Bill Woods wrote:
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?

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

"Bill Woods" wrote in message
...
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?

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

Elessar wrote:
"Bill Woods" wrote in message
...
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?

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


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.