555

Duckon 2012 prototype finished

The 3D printer figured big in this year's blinkie design. Not only is the battery holder printed, but I used a gerber-to-gcode conversion script to enable me to use the RepRap to lay down the ink on the blank PCB to make the prototype, and by the time June rolls around I may have a printed sleeve to go on it that diffuses the LED light.


I used the Gerber to GCode converter, tuned up a bit (added some experimental backlash compensation.

That failed the first time, the extra fine sharpies don't lay down much ink. The 2nd try I printed each side 3 times, then went over traces with a regular (fine point) sharpie as much as possible (my hand is too shaky to do the very close traces). That went OK.

Then a quick drill of 52 holes and about 90 minutes of soldering (soldering tightly spaced LEDs when you have to solder top and bottom due to the hand-etched board is time consuming) and it pretty much fired up right away. I did miss a couple of solder joints and had to touch those up.

All I have right now is the test pattern for the LEDs, so I need to do a bunch more programming to get a wide variety of patterns. This one will allow selecting of patterns as well and remembers settings when turned off (since it never actually goes off unless the batteries are removed, it actually starts right up where it left off).

The battery holder for the 3 LR44 cells is printed on the RepRap. I am going to play around with the idea of a printed diffuser for this blinkie, to be sold as an add-on for a few bucks. IMO a diffuser makes any blinkie look cooler.



Thanks. Maybe in the future I'll get this done in time to present it at an earlier concom meeting and be able to make Isher.
Yeah, it took about 3 revs to get something I like. On the near side you can sort of see a couple of slits down the side that allow that side to spring a little, and there's a ridge inside to form a detent to hold the cells. On the far side there's a slot down low where something can be inserted to push the old cells out when replacing them.

Button cell holders are hard to find in general because usually they're designed into the case of a new product. Last year I used a CR2032 cell; holders for those are available because they're used as battery backup on mainboards, but they're a bit large and a single cell only delivers 3V so you can't really run blue LEDs directly from them.

I just ordered 1000 LR44s for this year's convention, and so that I can do some battery life testing with the new design. My estimates say 18 hours runtime but that's with the light test pattern which only has one LED on at a time, but on the other hand it's using the mAH rating of the cell, and this circuit will run until the cell voltage drops pretty low. Last year I estimated 23 hours runtime and actually got more like 60.

It also depends on the LED color. I intentionally used blue this time because that's the worst case scenario. When people actually build they'll have a choice, probably red, green, blue, maybe some other colors.

I really need to come up with a design using RGB LEDs too, but to do that right I need to get PWM working with charlieplexing and that's a nut I haven't tried to crack yet. The new method I have of running the charlieplexing may work better for this.