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| Very small and thin transparent enclosure |
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| Kasper:
Be careful what material you put infront of the IR sensor. Transparent to visible light does not mean transparent to IR. You also want immunity to sunlight if it's outside. I'm guessing by IR sensor, you mean PIR motion sensor? If thats true, safest bet is get a PIR with window (fresnel lens) with zones and detection distance that meets your specs. And don't put any other material infront of it. |
| jmaja:
The IR is a a set of proximity sensors using a set of IR LED's. They work at 850 nm so very close to visible light. Seems to work OK through some clear plastics I have tested, but naturally the actual material to be used has to be tested as well. The goal is to measure visible light lx as well and the proximity sensor has a sunlight canceling system, which seems to allow measuring in direct sunlight. Then there are visible LED's to inform the user + BLE to send data to a mobile phone. Sensors and LED's are on both sides of the PCB thus the enclosure needs to be transparent or have windows on both sides. |
| mikeselectricstuff:
For prototype qtys : a) two lids from Hammond clear plastic boxes, back-to-back. b) a sandwich of 2 sheets of acrylic, with a spacer frame +PCB in the middle For production, the tooling cost for an injection mould for a simple shape like this wouldn't be very expensive |
| jmaja:
I ordered some clear heat shrink tubing and did some testing. https://www.digikey.fi/product-detail/en/3m/FP301-1-48--CLEAR-24-PCS/3M161366-ND/3864906 This one has no adhesive. The IR proximity sensor seems to work just fine through it. It increases the base level, but SNR is about the same. The PCB+battery is now about 24x61x4 mm. If I use the heat shrink tube, how could I seal the ends? I'm starting to like the idea of "plastic wrapping". What other ways are there to achieve this? Vacuum bagging? Laminating? |
| Kasper:
I like using hot glue to seal the ends of heat shrink tubing but thats usually with much smaller tubing and I've never tested its waterproofing quality. You could try hot glue then pinch with needle nose pliers to crimp it shut. |
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