Let's take a look at our fake carbon dioxide detector from eBay these are all over eBay This particular one displays temperature, humidity, and the carbon dioxide level in the vicinity. I'm not sure why people necessarily want to know this I Can think of more useful things to measure, but unless you're living in a hermetically sealed building, the level of carbon dioxide isn't necessarily going to go too high. However, let's check the accuracy of this when exposed to pure carbon. dioxide.

So for that I have my SodaStream which has a carbon dioxide port in the back that puts the carbon dioxide into the drink I'm going to spray it directly into the center I Can see in here and we'll see how it fares the loud noise coming up. That's quite a lot of carbon. dioxide. The reading is not changing significantly.

It's certainly not enough for the amount that I've just bombarded into. however. uh, it is reading something. Watch this if I Scored some isopropyl alcohol into my hand just to get it vaporized and rub it together to create a nice bit of that vapor and I hold it.

There's going to be a loud alarm noise. it goes off the scale. So this thing is detecting alcohol and it makes me wonder, have they just put in uh, basically a a breathalyzer sensor module and I tested this with various chemicals. this, uh, this stuff is still all over the hand.

It's not going to return for a while to normal levels. uh I tested it with uh methylated Spirits it triggers it I tested with the isopropyl as I've just done it triggered it. If you have a re-sip of wine or beer and you're blue into it, it triggers it I Was going to have a glass of wine before making this video and thought that would not be a good idea because my breath would have actually been registering in this I Looked up online and I found there are alcohol sensors mq3 alcohol sensor but I also apparently detects petroleum distillates and I tried it with later fluid no reaction I tried white Spirit no reaction I tried it with butane gas, no reaction. it just seems to be alcohols.

The one slight variation uh by using a puff of this device for inhaling Nick o 10 it did actually register that I don't know if it was just a I'm not sure if it was the propylene glycol, the glycerin, then n-i-c-o-t-i-n-e or the uh, the chemical flavorings that were included in it. They don't tend to clear all the flavorings, they just say flavoring. Anyway, let's open this up and we'll see what's inside. I should mention it's rechargeable by USBC Port it's got the on off button.

It's notable that it may be designed for a natural carbon dioxide sensor because when I put it outside, it gradually went down in the level to and stuck at 400 PPM and that is the ambient outdoor level. So I wonder if it self-calibrates if you place It Outdoors by going down to 400 PPM Well, the lowest it goes down to. if it goes down, learn that it just retail calibrates that as the base 400 PPM level. Typically outdoor air is about 78 nitrogen um 21 oxygen and between uh 0.03 and 0.04 percent uh, carbon dioxide a bit higher indoors because of course we're breathing all that oxygen and exhaling carbon dioxide.

Uh, there's also ozone and Argan and other exciting stuff in the air, but they're not relevant here. Why I'm seeing here though is a very nice oh oh, that's open I am seeing quite a nice project case. If this turns out to be uh, program one somewhere reprogrammable then it's possible. You've got a nice color display.

You've got the battery charging circuit. There's a little sensor there not being able to identify that I've had we look before, but we'll take a closer look at this. I'll get the circuit board out and we can have a look. Um, there's the Sounder there's a little uh switching regulator Supply I shall monitor some voltages off that um I'll do that now.

I shall get the data and we'll take a look at it and see if we can find one moment. please and resume with the reverse engineering. I Have got a glass of wine here. This is purely for test preferences so I can blow in the center and annoy it with my alcoholism one moment.

Um, oh yeah, that set off the party alarm. So there we have it. It's a it's a party alarm, that's it. Oh, she'll put it out the way because otherwise it's going to keep moving off every time.

I Breathe roughly in its direction. Let's take a look at the circuitry I shall Zoom down and we'll do a block analysis of this instead of doing it to every component because there's quite a lot in this. Noting: the microcontroller here has been lasered. They've removed the logo off, but they've left a little sort of s shape and they're not sure what that is.

But given that, this is so, shall we say, modular. It's got data improved in this module. It's good analog input from this module. It's switching the output to the Beeper Um, and it's got an input from the charged circuitry.

I Would say that this is most likely Arduino-ish if you know what I mean. It's very modular, but then it isn't everything these days. So the power supply for the charger USB charge comes in here. It will not be recognized by modern, fancy Usb chargers if it's USBC.

If you, if it doesn't charge, plug it into a dumb charger. If not, put the resistors in the two meager resistors that would have made it compatible with other chargers and told it it's not even a high current. It seems to charge about 350 milliamps because that resistor there is about 2.6 K the one that sets the current on the Lth7. uh, charge control.

