Passive infrared motion sensors: a two-bit camera powered by crystals

[@rocbolt]

I swear one of the best parts of growing up is being able to tear apart stuff without being yelled at

[@jpreale]

That plus getting whichever the hell box of cereal I want.

[@Orrsmen]

I dont know why i didnt try sooner

[@pistonburner6448]

You had a girlfriend who liked it rough too?

[@nailsofinterest]

I was lucky then. My dad tore apart stuff and had me help!😅 loved it!!

[@goosenotmaverick1156]

You definitely found a nugget of truth there 😂

[@shoy]

"but I've got a dremel tool with a cutoff wheel so that won't stop me" are fantastic words to live by

[@Orange_Tree_]

I unironically want these words on a tee

[@anteshell]

Dremel works in social relationships too.

[@kimvibk9242]

"The Dremel of Insight"

[@avanillagarden]

@@Orange_Tree_ careful, you're gonna wake up the t-shirt bots

[@MonkeyJedi99]

Earlier today, the mechanic I watched did something similar. "I want to see how this actuator is broken inside but it's plastic welded so I can't open it up." Then he jump-cut to him using an angle grinder to cut it open.

[@JamesRibe]

Do you mean to tell me that manufacturers made these devices work via the magic of buying two of them?

[@IndianaDipper194]

comment of the year award 2024

[@submachinegun5737]

It’s a fascinating bit of engineering. When there’s two of a device they can interact and reference what they should do with each other and basically each device keeps each other sane. Kinda like how being alone for long times makes it much easier for people to go crazy

[@rarelyevenusedaccount]

crazy? i was crazy once

[@Bbaass_TMH]

* the magic of selling you two of them

[@submachinegun5737]

@@rarelyevenusedaccount they put me in a rubber room. A rubber room with motion sensing lights. And motion sensing lights make me crazy

[@redundantqwail9088]

The delivery on "We matter, and above absolute zero" was incredible. Batting 1,000 out the gate

[@dielaughing73]

I guess that means we matter to some measurable extent. Not a very high bar but I'll take it

[@sponge1234ify]

​@@dielaughing73Approximately 1 bar, in fact!

[@badLuckRiley]

Friend, are you trying to indicate a 100% success rate? Because that would be batting 1.000 or “batting a thousand” in baseball parlance.

[@BariumCobaltNitrog3n]

Ouch! Getting a hit once in every ten at-bats is not good. Average average is .296-.303 with 3 hits out of 10 interviews with an umpire. A very good player will make good with the wood 4 times and the best of the best got to a place with a base 4.6 times out of 10 visits to the chalk box wow! 1943 Josh Gibson's record from the Homestead Grays (Negro League) still stands. 70 games, 249 at-bats 116 hits 20 home runs

[@MajorOutage]

@@badLuckRiley The irony the "batting one thousand" in numerical form is just 1.

[@michaelcalvin42]

I've been watching your content for years now, and quite frankly, yours is one of the best channels on KZbin. Your videos are always so well put-together and researched, with sky high production values. Here, have a contribution from viewers like me.

[@freelancer001]

Jest jeszcze wiele kanałów wartych zasubskrybowania

[@TechnologyConnections]

Wow, thank you so, so much!

[@michaelcalvin42]

@@TechnologyConnections No, thank you! Please keep up the good work!

[@realimpmen]

that's a lot

[@vijfsnippervijf]

​@@michaelcalvin42 Both of you deserve a thanks from each other as well as from me!

[@GlassFoxGear]

I'm not even joking; I was just talking to my very patient wife and informed her that even though I've seen motion sensors everywhere, I had no clue how they worked. This is the power of this channel.

[@Alexis-lt3zy]

speak of the Alec!

[@user443]

All of us watching this channel almost certainly have a very patient partner

[@GGanon]

Alec making technologies connect in our brain since 20xx idk when he started you get what i mean

[@DoctorOnkelap]

lol, discoball loop

[@Marc_Fuchs_1985]

Yeah, same here. You don't NEED to know how they work, but doing so lets you appreciate the world of technology more. Like I regularly keep being astonished about cars and bicycles. We are very used to them of course, but that doesn't change the simple fact, how much of incredible enginuity is in those things. I mean, bikes are simple, but exactly this simplicity is the gorgeous thing about them. How they take the rather pathetic amount of energy the human body generates and enables us to transfer as much of that as possible into a usable amount of motion energy. Technology is awesome, it's sad we have reached such a level, that it gets abused a lot.........

[@ArrowNought]

"Motion sensors, you've seen them.," Which made me think the next line would be: "And they've seen you too"

[@DantevanGemert]

That would have been so good!

[@Games_and_Music]

Yeah, when i heard him say that, i said: "But have you wondered how they see you?" Considering that the thumbnail says: "They 'see' heat", i kinda expected him to say it, but surprisingly it was just an ordinary sentence.

[@GigaDanMan]

Right??

[@xdeama]

the disco ball loop pun was 10/10

[@noxious_nights]

agreed

[@g.tucker8682]

Yes, very funny… although not a pun.

