Sew-on coat-buttons — Blinky – Shiny – Tiny!



This one comes in three versions. The simplest one is just a PCB with 8 LEDs + resistors. Quite easy to assemble (0805 LEDs + 0603 resistors). The next step up on the difficulty scale is the ATtiny13 single-color version. Soldering an DFN10 package is a bit of a challenge. The 3rd one adds another complication: dual-color LEDs with 0402 resistors. The last one does require a good magnifier (head-band or magnifier/lamp combination).

The code is pretty simple, just a bit of software PWM (interrupt driven) + stuff like: “turn the LEDs on… wait some time… turn the LEDs off again”. It also uses persistent storage of the blink-mode (EEPROM). The modes can be cycled through by shorting two pins before powering up the device.

These pins (and the ISP) header are accessible from the front, even when the ‘button’ is attached to a piece of clothing.

The minimum operating voltage varies depending on LED color. It starts at about 1.8V for the warmer colours (RED, ORANGE, AMBER), then comes GREEN (2.2V), then BLUE, WHITE, PINK (2.5V) and finally UV(purple) with 3.5V. The upper limit is 5V.

The latest (final?) version of this board comes in black and was made by hackvana again.

coat-button-V023b_front coat-button-V023b_back

Some tips for assembly for V0.23.b:

This is an SMD job! You will need: extra flux (paste preferred), pointy tweezers, suitable soldering iron with 1-2mm tip (chisel), lots of light, magnifier (loupe, head-band…), solder-paste, hot-air station / skillet for the ATtiny13 chip.

  • The small transistors (DMG1012T, SOT523) are completely optional and require different LED resistors. They were added “just in case”. If you want to use them, you must cut two traces, as indicated on the silkscreen.
  • Make sure to solder the ATtiny13A first! You will run out of space for your soldering iron very quickly on this board. In case you haven’t noticed already, it is truly tiny!
  • The single-colour variant (SC13) needs the 0603 resistors populated on the back side (and the transistor if you should want to use it).
  • The dual-colour variant (DC13) needs all of the 0402 resistors populated on the front side. You will need a good magnifier for this job (head-band, monocle…).
  • Pin #1 of the ISP header is marked by the square pad.
  • Pin #1 of the DFN-10 footprint is the bottom right one (text upright).
  • DC13: RED -> 1k resistors, GREEN -> 680R resistors.
  • coat-button-V023b_asy-notes

Changing modes using tweezers (paper-clip, piece of wire…)

As always, you’ll find source code and so forth in the ‘Projects’ section. If you’re interested, you might find some of these boards on tindie.

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2 Responses to Sew-on coat-buttons — Blinky – Shiny – Tiny!

  1. kevin groce says:

    What an awesome project ! Going to make some for sure.

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