World’s Smallest LED Blinky

[Mike Harrison] is known for incredibly tiny soldering. Now he’s claiming a “world’s smallest” in the form of a stand-alone LED blinker, and we think he’s got the record.

He brought it along with him to Friday’s Beagleboard Bring-a-Hack, and we got a close look at the diminutive assembly. The project was dreamed up when [Mike] saw an announcement from Seiko about a new supercapacitor in a tiny package (likely the CPH3225A giving the blinky a footprint of 3.2 x 2.5 mm). With that in hand he added a PIC 10f322 microcontroller in a SOT23 package, an 0603 smoothing capacitor, and an SMD LED.

With such a tiny package, the trickiest part is figuring out how to charge that supercap. [Mike] used a drill and hand files to make a square hole in a CR2032 battery holder to serve as a jig. The bottom of the supercap rests against the battery as a pogo pin makes the second connection to a terminal on the side of his assembly. It charges quickly and will happily blink away for about six minutes after charging.

Mike set out to make two of these, but dropped the second supercap when at his workbench to be forever lost in the detritus common to every electronics workshop. When he first pulled it out at the meetup we were on a rooftop terrace and we were more than a bit concerned that this would just blow away. How do you begin to fabricate such a tiny assembly? He used UV cured epoxy to glue them together first, then somehow completed the soldering by hand!

21 thoughts on “World’s Smallest LED Blinky

  1. DUDE! You have a pre-made career in motorcycle gadgets! Every last one of them needs a turn signal reminder that gets visible and obnoxious after X seconds. Yah.. there’s stuff out there that does it, but you’re hanging a kitchen sink on the windshield. And a lotta MC gadgets after that still! An MC fuel gauge that uses a drilled thru petcock mounting screw as the sense port connection. A tiny voltage monitor, go, no-go, whoops dead!

    Yup… additional challenges… but the MC world needs your kind of construction. Worth a few moments of your consideration… even if you reject it.

    1. Hm, there could be something universal here? Something perhaps with a tach- or speedo-sense as well as flasher sense to trigger the TURN ME OFF superflasher? I usually only forget in parking lots, but still, it happens sometimes…

      Don’t need micro construction for that (even though I’m good at it), just need something solidly designed and engineered, and not as expensive as other MC farkles and gadgets tend to be…

    1. This supercap has 160ohm internal resistance, that’s like 18mA max at 3V. I believe LED is way below 18mA but it could be useful to smooth the voltage a bit to avoid microcontroller resets and brownouts.

    2. It will work without, but extends the runtime, as it prevents a voltage dip when the LED is on, so it takes longer til you hit the voltage where the PIC drops out.
      I didn’t have any 10LF322s to hand, which should work down to a lower voltage, but even then, the 10u cap eill improve LED brightnesd

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