failure causes for wearable electronics?

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westfw
 
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failure causes for wearable electronics?

Post by westfw »

So... I built a neopixel-based "hair ring", that's supposed to light up my hair with assorted effects.
It's essentially an ATmega168 based "Freeduino" (Duemilanove-like) board connected to a a 12 pixel ring (with 470uF cap and some epoxy.) (I should admit than none of the components are actually from Adafruit, I guess.)

Anyway - twice now, I have tried to wear it, using a plug into a USB charger for power and on/off switch. And twice now, it has FAILED relatively quickly (although it worked for "a while) - no lights at all. In both cases, I brought it back home and re-upload the sketch, and it starts working again! (without having to reprogram the bootloader, BTW.)
(for the second time, I had added a RESET pullup and switch, but they didn't seem to help.)

I can't figure out how it would fail in a way that exhibits the symptoms. Does anyone out there have experience with causes of unusual failure modes in wearable electronics (and/or fixes for the same?) I guess the next addition will be a diode on the RESET line to prevent power transients from putting the chip into program mode, but ... that's quite a stretch. I know hair is a static-rich environment, but ... not so much here and now, and I'm not sure static explains the semi-permanent failure (till re-upload, rather than till re-power-up.)

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bidrohini
 
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Re: failure causes for wearable electronics?

Post by bidrohini »

Please check if any short circuit is occurring when you're wearing the band.

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adafruit_support_mike
 
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Re: failure causes for wearable electronics?

Post by adafruit_support_mike »

To fail badly enough to require a full reload, I'd expect something like high-speed voltge spikes on the power lines.

Flexing PCBs and putting tension on wires are common issues in wearables. Give the hardware a good shake, poke various points with a probe like a chopstick, and move any wiring around one wire at a time to see if you can find any instability.

The next condition wearables experience is body heat. Try alternating between a hair dryer and a fan to heat and cool the hardware to see if thermal cycling has any effect.

Body contact also involves moisture. Stretch a piece of cloth over a bowl of water at body temperature, place the circuit on that, and cover it with another piece of cloth to see if surface adsorption or condensation create shorts that cause problems.

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