There's something really annoying about this. It's got a one amp hour Lithium cell that connects to here. It could have connected between this positive connection and this one if they'd put this chip in because this is a protection chip for the cell with its little filter, capacitor, and resistor, but they didn't include them to save a wee Penny and it's on the battery instead. No, it's not.

There's no protection, so it must be monitoring the voltage. Maybe with the is it monitoring with the microcontroller? Who knows. Um, if they were trying to save money, they've really screwed up because this bit here is a boost circuit for five volts from the battery supply. and uh, I haven't found anything it's used in.

It goes to the output. the serial programming Port here. presumably it goes to this, uh matching serial program Port and this infrared module Port I translated that, but it's not actually used by any of the circuitry that I can see on here. so they could have saved money by just not including all the circuitry here.

Accountant: Eat your heart out. Uh, other things, it's got the module here. This is quite interesting. Um, but that is the gas sensor module with three connections, 3.3 volts, zero volts, and an analog signal back.

We'll look at that in more detail and we've got a Dht11 which is 3.3 volt, zero volt and data and gives you temperature and humidity. It's a very generic module notorious for being not terribly accurate. No Facility for compensation included. Uh.

Things that are worthy of note that are really interesting: There's an A1 Shb transistor here which switches the circuit on and it switches on the 3.3 volt regulator. It connects it to the battery. It can be turned on either by the processor using a transistor to pull the gate to the zero volt rail, or via this switch over here which can pull it to the zero volt rail via a 1K resistor and uh, basically speaking, you press the button. It wakes everything up, um, and then once the processor is booted, it basically sends a signal transistor.

The latches are on and when you press the button, it can sense the buttons being being pressed and it will then effectively turn the uh. the mosfet. The transistor of the mosfet drops out. If it detects you, know that you've released the button.

Uh, this little module here. let's zoom up in that enhance. there is the enhanced image. Let's zoom in.

Things worthy of note: It seems to be using a standard tin oxide style sensor which has a heater. In this case, it's got a ridiculously high value of 10 key which I find hard to believe, but uh, they are. It's a thin film technology version. We'll cover that in a moment and that has a resistive sensing element.

the tin oxide element in series with a 10K resistor and that provides the analog output for stable readings. And it's a bit odd. They've got 3.3 volt providing the heater Supply but also going to this customizable regulator. the 65 K5 is that right? And it puts out 1.76 volts because you can choose the voltage.

The best thing about that regulator by far is the name of the manufacturer, which is Shenzhen Fine, Mad Electronics Group that's a great name. Fine Mad Electronics Group that's great, but it's programmed between 1.5 to 5 volts and 0.1 volt increment. So I'm guessing that this is supposed to be 1.8 or 1.7 Let's depends the tolerance. They kind of didn't need it.

I Shall show you why. Let me bring in the schematic and we can talk about that. Can you tell the wine has been partaken at a high enough level to do the scientific tests, but also far too high level for, uh, sensible electronic discussion? This is a good thing. Um, there is also a bit of a monolithic F up in this circuit, but not to worry, it's fine.

Here's the USBC charging port. it goes to Lth7 and the charge pin it. There's also option for a Tp4056 on the board, but the charge pin goes over to the microcontroller. That's the F up because it's leaking current.

There is a programming resistor I think it's actually concurrent 2.6 K which sets about 350 milliamps. Certainly that's what I measured it at the output of that goes to Lithium cell with no protection whatsoever. and then it goes to mosfet and the mosfet effectively is being pulled off pulled off. Yes, that's not the correct terminology.

It's being pulled off I Like it with this resistor, it's being held off on its gate. It's an A1 SHP which is a P-channel mosfet and the ways of turning it on are for this transistor to be turned on. I Just thought there's something. There's something wrong here, but that's okay.

Uh, this uh button must also have another. That's why it's got the 1K resistor. It's also got another resistor over to the processor. Slight error in this schematic, but that's okay.

But you'll get the gist. and it's an interesting to note: when you push the button, it bypasses the mosfet with the resistor. What that does is uh, it allows this, bypasses the transistor with the button. Uh, and it turns this mosfet on.

The mosfet enables the 3.3 volts. The processor boots up when it's ready it. after a slight time delay, it turns this transistor on and it locks the thing on. If you release the button before it's locked on, it will just drop back out again.

So once it's ready, once it's booted up, it, uh, it locks. It bypasses the button, but it must still be sensing the button because that's how it's turned off. So I've got that slightly wrong. There's obviously the button, is maybe pulling to the ground.

