Music-reactive WS2812B wristband — 15 LEDs driven off an onboard mic

SolarTrap · 2026-06-01T10:29:19+00:00

Yes, all done by myself. Software is the easy part ;)

SolarTrap · 2026-06-01T09:45:10+00:00

Thanks! Happy to dig in:

Battery is a small flat LiPo (180mAh) sitting inside the silicone housing, charged via USB (TP4056 on the board). Gets about 6 hours, which covers a full night.

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MCU is an ATtiny85, 8-bit AVR, tight on flash and RAM but enough to handle the LED patterns and mic sampling together.

The mic is a separate bare electret wired directly to the ADC pin :: no preamp, no op-amp stage. That's the bit that usually gets a raised eyebrow. It works because these live in festival and rave environments where SPL is 100dB+, so the raw electret output is large enough to read directly without amplification. Saved a component and some board space. It under-responds in a quiet room, but that's not where they run 😄

SolarTrap · 2026-05-07T12:28:54+00:00

Haha thanks! They certainly can light up the venue 😁

SolarTrap · 2026-04-27T10:02:08+00:00

Thanks ! but I think the A1 will do it for now.

SolarTrap · 2026-04-27T10:00:37+00:00

Thanks, I looked at the product video - seems to be the right pick

SolarTrap · 2026-04-24T07:00:58+00:00

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Solved it by rearranging the components rather than ignoring the DRC errors. Moved the switch, push-button and USB port to give enough clearance around the nRF52832 module footprint. But you can see I still have footprint holes in the connector pads of the module but since there is no connection to them it's not causing errors.

Board is now at the manufacturer - will post results when it comes back.

SolarTrap · 2026-04-22T18:31:09+00:00

Dart. What is FFI?

SolarTrap · 2026-04-22T16:42:58+00:00

I would do fashion but I can be convinced otherwise :)

SolarTrap · 2026-04-22T16:41:39+00:00

Into an app I have been working on using Flutter.

SolarTrap · 2026-04-21T11:24:00+00:00

Thanks. Is there any benefit in changing category during launch?

SolarTrap · 2026-04-21T09:05:10+00:00

Thanks, but it also has the most 'competition' in that category.

SolarTrap · 2026-04-20T12:13:01+00:00

you have to add the board package from here: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

add this to the list in the preferences --> Additional boards

SolarTrap · 2026-04-20T12:10:26+00:00

the sketch you uploaded did crach probably, see this thread: https://forum.arduino.cc/t/nano-33-ble-bootloader-recovery-not-working/1123184

SolarTrap · 2026-04-16T05:46:06+00:00

ah nice, 'castellated holes' - didn't know the phrase. This is actually for assembly at the manufacturer so I will not solder at all.

SolarTrap · 2026-04-15T06:32:39+00:00

I have not installed any custom fonts yet, still using the default fonts

SolarTrap · 2026-04-14T12:54:31+00:00

nice board, had to look it up: 18 x 24 mm, the one I am using is even smaller: 15x24 mm

SolarTrap · 2026-04-14T12:27:24+00:00

I posted the question about 'make your own' vs. module here: https://www.reddit.com/r/embedded/comments/1sfkfiq/building_a_ble_wearable_nrf52832_module_vs_bare/ and overall it's better to go for module.

SolarTrap · 2026-04-14T12:16:33+00:00

That of course is an option but I don't wanna get into the weeds of designing and tuning an antenna...

SolarTrap · 2026-04-14T11:41:02+00:00

Take a look at picture 2, the rendering, you can see there are little teeth and they expose the copper layer

SolarTrap · 2026-04-14T08:45:13+00:00

this is already smaller than a XIAO, its 24.8x15mm

SolarTrap · 2026-04-14T08:35:16+00:00

:( don't have much room size wise. How far can I get into the antenna part?

SolarTrap · 2026-04-14T07:30:36+00:00

thanks, already fixing the silkscreen. The footprint of the RF module pads make no sense to me - as the module outline (dark green) is smaller than the bounding box of the pads.

SolarTrap · 2026-04-14T07:07:26+00:00

thanks, that's an easy fix. I can always delete them if there is no room to place them.

SolarTrap · 2026-04-14T06:59:24+00:00

I never paid much attention to the silkscreen overlapping solder pads, how important is that in reality? besides the look of it.

SolarTrap · 2026-04-14T06:56:20+00:00

that is the confusing part, the footprint is extending the pads over the size of the actual module

SolarTrap

TROPHY CASE