Teardown of a big HEPA air filter unit (with schematic)

it's a big huge thing it's a air filter unit so we'll start the video at the bigger bench and once I've disassembled it into little bits we can take it back to the usual bench so this thing is one of the many HEPA air filter units that were sold during the pandemic I've just turned it on accident no I've touched something I've it's got touch buttons here it's very easy to touch them let's uh press this button so it has three fan speeds draws air in through the filter and then shoots it out through this Grille at the end the fan speeds are low medium and high oh that'll be high then and that'll be low which also doubles up as night mode it also has an ionizer and also timed on our Time Buff which is utterly pointless the cover comes off I should say uh these are all very very similar between the different brands basically it's a filter a fan that pulls the air through the filter and then blows it out the other end they're very very simple it's all about the flourish and the The Touch button controls and the features and air monitoring this one does not appear monitoring the whole unit incidentally was brand new cost 30 pounds from eBay inclusive shipping and rather predictably because it is push pandemic you can't get the filters anymore I think a lot of people have been cut out by that here's the filter it claims to be four layer it's got the outer debris filter it's got the HEPA filter we'll take the filter apart already I'm apparently uh so there's the inner HEPA filter complete with debris already and then it's got uh what I'm guessing is carbon fiber I didn't expect it to come off with velcro that's quite handy that's uh remind me of Frank Tedesco and his piano music um and then it's got the final stage which is a cold catalytic conversion filter that does things to organic invisible things that nobody can see so you can't really prove it doesn't do it we'll take it apart we'll take a look for that here is the fan that is pulling the ear in from this chamber here there's also a little module because these units all have loads and loads of different features and the more you pay the more features you get there's positions for modules that might be an incoming air quality module not really sure there is a thing here that would pop off and that is probably for an external air quality monitor there's a position for a magnet a magnet in the cover so when you clip this on maybe it only enables it when the magnets in place maybe that's pre-ionizer I'm not really sure the main thing is we're just going to take this apart so I'm going to pause momentarily while I take the screws out and then we'll see what's inside one moment please and we're in that required slight unreasonable force due to this rather annoying screw here it turns out that the way they are symbol is to make it look screwless-ish to a degree is that the final bit of a bezel that it's put in is this uh plastic ring gets pushed down the from the top here and it looks as though you could possibly get a spudger in there can you maybe you can oh no I don't I'm not sure you can maybe you could get down there yeah maybe that would work it's not easy anyway the gist is that uh it's a part here is the centrifugal motor here is the 1.5 microfard capacitor for that motor there is the ionizer module down there with its little air I don't know if you can even see that you see the two little carbon fiber bristles let's explore that as well and here's the control circuit board presumably with the power supply on it because I can see the mains come on right down here and I can see the output to the motor the motor has four wires um with uh auxiliary couple of wires coming out from the motor to here I wonder if that's just three different speed settings that are just switched individually I wonder if it's just like multiple ratios of windings I don't know if it's going to be rotational control I don't think there's any feedback I think it is just switching windings and so I'll take the circuit board out of this and then we'll take it through to the bench and we can take a closer look one moment please the reverse engineering is complete that took a very very long time because of some weird circuitry here it's a very very optimized circuit but very interesting as a result so I'm going to zoom in a little bit I could not really get a big picture of the circuit board because it started off quite big and also got a bit of reflection as well but I've got enough for us to actually work on I've got a better image as well but the main things to note are that it divides into distinct modules we've got incoming filtering and the buck regulator power supply we've got the microcontroller We've Got The Touch button inputs and then we've got Triax four of them on the output one Spectrum the ionizer module and the other three switching sections of windings in on the motor the touch Springs despite being touch buttons don't actually touch them if they're actually exposed because they are referenced directly to it means voltage that's how it works it's looking for a ground path via you and when it's mounted in the front plate here those Springs sit into these recesses and when you put your finger on it it passively couples and it can detect that your finger is there I should put that down I'll give you a closer look at the circuitry because I divided it into two so effectively this is around this way the supply comes in and there is a class X2 filter capacitor and a metal oxide varista here which is used to clamp voltage spikes and prevent interference