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I have a small 5 V PCB e.g. a Pi Zero.

This is inside a PLA plastic enclosure currently. It is quite considerably larger than the PCB approximately 5x as wide and 3x as tall. The PCB is raised above on feet so there is airflow above and below. Holes are also giving air flow.

From a safety POV, would this be OK considering it is 5 V? The USB power supply is on the other end of a 3 m cable outside of the box.

Velvel
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sungstack
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  • What exact aspect of safety are you worried about? The plastic setting on fire or emitting toxic chemical vapors, or some electrical shock hazard? The latter would depend on the power supply and othet connections to PCB. – Justme Aug 21 '23 at 06:10

1 Answers1

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You can get UL94V-0 (flame retardant) PLA, at a price. It also generally requires higher temperature for printing.

If you have ordinary PLA it may not be as safe as an inexpensive ABC enclosure, and certainly will have a lower temperature at which it softens.

If you have non-flame-retardant PLA housing, it's a judgment call as to whether your USB could plausibly generate flames under possible fault conditions. The power is adequate to do so. Personally, even with just 5V USB input, I'd be reluctant to do it for something that was powered 24/7 and unattended, and would certainly never give or sell it to someone.

Note: I just did a brief informal test (roughly similar to UL94V-0 testing method) with a brand-name (MG Chemicals) PLA and it does support a vertical flame (burns with a similar blue flame to polyethylene and drips burning plastic) so it would not pass minimum flammability standards for a commercial housing.

Spehro Pefhany
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