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Not a bad unit, with a very bold design using a microcontroller to run two independent switching converters. The double MOSFET for the fan had me puzzled at first until I reverse engineered it.
The UVC LEDs are actually near-UVA running at less than 10mA each. And before anyone points me to the "research" showing that UVA can also kill bacteria, I'd suggest you actually read it with scepticism regarding the vague results that "it MIGHT be effective in killing SOME bacteria". It looks like marketing research to sell cheap disco lights as having germicidal properties. (But I'm always open to more solid research on this subject.)
That aside, this little cooler unit is quite interesting in that it doesn't just rely on soaking water up wicks in the airflow to give an evaporative cooling effect. It does have those wicks, but supplies water to them - and also directly into the air with an overhead ultrasonic atomiser system.
For the cost this whole unit would be useful just for the case, fan and directable vents. (mumble, mumble, ozone.) It could also be used as a crude low level hazer with the wicks removed and a fill of well diluted fog fluid.
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This video is going to be something a bit larger than normal for this bench. It's not going to fit that well, but it doesn't really matter because i'll open it up and take it to bits and then it'll be smaller. So this is one of these air conditioning units. It's got a fan in the back and it's got a little pull-out drawer in the front and it's got wicks in here and there is a water reservoir.

But it doesn't rely on that as the main thing for the water when you use this or you're. Partly supposed to soak this with water so that it does evaporate of cooling and then you're supposed to lift the lid off and there's an ultrasonic atomizer down here, the ultrasonic atomizer fires water down into this little v down here, which is uh, probably just to let It blow down to a certain level before the fan catches it, and that then throws it through and that will keep these wet to a degree, but it'll also blow a mist of water out the front. So i'm going to pour some water into this. Oh, incidentally, this thing has oh, very exciting, uvc sterilization, as in it doesn't look right and next press.

That button shows a red led which, after a while, goes green and then goes blue color changing led it's just one of those gimmicks that they just throw in so that's uh, three settings, uh, uvc, color, changing and off the fan has three speed. Sets i'll show. You that in a moment, because i'm going to pour the water in first and then i'll show you the mist coming out of it. If i can show you the miscommunity, so i'm going to put the water in like this, and it has the three fan speed settings for what appears to be 12 volt fan, which is odd, because it's a 5 volt supply when i turn it on i'll turn.

On the low setting i'm going to try and set this up now, i don't think you're going to see that fog coming out right. Tell you what one moment please! Now you can see it! That's a fog of water! That's blowing out the front of the unit that produces quite a good coverage. Uh, there's probably other uses for this okay right time to take it apart. One moment please: i've poured the water out, let's begin the destruction, so the construction of this is well there's a fan in the back um.

The power comes straight onto this. We've got a cable coming out to the little uh ultrasonic atomizer and i don't see any obvious screws. There's some screws holding the back panel on, but i think these little clips here may give access. We shall find out shortly.

Oh yeah. That was easy! Oh! Oh! That's very modular! Oh look at that! Just really because the cable's coming onto this, it's just these two cables, one going down to the fan and one going to the ultrasonic transducer, that's very convenient the little inductor. That's the ultrasonic transducer inductor! It's a little step up transformer excellent. Let's take a look at those leds.

First i'll get this out the way. Let's bring this down to a more sensible height, i shall bring in just a random lamp box focus down to there. Okay right, that's perfect! Give it something to look at, let's plug this in and zap ourselves, see if we can blind ourselves with dangerous ultraviolet light, so the uvc they're just standard uh near uv leds, that is it! It's not ultraviolet uh, germicidal ultraviolet at all and there's the color changing led. Oh joy, right here.

Let's whip this circuit board out, i can see a use for that case. Powerful fan 5 volt input, even a 12 volt little boost circuit. If that's uh accessible for bypassing um could be useful for other things, based on recent projects involving room air uh, what do we got? There's the boost circuit for the fan, but i tell you what i'm going to take a picture of this and then we shall reverse engineer it and see what we can find. The reverse engineering is done.

