Nice application, but Clive, you forgot to plug it in to show the diaphragm vibrating - you could use a laser pointer to reveal the size of the deflection and even reflect the beam on the the wall to show lissajous patterns and any harmonic modes of vibration!
Would need to convert displacement into significant rotation for a usable effect, but this is effectively what digital projector micromirrors do although I think they are electrostatically operated.
It made me laugh too - until I remembered I sent my mates 11 year old son (who loves taking things apart) a link to this channel a few months back. He loves the channel so would have seen this by now. I might have to have a talk with him....
Yeah I'd suspect so & I'd guess the most annoying noise would be from the valves snapping shut rather than the diaphragm, that was the case on an old school aquarium pump I took apart in my youth.
I had never heard of this type of air pump before so thank you for posting. It would have been nice to see the air stone placed in a glass of water so we could see the output air level. I will have to buy one to test . Thanks for the video Clive.
What a man! What a gentleman! Perfect, clean style to deliver the valuable information with a blend of sarcasm, humor, excellent language and intelligence at the same time! Wow!
Old buildings used 70.7 volt systems for distributing audio over wide areas, and transformers to step the audio voltage up and down for 8 or 16 ohms. That kind of audio transformer would work well for this test if a pair of the transformers was put in parallel on the 8 ohm side, and in series on the 70.7 volt side.
You can check the volume of air per minute by filling a container with a known quantity of water, turning it upside down over a basin full of water so that nothing leaks, stick the air output in there, then time how long it takes to empty.
I want that meter, not because I need it, but because I want to plug everything in it and see what the yearly power consumption is. I'm surprised Audible hasn't contacted Clive to read books to help people fall to sleep with the calm, kind voice and demeanor. He is also an inspiration for many of us to 'learn by doing' and start practicing. I have my kit and tools to start practicing this weekend how to solder :)
Find a screw on wire cap that is about the same size as the hose. Drill a hole in the small end and another hold halfway on the side. Screw it onto the hose end, feed another hose in the hole you drill on the side. That small hose should pull a vacuum via Venturi effect.
I think the device you're referring to is a pressure accumulator, definitely the capacitor of the fluid power world. Also, quite terrifying to charge on hydraulic systems.
Shame you did not show the air pump working, either pumping well or not. As previously said would love to have seen the piezoelectric crystal in operation.
I wonder what the longevity of this is versus a more traditional pump? Having had a fishtank for some years, the noise of the traditional pumps can get quite grating if you're in the same room as them... :P
I wonder if they have a larger size as I use an aquarium pump as my air assist on my laser machine and it is louder than the screams from hell. Something around 50l a minute is needed.
Sure they are. You would just need about 111 of them @ 0.45 lpm in parallel to get your 50 lpm. Of course the noise would be additive, too. There are lots of other pumps that might do what you need. Industrial and medical surplus suppliers always have odd air pumps.
Due to the nature of the mechanism, they're only rated for tanks up to 45l in volume, it's unlikely piezoelectric would work well with larger tanks due to the difference between the air pressure produced and the water pressure at the lower depths, unless you only wanted to run it nearer the surface.
Looks like both sides of the piezo are used to pump the air and you're right, that first air chamber is used as a buffer but not before it goes out but before it goes into the second chamber. Good question is would it work better if there is a valve on the air inlet?
Clive, the ‘swept volume’ increases with the deflection of the disc. So a decent sized disc is required to give a reasonable throughput but there is a minimum volume requirement per pulse to allow the valves to open and close efficiently. The depth of the chamber is just sufficient to hold the valves. The material and flexibility of the valve material determines the length required and hence the depth of the chamber
I think you somewhat mixed piezoelectric crystals with electrets. Piezoelectric effect is an intrinsic property of some crystalline materials, while to get an electret you indeed have to warm up some sort of polymer (typically to its melting point) and then cool it down in a strong electric field. This allows the dipoles to be fixed in a particular orientation, and this makes an electret. Although the Wikipedia mentions that some polycrystalline materials can be "poled" (a very similar process which ideed involves heating to a curie point is a strong electric field) to reveal piezoelectric properties, generally a piezoelectric crystal only needs to be wisely cut (as in crystal resonators), while to make an electret one inevitably needs to perform the described process.
I'm under the impression that most manufactured disks do rely on setting a charge thermally. The water atomiser disks certainly lose their ability to function if they are operated dry and heat up to their Curie point.
This certainly might be the case... Just wanted to stress that for the piezoelectric materials this thermal procedure is optional. Anyway, thanks for the video, very interesting indeed.
Don't know for sure, but I guess that most probably this process is indeed reversible. Although I don't think that it is possible to restore that crystal at home (unless you're Ben Krasnow).
There has to be another hole for the pumped air inlet. The tiny one in the thin piece that was popped off the back is just to allow air to move in back of the diaphragm. It relieves pressure on the back due to ambient air pressure changes so it won't limit the deflection of the diaphragm.
Use of these disks in ultrasonic mist makers always concerned me. Are they silent only because the noise they make is above human hearing? So are they doing the same thing to your brain that they do to the water -- atomising it, but in a way such that you don't notice. That his pump operates at line frequency is reassuring.
Clive the check valve is referred as a duckbill check valve. Very interesting way og pumping air (gas). Wondering how a piezoelectric element would work as a liquid pump? The element could be driven harder as the liquid would cool the element.
1. What does the disc look like when powered? 2. If it is a tuned resonant cavity would it not need to be a different size for 50 vs 60 hz? Or maybe it's split and slightly better performance would come from adjusting it to your mains freq...
Maybe that reservoir is there to keep it quiet? I've got a tradition AC air pump and replaced the tubing setup. It's now louder than before, probably because more sound energy is making it to the end of the tube. I've though about adding a small buffer to make it quite. Such a thing would be more noticeable on a piezoelectric pump, I would guess.
I think the tiny hole is there to vent the other side of the piezo that probably moves just a little. The main air intake are probably the cuts where you tryed to insert the spudger to open the pump first.