[@proCaylak]

9:21 if you wanna skip to that part

[@zzzaphod8507]

the disco ball loop pun was 10/10

[@vibaj16]

not a pun

[@runaway9098]

I like how the end of this one had a PBS style "this show was brought to you by viewers like you. Thank you." It really added to the whole "mini documentary/educational tv" vibe your channel has to it.

[@wtmayhew]

@@tooltime9260 Equal opportunity propaganda though. Ever notice that PBS programs are supported by the David H. Koch Foundation? As in one of the Koch brothers.

[@teaser6089]

@@wtmayhew I don't really see any propaganda on PBS, then again I mostly only watch PBS space

[@wtmayhew]

@@teaser6089 Exacctly, that was my point. The original comment seemed to be a knee-jerk dismissal of PBS. My point is that arch conservative Kochs are willing to support PBS. PBS Newshour is probably the best TV news, willing to give five or even ten minutes to a single topic. If anything, PBS engages in a certain amount of both-sides-ism, giving voice to countervailing opinion on some stories where there is not a true other side. A combination of PBS, CBC and DW together make a pretty decent news diet.

[@japzone]

I actually kinda like it when a KZbinr uses the "Brought to you by viewers like you. Thank you." Might be cheesy, but I think it works well.

[@barsa95]

The way he timed his paragraphs to end each seven seconds to exactly match the loop of the disco lights is amazing, he also mananed to squeeze a joke in it. I just love the detail and the incredible amount of work and planning he puts even on simple explanations

[@mackpines]

“You’re glowing today.” Thanks. I needed that.

[@aromaticsnail]

"No, you're getting me hotter" Stoooooop🤭 "You still don't get it! It's hot today...get out of my way!"

[@bennyklabarpan7002]

Apply to the CIA

[@ghoulbuster1]

He glows? RUN IT

[@adamk.7177]

Bro that's radiation

[@chunkydurango7841]

Glowies?!

[@KanalFrump]

Very nice work. Greetings from a PIR nerd. Some notes - the hidden "disco ball" mirror array inside some sensor devices are actually an array of parabolas as in car headlights. These are individually designed to focus infrared light from a specific incident angle to the very center of the pyroelectric crystal elements inside the detector. Similarly, the lenses in a fresnel lens-array are also each designed to focus light in the same manner, such that from a selected coverage pattern of incident angles, each has a lens that causes light from that direction to be focused to the middle of the detector. As part of the design process the effective coverage pattern pattern is raytraced with a simple stochastic photon model from the detector crystal elements out and through lenses and/or parabolic reflectors and into the environment. This gives the predicted coverage pattern which conceptually is like a cluster of big chunky and hazy-edged beams of "inverse light" - detection lobes with alternating polarity, a bit like an antenna gain map. We then analyze the predicted performance by passing thermal contrast dummies through these beams which generates simulated waveforms across the detector crystals. Based on this we can tune the design for the intended application - indoor, outdoor, different mounting positions and angles etc.

[@x--.]

Uh, I think we need a Connextras visit to this lab, stat! Please and pretty please.

[@Delfigamer1]

I would like something like that as well! But in the meantime, if any of the readers want to see some pictures, "pir motion sensor field of view" in google seems to give exactly this kind of sensitivity diagrams.

Thank you for a very informative comment! I still don't understand some bits about the whole design. For example: why is it, that when I'm moving very, very slowly in front of one of these detectors, it doesn't activate? Is it because of how the logic part is programmed, that it ignores "blips" of signal which come in long enough intervals to avoid false alarms caused by some natural gradual changes in the environment?

[@KanalFrump]

When you're not moving, you're invisible to a PIR system. As Alec correctly showed in his video, the "motion detection" is based on threshold triggering a circuit based on a super tiny charge (or capacitance) differences between the two elements in the detector. And those elements are reacting only to changes in total impressed thermal radiation as received through the optic - i.e. the lenses or "disco ball", which is akin to the segmented eyes of an insect if you imagine that all eyes share the same two "pixels". Those conceptual beams of "inverse light" with alternating polarity that I mentioned earlier, are kind of like projected images of those two pixels. So conditions for detection to happen are that 1) you or parts of you are glowing at a different temperature than the background environment. 2) you are moving laterally relative to the motion sensor such that you cause asymmetric changes to the impressed radiation on the two pixels. The 2nd clause of the above also gives the "achilles heel" of most (but not all) PIR sensor systems in that moving in a very carefully controlled straight line directly towards the sensor can also defeat detection since the effected change is symmetric and so cancels out, giving no signal.

[@jagmarc]

Maybe someone could manipulate it somehow and from it make a scanning thermal camera.

[@ihavetwofaces]

3:49: Elmo says: "today's ability to detect people moving in a room is brought to you by the letter H".

[@chrisbrasher6177]

Oh god. 😂

[@CptJistuce]

"And by viewers like you."

[@arkie87]

after you watch the video, do your happy dance dance, since you learned something new.

[@S3t3sh]

@@CptJistuce This is too far down the list 🤣

[@defeatSpace]

Green Light 🟢 Red Light 👹

[@OrphenStudios]

I found your channel a month after I lost my dad cancer during a nearly two week period of no electricity due to a tornado. I was in my car charging my phone and feeling absolutely dead inside when I found your videos on televisions. Been a fan ever since. You helped get me through a bad time. Thanks for all the videos. Your work has impact!