It's an interesting little circuit this little chip here. This microcontroller is doing quite a lot, so i shall zoom down this, so we can get a closer look at it. The back of the circuit board is the top section of the picture here and it's flipped. So, let's say, for instance, this inductor here this three pin inductor matches to the front of the circuit board.

The microcontroller couples to it's got is a double sided board, but the back is really just used for the ground, plane and also random tracks from the microcontroller to the separate modules on the circuit board. The modules are as follows: there is the piezoelectric crystal driver, the little water atomizer, which basically has an s10 mosfet. There are three mosfets in this board and s10s two s10s driving inductors and an a2shb for the fan. The reason they've used.

The s10s is because they've got a higher voltage, they're rated for 60 volts instead of 20.. The microcontroller drives them with this exact same circuitry, a 330 ohm resistor and then there's a 10k resistor across mosfet to keep. It turned off then from the gate to the ground, but it's got no transformer and when it wants to actually atomize the water, the microcontroller supplies a stream of policies to this mosfet, which pulses this little inductor here, which uh applies, the appropriate voltage and frequency to The uh, the crystal the fan is just plain weird: it's got two sections, there's a mosfet that switches the fan on off and there's a mosfet uh that is used to actually boost the voltage up from five volts. I was looking for the boost converter chip.

It's done by the microcontroller again when the microcontroller wants to actually turn on the fan. It turns the a2shb on, and then it also starts pulsing this and the frequency it pulses at will determine the voltage that's developed across this circuitry. I shall show you that in a moment, uh the leds, the amazing ultraviolet, the uvc germicidal fakers - are just in parallel with just one single resistor for both them. The rgb led has its own resistor and then three white leds for the different power settings.

Just have one resistor for them all, it's very straightforward. The other thing worth noting here is that the microturn here's, the incoming supply there is a decoupling capacitor close to the microcontroller, but then also a resistor and capacitor just to create more isolation, because there's two very nasty inductive loads in this circuit board. I shall expose the circuit board for you to take a look at and then i shall bring in the schematic. It looks fairly cluttered it's not as cluttered as it looks.

It's all modern. Here's the usb supply command the decoupling capacitor, a 20 ohm resistor, leading down to another capacitor which just provides that isolated supply. That just means that the spikes and glitches happening with five volt rail from these pulsed inductors are less likely to crash the microcontroller, which would be a very bad thing. You don't want these mosfets staying on all the time, because if they do, it will cause problems with high current, because these inductors will just saturate and then pass a lot of current uh.

There's the leds clustered as the one rgb led the two ultraviolet leds and the three white leds each with their own one 100 ohm resistor. The two push buttons are just pulling down to the zero volt rail the ground. Here each mosfet has the 330 ohm resistor feeding. I don't know why i wrote 330 of them up there as well, but then i don't know why i wrote the fan twice as well.

It's just uh. I drew the fan symbol in afterwards and then just wrote fan above it, even though i'd done it before, but that's, okay, we'll get back back to that in a minute. So the gates of the mosfets are pulled to the zero volt rail with a 10k resistor. Just to make sure that when this system is powered up and the microcontroller isn't stable, it defaults if the output's just floating it makes sure these mosfets are off.

This is kind of important, mainly with these two. When it wants to power the atomizer, it starts feeding a stream pulses to this one which energizes this inductor, and this is the way the inductor is showing the drawing. But i thought that there'd be a fairly heavy primary section. Then the atomizer would be over a sort of higher voltage section.

I don't know if they're actually using a low voltage higher current, i would have thought it would be higher voltage lower current, like in piezo sounders um. So i'm not sure why they've drawn it that way. One day i'm going to clearly have to unwind one of those transformers. The fan is interesting.

Here's the boost circuit for the fan, which is the inductor and that's round about 4.7 micro, henry 4.7 micro henry. They drop drop is 4 7, like 4.7 ohms. It's not it's very strange. I don't know why they do that.

The circuitry, when it wants to set the output, will switch. The output under load between 7.8 volts for low 9 volts for medium and 10 volts for height, so decisive and so accurate that it's almost like they said all right, so 8, 9 and 10 volts, roughly it's quite clever, but to step the voltage up. It provides the appropriate number of pulses to this inductor when this inductor is pulled to the zero volt rail. It builds up a magnetic field in it and then, when this turns off that field collapses and it diverts the so say.