I was just playing this in the background while working on a project, all of a sudden "and they just part, like piss-flaps really" and just about fell off my chair. Thank you for the laughs, Clive
Clive the tiny hole on the input side is to keep a slight negative pressure in the chamber to make sure the inlet valve closes quickly when the disk reverses direction.
1) "Duck-bill valve" 2) Murata announced and video'd a number of applications with their "PiezoMicroBlower" back in 2011 - works in the ultrasound region and can hovercraft-carry a 9V battery powering it. 3) The Murata device uses no apparent valve - the frequency is so high that non-linear flow-resistance is sufficient to create a valve-action. 4) IPA or ethanol embrittles hot-melt glue and makes for easy removal Great video, nonetheless!
That is incredible! That tiny deflection seems it would be inefficient to pump any air at all. P.S. I think that, "zz" is a "t" sound in Italian only when there are two z's back to back. (I believe, but I'm moot 100% sure.) I don't think the etymology/origin of the word is Italian anyways.
How about connecting the piezo via a bridge rectifier to get 100Hz? You're in with a decent chance that the valves fitted would cope with that. But with the same power input you'll get a smaller excursion of the piezo so you want to increase that. Also the sound gets more noticeable at higher frequency.
+bigclivedotcom and Ray Kent -- When a piezoelectric crystal is given DC only, it deflects in one direction only, and stays that way until power (essentially just voltage) is removed. So you would have to make sure there was no capacitor storing DC. But the piezo device itself stores energy, and acts like a capacitor in that way. So I think you'd have to give a discharge path, maybe just a resistor, but probably some active circuitry with a transistor, though a mere NE2 neon light might do enough. What say, Clive?
YodaWhat I think that what you said is technically correct, but you're missing scale. Similar sized piezo elements are used for tweeters and beyond into ultrasound. That suggests that they have very low capacitance, though I can't give a figure offhand. If driven direct from a bridge rectifier the discharge is catered for by the reversal of current. It's true that there would be an average dc offset from that set-up, but a series capacitor and parallel resistor would deal with that, if needed.
Piezoelectric devices are modeled as a combination of inductor and capacitor, which both stores energy and resonates at a certain frequency. While they can work at other frequencies, efficiency is then lower. High-end audio equipment compensates for that by brute force: Shoving more watts at the tweeters. And it is always alternating current. The scale of the air pump device is actually far too small to resonate efficiently at either 50 or 60 Hz, and it shows no evidence of extra (vibrating) mass being added to lower the resonant frequency. So yes, on that front it would be better to use higher frequency. But it has to be AC, not DC. While a bridge rectifier receiving power through an AC-rated capacitor will give pulsating DC current to a load, it is not clear that this piezopump is enough of a load to get serious pulsation. If efficiency is ignored, a dummy load resistor across the piezo element could force the issue, of course, but it will certainly be inefficient. If Clive were inclined to re-engineer devices, I would suggest using the first harmonic at 150 Hz from a squared-off 50 Hz sinewave, or even a variable-frequency oscillator circuit. But there are other RUclips channels for that kind of modifications.
Y'know.. that is actually genuinely interesting. I'm thinking up fun projects with a bunch of these, a custom driver and a 3d printer. You could tune them for one thing.. They'd last forever too.
The larger the disk the more the center will move for given angle of deflection. That combined with the larger diameter makes for a larger air volume on each 'stroke' than with a smaller diaphragm. I wouldn't be too surprised if that was a stock part of some sort from the supplier.
Oh no it was full of air and you opened it and let all the air out but it's an air pump is that like the equivalent of electric smoke? I'm rewriting these trying to find maybe a video I imagined of Piezo water foggers I don't know what to call them.
The capacitor and inductor are not AC mains filters. They create a resonant LC tank circuit to drive the piezoelectric element near its natural mechanical oscillation frequently. Based on their values, the disk will probably vibrate somewhere on the order of 100kHz, independent of the 50/60Hz mains frequency - well above the audible range. The air space above the diaphragm acts as a tuned resonant cavity and lens in order to get the pressure waves to constructively interfere at the outlet valve and create sufficient amplitude to overcome the forward pressure drop of the "piss flaps"/acoustic diode. The cavity is much too tiny to accomplish this for a 50/60Hz pressure wave due to their long wavelength, but at 100kHz, the wavelength is only around 3mm. The 1M resistor does indeed appear misplaced. It should be across the capacitor so you don't get a shock after unplugging the device and touching the AC input plug pins. My guess is that the designer originally did put it there, but someone less familiar with how resonance works decided to switch to a cheaper capacitor and inductor, detuned the oscillator, and discovered that the circuit would work more reliably by removing/relocating the resistor parasitics.
The air valves would not be able to open and close at such a high frequency. The disk does seem to vibrate at mains frequency. One theory about the inductor and capacitor is that any mains borne noise would be made audible by the piezo disk like a speaker, and the filtering reduces that.
bigclivedotcom I agree that the valve probably doesn't rectify air at 100+kHz, but I don't believe it has to. Each time air does escape, the average pressure in the cavity will change, the speed of sound in the gaseous medium will shift slightly, and the point of peak constructive interference will move slightly. Likewise, the resonant frequency of the piezo element will shift slightly throughout the whole AC mains cycle as the amount of energy dissipated as heat or compressive work will rise by the square of the voltage and steal energy from the resonant system faster at peaks, correlating with a higher resonant frequency at higher voltage and lower frequency nearer to AC zero crossing cycles. My guess is the valve actually actuates at some integer fraction of the piezo disk's oscillation frequency and quite possibly, the valve never fully closes - instead becoming more and less flow restricting. The fact that the whole resonant system shuts down every AC input zero crossing can explain the audible noise at 100/120Hz without necessarily being meaningful at all towards the pumping mechanics. The easiest way to find out would be to put an oscilloscope across the capacitor and see if there is a high frequency riding on the slow AC mains carrier.
