Airwick fart neutraliser - with schematic 

I got a dog because someone said they have a great sense of smell. Turned out all the farts were coming from the dog.

"triangular screw heads!" I like the exitement about getting into the off limits terrain.

Only thing worse than a fart is a fart mixed with chemicals.

What a relief to see this. I have a Hathaspace in the bedroom that reliably detects farts. Even under the covers, 30 seconds after the fart it auto increases fan speed. Until this video, I was half worried that there was a call center somewhere filled with people listening for farts.

"Touched it provocatively..." This is why, as a person who is utterly confused every time you go into details about electronical bits, I love watching your videos. Stay awesome!

It takes a smart feller to understand a fart smeller device😅.

Somewhere there's a man named Arnie who has the honor of having a fart sensor named after him.

My wife is the absolute best fart detector there is.

I had a wall mounted flammable gas and carbon monoxide detector a decade ago. One day I was walking by the unit and passed a lot of wind. About 30 seconds later the shrieking alarm sounded and the LED display on the unit flashed “GAS”. Took me a minute to understand why. The wife came from the upstairs to see what the problem was. I explained that farts contain methane, methane is a flammable hydrocarbon gas, and the gas sensor in the detector treated it the same as utility gas. We laughed almost to the point of falling to the carpet. Good times.

They use the transistor as a diode so it has the same temperature coefficient. It's a fairly stable current source for the heater.

At 7:10, you start talking about the strange arraignment of the 2 transistors. Those transistors, the diode, the 33 Ohm resistor and the 1k Ohm resistor from a current mirror. Or it might be a differential amplifier, as you might see inside an Op Amp. The 1K is pulled to 0V and acts as a constant current sink from the 2 bases. The transistor emitter on the left is held about 0.7V below Vbat, while the base-emitter junction has it’s own 0.7V drop. That base is about 1.4V below Vbat. The base of the other transistor is at the same voltage, so it’s emitter is also about Vbat-0.7V, leaving 0.7V across the 33 Ohm resistor. 0.7V/33Ohms = 21mA. That regulated current is provided to the sensor heater, making it a constant power heater. For this to work, the 1k needs to be grounded by the MCU, and might be tied to the right transistor collector. The sensor output is resistive (100k-500k), according to the datasheet pointed to by moe.m. If one side of that sensor is tied to the transisitor-1M resistor (top right corner, page 2), it might form a voltage divider that could be measure by the MCU (that’s a pretty high impedance, and an ADC would have a difficult time acquiring a measurable signal.) Why the transistor? I’m guessing the sensor resistance and a hidden capacitance form an RC circuit with a discharge time that can be measured. The capacitance is charged by the transistor before the measurement, then turned off to begin the measurement. The time required for the capacitor to discharge to some voltage is measured. (I’m not really seeing how the sensor works with one of its connections open….) The ceramic resonator would be necessary for a stable time measurement, otherwise the MCU would have used an internal RC oscillator as an unstable clock source.

The german magazine "Heise" wrote a report on how to salvage the sensor and how to connect it to an Arduino and that was back in 2014.

Very topical. Based on current USA NY court reports one of these devices might have beneficial application near the defendant's chair. 😜

I bought my first CO/CH4 detector for the house years ago. Decided I'll plug it in initially in the kitchen to test it out. My cat (dearly departed Da Vinci) decided to investigate it, then just sat under it the for longest time, and, well, farted. The detector went off promptly, causing him to leave most hastily. A good time was had by all.....

The minute you said you'd 'Drill It Out ' - it started turning. Brilliant. Just... brilliant.

I knew you'd break the fart neutralizer. One way or another.

The air freshener industry is the best example of generate a problem and sell a solution. Air not fresh enough? Open a window.

Clive is about to fart but not yet..... One moment please!

Arnie? No problemo, it'll be back. Interesting device. 10/10, would test.

Triangular screw heads, Hard to break in to. Fart Knox , as it were. Presumably the neutraliser uses negative fartback.

The slide switch with flowers in increasing size is a nice little touch.

the three transistors in middle is a current mirror with current control, the one use as a diode is a temperature compensation.

I take the existence of this device as a personal attack. My lawyer has been notified.

Finally, a device that can detect who dealt it.

I had one like this but it was telepathic. It makes scents when you think about it.

This is awesome. I still glazed over when i saw the circuit diagram but that’s because its late. I’ve never seen someone bust it out with the big zooms and diagrams.

Hous of Commons might be a potential application...

I like how you referred to my farts as 'Aromas' Clive, I'm flattered

It surely took a long time to reverse engineer. You do it so we don't have to do it. Thanks! A lot!

Nobody needs an airwick freshener when you have your special woofle aroma for masking the lead solder smell

The oddly connected transistors form a constant current supply for the heater of about 18mA. The IC can urn this on and off, and can also sense when the heater is actually drawing 18ma. If the resistance goes up to a level where there is not enough voltage to cause 18ma to flow, or a low battery does the same, the sense output (collector) goes low, otherwise it's high. I'm not sure why you would want to do that, but thats what it does.