For instance, this is positive and then this is negative. It builds up that field and then it turns off. This goes negative. This goes positive and then that means that the current flows through this uh shortcut diode to this capacitor.

There is a zener diode across that the only time exceeds the zener. Diode is, if you do, i do and power the circuit up. The fan disconnect to see what voltage it goes up to. It went up to 15 volts, but it depended on the power setting.

I think it was really struggling at the end, so it's probably more like a 12 volt zener diode, so that provides the plus volt supply to the fan. Then the negative side gets switched and you think well, why don't they just when they want to run the fan? Why don't they just pulse this to step the voltage up in reality, even if this isn't running, if you connected the other side, the fan negative. Without this mosfet here, current would flow through the inductor through that diode and it would uh feed the fan, and i tested that i turned the fan off. But then i bridged the uh mosfet here and the fan ran at a fair lick.

Just on the five volts. It was five volts minus a short shortcut drop uh. I measured 4.5 volts across it when i was running it like that. So when the processor wants to turn on the fan, it just enables this transistor to activate, in the first place, to pull the negative connection to the zero volt rail, and then it starts pulsing this inductor to step the voltage up.

It's quite neat that is it. It has other functions apparently built in after a certain length of time. It will turn off the atomizer um. I also mentioned turning the uvc lights off the sterilization lights.

I'm just thinking. That's a gimmick, though strange uh, but there we go. It's very modular. It's a neat unit.

Uh, it's got potential. The fact the fan runs happily at five volts suggested. If you wanted to make some sort of uh air handling unit for other reasons, ozone generator, then it would be quite an interesting unit if you just disregarded the ultrasonic atomizer and you just fed 5 volts straight to the fan. You'd get a good airflow through it, and you could also then use that to power a 5 volt module of your choice in here, but as it is, it works really.

Well, it's very modular, just it clips together very decisively and uh the way the the circuitry here is just basically two connections just plugged onto that circuit board. Well, let me just plug them on right now plugged on to i could get a job in the factory kind of. I don't think they would employ me, though. So here's the one that just goes on here, two identical connects.

I wonder if they ever get in the wrong way round: two identical connectors stuff. The wiring in here i've already pointed leds that way and then just slot it down like oh hold on it. Hooks in like that and clicks. Am i i'm gon na burst this now? If i get the wiring in the way, i don't think so.

I think i'm just not. Oh there we go. Maybe i won't get a job in the factory, but it all clips together very sensibly and this uh, the deflector here in the front of the atomizer. The two screws are also holding this sort of like the chromatin that secures the atomizer in place.

It's very interesting unit quite well built it wasn't that expensive, i think it was about. I think it was about 10 pounds, so i'm going to go and check that one moment please. So i paid 13 pounds. Apparently, it was like something like 11 pounds, plus 2 pounds, processing or vat or whatever um, but it's now gone up to thirteen pounds.

Ninety nine, presumably with v80, on top of that as well free delivery that came from a seller called very catchy name rage. Man, rage dash man, mini air conditioner, portable cooling fan, led cold water travel, cooler unit. Uk. I think the main identifier for these is the fact they've got the two buttons and the three leds, but um.

It's a neat enough unit. The case is nice, it's nice and robust. It does spare that haze of watch out the front and it's running, it's not mega noisy and it has a potential if you just want a case with a fairly powerful little fan. That will run from 5 to 12 volts and you get a bonus atomizer as well, but there we go interesting, not too bad.

11 thoughts on “USB swamp cooler with fake UVC “sterilisation” (with schematic)”
  1. Avataaar/Circle Created with python_avatars Bo7tkiller says:

    My guess a machine with plastic slats containing water and could be frozen before use would be more efficient. When my father was a kid, his family would make a temporary OG swamp cooler by putting a 1lb block of ice in front of a table fan.

