Seeking advice on flat fresnel lenses for PIR sensors

Hardware
1

Hi all,

I'm building a multi-sensor node, but I'm also trying to factor in Partner Approval. Thus it must look nice.

I want to use a PIR sensor as well as mmwave, but PIR usually has a white domed fresnel lens, which has to poke out somewhere. I am wondering if anyone has any ideas regarding making a flat fresnel lens which would allow for a slightly recessed PIR sensor that is flush with the rest of the enclosure.

I am aware that the dome is a type of fresnel lens, but it isn't a flat one, which most fresnels are.

I have searched extensively and haven't found any on 3D printing sites, so either this is a stupid idea and can't be done, or else it's novel, in which case there's some modelling ahead, but this seems unlikely.

Anyone ever seen a thing like this? Or know of a formula one can use to calculate the focal depth of a fresnel?

Thanks everyone.

2

Try a google search using “ flat fresnel lenses for PIR sensors”
Also note that a flat lens will reduce the area it will sense

3

Interesting. Brave Search's Leo AI gave me this:

Flat Fresnel Lenses for PIR Sensors
Flat Fresnel lenses for PIR sensors are designed to focus infrared radiation onto the sensor, enhancing its ability to detect motion. These lenses are typically made from materials like high-density polyethylene (HDPE) or polycarbonate, which provide durability and efficiency.
They are used in various applications, including security systems, smart home devices, and automatic lighting.
For example, the PIR FRESNEL LENS_PD05-12005-WHITE from Fresnel Factory Inc. is a flat lens specifically designed for use with PIR motion detectors.
Additionally, manufacturers like MUHWA Industrial Co., Ltd. offer custom flat Fresnel lenses for PIR sensors, ensuring they meet the specific requirements of smart home applications.
These lenses are also available from suppliers like 3Dlens®, which provides flat passive infrared Fresnel lenses at competitive prices.

4

Why both technologies?

5

Hi @ghayne,

I like to use as many sensors as possible, because no single sensor is infallible.

It's not simply motion, you can draw inferences from many things. For example, is the media player on in the lounge? That's a good indicator someone is sat there watching.

So, I feed all of the available sensors for a room into a Beyesian filter. It considers the multiple sensors firing at that time, and makes a call about whether, overall, it seems likely the room is occupied.

Thus, PIR + mmwave, because the more input data you have, the better the Beyesian filter works.

6

In this video Andreas Spiess reviews some low profile PIR sensors

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7

Have you checked linknlink emotion presence detectors https://shop.linknlink.com/
zone detection with web hooks and mqtt.