Teardown of a big HEPA air filter unit (with schematic)
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- เผยแพร่เมื่อ 11 พ.ค. 2023
- I got a big floor-standing air filter unit so we could take it apart and see what's inside. These were being sold at a very jacked up price during the pandemic, and then the price crashed when the residual stock had to be cleared. There's a good chance that you'll find these stuffed into cupboards of public spaces, or just thrown out after they have served their purpose of ticking the pandemic air quality box. In some cases the units will have been used without even taking the plastic wrapping off the filter first. (I came across two like that.)
The curse of these units is that they are sold in the same way as inkjet printers, where you are tempted by a cheap unit - but then pay the price later with the cost of replacement filters. Or worse still, the seller just stops selling the new filters and you are left with a useless unit.
Pink background is a silicone bench mat courtesy of Scott (Defpom's Electronic Repair channel).
The function is very simple. Air is pulled in through a multi-layer filter and then blown out the top past the obligatory ioniser. They don't need a circuit board or touch buttons. You could literally have an on/off switch and an optional high/low speed selector switch.
Because of the multi-tap motor winding, only one of the speed connections should be powered at any given time. Powering more than one would effectively add a shorted winding section.
If hot-wiring the motor the unused taps must be insulated.
Motor wiring:-
Black - common (I'd expect there to be a thermal fuse on this connection.)
Red - high power
White - medium power
Yellow - low power
The buck regulator number is LN8K05
The processor is an SC92F83A2
The triacs are JKT1D8W
I'd guess these units are mass produced in China with labelling and pricing to suit the company selling them.
The design is very cost optimised, and much more interesting as a result. They've literally squeezed every feature they could out of a cheap processor.
The filter construction is unusual. The honeycomb frame with loose carbon granules is quite neat.
Note that I flipped the 5V capacitors in the power supply schematic due to the odd topology. The negative side should be at 0V.
The bit that goes "PING" took me a moment to get my head around. It's genius. Basically a hardware envelope generator for a bell noise, where the processor just needs to provide a square wave at the desired frequency.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.com/coffee.htm
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#ElectronicsCreators - วิทยาศาสตร์และเทคโนโลยี
Perhaps one day the EU will use its "right to repair" anti-obsolescence laws to force manufacturers to enclose a circuit-diagram inside their devices, like we used to find in the good old days when opening up a transistor radio or a hi-fi cabinet.
These days though, it's the firmware that matters.
The Chinese would copy it 😢😢😢
But what would Clive do then?
Reverse engineering schematics are his bread and butter.
He takes 'em apart, so we don't have to....
aledgedly.
@@kitsuneneko2567 I think requiring having a secure repository of firmwares for programmable chips or having the company provide preprogrammed chips for the 10 years after end of sale would be a good thing.
Though if it was just me, firmwares should be source available.
@@smartgorilla - Huh? They already make it.
Finally, a teardown of the machine that goes "ping!"
Replacement filters for these are relatively simple to DIY. The most important part virally is the spun blown polyester materiel, which being electrostatically charged, does the work of trapping viral particles. (Yes, the gaps are bigger than the SARS COV2 virons, but the static grabs them.) The frame no doubt can be 3D printed, and the debris mat and the activated carbon filters bodged. Many viral particles are attached to spores etc, so the debris filter is actually quite useful.
There is a paper showing that once UK hospitals started using portable air filtration systems (previously considered theoretically as useless), staff infection rates for COViD dropped dramatically - by 40% I believe.
i just printed an adapter for the xiaomi (silver) h13 filter. its cheap and real true hepa filter.
th-cam.com/users/shortsuWRwTAqBsqQ
I believe the greenish material on the back of the filter pack may be a biocidal filter. I have some sunpentown "magic clean" air cleaners which have a green nonwoven fabric bonded to the back of the HEPA filter, and that's what the manual for those units says it is.
A different bench? Dorothy we're not in Kansas anymore
😁
Pink!
Really nicely made thing actually. I love the decay circuitry for the beeper. I got a name brand air filter with air quality sensors being sold cheap as is due to shipping damage, and the repair was pretty easy.
I got it for my bedroom. It hardly ever runs up in speed unless someone's cooking food, or I'm soldering. Aircon's filter seems to do a decent enough job keeping the air clean.