  2. Avataaar/Circle Created with python_avatars fhhsvnggbh says:

    Ive got one very similar to that, i replaced the sponges with dishwashing sponges. It works well in an airconditioned offices. It adds to humidity but hey i was cool.
    Mine has the spots for the uvc but nothing there. The colour changing is still there
    I use it now as a smell machine ie tip essential oils in the resevoir and turn it on to make the place smell better.

  3. Avataaar/Circle Created with python_avatars HULL GUITARS USA says:

    Here’s some interesting info about genuine UVC LEDs. This is a copy/paste of a conversation I had with some fellow electronics/photonics nerds regarding this technology. A lot of us hobbyists and professionals online, in places like the laser pointer forum LPF and budget light forum BLF, and others.

    Clive, I think a cheap Spectrometer would be a cool DIY build. Like the one shown on “les’s lab YouTube channel” Not really necessary, but it would be a fun build, and I’ve seen several instances where you’ve wanted to measure the wavelength of light. Once you have a spectrometer…,you can’t imagine all of the incredible uses!
    Here is the copied info…Maybe it’ll help some folks….. and it’s just interesting stuff regardless!

    All genuine UVC LEDs have a quartz/sapphire glass window and/or ceramic Gold plated body. This is necessary because UVC easily damages Plastics and other materials used in UVB and all other LEDs. Therefore if the window wasn’t quartz, it would quickly degrade and discolor.

    I’ve Bought and tested close to 100 different UV LEDs over the past few years… Including deep UV (UVC) i’ve tested everything from the dirt cheap Chinese knock off‘s, to the highest end chips costing $100 or more from Nichia and other quality manufacturers. (usually as a sample or with a big discount because I can’t afford $100 for a single LED 😂)

    I’m not a professional optics engineer, but I have an industrial electronics servicing business and lab… so already had the equipment. I was interested in this stuff for my own hobby and professional uses. And it was fun as hell!! UV photonics technology is super interesting, even to regular folks Who aren’t nerds.

    I’ve always dabbled in optics and lasers. I spent several years putting together a professional optical “breadboard” and test bench. All dirt cheap from government and Academic auctions. It really is the golden age of science and electronics! Over $20,000 worth of optical equipment, and decommissioned military/medical/industrial lasers. Photonics and laser stuff is about the most expensive hobby there is. Besides burning money 😁 A simple mirror, lens, or optical mount can be hundreds of dollars new. no way I could’ve afforded it. But I paid pennies on the dollar! Or less. Government auctions are awesome.

    There are genuine deep UV LEDs being made in China that are pretty darn cheap. $1-$2 each! Pretty low power but decent quality.

    But UVC LED technology is still so new, that the output powers are exceptionally low when compared to UVB. So you need an array of about 25 LEDs to approach timely “sanitizing“ power. Which is not going to be cheap, especially if you get Nichia or other high end chips. For a 25 LED array of decent power UVC nichia LEDs… You’d be looking at over $1000 easy. And if you went with their most powerful chip, a array of 25 would be about $2500 😂

    But power density will increase slowly just like it did with 365nm UV LEDs. Cost per milliwatt of “radiant flux” will go down with time.

    Currently, decent cheap quality UVC LEDs average 5-15mw (Milliwatt) of optical output power. So when they sell UVC LEDs labeled as “1 watt“…. that means 1 watt of input power. You have to look closer to find the optical output power rating.

    If you got 1 watt of REAL UVC optical output… That shit could fry your skin and eyeballs really fast. Even worse is that real UVC leds can be almost invisible. Which is Dangerous shit!!😂

    thankfully many chips include a visible LED inside the same package. Usually 365 nm or higher UVB. As an indication light, so people don’t accidentally leave it on without knowing it… Easily burning their eyes. Or the board it’s eventually mounted on….in a finished product…. has a tiny colored LED next to the UVC led. To indicate when it’s on.

    Although 100 mV is pretty much the limit for current UVC led technology…… its possible to get 1000MW (1 watt) of optical power out of 365nm UVB leds… or even more. It will be incredible if UVC LEDs reach this level of radiant flux in the next few years.

    Sorry to ramble on. Hope this helps someone or you find it interesting.