My money's on some kind of pressure resonance. As you pointed out, the piezo is moving a tiny amount, normal air pumps in this context move a diaphragm monstrous amounts in comparison and are still weak as hell.
The quietness is surprising, I would expect that to produce a fair bit of hum, since it is essentially a speaker plugged straight into the mains. I would wager that the entire casing is an acoustical contrivance designed to suppress that hum.
Clive, The thing I expected, and the "thing" I expected you to make a bit of a "thing" of was the frequency of the output of the pee-ay-zo. Especially with you saying it seemed quite efficient and yet quite quiet, I suppose I was expecting all the dogs in the neighbourhood to be throwing themselves under mororbikes. Have I missed something - or are we just talking about a bit of mains hum doing the business? From what I've seen of this sort of thing, mechanical pumps just spin a sloppy impeller, in a hole - no close tolerances but quite nippy to create pressure, I was expecting the same idea just to shift a reasonable volume of air.
I scrap a lot of stuff, and among what I've salvaged are some "buzzers" that are piezoelectric. I'm assuming that what's inside the plastic case is similar to the disc you show here. I've also encountered those discs loose, used in some drum boxes. Connecting a meter across it shows no continuity, but connecting one to my scope it really does rather well acting as a microphone. I remember some years back gong to a trade show and seeing some fans that worked on this principle. They had blades, but they didn't rotate, they just vibrated. I've never encountered them since then, and have wondered why, whether they actually went anywhere. Perhaps they weren't capable of high enough volume, or something like that.
LOL You did it again Clive. I was just taking a swig of drink AGAIN and at that moment you said PISSFLAPS. I about choked. Anyway . This actually reminds me a bit of those old beigey coloured crystal ear pieces for use with crystal sets . They had a similar arrangement inside , but square , with crystal coated on a thin metal plate and a very thin metal foil diaphragm . (showing my age again!)
Thanks Clive. Interesting device.. (I also got looking at that Flame safe candle flame effect light on that link) . Sorry to go off the subject , but years ago I had dealings with a very "realistic" candle flame effect light , or lights , that used a "loose" incandescent bulb, shaped like a flame , that were gently moved by a coil (similar to those LED candles) . They were almost impossible to distinguish from a real candle , even close up. I have yet to see a modern version that comes as close to the real thing as those did.
Kind of curious how much the piezo disc deflects by, at 60Hz it should be visible and could probably be measured by finding the point where something just touches the end of it's oscillation and comparing to it's rest position.
regarding its sound: you should have waited a few seconds before plugging it in, i have no idea if you were talking over the humming sound before (background noise/static?) or if it was the pump :)
I suspect that this is carefully sized to make use of resonance. I suspect the disc size would be different for 60 Hz. I also wonder if the performance would be significantly affected if it were used at higher altitudes. This appears simple on the surface, but I suspect a lot of design and experimentation went into the final product.
It could be nice to see the piezo running after opening it with some sort of grain on that to for the demonstration of its vibration. Or you could dip the stone in a glass of water to see how much air it pumps.
I have a piezo ceramic disk attached to the compressor in my fridge. It works to keep the fridge from overheating and recycling, the compressor that is. Could you please get one and tear it down and explain how it works. Thanks.
I've not come across a piezoelectric disk used in that application. The only disk that comes to mind in a traditional fridge is the thermal cutout disk on the compressor if it stalls.
Working with piezoelectric transducers the inductors are almost always included as a way to dissipate the ringing of the crystal which can cause surges.
I think it's thick so that the valves could sit as close to the diaphragm as possible (perpendicular to it). You need some pressure differential to open the valve and the more space there is between the diaphragm and the valve, the bigger the portion of the diaphragm's movement that is used to build up the required pressure difference. If they put the valves down flat and had a 90 degree bend running to them, that might be too much air to compress enough to push the valves open (and even if it did work, it would be much less efficient).
A couple of months ago, somewhere in China: "That guy on RUclips always mocks our power supplies for not having discharge resistors. Let's put a 1 Meg discharge resistor across one of the other resistors and call it a day...."
As for the exact sizing and weird ports, it could be acoustically designed to have some kind of a standing wave inside in order to move more air. Actually, I'd guess that's more than likely.
If its putting out 500ml per minute that would be 500/3600 ml per cycle. If you assume about roughly half the diaphragm is moving 3.14 x radius2/2 x deflection= 500/3600 so not a very large deflection
Minuscule deflection of the disk therefore a bigger diameter of disk needed to provide a given amount of air. Actually quite a big assembly for a small amount of air.
I would be very interested to see a volume pumped per minute vs input frequency... I suspect at a certain frequency, it will be like a heart in fibrillation, where the valves are ineffective, but I'm curious to see what point that would be at...
Hi Big Clive, I'd like to see you revisit this piezoelectric air pump operation. I think something else is going on with the Piezo. I have never heard a 50 hz piezo. I got out of bed to write this couldn't sleep thinking about it. My idea was, it is running on a harmonic of 50 hertz, tuned with the inductor and the first parallel cap introduced some nonlinearity. But then I calculated it turned out to be the 800th harmonic, so I backed away from that. (call that idea a maybe) If it was running on 50Hz, I think you would hear it, (2 watts), I never saw a scope shot in your videos, but I'd like to see the waveform across the piezo. Maybe a frequency counter would pick it up, by indirect connection. The 150uh inductor means the piezo's capacitance would need to be very large to tune at 50Hz, (improbably large) After 30 minutes searching, I'm still confused, I found similar piezos made for 22kHz, 27kHz and 40kHz, and then one popped up, operates at 60Hz. ¯\_(ツ)_/¯
There no feed back on the piezoelectric disk, so it is vibrating at mains frequency, presumable this allows time for the air to move out of the way and for the flap valves to open and close. I guess the air trapped above the disk acts as a spring, storing energy on the up cycle. One might have expected the disk to have two open chambers on each side to allow both the up and down stroke to pump air. Have you considered connecting the disk to a signal generator to see how efficiently it can be excited at other frequencies. Apart from the poor power supply, a weakness of the design must be the risk that the disk will fracture. It would have been nice to know the pressure the pump can achieve and the volume of air moved.