[@A.X.76]

Thanks for the “thermal positivity” today. I’m glad that I’m not an “absolute zero” and your reminder of my “potential” warms my heart…

[@bassmanbuck]

"Have you ever wondered how one of these works?" Yes... literally this morning

[@goosenotmaverick1156]

Only every time I see one. And I see a lot of em, I'm an electrician. We use IR and ultrasonic both but I always wondered about these ones.

[@georgecaveington1661]

i just started watching and man missed opportunity to say 'you've seen them. but ever wonder how they see you?"

[@adamgreenhill110]

Same! After the "Falcon Sensor" global outage, I was reading about the kernel level code thing. Then I started thinking about actual motion sensors... And then this just uploaded!!

[@redpheonix1000]

Funny thing is this goes for almost every video he makes

[@dielaughing73]

I hadn't really, but I did just get a dead one replaced out the front of my house and I did vaguely wonder why the old one died

[@pufthemajicdragon]

Yes. Yes this is PBS. Or rather, it's better, cause PBS on youtube has sponsors and ad segments. Thank you for doing what you do, doing it so well, and not muddying the pure knowledge with sponsored talking points.

[@MonkeyJedi99]

When I was a kid, PBS only had "underwriters" whose names and maybe a single sentence about what they did was read by an off-screen voice in a fairly inflection-free voice. Much like National Public Radio still does.

[@vappyreon1176]

Not to mention all the "educational" documentaries on stuff like national geographic filled with outright lies and overexaggerations

[@darksu6947]

​@@MonkeyJedi99How often are you listening to NPR? I hear adds all the time. Maybe it depends on the area you live in.

[@rossperk]

Although you have to admit, Sesame Street had a FUNKY funding credits jingle from the 60s through the 80s.

[@MonkeyJedi99]

@@rossperk I still occasionally sing the "12" song.

[@armin762]

Can't believe Technology Connections doesn't have a disco ball!

[@adamgardner3364]

He needs to fix that ... by buying two of them.

[@josephgaviota]

@@adamgardner3364 and taking one apart ...

[@MajorOutage]

@@adamgardner3364 Work hard, play hard.

[@steve_main]

all I can think about was when you said viewers like you was what is this PBS.. and then you made that statement like two seconds later and all I could do was scream " get out of my head" but at the same time absolutely love that connection that you can say three words and bring so many people back to a point in time in their life at the same time.. Love it, love the channel

[@cmdOptEscape]

9:25 Funniest thing I've seen this week, easily. There's no other KZbin channel that teaches me so much information about random technologies while simultaneously making me constantly actually laugh out loud. Thank you, Alec ♥️♥️

[@H1nD009]

I have 20+ years experience in engeneering and electrical components, and regarding the pyroelectric cristals, i can happily confirm that IS indeed a letter H printed in them

[@KairuHakubi]

so THAT's where Hs come from I thought the only way to make a letter H was when two friends at a sleepover.... uh, i've said too much.

[@korbindallas4552]

I have 20+ years experience in Sesame Street and the English Alphabet. I can happily confirm that it IS indeed the letter H printed in them.

[@WhatALoadOfTosca]

I have years of experience watching KZbin videos so I too can confirm everything in the video is entirely accurate without question and that anyone commenting must also be experts.

[@BrandonFrancey]

What? I'm so confused. I was laying down watching this video and all I saw was a large I printed. Why is everyone talking about H's?

[@shaystern2453]

@@WhatALoadOfTosca I have 40 + years of breathing engineering, so am also an accomplished know-it-all

[@Hexagonaldonut]

Interesting point regarding how these things work: They won't just create a voltage differential if something WARM passes in front of them, they'll also do it if something sufficiently COLD passes in front of them, because really they're just detecting thermal differences, not necessarily increases in heat specifically. In most situations this doesn't really matter, but it can be relevant if, for example, you have a passive infrared sensor above your door on the inside that unlocks it when it detects motion, and you're on the other side with an upside-down can of spray duster. Relatedly, this is a fantastic way to get into places you aren't supposed to, assuming no one happens to be in the immediate vicinity to witness a conspicuous cloud of vapor coming out of the top of the door gap, because literally 95% of request-to-exit sensors (the aforementioned sensors that unlock doors when you're on the inside heading out) are strictly PIR, and thus very easy to exploit in the right situations, unless they're one of the rare few that also use microwave radar (allowing them to detect the rough shape and directionality of things in addition to thermal differences). This ramble is brought to by someone who's probably watched too many DEFCON talks. And also a lot Deviant Ollam. (You should watch his stuff, by the way, he's great.)

[@EthelredHardrede-nz8yv]

He has a comment here. I never heard of him before.

[@nyetloki]

Thanks. now how can I get a free ticket to fort knox

[@oremooremo5075]

What does the cloud do?

[@nyetloki]

@@oremooremo5075 the cloud is condensated air. It's a byproduct of the cold air traveling in a warmer environment. The cold air itself is what triggers the sensor (due to detecting an uneven temperature change across it's face). The cloud doesn't matter.

[@Senthiuz]

Sometimes, they'll put a sensor on the other side of the door and disable the automatic exit sensor (requiring the exit button) until the other side is clear. But that's prey to any of the other methods of blocking these sensors.

