Preview: I’ve got big plans for this little bulb

My friend Brian just gave me this light-bulb. It’s an LED bulb that stopped working. Whether it’s burnt out or not I’m uncertain. But I plan to find out what booty there is inside.

A little smash with the hammer will take care of the glass enclosure, but I’d like to document my findings and regular readers will know I have notoriously poor video recording equipment. I’ve been hitting eBay this week and as soon as I can get my hands on some cheap used equipment I’ll set to work on this bad boy and report back.

If you need something to quench your light-bulb curiosity, look back on this other LED light bulb which I disassembled a year ago. It turned out that reprogramming it wasn’t all that hard and it now serves as our holiday porch light; fading red and green at Christmas, pulsing red at Valentines, and fading purple and orange on Halloween. That was a fun one!

The initial posts:

The in depth version is over at Hackaday.


Light bulb microcontroller salvaged with HVSP

The ATtiny13 microcontroller from that LED light bulb is now waiting for new firmware. I used High Voltage Serial Programming to erase the chip, which clears the lock bits. I then reset the high fuse back to 0xFF. It was 0xFA before which disables the reset pin (and enables brownout detection) making In System Programming impossible.

I finished mapping out the PCB and it does use the example circuit from the buck converter's datasheet. Looks like it was outputting 12V and using a 7V zener diode to step down to the 5V source the tiny13 needed. I'm going to depopulate the PSU and patch in a 12V feed for further testing. I'm thinking my first project will be a red/green flasher for a Christmas porch light.

LED lightbulb schematic

I had a bit of time to test out the PCB from that LED light bulb. I've just been using continuity tester and ohm-meter for this. Here's the LED logic. High-side transistors but I haven't quite figured out how the resistors are wired. I've also established the A/C side of the switching regulator but I'm having trouble figuring out the output. Similar to the example in the datasheet but not quite the same.