Hi, BigClive. I was wondering what printer you use for all your beautiful printout cards? Always gorgeous. Did a quick look and didnt see any BCDC videos dedicated to any printers, sorry.
The space is called a plenum. The power of vacuum to fill the empty plenum through the hole is great while the amount of back pressure to empty the plenum the through the empty hole is small upon each cycle of the diaphragm. Pressure is recuperated because presser that is built up inside the plenum can compress the gas momentarily before the pressure can escape entirely back through the hole the energy of it is used as part of the uptake again. The pressure released through the stone and the built up pressure in the plenum might work In an alternating cycle that has the little thing running like a 4 stroke.
Love the cutdown power supplies, When I see the power supplies on tv's and computers and things I was always thinking it was a waste of components made to confuse people.
This would appear to be a resonant circuit and the piezo element acts as a capacitor... It's possible the extra 1M resistor is added after assembly and testing to "tune" the circuit for maximum air flow. Or not ($0.02)
I wonder how good it would of worked in an actual fish tank. Water pressure and all that kind of stuff makes the pumps I have work pretty hard. If it worked, would buy one in a heart beat to try it.
I'd be interested to know. I have some deep tanks, the depth just kills any pump I put on it. I've thought of going to a piston pump and small air tank over the diaphragm ones.
Into steam punk? A mini bike pump should give more than enough pressure. You don't want to stand there moving it in and out? How about cranking it with a microwave turntable motor? Nice slow action, quiet, but I don't know if it's powerful enough. I've made a water pump using the motor and gearing of a wind-up torch. Runs at 2 watts and can deal with a 3 metre head of water! Yeah, but very low flow rate.... Be warned, not all of their generators are effectively brushed dc, so you might only use the gearing.
2009dudeman hi! Please check my maths, I'm bollocks at it, but for the flow rate Clive cites I get a rough equivalent of a 1cm radius piston with à stroke of 1cm at a frequency of between 2 and 3 Hz. Well below audio except for the motor and gear train. For a small dc motor, have a look at what are called solar motors with built in high ratio gearing. The bike pump will cope with the pressure, but will à very low power motor provide the throughput? My bet is that if it's rated at about 2 watts then it can.
I wouldn't normally recommend this to anyone but you can put a europlug directly in a British socket if you put something in the earth hole to move the shutters out of the way.
so if the seal was to fail, would water run onto the pizzo putting the tank water at 130vac relevant to ground? Although the seal looks quite good, I guess its a possibility?
Nice application, but Clive, you forgot to plug it in to show the diaphragm vibrating - you could use a laser pointer to reveal the size of the deflection and even reflect the beam on the the wall to show lissajous patterns and any harmonic modes of vibration!
Would need to convert displacement into significant rotation for a usable effect, but this is effectively what digital projector micromirrors do although I think they are electrostatically operated.
Viewing the signal with an Oscilloscope would be helpful.
I wanted to see how well it worked when the stone end was submersed
Justin Richards When you were stoned and submerged in what exactly ?
@@kissingfrogs ruclips.net/video/ydoKydWKjK8/видео.html
Piss flaps? Nice one Clive
love it made me laugh
Thought that was what he said...... More commonly known as duck bill valve! 😂
It made me laugh too - until I remembered I sent my mates 11 year old son (who loves taking things apart) a link to this channel a few months back. He loves the channel so would have seen this by now. I might have to have a talk with him....
Has Clive just lost his female viewers?
I laughed :-D
11:38 "that just part, like, like piss flaps really"
Big Clive 2018, best quotes
The first resistor is marked "C1" on the circuitboard.
It may have been for a series capacitor, but they might have found that the piezo disk was oversensitive to transients with a capacitor in series.
At least that explains the discharge resistor. Funny that they still bothered to populate it.
I'm glad I'm not the only one who noticed that :P
I would say the size of the cavity and the convoluted air inlet is for sound dampening.
Yeah I'd suspect so & I'd guess the most annoying noise would be from the valves snapping shut rather than the diaphragm, that was the case on an old school aquarium pump I took apart in my youth.
I had never heard of this type of air pump before so thank you for posting. It would have been nice to see the air stone placed in a glass of water so we could see the output air level. I will have to buy one to test . Thanks for the video Clive.
What a man! What a gentleman! Perfect, clean style to deliver the valuable information with a blend of sarcasm, humor, excellent language and intelligence at the same time! Wow!
Clive, this is one of your timeless videos. At one point I even thought you may get the jack hammer out on the device. Still you never dissapoint!
Still laughing about the'piss flap' analogy. You are worth every add we are forced to watch.
Plug a speaker line output into your mains (somehow) and modulate some music on top of the 50 Hz mains. See if you can make the pump play music. :)
Old buildings used 70.7 volt systems for distributing audio over wide areas, and transformers to step the audio voltage up and down for 8 or 16 ohms. That kind of audio transformer would work well for this test if a pair of the transformers was put in parallel on the 8 ohm side, and in series on the 70.7 volt side.
You can check the volume of air per minute by filling a container with a known quantity of water, turning it upside down over a basin full of water so that nothing leaks, stick the air output in there, then time how long it takes to empty.
or you could fill a balloon for 1 minute and check its volume by immersing it in water
I want that meter, not because I need it, but because I want to plug everything in it and see what the yearly power consumption is.
I'm surprised Audible hasn't contacted Clive to read books to help people fall to sleep with the calm, kind voice and demeanor.
He is also an inspiration for many of us to 'learn by doing' and start practicing. I have my kit and tools to start practicing this weekend how to solder :)
Can you reverse the valves and use it as a vacuum pump? Then one could use it to replace their wound vac when it ran out after a week. :-)
Quality post, mon ami.
Find a screw on wire cap that is about the same size as the hose. Drill a hole in the small end and another hold halfway on the side. Screw it onto the hose end, feed another hose in the hole you drill on the side. That small hose should pull a vacuum via Venturi effect.