Plus, also, that might. oh, you know what? Nope, that wouldn't work. anyway. There's something else going on here that if the button is pulled down, there might be a resistor there, and then another resistor from the 3.3 volt rail there that would work anyway.

Carrying on the microcontroller, uh, can control the Peeper the bit that detects my alcoholic breath, allowing me to breathe gently in its direction. Oh, no party alarm, but also, rather disastrously, it controls the backlight. I'm not sure what the current of the backlight is I was looking for The transistor for the backlight is the LEDs for the backlight. The resistor was there, but I couldn't measure it so low.

It's pretty much a link going straight to the microcontroller. Three points evolved. It's going to be close to the voltage of the Uh LEDs anyway, but the microcontroller is working hard in that PIN The sensor module is connected to 3.3 Volt Rail and the zero volt rail. I Just didn't mark this zero volt.

There we go and it sends its analog signal back. And this, uh, is the Dht11? Is that what it is I can never remember Dth11. It's a Dht11 indeed, the horribly inaccurate but cheap uh, humidity and temperature sensor. And it's got the 3.3 volt zero Volt and it sends data back I'm thinking this, we know it just makes sense the display.

Oh, actually, you know what this, might have a this it clearly has. Wherever this is. got an LCD display Driver: These uh pins here. Let me show you the module.

Try not to breathe in it too hard. these pins here. it'll be power and data to agree. Parallel data.

Is it driving it directly? Maybe it is an LCD driver. But these pins here go straight through and onto the LCD panel. That's that. Means it's not.

It's not smart. it's that chip is an LCD driver in it. and there's the Uh LED backlight at this end. Interesting.

So what is that chip? then? no, no. That has cast out into my mind about whether it is no Arduino-ish thing. Oh well. there's something else worth noting on the circuit board here.

You've got a little connector position here in a connected position here. and it's connected through to this little Center position. Whatever it is. Uh, you can.

Basically, if you leave the circuit board in position, then you don't need the connector. But if you add the connector, then you can snap that circuit board out and mount it remotely. It's a center of some kind. I Don't know what it is.

Maybe it's an extension infrared sensor for remote control units. I I Haven't a clue why you'd want to do that. Let's talk about the center. The little circuit board of the sensor has the 3.3 volts coming on and it's got the heater.

I'll show you why. it's got the heater. in a moment it's 10K that would pass 0.3 milliamps and it would be one milliwatt which is extraordinarily low. There's the 1.6 volt regulator.

Now in these sensors, you have this the tin oxide coating which usually which changes its resistance. the more impurities are there are the uh, lower its resistance scores because it's blocking oxygen. I'll show you that in the next page I'll have to draw it out and that forms the potential divider this 10K resistor. but this is not connected to the the heater in any way which is.

Use these things. So they could have used the sensor down here and they could have used a resistor of their chosen value to tune that up there. and they could have actually used that as the output. and they wouldn't have needed the voltage regulator because they've already got a fairly stable 3.3 volt.

Supply I Don't know why they did that, did they just know not know what they were doing or something? I'm not sure maybe there's a reason they didn't do that. Anyway, let me show you tin oxide sensors because they are interested in their own right. I'm assuming it is 10 oxide. it kind of fits the description of tin oxide.

Have you seen those little centers that have the domed top? and it's a mesh top. And the reason it's a mesh top is because it's designed to prevent explosions because there is a little heater inside and it's got six pins sticking at the bottom, usually in a set of one, two, three, four, five, six sort of pattern. round it in a circle. What's actually inside those is, uh, a pin here and a pin here with a heater.

I'll just draw as a zigzaggy lane here and around that is a aluminum ceramic tube. Is that right aluminum oxide tube? It's a ceramic tube and it is coated with tin oxide. Then you've got the other two pins which are linked like that. They're just basic for support and they connect to that.

Now, this is not my area of expertise. If you can contribute some to this by all means, let me know because I Don't know how the the different sensors detect different gases, but the classic thing is there's a layer of tin oxide in this and when it's heated up, its resistance is affected by the availability of oxygen. So normally oxygen would fill in all the sort of gaps on this tin oxide and it goes High Resistance as stuff like smoke, carbon monoxide, carbon dioxide. If you get the correct sensor, alcohols, whatever it's tuned for, and they may dope the tin oxide to actually change its characteristics.

What that does is it actually takes the oxygen away and it blocks the oxygen from getting to it and that actually lowers the resistance. It allows the electrical current to flow along the surface of this material and what you end up basically is with a gas sensitive resistor and normally the heater passes a fair amount of current through that. But because these little chips use the thin film technology, they have the heater. Heat They have a thin insulator on top and then they get the tin oxide with the wires going onto the top of that.