  4. Avataaar/Circle Created with python_avatars Andrew Curtin says:

    Guh…ive seen these way too much lately. In virginia no less aka humid as fuck centeral. And they claim they "are portable ac units" dont buy these unless its actually dry as shit where you are, if its humid itll do jack and just get super moldy

  5. Avataaar/Circle Created with python_avatars Erik den Houter says:

    These things do work a bit when you ventilate the room very well, e.g. wind outside with open windows. But when you close everything, the only place keeping a bit cold is right in front of the device, a nasty island of comfort, because the rest of the room keeps rising in temperature and humidity.

  6. Avataaar/Circle Created with python_avatars siberx4 says:

    They built themselves an open loop boost converter with no feedback, relying on the fact that the fan is a (mostly) known load to set the duty cycle on the transistor blindly for their low/medium/high settings just to save themselves a comparator or analog input; fascinating. Especially since it meant that the zener became a required component instead of an optional one.

  7. Avataaar/Circle Created with python_avatars Steve L says:


    Add a public comment…

    Steve L

    When the ultrasonic crystal is not powered, what keeps the water from a full tank from dribbling out?

    Any idea what the voltage and frequency driving the crystal is?

    Physically, what does the ultrasonic crystal look like?

    Mad scientist idea; Adding a heater and pot infused e-cig fluid to the hopper could make your next disco gig a real "high"!

    If we hear that the Isle of Man has slipped it's moorings and gone adrift, we will know that you tried the experiment, and it was a "hit"!

    Thanks, Clive 🙂

  8. Avataaar/Circle Created with python_avatars Christian Halstead says:

    Hiya Clive it's me again .

    Have you ever considered making a video on adding a Bluetooth adapter to an old radio cassette player? There are several videos showing it done . I'd like to attempt it myself but I'd only feel brave enough with your comprehensive help .

  9. Avataaar/Circle Created with python_avatars SquidCaps says:

    Swamp coolers on the coast is a waste of time.. I have one, humidity never drops below 55%.. But it was not the main reason, it is a big unit with a powerful squirrel fan, it can suck in cool air at nights and blow it across the house, in line with the prevailing winds.

    Too bad this is an "eco" house designed to trap heat in the structure. So, one it warms up, it stays warm. I can pump in cooler air, when it is 29C inside and i pump in sub 20C, i can get the apartment to lower to 26C, and within one hour, it is back to 29C.

    But in the odd days that humidity is lower, it is a nice "bonus". I've been thinking about using a peltier, a radiator and a closed waterloop… The damn thing is so big i could easily fit it in there..

  10. Avataaar/Circle Created with python_avatars Mr Byamile says:

    live in Denver Colorado, it's been more humid than normal and still only 40% humidity today. Was 100* F (38* C) yesterday and my large house was 71* F (21* C) all with a swamp (evaporative) cooler in first floor window. Amazingly effective most the time here. I still think these little desk top things might only work if it's right in front of your face. The cooling is directly proportional to the amount of water you evaporate, my cooler has a constant water supply (with float control), huge fan and 3 large meter square pads. That thing holds a couple hundred cc of water, that doesn't translate to very many BTUs when evaporated. I suppose still better than just a fan alone.

  11. Avataaar/Circle Created with python_avatars Subgunman says:

    AAAACK! Finally got the time to watch the rest of the last live stream and it was gone!! I managed to catch the first three or so hours and I was left in stitches! LMFAO with the antics of the other two members of the MBC!!! Your expression at their shenanigans reminded me of the the American comedian Jack Benny when someone really pissed him off !
    Interesting device, been using "negative ion generators" for over 30 years, mainly in my vehicle and especially on long trips, its quite invigorating and keeps me far more alert while driving. My most recent purchase was from a truck stop back in the states and it was quite similar to a large one you showed when you shared the type of plastic containers you use for storage. It operates off of 12VDC and I keep it running 24/7/365 in my store rooms (through regular rotation) it helps kill off mold and that stagnant air one finds in a damp environment here in Crete. I need to take it apart every two months to clean the needles and the large stainless assembly in front of the emitters.

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