This move to touch-sensitive switches and flat touch-screens is so anti-accessible for people with any kind of sight issue. I don't see what was wrong with proper push-buttons, toggles or dials.
I hope it's just a fad and passes quickly.
Imagine trying to control that air filter unit whilst being partly/fully blind.
They could add braille underneath the touch areas, but it's probably purely a cost saving feature.
Good interfaces will produce a unique sound for each button touched. Not all of them do it, though.
Would require braille and a vibration
Putting the needs of disabled people before profits, is extremely anti-semitic. There are still some Tel Aviv mansions without gold plated driveways 😢😢 Now get back to work and keep paying those taxes 😉👍
It's also more difficult for people without sight issues. Good accessibility is better for everyone.
Would very much like to see you do a dedicated video on how to reverse engineer a circuit board, from analysing the board to producing a schematic diagram.
There are basically 4 steps:
2 - Follow the traces.
3 - Identify each component.
4 - Draw the schematic.
Oh, I forgot 1:
1 - Have about 30 years' experience so you understand what each section actually does and don't go completely down the wrong path after the occasional mistake you'll inevitably make in steps 2 and 3.
@@RFC-3514 Yeah I was about to say 'it's mostly just knowing what different circuits and components do so you can intuit the functionality' lmao
@@RFC-3514 That's so true. With miniaturization it's so easy to read prints and paths wrongly. A very sensitive continuity probe can help finding paths on SMD and multi-layer designs.
Experience also helps identifying common circuit design patterns, which saves a lot of time and makes you appreciate more the ingenuity of clever designs.
If those filters were available to buy, this seems like a halfway decent little air filter. I like the way they suspend the carbon across the face of the filter.
Sharp did that too.
Got a Rovacs one (because of 3D printing inside, not Covid) and the filters are build exactly like this, too...
Wild to see 8051's still being used in modern devices, as a young lad I designed those into production test equipment at work some 40ish years ago. Nice uP to work with.
The 8051 architecture is very common in generic Chinese processors. A strange and pleasing legacy from the early 80's.
And bizarre to see the clock speeds and amount of RAM available on them now!
The 8051 is a really nice MCU, because it's so incredibly standardised. You can take any 8051 and know what peripheral layout and everything you are going to get. Some 8051s may be faster than others, but it's pretty much the jellybean equivalent of MCUs when you don't want to bother with choosing between fifty zillion PIC, AVR, STM32, GD32, etc. MCUs that would offer a similar basic feature set and likely cost more in the end.
For all the hype about 32-bit MCUs, often - like in this kind of case - a simple 8-bit MCU is really all you need. Nobody said 555 timers or 74-logic chips are obsolete either :)
It seems like the filter would cost the majority of the unit, with so many parts to it. I did enjoy that one. I love it when a company can make something in hardware, using a trick method. Well done, Clive.
It definitely falls into the "printer ink" business model, but they may have somewhat misunderstood it, considering how hard it is to find new filters even if you do want to buy one.
@@RFC-3514 most cheap printers stop working after one ink change if you're lucky, after which you need a whole new printer. So the idea seems to be "make the whole appliance consumable".
@@falsemcnuggethope disposable electronics is really a plague.
@@falsemcnuggethope - Not from any competent printer manufacturer. They actually sell the printers at a loss, the real money is in the consumables.
@@RFC-3514 which one is that then? Epson, Canon, and HP are out of question.
I like the springs as capacitive touch electrodes. May try that on a future board. Thanks for another interesting video!
The optional module location is probably a pressure sensor to let you know the filter is dirty
I think you put the capacitors in reverse on th 5V supply ;)
always difficult when positive is below negative :D
Darn! You're right.
The amount of good quality appliances that have been thrown to landfill because of a simple faulty capacitor is depressing to think about.
I love how excited you were when you were talking about the piezo buzzer! In fact you seemed extra enthusiastic about this one 😅 and I love the energy!
The whole thing was filled with some super fascinating circuitry honestly 😊
High Efficiency Particulate Air filter.