And because it's all done super small and thin, they can have a much higher value of resistor for the heat because it doesn't have to get so hot. Um, very. I'm not sure about the science of this because everything I look at like ozone 10 oxide, carbon dioxide, 10 oxide. It must be different.

Metals The tin oxide seems particularly suitable to this. It's a very in narrative. It's very innocuous material. Uh, but there must be Dopey In some way they must be treated in some way to make it very gas selective.

Very interesting, but that is it that is the gas sensor. There was something in my mind there about the tin oxide centers I Don't know I Just completely forgotten what it was there. but it's nice that it just acts a resistor because literally, that resistor. there.

you just put it in a potential divider and it is isolated electrically from the heater that's actually connected to let short connect to the right bit. Uh, and that will form a very simple resistor divider. and I Have to say that when I blue on this, the resistance changed from. let me see I made a note of this: I made a note of that somewhere the resistance changed.

Uh, that so that the voltage and the divider output went from about. hold on. I'm just going to find that one moment, please. Here's a better idea.

I'll demonstrate it here is Wayne I shall put a probe on and I shall measure between the ground and the analog output of that and it shows a voltage about 1.5 volts. See one point? Yeah, 1.5 because I'm breathing on it and I've been drinking wine, right? Watch what happens when I really drink wine I'll spill some of this in the wine in my mouth and blowing it. Um, see, the boat will shoot up. That's how significant the change is when the ethanol in the wine hits it from my breath can of Interest That's a huge change isn't it? It literally went from like about 1.5 to about 2.5 volts or whatever that was.

So that's a kind of interesting. So there we have it. This thing's going to go off again. It's going to keep going off, isn't it? Because because I'm breathing on it.

Oh, there's a switch. So interesting thing. it makes me wonder this looks at a standard case. It's got the port here.

It's designed for gas sensing. Did they just go to this company and say we want the cheapest one you can give us and uh, they said well, you know if you want carbon, dioxide, it's going to be quite expensive because the carbon dioxide sensors are quite expensive and they maybe said what's 30 so you got and they said, well, obviously it's the breathalyzer alcohol sensor but that's not any good. Uh, and they said well just put CO2 on it anyway. No, no, we can't do that.

Do it or we won't buy our product. Okay here it is your cheapest carbon dioxide sensor that is actually a party sensor that can detect wine at a considerable distance. So I'm gonna blow in again. Foreign.

Just blowing at it isn't that great. There must be a use for this, but it's nice that they actually use a real sensor. What comes to mind is ghost detectors. You know how the ghost detecting industry tends to rely on random elements and things that react to the environment? That's what this is doing, but it's using the cheapest sense they could get to react to the environment.

So it changes notably as if it is monitoring CO2 And how is your average Karen going to realize that they're not actually monitoring the CO2 Another nice thing about this is the case because this stick-on bezel on the front has no text in it at all. It's basically screen printed black and then they've put the adhesive layer on it so, but just peel off and stick on all the customization of this product is done on the LCD display a full color LCD display which is quite nice. Let me just check. Is it full color in the sense that hold on or is it just segmented out? Oh, I'm not seeing hold on hold on one moment I'm just going to check this I am not seeing pixels I Thought this was a a generic Uh LCD display.

RGB And you know the sections. They were just displaying graphics on it. It actually looks as though it is perhaps a dedicated LD LCD display designed for the application with seven segment uh sections. That's unexpected.

I Thought they were going to use a generic LCD display that spoils the concept of reusing this with your own project if you could decipher what processor it was and actually reprogram it because it does appear to be designed for a specific function. No, that's going to ruined things of it. But having said that, it was worth taking apart. Worth getting.

Just the fun of it. The fact it is so utterly fake. And yes, yes, yes, it's uh, it's detecting my Wayne Again, that's what happens. But there we go.

that is your fake detector. Uh, something else worth noting. Some of them are so fake, they even they don't even have a sensor. They just fake the values like those uh Health watches that fake your heart rate, your blood oxygen level, and uh, everything else.

They just fake everything There's a lot of fakery on eBay This is not a surprise, but things in its favor. It's quite an interesting design and it does have a decent battery to to give you fake readings for a good length of time and I like the fact that when you put it Outdoors it does seem to actually try to compensate down to the ambient 400 parts per million. uh, of what it would perceive as the lowest level you're going to get of carbon dioxide and then it just maybe I don't know if it's got memory and it maybe it will default that as the base level every time it goes lower than 400 parts per million. It sets that as a new defined standard that everything else is based off, even if it doesn't have the carbon dioxide sensor.