[@pufthemajicdragon]

My favorite use of motion sensors was in the old movie Sneakers. "You can wear this neoprene suit or you can walk REALLY slowly." Turns out, it works. Walk slowly enough and you won't trigger one of these sensors.

[@jan_harald]

from my experience, it's gotta be excruciatingly slow, though but it also depends how well the sensors are tuned, I guess

[@jameshughes6078]

If you move fast enough, will there not be enough time to heat up?

[@FntX-Video]

This way I demonstrated a few years back that the alarm mounted in our workshop is useless if the intruder knows where it sits... and we had a lot of guests coming by so it was basically useless if you carry this knowledge.

[@joshbbglover]

I'm pretty sure Mythbusters tested these sensors as well. If you walk veeeeery slowly past them, they don't trigger.

[@bartoszpiszczek]

I do this, when I was 10. Being very slow don't trigger red diode. That was fun.

[@Jyodann]

Really entertaining presentation of many of the daily items we take for granted! Truly awesome content :D

[@ramaolarte]

I have 23 years of field experience with home security, and it's the first time I truly understand how these things work. I guess i must thank no one ever asked me too much about it... But now I'm prepared hahaha...

[@Martijn4president]

Honestly, finding a new video of Technology Connections in my feed feels like getting a present

[@kairon156]

As a ~Canadian~ person I enjoy the "This content is in part, funded by viewers like you." trope. Also Thanks to the people who can help interesting channels like yours continue to make good content.

[@vandorb12]

Us down south have heard it many times before from our local PBS stations, all supported by viewers like you. Thank you.

[@TheRalliowiec]

WBGH Boston

[@nolifenerdwhohasnevergotten]

​@@vandorb12 The PBS station in Buffalo thanks both Canadian and American viewers for their donations and they even brand themselves as "PBS Buffalo/Toronto". I think about a third of their donations come from Canadians. I've donated!

[@OntarioTrafficMan]

​@@vandorb12It's also PBS that we hear it on in Canada. We get PBS Buffalo in Toronto for example and when I was a kid they had a lot of good children's programs

[@timowagner1329]

might i ask why that is specifcally canadian?

[@barkspawn]

Pretty certain the H is actually a large MOSFET called an H-Gate. The bright H is the gate and the dark squares on the top and bottom are the drain and source. I'm guessing the infrared sensitive material is impregnated onto the h-gate in order to induce a voltage to switch the transistor, which in turn provides enough current to switch the larger one beneath it. The advantage of this design is that you can have an extremely low standby voltage to switch on a relatively high powered device like a floodlight.

[@TechnologyConnections]

Ahh! That would make a lot of sense.

[@jan_harald]

that makes sense, the H shape doesn't really make sense otherwise, imho

[@cheekibreeki904]

And that's the power of H

[@TheePIB]

@@cheekibreeki904 A power of H that Sesame Street never mentioned!

[@ljwithnok2615]

​@@TheePIBconsidering this episode was PBS ready, it makes sense that it's sponsored by the letter H, and viewers like you

[@brentgauspohl9779]

Thank you for the years of high-quality explaining (and snark). It's great to see that millions of us are appreciative of how people like you (and The Engineer Guy, and a dozen plus more) are masterfully scratching the same itch that "The Way Things Work" and similar material did decades ago.

[@TechnologyConnections]

I'm honored to be compared to the Engineer Guy - thank you!

[@RichardZbranek]

That loop joke was hilarious! I am kinda disappointed it did not end with the disco ball looping and Alec repeating his line. Great video.

[@shmehfleh3115]

Big Clive taught me all about these things, and how integrated they've become over the years. The modern ones just need 5v and ground, and they spit out logic-level signals perfect for Arduino projects and stuff like that. There's also a drop-in replacement for PIR motion sensors that uses short-range RADAR. It doesn't even need to be able to see the thing that's moving; it can detect right through a plastic project box.

[@MrDuncl]

After disappointing weatherproofing of a very exposed outdoor PIR light I bought a radar controlled one. The only disadvantage is that it is quite a good weather radar. I have to switch it off if it is blowing a gale or it will be on most of the night.

[@Diamonddrake]

I very much appreciate that you don't have baked advertisement segments!

[@WhileTrueCode]

indeed! unfortunately, most _other_ youtubers arent as respectful to their audience. for them, i suggest you install SponsorBlock extension EDIT: sponsorblock is not an adblocker; all it does is jump the video timestamp past the trash segments. it drives me NUTS that youtube allows in-video sponsorships. isnt the point of paying for Premium to not see ads? 🤠

[@cjc363636]

His channel is like classic KZbin from 2010 or so.... And I love that!!

[@MidnightThunderYT]

Me Too! I hate baked in advertisments so much I have a browser extension installed that skips over them via a crowdsourced database (Sponsorblock). I find it impossible to watch KZbin without it!

[@colley001]

I used to enjoy demonstrating how a glass window that you could see through with normal vision cameras allowed people to walk past infra red sensors provided the glass was not more than 10’C different (hotter or colder) to the ambient background temperature… and so to get past visible cameras too wear a balaclava and carry a full length glass window from one side of the yard to another without setting off any alarms. Great job!