I repaired a fan machine with a simple 4 position rotary switch because the filter cap dried out. Don't have to worry about that anymore. It's a regular 4 wire motor (3 speed + common.) My family (myself included) is proud that I came up with that idea. $12 switch designed to switch up to 30 amps of current (it was designed for a heater fan thing pos 1 for fan pos 2 fan + 750 watt heater and pos 3 has the fan and 2 750 watt heaters), so it shouldn't have any problem with the inductive "kick" that happens from time to time.
That beeper was so clever.
I'm borrowing that one for the next project where beeping is a thing.
Active Carbon is/was used in gasmasks - so it removes more than (bad) odors.
It absorbs several toxic gases (namely ammonia), must most people won't have those at home.
We use activated carbon at work for some equipment. They do remove various gases but you need more than a few granules. We use tens of kilos in cartridges. And several cartridges stacked. If we forget to turn on the filtered air supply the equipment goes haywire if you as much as fart in the same building. Even farmers spreading manure on the fields miles away will cause problems if the wind direction is right.
LOL... Science goes out the window when marketing gets involved... I can see the B.S. now... The Hypergravitic super heterodyne double polarized catalytic dilithium crystals cleans the air and gives you that fresh outdoorsy pine scent... Ohhhh So good... Sign me up!
Sounds like a very high-speed filter module - "Our filter propels air at Warp velocities" ! Presumably at full power we get a looped recording of Mr Scott's "I'm giving it all she's got, Captain" 😃
@@phils4634 LOL... Exactly!!! 🤣
From what I remember, titanium dioxide nanoparticles only really do the catalysis thing when UV light is present, or at least they do a lot more of it. Zinc oxide, by the way, is also sometimes used for the same purpose and the two have gained some interest for use in slowing bacterial growth.
But what I think would work better in this application is an ozone generator used to continuously regenerate the activated carbon.
The decay circuit is really neat. Might have to use that one myself one day.
As for the filter itself I have landed on using Levoit replacement filters for my projects, mostly because they're circular in shape. That means the shape is always convex even if it's warped a little, which is easier to form a good seal around. From what I can tell they are very similar in construction.
I can confirm that the LG-branded 'portable' air conditioners sold in the US have a similar sounding beeper circuit.
The LG window units do as well.
The pitch is juuuust wrong, I think they were going for immitation, makes it feels premium. Wouldn't think its LG making these or rebranding them
Most filters, even the really expensive ones like the two I have at home (allergies!) follow the same principles. However, being a recognised brand, 'compatible' (Chinese) filters still exist for them. Not sure which works out cheaper in the long run (though one generates a lot less e-waste).
Bought a Philips branded one, in the hope that filters will remain available for a while. The filters look very similar to the ones in this video, especially the carbon granulate thingie. However, the pre-filter is fine nylon mesh, the carbon granulate filter is a separate unit and the hepa filter is a separate unit. Each one has a different life span, so i guess it's pretty good to have three separate filters.
It works well. Ever since i put one in my bedroom running round the clock on low, i've had to use way less cetirizine.
I have one from Xiaomi and it has been running for 4 years 24/7 since I also have allergies.
I always feared the filters would Dissapear after they bring out a new model but they still sell them..
For a great price at that.
I don't really need it to filter anything besides dust and allergic related things so im reusing the same filter for 4 years now
I have one of these as this is an old, old building surrounded by fields of rapeseed and have asthma. Its actually a really unit and made a difference to my sleep. I have spare filters and a supply. The side cover houses a wifi module on mine which chats to Home Assistant
I bread-boarded the beeper circuit and am driving it from an Arduino Nano. It does make a fairly pleasant ringing sound, although those piezo buzzers want to work at 4,000 hertz for best output, so it's very high pitched.
The beeping is controlled by an analog synthesizer envelope generator!
This sounds like an engineer somewhere getting a case of _ideas._
I do appreciate the sound generation circuit.
I hope you get the gunk out of your respiratory tract soon, Clive! Best wishes!
I am glad he said something about his voice - I thought I was losing my mind or my headphones were a little bit messed up because his voice sounded higher pitched.
Yeah. Still a bit hoarse.
Oh, I love the piezo-bind circuit. Clever thing.
Nice video, thanks! (I also love the little 'ping' circuit.)
I always wonder about the materials used to make air filters, off-gassing? So after all the "hi-tech filtering", they then introduce synthetic volatiles into the air. Kinda defeats the purpose.
