest project I've built so far

Based on this photo from BroHogan's gallery of Geiger counters, it was supposed to be a simple encasing using Adafruit's Arduino enclosure. Everything looked neat and clean inside, even with room to spare.
I wanted to use LiPo instead of AAA batteries, to avoid opening and closing the device every so often. This required the use of a LiPo charger, for which I picked the one I already had, the seeedstudio's LiPo Rider.

I spent countless hours trying to put this puzzle together:
  • only 4 places for screws;
  • small(ish) charger board must to be solidly anchored to the case (since an USB cable will be plugged in frequently), yet it does not have any hole for screws;
  • 6 wires (battery, V out, switch) must be soldered to the charger SMD board;
  • 12 wires need to connect the Geiger board to the LCD, on the other half of the case;
  • trim pot suspended somewhere (since there is no room for it on the PCB);
  • power switch to fit in the rectangular opening of the bottom ;

When I thought I figured it out, the two halves of the case wouldn't close because things inside were too tall/thick. Back to the "drawing board". Took out the ATmega328 from the Geiger board (it was touching the LCD connectors, which were already minimized for space), and replaced it with a cheap ($4) "Arduino Nano" (or is it "Mini") from ebay. This also helped immensely with the wiring: instead of connecting 12 wires between the case halves (Atmega328 to LCD), I had to solder only 3 (Vcc, Gnd, Int).

After a few more kludges (e.g. re-positioned the inductor on its side, removed the (over)power(ing) LED on Arduino Nano), I ended up with something , as the saying goes, "only a mother can love".

The lesson I learned from this experience is that, if one wants a seamless, solid, beautiful, project, one needs to either design the board for an enclosure, or the enclosure for a board. Trying to mix and match the board with the enclosure leads, at best, to something ugly.

Did I mention that I worked on it on and off for about 3 months?
The red light in the bottom left corner is the "charging" LED. (And then there is the somehow annoying LCD's backlight, visible through the translucent enclosure.)

The power switch is advertised as being the smallest rocker power switch out there. I only had to file off about 1mm on the upper side of the original rectangular opening to make it fit.

Another lesson I learned: use a transparent enclosure only when the inside looks perfect and you want to show it, and by "perfect" I mean even no visible wires.

Stay tuned for the next version of this Geiger device. (You did not think I would stop here, did you ? :)

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