[@20chocsaday]

It also helps if you you are drenched in rain. You are just like everything else while you keep your head down and your hands behind you.

[@pistonburner6448]

We have learned from the documentary film named "Predator" that you can also cover yourself in mud to avoid detection.

[@20chocsaday]

@@pistonburner6448 How often have you tried it? I get wet in the rain without trying.

[@roberth721]

​@@pistonburner6448 did you see the Mythbusters episode where they tested the "Predator" mud scene?

[@pistonburner6448]

@@roberth721 Nope, but I will now! Thanks for the heads up! (Please don't spoil it for me, but I'm assuming it does in fact not work except maybe for a moment)

[@brewski118sempire]

"what is this, PBS?" Yes yes it is and im thankful for that. PBS and stations that broadcasted educational content helped foster my love and thirst for knowledge. You my good fellow are doing the same in the digital world. You have our thanks.

[@just_docs]

9:14 you are such a legend, honestly. Best channel on YT.

[@SuperRobertByrne]

Only 16 minutes? This will be an amazing appetizer for my next 5 hour video on vinyl binge!

[@LittleDancerByGrace]

I literally just came over here from watching that series for the first time.

[@newq]

One of these devices is responsible for me seeing a mountain lion last week. I'm the crazy guy who rides his bicycle at night and mountain lions are known to go after cyclists. If that big cat hadn't been spooked by the lights coming on as I passed a nearby house, I might have become a statistic! I'll tell you what, it scared the bejesus out of me... DAMN big kitty. I made a beeline back to civilization immediately after.

[@goosenotmaverick1156]

I just want to know where you were at night riding a bike that not only had homes, but mountain lions too all in the same place 😂 I'm glad you're alright, I ride bike quite a bit but can't imagine having a situation like this happen to me. My Heart rate would be like a hummingbirds wings 😂

[@soaringvulture]

@@goosenotmaverick1156 Well, Sunnyvale, CA is one such place. People's driveway cameras pick up mountain lions all the time here.

[@AdamKnappdoesthings]

@@goosenotmaverick1156pretty common in California. They don’t (usually) mess with people but that’s changing as we take more of their habitat.

[@sq3rjick]

Becoming increasingly common here in Colorado as well.

[@davemeise2192]

Lots of cities in British Columbia too.

[@Montana3DForge]

Quality, jokes, and general structure of your videos are at an all time high. you haven't made any BIG noticeable changes to your video editing and recording but the main idea and how things flow together is becoming smooth as butter. Keep up the good work -from a guy whos been watching you for years.

[@Marc_Fuchs_1985]

Same here, though I found it sad, when he dialed down the snark a lot. I like it when the channels have a lot of personality. And people who got snarked at didn't really took it personally, did they? .................... Oh right, this is the internet.........

[@quinnkirlew9892]

The PBS joke was spot on Alec. The jazz at the end always reminded me of the old programs. I used to watch it all the time as a know-it-all kid, but stopped learning in my free time for a long while in an effort to "reinvent" myself. Your videos poke at the curious nerd in me and make me excited to know stuff. Watching a few of them totally kicked off my interest in researching everything and anything that I want to know the science behind, of course bolstered now by the power of the Internet. Maybe I'm getting a little touchy feely, but I just wanted to say thanks for making me feel smart again.

[@TechnologyConnections]

Thank you so much!

[@nicolassf]

Simple explanation like always

[@DeviantOllam]

Waiting with bated breath to see if a can of office duster or a can of tech spray / freeze spray shows up in this video! 😁👍💨🚪

[@lavuy6744]

same but I only know about that because of you.

[@zdazeeeh]

I knew I was gonna find you here :D

[@joshuaobelenusable]

Now I am curious if it's the cold from the spray that is triggering the REX or if it is the sudden return of the heat between the clouds of spray...

[@gtdgabriste1]

Or a mist of bourbon sprayed from the mouth of a rebellious red teamer in front of a bank?

[@demondoggy1825]

No funny door opening D:

[@RandomBitzzz]

@15:04 - I was thinking "this sounds like something you'd hear on PBS" - and the Alec said it... 🤣

[@CptJistuce]

Same.

[@TheFastgeek]

Exactly. Get outta my head, man! 😉🤣

[@lillyclarity9699]

I was waiting for a PBS shoutout after your very specific wording..."viewers like you, thank you." is one of those lines that I had heard repeatedly as a kid without fully understanding the meaning so it got burned into my mind. Honestly, I'd be surprised if I was the only person who grew up as a poor kid who will never be able to forget those words in that sequence. PBS was the only channel on rabbit ears that had cartoons!

[@ThraceFulton]

Your content is of a type and quality that would be top-of-the-charts good on PBS, and deserves as much recognition as the childrens' programing that so many of us grew up watching. If ever you decide to take this production to the public airwaves, you have my axe.

[@MacCrunch]

I love how you simplify complex concepts and make them easy to understand. The details about pyroelectric crystals and their functionality are especially intriguing.

[@josipcuric8767]

Technology Connections I forgot your name but Ive been following you for years now and every time you upload a video I still get the same excited feeking of wanting to tuck myself in a bed to enjoy your videos, they NEVER get old

[@jim0077]

As a former designer of security equipment including many motion detectors you did an amazing job breaking it down and explaining how PIR's work. I really enjoy your videos. Keep up the great work!