I have already seen this kind of small silicone check valves on industrial equipment (water treatment, pumps etc.). It is very efficient and reliable.
I think the device you're referring to is a pressure accumulator, definitely the capacitor of the fluid power world. Also, quite terrifying to charge on hydraulic systems.
Put a drop of alcohol on hot melt glue and it releases like MAGIC!
I did and it seemed to work.
That's a brilliant tip. Does any alcohol work.....IPA or do I have to dip into my whiskey stock?
John Carr IPA works brilliant don't know about others
John Carr IPA works, haven't found ethanol to work quite as well.
Ethanol works great. But you have to drink a lot.
Shame you did not show the air pump working, either pumping well or not. As previously said would love to have seen the piezoelectric crystal in operation.
I wonder what the longevity of this is versus a more traditional pump? Having had a fishtank for some years, the noise of the traditional pumps can get quite grating if you're in the same room as them... :P
I wonder if they have a larger size as I use an aquarium pump as my air assist on my laser machine and it is louder than the screams from hell. Something around 50l a minute is needed.
Get a few of them
They aren't additive like that.
Sure they are. You would just need about 111 of them @ 0.45 lpm in parallel to get your 50 lpm. Of course the noise would be additive, too. There are lots of other pumps that might do what you need. Industrial and medical surplus suppliers always have odd air pumps.
Due to the nature of the mechanism, they're only rated for tanks up to 45l in volume, it's unlikely piezoelectric would work well with larger tanks due to the difference between the air pressure produced and the water pressure at the lower depths, unless you only wanted to run it nearer the surface.
Looks like both sides of the piezo are used to pump the air and you're right, that first air chamber is used as a buffer but not before it goes out but before it goes into the second chamber. Good question is would it work better if there is a valve on the air inlet?
One of the nicest, well thought designs I have seen in a while, thanks Clive.
Clive, the ‘swept volume’ increases with the deflection of the disc. So a decent sized disc is required to give a reasonable throughput but there is a minimum volume requirement per pulse to allow the valves to open and close efficiently. The depth of the chamber is just sufficient to hold the valves. The material and flexibility of the valve material determines the length required and hence the depth of the chamber
Wow amazing, Wouldn't thought there was enough movement to operate the valves.
I think you somewhat mixed piezoelectric crystals with electrets. Piezoelectric effect is an intrinsic property of some crystalline materials, while to get an electret you indeed have to warm up some sort of polymer (typically to its melting point) and then cool it down in a strong electric field. This allows the dipoles to be fixed in a particular orientation, and this makes an electret. Although the Wikipedia mentions that some polycrystalline materials can be "poled" (a very similar process which ideed involves heating to a curie point is a strong electric field) to reveal piezoelectric properties, generally a piezoelectric crystal only needs to be wisely cut (as in crystal resonators), while to make an electret one inevitably needs to perform the described process.
I'm under the impression that most manufactured disks do rely on setting a charge thermally. The water atomiser disks certainly lose their ability to function if they are operated dry and heat up to their Curie point.
This certainly might be the case... Just wanted to stress that for the piezoelectric materials this thermal procedure is optional. Anyway, thanks for the video, very interesting indeed.
YS akaYSembed
Can the crystals be re-energised if they reach their curie point and fail?
Don't know for sure, but I guess that most probably this process is indeed reversible. Although I don't think that it is possible to restore that crystal at home (unless you're Ben Krasnow).
@@bigclivedotcom Thanks for the demonstration. How is piezo disk is air seal ? Is it just an adhasive or rubber gaske?
Unreasonable force stops being unreasonable when it's necessary to open up a device. So then it'll be reasonable but nonetheless destructive force.
You are technically correct. Which is the best kind of correct :)
There has to be another hole for the pumped air inlet. The tiny one in the thin piece that was popped off the back is just to allow air to move in back of the diaphragm. It relieves pressure on the back due to ambient air pressure changes so it won't limit the deflection of the diaphragm.
It's pizzaelectric!
Do R/C! Zzzapp, mmmmm pepperoni!
putana-electrico
Watch it, buster - that's my trademarked brandname for my toaster oven company.
Jafafa Hots I invoke fair use!
Use of these disks in ultrasonic mist makers always concerned me. Are they silent only because the noise they make is above human hearing? So are they doing the same thing to your brain that they do to the water -- atomising it, but in a way such that you don't notice. That his pump operates at line frequency is reassuring.
Hi Bigclive, the big resistors are rated at 5 watts. Oh, & I'm fairly sure is't peez-oh. Nice to see the welcome return of the vice of knowledge!
The vice/vise of knowledge. The Hammer of Persuasion. I love these too names.
Clive the check valve is referred as a duckbill check valve. Very interesting way og pumping air (gas). Wondering how a piezoelectric element would work as a liquid pump? The element could be driven harder as the liquid would cool the element.
1. What does the disc look like when powered?
2. If it is a tuned resonant cavity would it not need to be a different size for 50 vs 60 hz? Or maybe it's split and slightly better performance would come from adjusting it to your mains freq...
Maybe that reservoir is there to keep it quiet? I've got a tradition AC air pump and replaced the tubing setup. It's now louder than before, probably because more sound energy is making it to the end of the tube. I've though about adding a small buffer to make it quite. Such a thing would be more noticeable on a piezoelectric pump, I would guess.
Thanks for the demonstration. How is piezo disk is air seal ? Is it just an adhasive or rubber gaske?
I think the tiny hole is there to vent the other side of the piezo that probably moves just a little.
The main air intake are probably the cuts where you tryed to insert the spudger to open the pump first.
I was just playing this in the background while working on a project, all of a sudden "and they just part, like piss-flaps really" and just about fell off my chair. Thank you for the laughs, Clive
You should have run it in the open to see what kind of visible deflection there was. Might have some fun with a frequency generator too.
Clive the tiny hole on the input side is to keep a slight negative pressure in the chamber to make sure the inlet valve closes quickly when the disk reverses direction.