Wouldn't surprise me in the slightest. Just like all the pollution from mining and processing lithium, cobalt etc to make "green" electric cars. Nothing industrial is ever "green".
I know people seldom comment on your modified thumbnail images for videos, but WE SEE YOU!! 😊
Ah yes, gimmicks in cleaning air. The same can be applied to the appliance that cleans your surfaces. There has been a few variations of vacuum cleaners that use micro- or nano-silver technology, ultra-violet, various claims on HEPA and there's one technology I have been using for thirty years of my life that, at least to me, works. Water bath filtration coupled with a device known as a Newcombe centrifugal separator. That said, for some reason, with that machine, each time you use it you don't get the smell. I have used it to clean other vacuum cleaners and air purifiers that smell like dog or cat and as soon as that mess hits the water, you don't smell it anymore. There is one weakness to the design: you have to empty and maintain it after each use otherwise your house smells like a sewage plant. I have made that mistake with the machine I used growing up and even other machines I have owned.
That buzzer circuitry was very interesting.
the more I think about it, the cleverer it gets
Actually synthesizing the _bing!_ noises with hardware instead of playing a digital file is a level of effort I would not have expected from this.
...imagine if someone said that 30-40 years ago.
You can probably replace that first stage filter. At a hardware store, ask for A/C window unit filter material. (I learned this writing the hardware manual for a “ruggedized“ minicomputer built for seismic thumper trucks .)
I really like your channel, the way you explain the tech is so well detailed.
I totally Subscribed. 😎👍💯
I bought an Acekool branded unit just like this one from German Amazon last year. Price has gone up from around 28 Euro to over 50, and I haven't bothered to check for replacement filters yet.
It's a pretty nice unit for keeping the living room free of cooking and other smells especially during the winter months when you cannot just crack open a window without risking hypothermia. For what I paid for it, it's a nice unit that does its job. I do dread the 'replacement filter' part, however. The manual says that it has a built-in timer that warns you after N hours of use to replace the filter.
It is possible to find a fairly decent English datasheet for the LN8K06 from Lishengmei Semiconductor (Lii Semi for short apparently) for those who might be interested in the 12V version of the high voltage buck regulator. It has a pretty clever feature that I haven't seen before, where the VCC input to the chip is also used as the output voltage feedback sense pin, which makes me wonder why other IC manufacturers don't seem to do this.
There are a load of clone chips that manage buck regulation with a three pin chip like the AP8003. I've just made a video about a disco light that cheats 10V from a 5V version with a 5.1V zener diode in series with the VDD diode.
Fascinating Clive thank you, looks a good cheap unit 😊
The LED configuration sounds like what I learned as "Charlieplexing."
And yes, a quick google suggests this is the same.
I got a HEPA air filter a long time ago. It's a Winix which apparently also has a "plasmawave" light (which apparently creates Ozone and helps weigh down particles or helps clean the air or something, so I usually have that off). It died at one point with no idea as to why. When I contacted the company it was just a few months after warranty and I was to late in reaching out to them (cause I waited to long after it broke). Really annoyed me but I still have it. I ended up buying another one and so far it still works. I think the other one might have gotten killed from a power outage or power surge maybe (back before we had protection hooked up to our fuse boxes).
I tried opening it up to see if maybe I could see if something was bad and could be fixed but since im not an electrical person I have no idea when looking at the circuit boards etc. :(
dang big c live, these videos like this where you explain super common failure modes and odd surface components are great for normies like me who are learning electronic stuff for fun. thx
High Efficiency Particle..A?... Accelerator? scientists love those!
Fantastic, recently did my edc torch and now the air unit I bought about 6 months ago (and a spare filter to be smug... but only one). Now I know whats in both :)
Per Wikipedia, nanosized TiO2 does, indeed, act as a photocatalyst and periodically oxidizes things. It has to be under UV light, though. To work with just visible light, it has to be specifically formulated (doped with other stuff) for that purpose. And in either case, there does have to be direct light exposure involved. It is still the subject of some research. However, I think it's generally agreed that putting some titanium dioxide pigment (which is pretty cheap stuff) in a dark enclosure and yelling "CATALYSIS!" would not, in fact, count.
THAT "END" IS THE TOP...