[@mann_idonotreadreplies]

COOL story bra

[@smashed_penguin]

We getting fancy up in here with those animated graphics.

[@nafion112]

Alec is an excellent hole-plugger. He sets down a piece of modern technology, of which I usually have a semi-general understanding of it's theory of operation. He then proceeds with plugging up my brain holes until my knowledge of the thing is reasonably "comprehensive". I think I underestimate how much better I understand the everyday world around me based on his videos alone.

[@EphyMusicOfficial]

You literally never fail to be both entertaining and educational. Your writing is clever and funny, but delivers points very concisely and easily. Even without being able to show what those lenses do directly, you were able to find a way to effectively demonstrate it with phone light that it just clicked for me. Thank you for this useless information. I don't know what I'd do without it!

[@matheussteinmetz]

My favorite notification is this channel ❤

[@terryenby2304]

My gosh your t-shirt brings back memories! VHS nostalgia. Thank you! Also, great video as per.

[@charlesurrea1451]

There's a CDS cell on that one board. A light sensor, tells it when daytime comes around. I was a smart kid, when I would sneak out of the house I would shine a focused flashlight on the sensor so the yard lights wouldn't turn on. I've come across a few units that won't detect body heat when the ambient is equal to or above body temperature. A trick I had learned while working at Radionics was that if you block the smaller lenses at the bottom with a bit of foil, your pets won't set off your home alarm.

[@CptJistuce]

"your pets won't set off your home alarm" Spoken like someone without large dogs. Past a certain point, large dogs and small people overlap.

[@vappyreon1176]

​@@CptJistuce*most* dogs

[@CptJistuce]

@@vappyreon1176 I honestly don't know what a "normal" dog is, having had pooches pushing past 70 pounds my whole life.

[@nyetloki]

@@charlesurrea1451 on the one he opened, it has a photodiode not a CDS sensor. Cadmium bans are making the latter rarer and rarer. Behave the same* but still

[@KlueBat]

I love supporting you work! Thank you for making entertaining and informative content.

[@DanielLopez-up6os]

Favourite thing about these is a security issue., is that some doors have acces control so you can enter only with a card, but you can leave by just walking towards the door. So to open the door from the secure side you can just hold a compressed air can upside down, so it sprays cold air/liquid and blast that at the top of the door at the gap between the two doors, and that usually triggers the sensor on the other side.

[@mann_idonotreadreplies]

Cool story bro

[@BariumCobaltNitrog3n]

Except most doors with that setup, a request for exit command only unbolts the door, you still have to push a panic bar or operate some sort of latch. It's a rare building the will pop the door open every time a stiff chilly breeze stumbles through the cracks. But those eager-to-be-violated systems do exist. Google pen test results to save dust-off.

[@DanielLopez-up6os]

@@BariumCobaltNitrog3n a lot of places have automatic motorized door to enter or exit but only to enter you need to swipe credentials. The very cold cloud of gas confuses the hell out of the sensor. I believe one of the defcon 19 talks has one section about this.

[@BariumCobaltNitrog3n]

@@DanielLopez-up6os If you say so, but I doubt the little circuit board is having an emotional conflict.

[@lightningdemolition1964]

Deviant ollam has a lot of content about the flaws in these systems.

[@RandomYoutubeUser-wy9lf]

Nothing feels better than watching a Technology Connections video minutes after release. Also, did anyone noticed the secret dialogue in the captions at the end of the video? Neat!

[@RipVanFish09]

Those messages are in every video. I always have captions turned on for that very reason.

[@RandomYoutubeUser-wy9lf]

@@RipVanFish09 Looks like I've been missing out...

[@RipVanFish09]

@@RandomKZbinUser-wy9lf honestly I would definitely say you have. :)

[@carlosgaspar8447]

Thanks!

[@dudo626]

Hvala!

[@colororb4105]

I'm glad we have these. I got an internet security camera for dirt cheap on clearance, and I set it up to turn on my lights when movement is detected. Turns out that lights turning off changes a lot of pixels and would always turn the lights right back on

[@mann_idonotreadreplies]

Cool story bra

[@marcberm]

I can't help but feel like the opening line should've been "Motion sensors, you've seen 'em, but have you ever wondered how they see you?"

[@guesswho2778]

that along with a "with the magic of buying two of them" joke (referring to the multiple crystals) would have been great

[@zephyfoxy]

This reminds me of an interesting bit from a Defcon video featuring Deviant Ollam, who covers various ways to defeat physical security from the perspective of a security consultant. He showed some pretty funny clips of using things like canned computer duster or even ice cold whisky to fool IR sensors tied to door locks; the ones that are supposed automatically unlock doors in secure areas when you're trying to leave so you don't have to "badge out", but shouldn't be able to get in without "badging in".

[@mann_idonotreadreplies]

Cool story bra

[@johannweber5185]

Danke!

[@GandyGamingHD]

You are genuinely answering all the questions of my childhood, one video at a time. Been a subscriber for years and with every upload, I realise you are American me. Just with a successful KZbin channel!