1) "Duck-bill valve"
2) Murata announced and video'd a number of applications with their "PiezoMicroBlower" back in 2011 - works in the ultrasound region and can hovercraft-carry a 9V battery powering it.
3) The Murata device uses no apparent valve - the frequency is so high that non-linear flow-resistance is sufficient to create a valve-action.
4) IPA or ethanol embrittles hot-melt glue and makes for easy removal
Great video, nonetheless!
That is incredible! That tiny deflection seems it would be inefficient to pump any air at all.
P.S. I think that, "zz" is a "t" sound in Italian only when there are two z's back to back. (I believe, but I'm moot 100% sure.) I don't think the etymology/origin of the word is Italian anyways.
it'd be interesting to run it faster than 50/60Hz to see how much more air it would pump
Or less as the valves physically need time to move. And yet worth a try
How about connecting the piezo via a bridge rectifier to get 100Hz? You're in with a decent chance that the valves fitted would cope with that. But with the same power input you'll get a smaller excursion of the piezo so you want to increase that. Also the sound gets more noticeable at higher frequency.
+bigclivedotcom and Ray Kent -- When a piezoelectric crystal is given DC only, it deflects in one direction only, and stays that way until power (essentially just voltage) is removed. So you would have to make sure there was no capacitor storing DC. But the piezo device itself stores energy, and acts like a capacitor in that way. So I think you'd have to give a discharge path, maybe just a resistor, but probably some active circuitry with a transistor, though a mere NE2 neon light might do enough. What say, Clive?
YodaWhat I think that what you said is technically correct, but you're missing scale. Similar sized piezo elements are used for tweeters and beyond into ultrasound. That suggests that they have very low capacitance, though I can't give a figure offhand. If driven direct from a bridge rectifier the discharge is catered for by the reversal of current. It's true that there would be an average dc offset from that set-up, but a series capacitor and parallel resistor would deal with that, if needed.
Piezoelectric devices are modeled as a combination of inductor and capacitor, which both stores energy and resonates at a certain frequency. While they can work at other frequencies, efficiency is then lower. High-end audio equipment compensates for that by brute force: Shoving more watts at the tweeters. And it is always alternating current. The scale of the air pump device is actually far too small to resonate efficiently at either 50 or 60 Hz, and it shows no evidence of extra (vibrating) mass being added to lower the resonant frequency. So yes, on that front it would be better to use higher frequency. But it has to be AC, not DC. While a bridge rectifier receiving power through an AC-rated capacitor will give pulsating DC current to a load, it is not clear that this piezopump is enough of a load to get serious pulsation. If efficiency is ignored, a dummy load resistor across the piezo element could force the issue, of course, but it will certainly be inefficient. If Clive were inclined to re-engineer devices, I would suggest using the first harmonic at 150 Hz from a squared-off 50 Hz sinewave, or even a variable-frequency oscillator circuit. But there are other RUclips channels for that kind of modifications.
Of COURSE we love these videos! Else we wouldnt be here. Keep em coming Clive. Cheers.
Clive you need one of those oyster shucking steel mesh gloves for the receiving hand when you are prizing open stuff...
Y'know.. that is actually genuinely interesting. I'm thinking up fun projects with a bunch of these, a custom driver and a 3d printer. You could tune them for one thing.. They'd last forever too.
The larger the disk the more the center will move for given angle of deflection. That combined with the larger diameter makes for a larger air volume on each 'stroke' than with a smaller diaphragm. I wouldn't be too surprised if that was a stock part of some sort from the supplier.
Oh no it was full of air and you opened it and let all the air out but it's an air pump is that like the equivalent of electric smoke?
I'm rewriting these trying to find maybe a video I imagined of Piezo water foggers I don't know what to call them.
Search my video for USB mister for the tiny foggers.
clive you make me and jess laugh so much, We love your sense of humor! 😄
The capacitor and inductor are not AC mains filters. They create a resonant LC tank circuit to drive the piezoelectric element near its natural mechanical oscillation frequently. Based on their values, the disk will probably vibrate somewhere on the order of 100kHz, independent of the 50/60Hz mains frequency - well above the audible range.
The air space above the diaphragm acts as a tuned resonant cavity and lens in order to get the pressure waves to constructively interfere at the outlet valve and create sufficient amplitude to overcome the forward pressure drop of the "piss flaps"/acoustic diode. The cavity is much too tiny to accomplish this for a 50/60Hz pressure wave due to their long wavelength, but at 100kHz, the wavelength is only around 3mm.
The 1M resistor does indeed appear misplaced. It should be across the capacitor so you don't get a shock after unplugging the device and touching the AC input plug pins. My guess is that the designer originally did put it there, but someone less familiar with how resonance works decided to switch to a cheaper capacitor and inductor, detuned the oscillator, and discovered that the circuit would work more reliably by removing/relocating the resistor parasitics.
The air valves would not be able to open and close at such a high frequency. The disk does seem to vibrate at mains frequency. One theory about the inductor and capacitor is that any mains borne noise would be made audible by the piezo disk like a speaker, and the filtering reduces that.
bigclivedotcom I agree that the valve probably doesn't rectify air at 100+kHz, but I don't believe it has to. Each time air does escape, the average pressure in the cavity will change, the speed of sound in the gaseous medium will shift slightly, and the point of peak constructive interference will move slightly. Likewise, the resonant frequency of the piezo element will shift slightly throughout the whole AC mains cycle as the amount of energy dissipated as heat or compressive work will rise by the square of the voltage and steal energy from the resonant system faster at peaks, correlating with a higher resonant frequency at higher voltage and lower frequency nearer to AC zero crossing cycles. My guess is the valve actually actuates at some integer fraction of the piezo disk's oscillation frequency and quite possibly, the valve never fully closes - instead becoming more and less flow restricting.
The fact that the whole resonant system shuts down every AC input zero crossing can explain the audible noise at 100/120Hz without necessarily being meaningful at all towards the pumping mechanics. The easiest way to find out would be to put an oscilloscope across the capacitor and see if there is a high frequency riding on the slow AC mains carrier.