Those catalysts work to get rid of some oranics such as formaldehyde like you mentioned by converting it via oxidation into heavier formic acid which would precipitate. But the carbon will do more to filter.
Great video and always great circuit analysis. I know this is an electronics channel, but interesting about the activated charcoal used in the filter - the same idea was used in World War 1 gas masks.
You can buy bags of activated charcoal on eBay for making various filter systems. I think it can be reactivated by baking it carefully (not in the microwave).
I got one of these for each bedroom, mainly because of the dual ionisers & the size of the filter (making it easier to create a replacement rather than buy one). The timer is actually useful since you can set it to n hours & then leave the room and it'll switch itself off when the time is up.
Overall a good device, though the full speed setting is really loud. Good to know about that capacitor replacement thing.
The fact that even pre covid you would very often run into the problem of not being able to buy new filters, i build my own around a standard industrial parts (cleanroom AC Filter).
The one i am using is 300x300x30 mm H13 and last about 4 Years with my two pre Filters. Yearly Filter costs end up being around 40 Euro.
Of course, when you mentioned the ping, I had to wind the video back to listen again! 😃
Thank you. Now I now I know what to look for on my home AC unit. The value of my squirrel cage blower motor start CAP might be getting low. I could hear it struggle this last winter. It's only about 4 years old since I replaced it. But, hey, it's Chinese.
That "module slot" at 2:11 looks to me like a holder for one of those "air freshener" scented pads.
Not sure its purpose. A similar unit had an air quality monitor in that position.
02:13 - that little square area (top left) might be (as it is 'Post' filter') might also be for an 'Optional perfume pod'??? 🤔🤔
😎🇬🇧
A very good Saturday morning to you sir from Wellington Somerset
@17:02 - Amazing how you figure this out. 😊
That beeps sounds reminds me of my Frigidaire a/c or whirlpool Cabrio washer.
Ozone melted my baby!
That's odd. They usually just burst into flames.
Thought you were going to mention an Etch-A-Sketch when you shook that HEPA filter....🤔🤣
The activated carbon lattice is not badly designed at all, but being only 1/3 full or so of pellets means it really isn't going to do as much as it could. If those chambers were filled up that would actually be an extremely effective design for it, and very much help eliminate odour and gas particulates.
Another great teardown video, thank you Clive. But can someone point me to an explanation of how that power line can be BOTH 5v (DC?) and L (240v AC?). I don't understand.
Imagine a live wire connected to a 9V battery. You can still measure 9V across the battery, but it will measure 240V to ground.
That "bing" circuit is fascinating. It seems to me that it's probably among the simplest ways to achieve that decaying sound without more complex hardware *and* software. It makes me wonder what other sounds could be made with similar circuits and possibly the addition of inductors or diodes. Seems hackable!
The "ding" sounds it makes when a button is pushed are really similar to my LG washing machine, interesting...
That ioniser is the electrical version of me....... Bipolar 😂😂😂😂
Perhaps you should take a peek inside an industrial version? I've heard MT-MB042266-GER is very good ;)
This look almost like Cooper&Hunter CH-P36W5 model. But this filter is fancier and you got more activate carbon granules.
I count five single points of failure that could present the rectified mains to the microcontroller with the single step buck regulator being the most likely and the triac controlling the ionizer next on my list, for being asked to quickly charge a capacitor if a firmware glitch mistimes the turn-on command. Add another if the cycle synch input resistors are physically small. Yet it works, with flair, until it doesn't. I like it.
In the case of the ionizer module it probably has a couple of series resistors and a single diode charging a capacitor. I'd be more concerned about more than one fan triac turning on.
So, no Colloidal Silver then ! Just the O-No-Zone ?
Cheerz Clive, another mystery dispelled.
;)
I always wondered about "dinger" circuits, like the ones that remind you a door is open in a car. I wonder if this kind of circuit was used in those
Local store sold this exact model for 90 euros under generic name and instead of ioniser it had UVC lamp in it most likely from the ones that generate ozon. 2:15 That slot in the plastic might be for that. Also in my country is basically given that they wont sell you replacement filters you have to order online,its even difficult to find filters for vacuums.😅
BigClive's big HEPA unit big tear-down. That's very big of him.