either causing problems in the equipment or actually anything going out there's a fuse down here which is actually neutral which is quite odd um then power supply is derived via a couple of diodes and some capacitors I should just show you this in the circuitry shouldn't I but it generates a 5 volt Supply but it's reference to the live this is important because of the way it switches the Triax and also it needs to be referenced to live for the touch buttons to work they're just an easy way to work it makes the unit intrinsically waterproof incidentally it was covered in a conformal coating which was also quite unpleasant to deal with because it made it very hard program the connections the microcontroller appears by nato51 based one um the LEDs to get it all into small number of pins they're Charlie plaques their Tri-State multiplexed and then look at the tracks and the output here switching the windings and I'll show you how the windings in the motor work as well so I shall bring in the schematics because there's more than there's more than one schematic huh leave the socket board here it can be some set dressing let's start off the power supply this is going to be the most complex bit to understand live in neutral come in from the supply the neutral goes through the fuse which is odd then there's the metal oxide Barista the class X to 100 nanofarad suppression capacitor and two 470k discharge resistors across it so when you unplug the unit you can get a tingle off that capacitor there is a 22 Ohm resistor and then two diodes in series it's just a sort of built-in redundancy of having an extra diode and then you've got a smoothing capacitor 2.2 microfarad 400 volt death beam capacitor then a little inductor then another death beam capacitor for double death beams and then it goes to this little nk8k05 best of luck in finding a data sheet in that all I could really find was a schematic my voice is messed up again still isn't it the little chip then generates a 5 volt Supply using an inductor uh I took a long time reversing this bit because the original schematic I found was for a completely different it was showing the reference on the primary side to the reference and the negative the ground the zero volt um it turns out that that chip can do both positive or negative and uh once I'd worked that out it became a lot easier but using that inductor and a local capacitor for its own power supply a couple of diodes and output capacitors it generates a five volt Supply and it references a plus 5 volts to the live and it gives us a negative voltage from the life of 5 volts to give the zero volt reference and the circuitry all it sees is the zero volts and five volts it doesn't get bothered by the fact that five volts is reference to the live it has to be referenced to the live for a couple of things next bit this is one of the couple of things this is a motor it has one two three four windings a base winding which is the high speed winding and then auxiliary windings on top of that that add in series with it adding to the impedance of the motor so you've got a high medium and low and to test this I actually got some Neons I wondered if it switched in combinations it doesn't only switches one triacon at a time and uh I put a neon on each output and plugged it in again and then tested it with that insulator between me and the Touch button and only one knee inlet at a time and it was AC it was switching so it is just standard tracks again these tracks were quite hard to identify I made a note of the number but uh to be honest I didn't find anything on these tracks at home I shall put a note of that down in the description down below there is a run capacitor which is used to give the motor Direction and uh the four connections to the motor are the black one one of which connection goes to that capacitor goes to the brown of the capacitor um and then you've got the red white and yellow which are the high medium and low and whichever one of those effectively goes live we'll introduce the phase shift of this capacitor into other windings and effectively it causes a rotational phase shift and that's what gives it Direction one of the most common failures and things like Motors and ceiling fans that use these capacitors is if the capacitors gradually reducing value as they do you can end up the situation it starts getting very sluggish to start or it just stays put and it just hums and it won't actually run until you give it a spin to actually start it running and that's a very easy fix just to get a new capacitor for it just read the value off the side of the existing one and also note on the side of the case Just for future reference but um that's basically how it runs the motor the ionizer module is quite neat because whereas the ionizer model it's still in the unit uh here's a little bristles here is the main Supply going to very standard chinesey type unit you've got the power supply up here which says Jin Yang and then rather pleasingly it's got two different colored wires going to the emitter and you know what that means it means it's probably a bipolar ionizer with one positive and one negative and that means there's going to be increased Corona discharge activity between them creating hydroxyl radicals as they say and a little bit of ozone that's what we want Trace levels of ozone and other active things in the ear that emulate nature that would normally be depleted indoors I've mentioned this if you want to see the ozone video just look for my my ozone video uh it's there's one specifically about ozone and a the output of these