So this thing if you drop a bad enough one panics and shuts down. As Carsten from the Kempinger channel would say, "Very Satisfying" I always wanted to replace the can in those hotel room auto air fresheners with fart spray but I figured they would know who had the room last. The letter banning me from their hotels would probably have been worth it though.

"...not like an old lady making her house absolutely stink of chemicals". Wow, I didn't know you knew my mum. Gosh, I've told her thousand times. Let's see now when I tell her that even Clive agrees.

The youtube commercial algorithm pulled up a trump pun running an old spice add on a fart detector video ,someone has a sense of humor

I could have done with one of these back in the eighties, when I had a Doberman, although - in fairness - it would have been like trying to neutralise a chemical attack. Bloody Bonios! Other than that, one couldn't wish for a better companion.

Great and interesting video as always, many thanks Clive.

I’m Out Clive: Thankyou Very Much Clive, Happy Weekend Man❤

Thanks for another great video Clive 👍

Fart on it to test!!...FART ON IT!!!...... we shall watch!

Thanks for the video, I am having neck surgery done on Monday and it will be a great time to go back and watch your videos, device builds especially. I only wish they would allow me a Dark & Stormy in the hospital! Though it probably wouldn't go along with the pain meds. 🥴

If that thing was in my bedroom it would switch on contantly until the battery runs out 😂😂

It's... unusual to say the least. I wonder how it would deal with a triple fart?

Ok, this is a very interesting device. Very nice device. Quite surprised by the complexity of its circuitry. I hope you keep the PCB. Might be able to find a replacement sensor. You may also be able to decap it in the future.

"Let's just chop some wires. Chop - Chop." I'm going to hazard a guess, you were never part of an EOD unit. 😁

I like the way your diagram looks. Looks like a control room with a mysterious power panel. Would look cool on a t shirt 👕

Love the way this video is right next to a Jack Vale Pooter video in my subscriptions feed.

Expect the price to hike as there is upcoming demand from NYC courtrooms. 😂

Those 3 transistors sound like they're hooked up as a current mirror to put 18mA through the heater, regardless of the applied voltage, ie, acting as a cheep 18mA current regulator. Keeps current constant at 18mA from fresh 4.5V new cells through end-of-life last-gasp moribund cells.

Funny story. My wife bought a natural gas alarm for in the kitchen, since we have gas appliances. It was constantly going off. We couldn't figure out why. Turns out, farts and hand sanitizer both set it off.

"Not like an old lady making my house stink of chemicals" My Dad is insulted....he has two of these (without the smell sensor) on the go....

The transistor arrangement looks like a long tailed pair. It's a current mirror. So it's providing constant current to the heater.

The transistor pair is a constant current source. The collector of the second transistor provides a low battery warning when the current source can no longer keep up. The epoxy chip is clearly an MCU. The "charge pump" is NOT, but rather an interrupt generator that wakes up the CPU every few seconds, to take a reading. The sensor is on the back and its wires are sealed to prevent perfume from poisoning it.

Fart neutralisers, farting Ninjas… I’m beginning to detect a pattern here Clive! Could it have anything to do with deep fried Mars Bars and 60 shilling perchance? 😂

Just after the turb of the century, I was living and working in Denmark and I noticed that when you went to the bathroom and turned on the light, the fan didn't start unless you were dropping a deuce or taking a shower. If you just went in to take a leak, it didn't go on. I thought the Dane's had come up with some sort of fart sensing technology. Then I realized that it was just a timer.

The shorted transistor/diode could be being used as a temperature sensor.

If you wanted to, you can buy modular VOC sensors from the usual suppliers, for only a few dollars. I note you can buy combination laser dust sensors and VOC detectors for less than $8 too, in case you need both functions!

good morning From Australia Clive! :D

What needs to be made is a fart clap-o-meter. Giving marks out of ten for potency.

I suggest sending the board to the dude who runs @electronupdate, he might be willing to decapsulate the chip. And regarding the weird charge pump arrangement, I'd speculate that they've shoe-horned an existing chip design and made some workaround circuitry to emulate the feedback signals that it expects to be seeing from what it is normally supposed to control.

If you get it working again, I believe this is desperately needed by Juan Merchan in New York.

It's not odd. It's a current mirror configuration. The diode is a reference and the circuit keeps the voltage over the 33 ohm resistor to the same voltage as the diode voltage drop, thus feed a constant current to the sensor heater.

I have seen that weird arrangement for the heater transistors. The heating element has PTC characteristics and once it is heated up the voltage on the 33 Ohm resistor drops to a point that the other transistor with the diode does not conduct anymore. This tells the controller that the work temperature has been reached.

2:05 I thought for sure you were going to say “because I don’t fart” 💨

Clive, I believe that set of three transistors is a PNP variant of the Wilson current mirror. Sorry if someone else already said this. I'm not going to read every comment.

Kind of crazy the amount of technology being put into an air freshener! I know these companies keep trying to come up with new ideas to sell more air fresheners (although they don't actually freshen the air, they just cover over any existing bad smells). If it works though a nasty niff detector makes good sense as it would save on liquid used.

