http://www.perkinelmer.co.uk/CMSResources/Images/44-4345CAT_SensorsAndEmittersInfraredSensing.pdf
Teardown Tuesday
What's inside a NESS Quantum Passive Infrared (PIR) pyroelectric motion sensor. How do they work?
And what's all this Fresnel lens stuff anyhow?
Teardown Tuesday
What's inside a NESS Quantum Passive Infrared (PIR) pyroelectric motion sensor. How do they work?
And what's all this Fresnel lens stuff anyhow?
Done.
Here's me looking all around for an explanation of a modern Chinese chip and here's Dave, 10 years ago, answering questions I didn't even know I wanted answered. It's blowing my mind, of course the sensor is a capacitor and amplifier.
The reason for using N/C contacts in security appliances rather has something to do with tamper protection. You want the alarm to go off not only if the motion sensor is activated by motion but also if some smart intruder decides to disable it by cutting the wire or if the cable just breaks and leaves an open connection. This is called "Drahtbruchsicherheit" – the appropiate English term would be something like "wire-breakage protection".
This is mandatory e.g. for emegency shutdown buttons and other equipment which needs to be fail-safe.
I have salvaged 2 Pyronix KX15DD, 1 Pyronix KK15ED and unnamed (with security company Falck logo) PIR sensors that all use solid state relays and exact same LHI968 sensor element.
Edit: Quite robust devices, when I found two KX15DDs one was smashed and top lens stepped on, took the parts home, put it back together and it happily flashes it's blue light to the movement again._
Thank you so much again for your awesome video. I Enjoyed it very much as every time
You don't need 4 wire for alarm and tamper.
2 wires and resistors are enough. You use 1k in series with tamper and 1k parallel with alarmrelay.
Resistor values depend on the system specs. 🙂
do one on countermeasures and iable material to trick em
How are some PIR sensors pet aware?
I can not understand how a cheap plastic lens can hanlde FIR Wavelenghts of 9µm? Are they made of a special plastic or coated? I thought you need special expensive lenses for this spectrum.
Sagan's adorable at the end.
Oh no, a spoiler!
Always wanted to know how these work !! thank you 😀
Thankyou so much for this video, Helped me so much with my coursework! Also just watching a pro pick apart a circuit/datasheet is great for my learning as a trainee engineer..
If half of the PIR sensor were covered with a metal plate (constant temperature heatsink), would it output a signal that is comparable to the amount of IR light reaching the remaining exposed element? So it would act a a highly directional long range photodiode, right? I'm trying to make a long range IR Thermometer that uses analog circuitry.
So let's say (hypothetically) that a company producing PIR sensors uses a subcontractor who, for cost reasons, uses a below-spec white-light filter. The PIR sensor is installed in a home, but due to false positives at specific times of the day, the owner deactivates the alarm. If an intruder breaks in and kills the owner, how culpable would the sensor company and contractor actually be in terms of lawsuits?
Not that this has ever happened, I just thought it was an interesting question.
21:45 Intruder! It's got antlers!
Laughed my ass off there 🙂
Because alarms are generally the least important thing, if you can prevent the person getting into an area in the first place or see them getting in you don't "need" an alarm.
The main things I was getting at is you can use the same ground for multiple alarm contacts, and with 2 resistors you can get four useful states, that is all.
>though we do more enterprise stuff with access control ect.
LOL how is that even relevant? I do alarms, access, CCTV, ip, radio, networking, netsec, programming and electronics repair. Most of our customers are fortune 500 companies. Double EOL can be fooled with 3 MOSFETs that break the green and yellow and switch it to a local resistor network under 1 msec so the panel doesn't pick up the "switcharoo". Modern alarms are wankery.
Hi Dave,
you don't have to use four wires to use the tamper switch. you can run tamper switch and alarm switch in series. (quick and dirty but serves the purpose)
greetings
YES, I'm also a dog person. I might still be good at electronics someday after all.
Dave, you did not tell us young players for what where you probing when you reverse engineered the circuit. I now have a gaping hole in my knowledge 🙂
25:35 to 26:06 was some hot ee pr0n
That bit at the end of the video is cute.
That's no Photoshop! That's a MS Paint!
Nice photoshop!