Passively increasing a PIR's range? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: October 27, 2023, 05:11:38 am
content: Hey everyone. I have a 360-degree PIR sensor in my garage which activates the lights upon detecting movement. This is situated in the far corner of the room, opposite from the inner entry door. It replaced a more directional sensor that died (and was crap anyway).My issue is, the inner door seems to be right on the edge of the detection range. I've had a look and there are no sensitivity adjustments on the unit itself (just an on-time and ambient light level detection).I'd rather not move the PIR if I can help it. Is there a way to "passively" increase the range. It doesn't need 360-degree detection as it's in a corner against two walls, so everything 180-degrees behind the sensor doesn't matter.

author: jonpaul
author_rank: Super Contributor
timestamp: October 27, 2023, 06:13:27 am
content: Halcion: Cheap Chinese PIR lights have little to tweak, usually a daylight sense and sentivity control.One solution:rewire the PIR light mains to a Room Light switch box, and add Occupacy sensor into the electric box.Old pro quality alarm PIR (C&K dual tech) had inserts with molded mirrors that could change the pattern or range.Jon

author: Berni
author_rank: Super Contributor
timestamp: October 27, 2023, 06:26:12 am
content: The white plastic on the sensors is actually a IR lens.So one could add a similar plastic lens on it to focus form the IR light, giving it a narrower angle but more range. Tho i have no idea where you would get such a lens. Normal lenses for visible light do NOT work for this deep IRAnother option is reflecting light. Most metalic shiny surfaces(even rough textures ones) act as a mirror at these IR wavelengths. So you might be able to fashion together a reflector that helps collect more light into the sensor.

author: bookaboo
author_rank: Frequent Contributor
timestamp: October 27, 2023, 06:48:59 am
content: The lens plastic is HDPE, used in milk cartons (at least in UK and Ireland). It's difficult to work with, any home made effort is unlikely to have as good results as off the shelf items. You could experiment with replacement lenses, many are available from the ususal suspects, for example :https://www.digikey.co.uk/en/supplier-centers/fresnelfactoryThe other thing to try is modding the circuit, most PIRs are variations on 2-stage low pass amplifier. Tweaking either of the feedback resistors will do the trick, should be fairly easy to reverse engineer.

author: jonpaul
author_rank: Super Contributor
timestamp: October 27, 2023, 08:18:53 am
content: OP mentioned it is a 360 deg PIR.Those have a number of sensors or one sensor with several mirror or lenses to direct the IR light in a full 360 deg around a ceiling mounted sensor.The sensitivity of the comparator or number of hits is the only controls in PIR I have used.Jon

author: soldar
author_rank: Super Contributor
timestamp: October 27, 2023, 09:21:01 am
content: Quote from: Halcyon on October 27, 2023, 05:11:38 amA CCTV IR LED illuminator should work. You can install it at the detector or at the door.You can install it on the door so the beam sweeps the detector when it moves.You could even try with some remote control.But even if installed by the detector it would probably work.You can put some reflective tape on the door, of the type you find on safety clothing or road signs.