[@scottdavis6734]

I must say I'm a retired engineer and structure design consultant, you are a great teacher. I hope your talent in simplifying and explaining is but to great use, you have an exceptional talent. It's one thing to understand how stuff works ( that's me) but entirely another to be able to simplify and explain it ( that's you) I have been watching you for at least 5 years perhaps longer and I always learn from you I feel embarrassed at my PhD takes a back seat to your ability to teach, explain and understand. Keep up the great work, I will be in the wings watching every episode.

[@quinton1661]

Speaking of ad reads, I actually was scared for a moment @0:34. I thought for a moment that you had finally succumbed to the corporate overlords and started doing sponsored segments.

[@MartinAlejandroLiguori]

I will never understand WHY I watch full videos of this guy explaining stuff that I never gave a single f*ck on how they work... but here I'm, it's fascinating.

[@nyetloki]

@@MartinAlejandroLiguori I watch his videos about things I fully know how they work and learn nothing, so it balances out

[@potappotapov1815]

Because they are superbly made I have nothing but pity for people who still watch educational content on network TV it all went to heck fast

[@youdontknowme5969]

I'm kinda in the middle---I have an idea how some things work, but I just want to see what he says about them. 😎

[@Samkaildyke]

You have a real gift at explaining things in a way that is so understandable, despite things being complex - the disco ball analogy and phone flashlight demo are just brilliantly intuitive explanations that really make me ‘get it’

[@blakeaham]

"And viewers like you" was so confusing as a kid, then I kinda figured it out and it has always warmed my heart a bit. It hit just as hard when you did it. Thanks for the knowledge amd entertainment

[@mceajc]

Thank you Patreon supporters! You are all great for supporting such a fantastic ... creator? influencer? investigator? ... person!

[@klaernie]

I think "educator" is the right word! Maybe also "connector".. 🤔

[@someoneelse7629]

Influgator? I want credit for the new word on wikipedia

[@OntarioTrafficMan]

He definitely influences my usage patterns for dishwashers, HVAC, etc

[@CptJistuce]

Edutainer.

[@mann_idonotreadreplies]

KZbinr u noobs

[@TiSapph]

Here's how that "H" sensor works: The entire chip is made from the pyroelectric material. The H you see is metal deposited onto the substrate surface. It's built like two series capacitors: The two large bars of the H each also have metallisation on the backside of the chip. The two bars of the H and the backside metallisation form two plate capacitors, with the pyroelectric substrate between the plates. The little horizontal bar of the H connects the two capacitors. There's no connection between the two capacitors on the backside, theres a gap in the metallisation. The external connections are only to the backside metallisation. So effectively its just two capacitors in series. Temperature changes polarise the substrate due to pyroelectricity, which in turn induces a voltage in the capacitors. The induced voltage is in the same direction, eg the front plates + and the back plates -. As both front sides of the capacitors are connected to another, they effectively have "opposite polarity". No voltage is measured across the entire chip for common temperature changes.

[@TiSapph]

The pattern you see on the surface is likely just from wafer slicing, as there is no need to polish the wafers for this application.

[@icecreambone]

only one/part of the sensor detecting at a time is also how your eyes work for edge detection - you have these photoreceptor cells arranged in a donut, and the neural cells underneath detect whether the donut or the donut hole are being activated

[@Rabid-Bunny]

Dude is literally the best guy on KZbin. Period

[@notmousse]

Your videos so gently remind me of when PBS aired informative programming.

[@stevethepocket]

I'm sure I'm going to be sorry I asked, but what do they do now, in your estimation?

[@notmousse]

@@stevethepocket Exactly what you're thinking I'd say, only worse.

[@nothingtoseehere93]

You know I was literally wondering how they work yesterday. Good timing

[@markhesse2928]

The dancing man who blips into existence is a hilarious bit--perfectly in keeping with the traditions of Technology Connections.😀

[@gregbell2117]

Thanks

[@poolbumone]

I don’t have Patreon, but love the content and want to support you.

[@TechnologyConnections]

Thank you!

[@RonLaws]

Fun fact, The reason these sensors don't trigger to someone walking past the window outside the building is because window glass is not transparent to infrared or at the very least IR is heavily attenuated by it. these days by design for thermal insulation.

[@bartoszpiszczek]

That's funny, beacause camera lens let infrafred pass through. They must use different glass type.

[@nyetloki]

​@@bartoszpiszczek double paned windows really reduce ir passthrough. Air gap

[@bartoszpiszczek]

@@nyetloki inside lens there is air gap too

[@vibaj16]

you mean transparent?

[@3str4ng3d]

@@bartoszpiszczek cameras can see NIR (near Infrared radiation) which is much closer (near) to visible light. Motion sensors trigger on FIR (far ir) which is a lot further than NIR in terms of frequency, and is blocked by glass. Warm objects only emit FIR.

[@nickloh912]

Would putting your IR camera behind the Fresnel lens array produce anything interesting? Thanks for the video!

[@TechnologyConnections]

Y'know I didn't even think to try! I have pretty strong doubts it could pick up the tiny change in heat the lens creates on a surface but I suppose it's worth trying!