My money's on some kind of pressure resonance. As you pointed out, the piezo is moving a tiny amount, normal air pumps in this context move a diaphragm monstrous amounts in comparison and are still weak as hell.
Clever!! Practically no power, just a speaker/squeaker driving on a bit of silicon??
The quietness is surprising, I would expect that to produce a fair bit of hum, since it is essentially a speaker plugged straight into the mains. I would wager that the entire casing is an acoustical contrivance designed to suppress that hum.
Clive, The thing I expected, and the "thing" I expected you to make a bit of a "thing" of was the frequency of the output of the pee-ay-zo. Especially with you saying it seemed quite efficient and yet quite quiet, I suppose I was expecting all the dogs in the neighbourhood to be throwing themselves under mororbikes.
Have I missed something - or are we just talking about a bit of mains hum doing the business? From what I've seen of this sort of thing, mechanical pumps just spin a sloppy impeller, in a hole - no close tolerances but quite nippy to create pressure, I was expecting the same idea just to shift a reasonable volume of air.
It appears to be flexing at mains frequency.
I scrap a lot of stuff, and among what I've salvaged are some "buzzers" that are piezoelectric. I'm assuming that what's inside the plastic case is similar to the disc you show here. I've also encountered those discs loose, used in some drum boxes. Connecting a meter across it shows no continuity, but connecting one to my scope it really does rather well acting as a microphone.
I remember some years back gong to a trade show and seeing some fans that worked on this principle. They had blades, but they didn't rotate, they just vibrated. I've never encountered them since then, and have wondered why, whether they actually went anywhere. Perhaps they weren't capable of high enough volume, or something like that.
The piezo vibrating fans resurface from time to time.
Did not expect to hear nothing when you plugged it in.
Yes but I’ve used pumps for out door fountains that make enough noise that you can hear it 10 ft away
And they have been about the same size if not a tiny bit bigger
1:28 it's actually pronounced "chocolate pudding" (it's Welsh).
audio transformer to raise the voltage then run it off a power amp?
LOL You did it again Clive. I was just taking a swig of drink AGAIN and at that moment you said PISSFLAPS. I about choked.
Anyway . This actually reminds me a bit of those old beigey coloured crystal ear pieces for use with crystal sets . They had a similar arrangement inside , but square , with crystal coated on a thin metal plate and a very thin metal foil diaphragm . (showing my age again!)
I had a crystal earpiece too. They were useful for fault finding because of their high impedance.,
The modern equivalent in the sound industry is this neat signal tracing gadget:-
www.vizear.com/
Thanks Clive. Interesting device..
(I also got looking at that Flame safe candle flame effect light on that link) . Sorry to go off the subject , but years ago I had dealings with a very "realistic" candle flame effect light , or lights , that used a "loose" incandescent bulb, shaped like a flame , that were gently moved by a coil (similar to those LED candles) . They were almost impossible to distinguish from a real candle , even close up. I have yet to see a modern version that comes as close to the real thing as those did.
Loved your X-ray tool and vase of knowledge 😄
Kind of curious how much the piezo disc deflects by, at 60Hz it should be visible and could probably be measured by finding the point where something just touches the end of it's oscillation and comparing to it's rest position.
regarding its sound: you should have waited a few seconds before plugging it in, i have no idea if you were talking over the humming sound before (background noise/static?) or if it was the pump :)
Pissflaps!! Sir, you are legendary.
That would make it pissflap electric then.
I suspect that this is carefully sized to make use of resonance. I suspect the disc size would be different for 60 Hz. I also wonder if the performance would be significantly affected if it were used at higher altitudes. This appears simple on the surface, but I suspect a lot of design and experimentation went into the final product.
It could be nice to see the piezo running after opening it with some sort of grain on that to for the demonstration of its vibration. Or you could dip the stone in a glass of water to see how much air it pumps.
The chamber is probably sized to resonate at the same or close to the resonant frequency of the transducer to help efficiency.
I have a piezo ceramic disk attached to the compressor in my fridge. It works to keep the fridge from overheating and recycling, the compressor that is. Could you please get one and tear it down and explain how it works. Thanks.
I've not come across a piezoelectric disk used in that application. The only disk that comes to mind in a traditional fridge is the thermal cutout disk on the compressor if it stalls.
Played the piss flaps back about 10 times and laughed harder every time!
Great Video Clive.
Thanks Clive. I was hoping to see the diaphram move with the power on.
Interesting. I wonder how efficient it is on 50Hz vs 60Hz - or does resonant frequency not matter much for that size of crystal?
Please demo it working or plug it in...I wanted to see how much it moved in and out.
Working with piezoelectric transducers the inductors are almost always included as a way to dissipate the ringing of the crystal which can cause surges.
It would have been interesting to see the piezo disc in operation. Just to see if it's possible to discern any noticeable deflection.
I think it's thick so that the valves could sit as close to the diaphragm as possible (perpendicular to it). You need some pressure differential to open the valve and the more space there is between the diaphragm and the valve, the bigger the portion of the diaphragm's movement that is used to build up the required pressure difference. If they put the valves down flat and had a 90 degree bend running to them, that might be too much air to compress enough to push the valves open (and even if it did work, it would be much less efficient).
I want to know if it will work off 240v I reckon it will, those transducers can generate fairly high voltages. Also you could try higher frequency?
A couple of months ago, somewhere in China: "That guy on RUclips always mocks our power supplies for not having discharge resistors. Let's put a 1 Meg discharge resistor across one of the other resistors and call it a day...."
I wonder if this could power my miniature bagpipes
Good question as I was wondering the exact same thing for my miniature bagpipes as well.
Put an audio signal directly into the pump.
Bagpipe lullaby.
The cap and inductor could also be filtering out audible noise on the line that the piezo could reproduce.
As for the exact sizing and weird ports, it could be acoustically designed to have some kind of a standing wave inside in order to move more air. Actually, I'd guess that's more than likely.
