Pico Temperature and heatshrink

Troubleshooting
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I’m planning to use a v3 Pico + 6Axis in a new wearable, and I have a few questions, mainly about heat.

Q1) I knew the PixelBlaze v3 Pico got hot from other forum posts, but I don’t think i realized it was THIS hot. How worried should I be about heat dispersion if I’m using it for a wearable (a shirt)? I was originally going to cover the entire Pico in a big piece of heat-shrink, over it and over the wires going in and out of it, for protection and for waterproofing – but now I’m worried that’ll be a bad idea, and it could overheat. Also, is there any way to protect, well, me and anyone else touching it from the heat? It’s hot enough to be unpleasant to touch if I don’t cover it. On the other hand, covering it will act as insulation, and maybe make it overheat more… What’s the best practice here? I see this post from 2022 with a reply in June 2024, but am not sure what conclusions folks came to.

If it matters, for testing, it’s currently not attached to any LEDs, and it’s powered by 5v USB to alligator clips to the Pico, with something from AliExpress similar to this Amazon listing I had on hand.

Q2: Is there anything I need to be aware of with the Pico vs a regular v3? It has the same chips / same ability to drive the same number of LEDs, etc, and it has the on-board accelerometer that the regular v3 doesn’t have, correct?

Q3: Has anyone tried a Pico in a wearable that might need to be washed at some point? I could probably heat-shrink it fully enough to be damn close to waterproof, but I’m not sure that’s enough to allow it to be hand-washed the way that the new generation of pebble LEDs are… any best practice suggestions?

I do have at least one regular v3 on hand, so I could go with my more standard approach, but the accelerometer and small form factor are both really appealing here.

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Yes heatshrink is ok. Tried and tested.

I’ve tested a pico entirely encased in foam, and it obviously runs way hotter than would otherwise, even with heat shrink, but still runs within its rated operating range.

Pico will quit way way after any human would, and is ok running at up to 85C.

In open air the chip itself gets hot to the touch, but not hot for silicon. Generally don’t let it touch bare skin.

Waterproofing is less important than allowing it to dry if it gets wet. Water will seep into any crack, but will dry out a lot slower. Water itself isn’t super harmful, even if powered, at these low voltages, but rust/corrosion will kill it. If you can waterproof it, great, but that will be quite a challenge with the button and wires, etc.

Perhaps better to put it on a connector that you can detach for washing.

Soldering wires to the pico will give you better heat dissipation than alligator clips, since the clips make contact with a small surface area, and soldered wires will wick away some heat.

The Pico + has slightly improved thermal properties pulling heat away from the chip. It still gets hot, but spreads it a little better than the first pico.

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I got a tiny heat sink with a Raspberry Pi kit which I instead put on a Pico. Worked great, but then the Raspberry Pi burned out. So … heatsinks do something!

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Thanks a lot. I’m going to finish v1 of this project with a regular PixelBlaze (although I’m using this barrel adapter you now sell combined with a USB-A → barrel cable) and am loving it), but may swap over after.

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