Honestly would be pretty awesome to put into a multitude of things, like a bathroom or kitchen extraction fan "you will not get away with stinking up the bathroom this time"

The transistor with the base tied to the collector - I think that configuration is sometimes used as a temperature sensor. So maybe it shuts off the heater if it gets too hot?

I think the odd transistors on the heater is so the processor can control the temperature. Heater resistance changes with temperature, changing the current draw. The processor detects the threshold and bit bangs the heater power. Maybe?

I could be wromg but if I remember correctly therewere some cheap for the time cut down 8051s. They were slow CMOS only pulled down and at most had two ports. Usually no UART or anything like that. ATmel did some re0ebgineering and turned them intoa 20 pin DIP which you can still get from Microchip. It was the 90's when I did a few weeks work on these so take that with more than a pinch of salt.

I checked my calendar, it’s not April 1, so this must be a real device ;)

Interesting, I was thinking at one stage to build such a device. With one pad never been soldered I think you should re wire this unit just for the sake of it. As always brilliant reverse engineering!

There are a handful of mcus with intergated opamps and comparators

Well as an American over half a century old, I've never seen or heard of one of those before.

It could be interesting to see waveforms and measurements from this circuit.

The "wired" transistor pair could look a little like a digital controled constant current source. I could imagine the tempeature of the heater have to be quite constant.

We have a courtroom in Washington DC that could really use about 6 of those.

My dear good fellow, how many of us mere mortals utter the words 'One moment please' I think that would make a great T-shirt.

Here in the USA I only recall the ones that went off at the time you selected

Does it also detect old farts? Because if it does I’m doubly screwed.

It's nice they had the capacitor on the motor, as though the two seconds it's on for would make a world of difference... This seemed needlessly complex, the whole thing could be replaced with a 555 and a transistor

This is a young man's game. At our age, we cannot trust farts.

This deodorizer would have been working non stop if this was around during the Kenny VS Spenny farthing episode

Muito intrigante 😮

Maybe a certain NY court might be very interested in this product.🤷‍♀

It seems to work like old school DVM/DMMs that used a pulse counter and a VCO.

I always see these in buildings in a state of not being used with vintage batteries still in them or the front missing. Some I guess found out how much batteries cost in them or would think they brought the wrong can where I had to tell them that glade cans work in them as well My grandpa stopped using them because he got sprayed in the face lol There's this other one that has a spare outlet but I think that one is currently sold for higher than what it used to cost. What I would do with those is solder in a power supply or mod the battery terminals which is probably easier for most people or have some rechargable batteries placed in those caps that change the battery size because back then almost everything used c or d batteries and those tend to get expensive after a while as well as their recharable counterparts . I got a plug-in one that claims to be "smart" but it's not exactly smart it just has a timer switch and a light up ring to tell you if it's empty, on and how open the vent is. And I did finally find those outlet protectors that double as night lights that have more than one color setting and what I found out is that they somehow also have a wiring fault detector in that tiny device that's not mentioned on the box.

I have Winix air cleaners at my home and they also are quite good at detecting farts. The indicator goes from blue (normal) to yellow (caution) to red (danger!), and the fan speed increases based on the level of stank. If you fart in my house, EVERYONE will be fully aware.

This thing was perfect, I've had them in my bathrooms years ago. Too bad they stopped selling the refills.

I'm super interested in fart detection as i have been thinking to have "bad odor" automatic aromatizer thing for years now. I dont like it to be all flowers all the time. Just then bad dump has been taken.

Can you de-blob a chip like this? Might be fun to try various solvents and abrasives and ultrasonics etc.

We had a line of commercials for years here. "The house smells like fish!" "Now it smells like fish and roses!" I suggest you load the sprayer with fart spray and then leave it in a inconspicuous corner of Ralphies house. He wont complain about the house smelling like something and something worse if you choose something awful. I should be a counsellor.

That first page of transistors had 'current mirror' or part of a 'differential input' written all over it, it looks like the front end of an instrumentation amplifier which would make sense to me as your not dealing with nice clean large signals and I don't believe there is a Glaswegian Kiss approach and it's going to be a bit more involved. It's all pretty specific so shame they never label blob chips

Seems the AirWick and Glade sensing sprayers are discontinued in the US and probably everywhere.

I would have imagined that the aroma of of punctured lithium batteries and aerosolized woofle would be more than sufficient for the bothy.

What could be easier? Remove the blob with minimal damage or try to poke around and try to reverse engineer the functions of the chip with an oscilloscope or something like that

Say it really fast: _One smart boy, he felt smart._ _Two smart boys, they felt smart._ _Three smart boys, they all felt smart._

Is the transistor heater circuit shenanigans used to detect once the element is up to temp? Low resistance when cold = high current = 'output' high and then the output goes low once heated and passing a lower current? Kinda like an ultra-optimised 'transimpedance comparator'?

Clive have you ever thought of going into marketing and advertising, you will be brilliant 😊

I always wanted a fart detector! I really don't know when I fart and always blame the dog! My wife hate me! 😂

I had one of those back in the day. My roommate and I tried our best to make it go off. It would work anytime we urinated but rarely after dropping the kids off at the pool.