If its putting out 500ml per minute that would be 500/3600 ml per cycle. If you assume about roughly half the diaphragm is moving
3.14 x radius2/2 x deflection= 500/3600 so not a very large deflection
Minuscule deflection of the disk therefore a bigger diameter of disk needed to provide a given amount of air. Actually quite a big assembly for a small amount of air.
That meter looks very interesting. What is the model and price?
I would be very interested to see a volume pumped per minute vs input frequency... I suspect at a certain frequency, it will be like a heart in fibrillation, where the valves are ineffective, but I'm curious to see what point that would be at...
Perhaps there is supposed to be a capacitor by that resistor, you can see the silkscreen marking on the circuitboard by the first resistor
It's a small ported loudspeaker, tuned to give max air flow at 1 frequency I think
Hi Big Clive, I'd like to see you revisit this piezoelectric air pump operation. I think something else is going on with the Piezo. I have never heard a 50 hz piezo. I got out of bed to write this couldn't sleep thinking about it. My idea was, it is running on a harmonic of 50 hertz, tuned with the inductor and the first parallel cap introduced some nonlinearity. But then I calculated it turned out to be the 800th harmonic, so I backed away from that. (call that idea a maybe) If it was running on 50Hz, I think you would hear it, (2 watts), I never saw a scope shot in your videos, but I'd like to see the waveform across the piezo. Maybe a frequency counter would pick it up, by indirect connection. The 150uh inductor means the piezo's capacitance would need to be very large to tune at 50Hz, (improbably large) After 30 minutes searching, I'm still confused, I found similar piezos made for 22kHz, 27kHz and 40kHz, and then one popped up, operates at 60Hz. ¯\_(ツ)_/¯
That lead doesn't look like it's rated for 130V, or even 250V.
John Francis Doe 120-240v :p
There no feed back on the piezoelectric disk, so it is vibrating at mains frequency, presumable this allows time for the air to move out of the way and for the flap valves to open and close. I guess the air trapped above the disk acts as a spring, storing energy on the up cycle. One might have expected the disk to have two open chambers on each side to allow both the up and down stroke to pump air. Have you considered connecting the disk to a signal generator to see how efficiently it can be excited at other frequencies. Apart from the poor power supply, a weakness of the design must be the risk that the disk will fracture.
It would have been nice to know the pressure the pump can achieve and the volume of air moved.
Hi, BigClive. I was wondering what printer you use for all your beautiful printout cards? Always gorgeous. Did a quick look and didnt see any BCDC videos dedicated to any printers, sorry.
I currently use an Epson ET-4500 bulk ink printer with glossy photo paper.
I love the cordless x-ray machine lol i did not know Stanley made medical equipment.
I love the X-ray machine. If you hook the peeezo wires up to your stereo it will pump air in time to the the music
"like piss flaps" .... Hell I spat my shreddies out laughing.... I do like the teardown videos.. great job.
The space is called a plenum. The power of vacuum to fill the empty plenum through the hole is great while the amount of back pressure to empty the plenum the through the empty hole is small upon each cycle of the diaphragm. Pressure is recuperated because presser that is built up inside the plenum can compress the gas momentarily before the pressure can escape entirely back through the hole the energy of it is used as part of the uptake again. The pressure released through the stone and the built up pressure in the plenum might work In an alternating cycle that has the little thing running like a 4 stroke.
the hydraulic capacitor you speak of is an accumulator
12:50 - "plenum chamber" is the phrase you were thinking of Clive ;-) ...even though it turned out to be on the inlet side!
Love the cutdown power supplies, When I see the power supplies on tv's and computers and things I was always thinking it was a waste of components made to confuse people.
If you plug it in again with the piezo disc hanging out, can you see it moving??
I wonder if there's some resonance stuff going on with that cavity to boost the output or something.
I reckon the air reservoir on inlet side is silencing. Clive it's a shame you didn't measure the output into an upturned bottle submerged in water.
This would appear to be a resonant circuit and the piezo element acts as a capacitor...
It's possible the extra 1M resistor is added after assembly and testing to "tune" the circuit for maximum air flow.
Or not ($0.02)
I wonder how good it would of worked in an actual fish tank. Water pressure and all that kind of stuff makes the pumps I have work pretty hard. If it worked, would buy one in a heart beat to try it.
I'd be interested to know. I have some deep tanks, the depth just kills any pump I put on it. I've thought of going to a piston pump and small air tank over the diaphragm ones.
Into steam punk? A mini bike pump should give more than enough pressure. You don't want to stand there moving it in and out? How about cranking it with a microwave turntable motor? Nice slow action, quiet, but I don't know if it's powerful enough. I've made a water pump using the motor and gearing of a wind-up torch. Runs at 2 watts and can deal with a 3 metre head of water! Yeah, but very low flow rate.... Be warned, not all of their generators are effectively brushed dc, so you might only use the gearing.
I was thinking more small DC reciprocating air pump. I like the idea of using a geared syncro motor though.
2009dudeman hi! Please check my maths, I'm bollocks at it, but for the flow rate Clive cites I get a rough equivalent of a 1cm radius piston with à stroke of 1cm at a frequency of between 2 and 3 Hz. Well below audio except for the motor and gear train. For a small dc motor, have a look at what are called solar motors with built in high ratio gearing. The bike pump will cope with the pressure, but will à very low power motor provide the throughput? My bet is that if it's rated at about 2 watts then it can.
just use thinner tubing
If I'm ever strapped to a chair or worse I have you. Love your channel buddy.
I wouldn't normally recommend this to anyone but you can put a europlug directly in a British socket if you put something in the earth hole to move the shutters out of the way.
I did that. But had a slight moment when it refused to come back out again. I thought the little metal caps were going to pull off inside.
so if the seal was to fail, would water run onto the pizzo putting the tank water at 130vac relevant to ground? Although the seal looks quite good, I guess its a possibility?
Like all air pumps it's designed to be mounted above the water level or have a one way valve installed to prevent flowback.