devices and what they do to actually replenish what are actually vital components of the air even if all the currents think they cause cancer and kill the babies that's just one of these things they just jumped on for some reason the tracks are switched from the microcontroller via 510 ohm resistors and it's interesting to note that to do that because this is effectively the plus 5 volt Supply it's pulling the gates of the Triax negative to the zero volt reel so it's taken them from the plus full on the Mt main terminal one to the uh the negative 5 volts and that just is much more efficient for turning tracks on it's much easier to turn them on by doing that most Triads can be triggered in any combination because these are switching you see they can be triggered whether this is positive and this is negative or vice versa or whether the gate is positive or negative they can be triggered usually in all four combinations of that but the most efficient the one with the lowest current which is useful here is to actually pull them negative with respect to the mt1 the main terminal one and this is so this is mt1 mt2 and this gate there is another Oddity here the microcontroller also has a zero voltage Crossing reference it can monitor the supply I don't know if that's just to detect when the supply is cut off I don't think so I think it's to detect the zero crossing point so that it can turn the tracks on as it crosses as the zero crossing point of the sine wave right there there and there because if you do that it means there's no interference there's no pop or click it's just a himself during the circuitry as well it just produces interference but to achieve that and I don't know why they did this I think it's nice that they did it they've got a couple of resistors from the neutral high value resistors um and there's a smooth filtering capacitor and a diode just a zener diode clip that and that just provides an input reference that will pulse positive and negative and at the point it changes state that's when it crossed the zero Crossing Point after this the circuitry gets super easy and weird and delightfully weird I have to say so there is the microcontroller again I've I've found one like listing that just basically gave a clue as to what it was it's a very Chinese industry microcontroller and it's based in the 805 one which is very common but I could not find anything other than a seller on a random Chinese website actually selling them so we've got the 5 volts we only have to worry about 5 volts and zero volts here and uh this this is the piezoelectric Sounder the bit that goes Bing and it's really clever I had to actually swap bastards and stuff that I had to test this because initially I couldn't work out what it was doing because it's a very odd way to drive a piezoelectric Sounder what it's actually doing is this PNP transistor turns on First and it charges this capacitor up via this resistor and then this transistor turns off and then this one puts out the square wave of the required frequency and because it's now being powered entirely by this little charged up capacitor instead of just going beep it goes Bing that's the actual ringing circuit it's not being done in software all it's doing is putting out a constant Square wave at that frequency so when you turn it on it goes it's actually just going BBB but each time before it does its Bing it's charging that capacitor up then it's turning that off and then just discharging this through the Piezo uh at that square wave and this resistor here is just because the piezoelectric would uh it acts almost like a capacitor and that you need that resistor across it to actually be able to actually make it pulse and make make noises that is so cute I really like that I was really surprised when I worked it out I changed that capacitor for a much bigger one and instead of going bing bing when it started it went beep beep it didn't do the Bing thing because it wasn't it you know it was able this was fully charged at a higher level uh so it can do that so that demonstrated that is that that creates that Bing noise very clever very neat it makes the software a lot easier the other things it's got are the touch inputs they're just basically those Springs on a resistor going to an input I'd wonder if these are either a high impedance input or and it's just detecting the voltage difference when you put your hand near it because you're effectively referenced to ground if you've got one of these and you find that it doesn't work in a socket that none of the touch buttons works and it works in other sockets it may just be because they're live and neutral swapped that's effectively how it works but it makes me wonder is it a dedicated touch input in this microcontroller because it was going to various random pins um oh yeah it was um these pins down here and that one up there I don't know if they're on the same port it would make it easier in the software if it was but I wonder if they're just standard inputs that they've used this trickery of just the high voltage differential between the circuit board and U and that plastic insulating plate between the springs is quite neat the LEDs only have four lines controlling them let me show you that in a circuit board as well uh these four lines here under that means it can drive up to 12 LEDs there are 11 in this circuit board at the moment there's one there for an option there's also a sensor input option uh probably an air quality Monitor and but to do that it uses what's called Tri-State multiplexing and you can drive 12 LEDs from four lines basically