Plastic to put in front of PIR lens

[Bill Woods]

I have a PIR for sensing people in our garden. I want to have the PIR located behind glass or plastic.

If the PIR is behind glass then the glass blocks the heat which triggers it. I image a clear plastic sheet would also block heat.

Is there some special plastic (like that used in the PIR's lens) which can transmit heat?

[Ian Stirling]

Thin polythene. It's what the lens is made of.

[Elessar]

I have a mini-IR camera and IR LEDs in a bluetit nestbox and use the bottom of a plastic milk carton (the 4 pint/2 litre sort) to protect the LEDs. It works fine - no obvious loss of IR. Of course PIRs might work on a different part of the IR spectrum.

-- LSR

[Ian Stirling]

Vastly different. IIRC, it's 700nm for IR LEDs, and about 20-40 times that for PIR.

However, the polythene from such a bottle may be suitable for both.