Let's take a look at an interesting pattern for Adelaide Meat by Sancy. Now Sansi is the same brand that I looked at recently who make the unusual ceramic core LED lights and the first thing I'm noticing with this pattern for red light is that it doesn't have the normal polyethylene polythene lens in the front. the fresnel lens that creates uh, strong patterns across the sensor when a human walks past it. some interesting to see how they've actually done this, if there is a lensing system, or if they've got some unusual approach that the back twists off.

it has a little tab that peels out for hanging from a screw or a double-sided tube if you wish and it twists off and reveals three AAA cells AAA Cells aren't my first choice for stuff like this, but it's very common and AAA cell has about a third of the capacity of a double a cell. I'd Rather use bigger cells, but there must be a reason they always go for the smaller ones. Let's see if we can spudger into this and get the cover off. First indications are that it's either very, very tight or it's actually glued on.

No, Nope, Nope. Hold on. Oh, is this gonna break? It's unclipping, but it is very well clipped. In my apologies, if there are any loud snapping, popping, clicking noises, the microphone tends to pick them up and kind of saturate result in a very high audio.

Peak This is not. This is not going to be pretty I may have to pause Oh No Maybe Not maybe not right. I'll take it away from the camera briefly just to try and unclip this. It is unclipped.

Here is our. it almost looks like radar, doesn't it? But it's not radar. Oh okay. oh, it is for now.

I Don't know if you can see that? I'll Zoom down. but this is a opaque, uh, infrared transparent thing. Can you see the ROV dots in it That pretty much indicates what's it? seeing those uh dots there that creates this strong pattern that goes across the center. Does this come off not easily? No.

I won't just pull off I will try and pull it off. No. I think it's there. riveted? Maybe not really sure.

Um. I shall pop this out further. I Don't see anything really specifically holding it in here? Oh, that might actually be this is somehow holding it in I Don't think so. Uh, pulling it with force does not seem to have any good effect.

I Don't really want to break things. There is a light sense down here I Notice halves. Oh, you know what? Oh right. Okay, that's gonna make things trickier.

I'm gonna have to desolder this. The circuit board has been placed onto the battery contacts once once they were in position and that appears to be what's holding it in place One moment. please. and resume.

Let's explore. The datumess is quite recent. It's right in the middle of the covert pandemic 2021. It did desolder from these two points.

These are the things it was holding it in. The positive one distorted fairly easily. The negative one did not disorder easily because it's got a large ground plane in this side and the other side in the pad is directly on those. It's not got separation tracks that would have been nice for taking it apart, but I guess they're not really thinking of it being taken apart.

I Did have to bring in reinforcements I Had to bring in the little soldier yarn with its huge bit just for that extra mass to try and get that to melt. Quite tricky. There are one, two, three, four, Five, six. LEDs In this site, there is hackability.

There is the password Center The gray. uh cup here is captive. It's actually held in by this Center being sorted in. There is a smart sensor and there's a little photo diode next to it.

photo transistor or footer diode. I'm going to say photodiode if we take a look at the circuit board itself. A lot of the work has been done by that module, so the module is located under here. I've just basically zoned off.

Let me show you the back of this to give you a perspective in this. uh, the area looking at here is just this little rectangle here just because it assuming the components a bit more and it's basically the sensor. It's got a three volt voltage regulator to provide a stable voltage Oodles of capacitors and then three potential dividers one with the light sensor and the other two are just fixed voltage potential dividers for setting, time delay, sensitivity, and the one with the photodiode is for the output enable which is the basically the dusk sensor. the switching device.

It's driving a tiny little mosfet with a 100 key resistor in series and a capacitor there just presumably to it doesn't cause it to fade away slowly around that, it it does go out straight away and I just guess it's filtering and then they've left their options open here. There are two 20 ohm resistors if you want to hack this for lower power, just chop one of them off. If you for some reason wanted to use a module for higher loads, then you could add more resistors to actually lower the compound resistance since they're all in parallel. Let me show you the schematic.

or I should mention I Found a data sheet for that chip, the Bs612, the passion thread sensor I found it at Adafruit Adafruit actually stocks those. They're very affordable so if you need a password, infrared module Adafruit may be where you need to go. So here is the supply. so that's three times: AAA You could swap that for a lithium cell if you want to think um, and the unregulated supply 4.5 volts goes straight over to the LEDs which are in parallel and then the resistor array which is in parallel and then down to the mosfet which is a 72k Alias a 2n7002.

A very classic mosfet but a slightly modern one I Think the difference between the 7000 the classic one the 7002 is this one has more protection than input which is quite good. And there's a little capacitor. and there's the 100K resistor. quite odd, the views capacitor there, but that's fine.

There's a three volt regulator n01f with a capacitors outside. There's actually another two capacitors on this side, but I abbreviated it. so let's just say times three there's Oodles of decoupling. It's quite well designed.

there's the sensor and it's quite interesting. The way it works. it's got the light level which is a fixed threshold which is a two Meg Ohm resistor and then the photodiode. It does offer suggest in the datasheet various combination resistors just to fine tune that value.

but in this instance the I Guess they've just chosen this as a generic component that works well with two Meg ohm and the other ones are all based on a one Meg Ohm resistor going to the positive three volt Rail Vdd and then I resistor going to VSS or zero volts. So you know it's so confusing. There are so many names that positive real and the negative or zero volt rail and these four and potential divider and present a voltage and it doesn't matter how much the what the supply voltage is to this chip, it's looking for a ratio of voltage to the positive voltage versus the zero volt reel. and by setting the potential difference, it is an analog converter.

Inside it sets a binary counter to determine the time delay and the sensitivity. It's our old digitally processed look of it inside and that is more or less it. This lens, although it looks opaque with its nice Scentsy logo in the front and those cute fresnel patterns in the back. Very odd When I looked at it with the thermal imagery camera, you could see the outline of your finger very dimly passing behind it.

so it is blocking a fair amount of the light. but it is. Also, you could see the Distortion because it was having that lensing effect. So they've kind of basically turned the sensitivity up and they've relied on this as being perhaps less ideal than a perfect lens purely because.

uh, it improves the Aesthetics. It makes it look nice having this instead of the sort of usual translucent dome in the front. It is quite a smart effect. Having said that, this is all translucent so it wouldn't really have shown that much.

I Think they were just making a statement, so that is it. The most interesting part of this is the Bs612 passive infrared detector. The way those work, they have two sensors in them and uh, they're configured so they sort of act against each other. Um, I think they're in series and uh, They drive a little field effect sensor normally in a pattern infrared sensor and as you walk past, the your heat signature generates a slight voltage.

In Those sensors. And because there are lenses, fresnel lenses here, which is just the Fresno lens is the one that's made of sort of Stripes of glass and it means you've got a very flat lens, has a equivalent to a big lens. When you walk across, it focuses your heat into a point of light that moves across those two sensors, and because it then undulates quite notably, it actually can detect that, but the ambient thermal output of the room that it's normally looking at will actually cancel itself out by those two opposing centers. It's very straightforward.

It's a classic thing: I Always thought this was going to be radar initially, but radar is not as efficient as these. I Measured the quiescent current 18 microamps in the off State on this circuit and that is it. So very simple three Volts for stability. The pattern for red module does it all and then just switches the LEDs on Via this tiny little mosfet and that is it.

Uh, very interesting and smart little device.