Quite a capable little microcontroller with integrated capacitive touch functionality, looks like the SC92F83A2 from Shenzhen SinOne Microelectronics. Perhaps the M at the end of the part number made it more difficult to find. Also really love the clever piezo sounder driver, where analog and digital work together perfectly.
That does look like it. I've removed the "M" in the description.
There is no intentional construction to put the fuse on neutral, all double insulated devices like this are designed to work with live and neutral either way around since most of the world has non polarized sockets. When they send units to the UK they probably put on the plugs in random orientation.
You will find if you swap live and neutral it will still work fine, the microcontroller will detect your touch from the Neutral-5V.
I have one of these clones bought from Kmart Australia, the one they sell is fully optioned with timer/ion/sleep/etc, and they have plenty of repacement filters avaiable in store.
Always good.👍 👍 👍 👍
"Delightfully weird".... Sounds like that one girlfriend I had years ago!
And great advice about those input springs being live. I had a faulty induction cooker and during trouble shooting, accidentally touched one of those death-beam powered springs. Be warned!!🥴
Great video, thank you Clive!
the size and shape of the hepa filter (including Velcro pre filter) is very similar to one that appliances direct sell in the UK, might be worth a look to see if its a match
1. you can use automotive air filters in some units as that is what they used.
2. the blank spots for parts of other models under windows vista is not allowed.
I have tried to use these units for my sneezing allergy, and both types that I used didn't help at all; however I left them on due to the COVID pandemic
i made an air filter unit diy, mostly cause i had some random parts. all i needed was the filter. then i got a couple of my spare computer fans and some spare wood. moves a decent amount of air and is easily ignored. hell i think i can fit a pressure sensor to detect when the filter is getting plugged up.
i ordered some cheap filters and I'm convinced the "carbon" is black plastic balls as they dont like carbon chunks, smell like it, or crumble the same.
Titanium dioxide is used as a white pigment in pretty much all bright white paint, and in powdered sugar. I doubt it's harmful, but it is quite abrasive when used as pigment in 3D printer filament.
That's a nice unit. It's just a terrible shame that they don't make it easy to get replacement filters at decent prices.
I love theses kind of video about fans air purifier etc what about air conditioning. Clive you're the best
We don't have much residential air conditioning here do to the lower ambient temperatures.
2:20 probably for wifi/Bluetooth. My window ac has a simular mounting with the the included wifi.
Inspired by Sharp Air Purifiers. The Sharp has a very quiet motor which is worth the price IMHO. The Sharp filter replacements are expensive but seem to be good quality; we DIY our own filters now.
I might have to play with that ping circuit a bit, with an arduino or similar...
1:54 If it destroys VOCs, you can measure those, there are air monitors that are capable of it, so you can prove it.
I can see some not so bright bulb taking the plastic cover off so they can get better contact between their finger and the spring. 😅
That makes the exact same sound and controls as my one but mine has a much bigger panel filter .
With the touch detector depending on live vs neutral connected the correct way round, this can't be sold to countries where you can freely turn the plug. Seems odd to me.
It turns out the chip does have touch sensing inputs.
"Oxidise Karens," eh? I think we've all wanted to do that before. I think I'll keep my finger away from the "Destroy Moon" button though.
I love the thumbnail on this one xD
Also I'm absolutely using that piezo driver circuit in my next project that needs one. I love how simple and clever it is.
The random Tedesco drop lol
I have a unit like this one from ~2002. Bought by my late aunt for her allergies. Astoundingly it's still possible to get HEPA filters for it, though I suspect the ionizer stopped working. If only I knew a TH-cam channel that reviewed ionizer modules... 🤔😁
20:48 So what you're saying is my white walls destroy VOCs? 😀
Apparently it has to have the powder applied on the surface as opposed to in a binder. But there have been paints sold as VOC destroying.
Cheers.
ah, i see you have the circuit that goes DIIIiiing.
The filter looks exceptionally similar to the Alen air filters… Ironically, they’re more expensive than this entire unit. 👀
I've heard you use "death beam capacitor" before, but I'm finally going to admit my ignorance and ask what does that mean?
There's a conspiracist who claims that the only reason there are 400V capacitors in street light LED drivers is to power the government's 5G directed energy weapons.