four minus one is three times four that's the number you can drive if you had five Lanes it would be five minus one is four times five gives you 20 LEDs it lets you run a lot of LEDs from a very small number of pins and the way they do it is they don't just toggle them high and low they actually make them high impedance or they actually they can go in three states they can be positive negative or floating and by arranging the LEDs in inverse parallel to each other in a combination you can drive 12 LEDs individually and if you need more LEDs on you scan it you Multiplex it it's got the five tracks out that's very simple just because of that referencing to the 5 volt and live it means it's just simple it only requires about 10 milliamps so they're using 510 ohms and it's got the zero Crossing detecting and that is it this looks so simple if you knew how much time it took to reverse the engineer that it it really it's too simple but now let's take a look at the filter so I shall zoom out a bit for the filter it's all very optimized there isn't a single pin of that maker controller left they have used the whole lot so here's the filter with its noise and if we peel off the front it just reveals the pleated paper filter that is the HEPA filter High efficient efficiency particulate filter or whatever it is it's got velcro around here so it's designed to have this peeled off these are supposed to be disposable you use them for x amount of time and energy warning comes up it may come up as a warning or it may beep um but after that you're supposed to throw them out and put a new one in you can usually clean these but it is paper so you have to be very careful you can vacuum it out and well in some instances you can use a Horrors and actually hose dirt out from the other side but this one has more in it and I think we're going to have to open this to see what it is it claims to have a cold catalytic filter called catalyst which is a lot of hype in the industry the air conditioning industry so what I'm seeing here is it looks like a plastic mesh hold on I didn't realize it was going to come out completely let's rip the whole wire I didn't realize this was going to be a complete separate uh layer with the carbon granules here I said carbon fiber earlier I actually meant activated carbon the charcoal stuff is this going to come out hold on let's just rip the whole thing a bit this bit as far as I'm concerned is a gimmick the air filtering companies will disagree so I'm going to guess that this one is based on titanium dioxide is it called Catalyst and the cold catalyst is supposed to if it's real uh remove volatile organic compounds from the air like formaldehyde and stuff like that so here's the other side of that pleated paper filter and here is this uh double side mesh can you see the carbon granules hold on I'll shine a light through it or I'll put a bit of paper behind it here's the drawing behind it that sure no it doesn't right say well I'll shine light down through it does that help I shall zoom in see the carbon granules in there so they've basically got this plastic support mesh now this doesn't really look like that what I'd expect the titanium dioxide I normally expect to be very very white but if that's the case then what they're expecting here is that if it was titanium dioxide it would be reacting with the volatile organic compounds and did be absorbed into or modified in some way quite realize that activated carbon it just removes odors from the earth it's got a reputation for being able to do that it is a standard thing but this is not what I was expecting this just looks like a plastic frame Maybe oh you know what as that got it on it it might have a coat in this side of this uh paper because it looks kind of sparkly and if it might have titanium dioxide I don't think it's the green form I think that's just the final stage um I did uh look up and uh found one website seeing titanium dioxide it's the future Asbestos and it was real scaremongering and then right at the bottom of their article it said we represent much safer technology with bipolarion ionization so it was just basically marketing hype science goes out the window when Market gets evolved so I don't know if this uh I don't know what the titanium dioxide if it is that is the cold Catalyst if there is one or if it's just a slight Sparkle on this it certainly isn't something I'd associate with the plastic I think this is purely the carbon filter but that is it I'm not going to be able to get a replacement filter for this because that uh that company seems to have stopped selling that one but there we go it was interesting it was well worth taking apart I did get it purely for us to take apart and explore and I have to say the favorite bit of circuitry in it is the Touch button Arrangement and also that little double transistor thing let me show you the double transistor here there's the Sounder and there's a double transistor in the back one for charging up the little capacitor down here via that 100 ohm resistor and the other one for actually making the square that makes it literally go ping so that's it it's a very nice wobbly little circuit uh it's very functional and well ultimately I suppose it works and the circuitry is designed such there aren't a tracking slots where they should be and it seems quite logical so uh it's not bad not bad at all

Channel: bigclivedotcom

Views: 54,775

Keywords: large, hepa, floor, standing, air, filter, teardown, circuitry, ioniser, ionizer, bipolar

Id: Xi_X-erjacU

Length: 23min 57sec (1437 seconds)

Published: Fri May 12 2023