[@goosenotmaverick1156]

I was just thinking an IR camera on one side and a small IR blaster on the other side might help demonstrate. And not 45 seconds after that thought, here was your comment 😂 Always late lol

[@DahVoozel]

​@goosenotmaverick1156 By IR blaster do you mean the Buddy heater?

[@goosenotmaverick1156]

@@DahVoozel I meant one specifically made for lighting areas to be seen by IR cameras. Used in security quite a bit from what I understand

[@E4S65]

​@@TechnologyConnections sounds like a great video for Connextras. I would love to see what it does

[@AMDRADEONRUBY]

Very a clever technology i love infrared sensors theses are very neat. And pretty effective way to control the lights ON and OFF.

[@goosenotmaverick1156]

Ultrasonic work pretty well too, but occasionally some folks will hear them when they're poor quality or failing. I work in one building fairly often that has two or three sensors I can hear and so can the maintenance guy.

[@mann_idonotreadreplies]

I'm glad you need to be poor to hear those sensors

[@goosenotmaverick1156]

@@mann_idonotreadreplies what does financial standing have anything to do with what I was talking about..?

[@ChrisEllorris]

You, sir, are a gift to humanity. It's not often you hear someone say they have enough instead of always trying to elevate to more and more money.

[@Alpejohn]

As I watched the beginning of the video, i thought to my self "I have never seen him put ads in his videos".. And then you talk about it in the end! I love your content!

[@ShadowRubberDuck]

“To quote some website I found.”

[@_..-.._..-.._]

15:00 Where’s my free tote bag?

[@justforplaylists]

I used to try to sneak past these by walking very slowly. I don't think I ever managed to though.

[@therealchayd]

Same here! We had motion sensors at school and used to play a game where we had the traverse a corridor undetected with the losers taking a forfeit.

[@michaelsmith4904]

You have to move REALLY slowly, but it can be done. I think it took me at least 15 minutes to move across the room and not trigger it.

[@suddenwall]

Ever watch Sneakers (1992)?

[@Jabbles22]

I've done it but I had to move quite slowly.

[@jongeers1954]

Motion sensor light above our back door - first, go out in the back yard and stand still long enough for it to go off. Move across the yard perpendicularly, even slowly and at some distance, and you'll trigger the light. From the same still/dark starting point, move directly toward the sensor, and you can move at normal speed and get pretty close before you finally trigger it. The segmented lens is visible and I always knew that was part of it, but it was nice to learn about the crystals.

[@MjStrange]

This is one of the best KZbin channels. Have been a watcher for years and this is truly the best example of what KZbin should be a person with a passion to explain stuff no big corporations butting in no crazy production spots, just someone who who has deep passion and curiosity. Who knows how to present what he has learned.

[@MjStrange]

Also as someone who works in the entertainment industry building video walls and live production engineer the fact that the background incorporates televisions so he can change. The photos is such an ingenious and simple ways of making a set.

[@mann_idonotreadreplies]

Cool story bro

[@WafflesInTheRain]

You are one of the best educators on KZbin. Thank you for all that you do.

[@StormsparkPegasus]

It's funny that Hollywood comes up with elaborate laser security systems that the heroes have to make visible and then do contortions to get through. When in reality...a cheap device like this covers the entire room, making their antics impossible.

[@nailsofinterest]

Well then they couldn't get through so the plot would be messed up. Lol

[@nyetloki]

@@StormsparkPegasus no both have their pros and cons. You can't creep past lasers with a room temperature sheet.

[@Tarodenaro]

2:10 POV: modern day hippies finding out that their crystal salt lamp producing at least something tangible to justify their -consumerism- purchases.

[@janLipija]

0:03 honestly kinda surprised the line here wasn’t “you’ve seen ‘em, but have you ever wondered how they see you?

[@ligh7ningx7]

my mind is officially boggled. it's astounding how complex the devices we use everyday are

[@frankly8087]

Your opening within the first 72 seconds made this video worthy of an enthusiastic thumbs up!

[@NutjobGTO]

03:45 Words to live your life by

[@wrexhammusic]

3:49 It's giving Arnold Rimmer vibes

[@Umski]

I was looking for the Red Dwarf comment 😂

[@Whalerguy]

Came here for this thanks

[@IanZainea1990]

8:10 You should have recorded the video with your phone and put an ir tv remote behind it. Your phone can see that. That would show the lens working in ir

[@freescape08]

I like this idea, I was thinking he should use the thermal camera to show heat from a stove focusing on the other side, but the phone sounds safer.

[@kylesebring]

Thank you for that intro Technology Connections. I've been watching you for years and just today I needed that.

[@Teckstudio]

Never really thought about it. And to be honst, didn't care enough to search for it. But the all seeing algorithm said I had to know. So I listend. Thank you! What an excellent presentation you gave - 🥰 - you are truly one of the reasons KZbin is still worth a visit! 🤩 Keep on creating!

[@Fadamor]

1:10 I remember being the first person in a high school auditorium before an assembly and the place was freezing. When the auditorium filled up with students, the place became uncomfortably warm. That's a lot of BTUs sitting in those auditorium seats!

[@mann_idonotreadreplies]

Cool story bra

[@debrachambers1304]

13:23 so a TINY person could bypass it

[@ntsecrets]

How do you not own your own discoball?