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Ultrasonic fogger

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by nikt0, Jan 17, 2007.

  1. dknguyen

    dknguyen Well-Known Member

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    he pretty much outlined it in his initial post did he not?
     
  2. RuiM

    RuiM New Member

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    It Seems you did not unsdurstand my question............ But I will make my question in another way/words.........

    I am also interested in do an ultrasonic fogger, but did not found any schematic in the google, yahoo, etc...... so I am asking if any of you can put any schematic of a funtional ultrasonic fogger....... and what is the correct frequency.......
    Thnks all...
     
  3. HarveyH42

    HarveyH42 Banned

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    Actually don't have a schematic for mine, came out of a busted humidifier. If you find one though let me know. I don't think mine was intended to be run for very long, driver gets very hot.

    Even if you had the schematic, you would need to find a source of a piezo-transducer for it. Probably a better idea to find the transducer, then build the drive circuit to fit its specs.

    If this isn't part of some school project, might consider buying one. Remember seeing some in the $20-30 range, just drop in some water and plug it in. Don't imagine this is the sort of thing that can be built better or cheaper at home.
     
  4. dave

    Dave New Member

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  5. RuiM

    RuiM New Member

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    well the piezo transducer i can get, the problem is to know what one to get..(or for what frequency, that is my main question)....... what freq shold it be? every guy in where say a diferent frequency so i have no ideia what is the right one...... any one have an ideia of what frequency does water starts to atomize?
     
  6. weglobal

    weglobal New Member

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    I would like to ask if anybody knows how much and if even these foggers generate RF , I am designing a sytem and I dont want to have issue with FCC since there is a regulation for anything above 9Khz.
    Thanks
     
  7. Externet

    Externet Member

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    Yes, they are ~1.8 MHz. If you want to name it ultrasonic, well.
     
  8. Externet

    Externet Member

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    Last time I checked, ~1.6; ~1.8 MHz was radiofrequency. What counts is if it is aired or stays confined within the gadget. The chinese nebulizer manufacturers export to USA seem not scared by the FCC. Measuring the emissions of your circuitry would be convenient along with your design work.
     
  9. Externet

    Externet Member

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  10. weglobal

    weglobal New Member

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    Thanks , agree with you I will do that .
    Thanks
     
  11. Hero999

    Hero999 Banned

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    That circuit will kill both the MOSFET, unless they have a high enough on resistance to limit the current to a safe level.
     
  12. Triode

    Triode Member

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    thought this might be of interest, its on sale for 17.50
     
  13. goofeedad

    goofeedad New Member

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    Been to alot of appliance parts suppliers and can't remember ever seeing a piezo transducer. Am I looking in the wrong stores? I would like to know where.

    Thanks
     
  14. peterpwhite

    peterpwhite New Member

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    Ultrasonic humidifier Ideas

    I bought one of the devices from the link, and was dissappointed that the circuit is potted. De-potting with paint stripper may be possible but foul and smelly and may destroy some of the markings on parts:( So I was very happy to see the picture!

    Many of the posts seem on the right track.

    Yes, the disc is a piezo transducer, it will have a circuit model topology like a crystal (resonator for the true geeks out there). Measuring the element values for the model is the tricky bit. I have a disc (only the small one, so far) and a network analyzer, so I will let you know the model parameters. I have a derivation of the equeations for the element values from a few measured parameters that will pop out a simulatable model.

    Yes, the circuit will use an oscillator. The PCB picture makes the circuit reasonably obvious. I believe they are using a single transistor oscillator circuit with a trim cap to tune the frequency. It looks to me that the oscillator drives a resonant (Note the BFCs) power amplifier stage (TO-220). My first guess would be that it is similar to a Peirce oscillator, having 2 (expensive, high voltage and Q) shunt load caps. I have allot of expereience (and scar tissue) with crystal oscillators. And I have studied the Pierce ciruit intensively so the circuit should be a piece of cake! I will take a look at the board layout to verify my assumptions after I measure my disc.

    Yes, this sucker is going to burn some power! The Transformer in the link to the Asian website shows 24VAC, 12 Watts, assuming the voltage is rms (as it should be) the max current would be 0.5 Amps rms. My unit is submersible, and is in a cast metal housing. I am certain the power device has a nice thermal contact to the housing, and the sinking will be excellent. My advice is to not burn your fingers and do plan on a beefy heatsink especily if your design is not submersible!

    I look forward to cracking this nut, and posting the meat!

    Pete White
    Alpha EE Geek
     
    Last edited: Dec 2, 2009
  15. peterpwhite

    peterpwhite New Member

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    Ultasonic humidifier Tranducer model

    I followed through on measuring an ultrasonic humidifier (fog machine) resonator disc.

    If you have little or no back ground in crystal resonators, most of what follows will be jiberish. Please note that I do not consider buying a crystal slapping it on a IC oscillator and adding 2 caps expereince, no offense. I highly recomend reading http://www.electro-tech-online.com/custompdfs/2009/12/AN-CU_GG_e.pdf for a fundimental understanding of crystal resonators.

    I measured the disc as a series 2-port on a 50 Ohm network analyzer and got a suprizingly strong resonance without adding shunt capacitance to each port of the resonator. This is only suprizing becuase I have never measured this type of resonator before and have more experience with crystal and SAW resonators.

    I have the small disc from Ultrasonic Water Fogger-The Mist Maker

    The disc has many other smaller lower Q resonances, which I ignored, so the model I generate will only be applicable for the primary resonance.

    The disc is series resonant at 1.612839 MHz and -0.4 to -0.7 dB
    The disc is parallel resonant at 1.83593 and about -20 dB
    The 1 dB BW of the series resonance is flow=1.5211MHz, Fhigh=1.679138MHz
    I measure the Co of the disc at 10MHz to be about 1.0nF (another surprize, huge!)

    From this data I calculate the circuit model using NDK's equations. Please note that NDK uses the component names: L1, C1, R1, Co. I strongly prefer Lm, Cm, Rm and Co, as there should be no confusion on which capacitor is which!

    For the small Disc equasions and some minor manual optimazation, I get:
    Lm=35.196uH
    Cm=276.67pF
    Rm=4 Ohms
    Co=1.0nF

    Note that the Lm and Cm have high precision due to the accuracy of the frequency measurments, don't truncate! Rm was optomized from the series attenuation measurment using PSpice and stray shunt capacitance of 0.5pF on each end of the resonator. Try simulating this with PSpice using a 50 source and load resistance.

    I then optomixed the resonator Circuit for the peak amplitude response and got 6.3nF shunt at each disc terminal (Cshunt, NOT Cload!, Cload is approximately Cshunt/2) +3.8dB. The positive amplitude response for a pasive device is probably due to inaccuracy in the broad band calibration I used on the network analyzer and the Q oc the resonator, but is still useful for the peak!

    The peak Q is of no practicle interest to the circuit designer, it happens at infinite Cshunt meaning a termination impedance of very close to zero ohms. It is impossible to drive a voltage into a short circuit it always looks like very small voltage and is useless! Around the peak amplitude response of the resonator and circuit is the only practical operating point especialy for a power Amp design!

    More updates when I reverse engineer the Circuit picture. Right now my circuit topology guesses are looking pritty good!

    Regards,
    Pete White
     
  16. JKL

    JKL New Member

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    I've been digging for something like this for ages! - There are soo many uses for a ultrasonic fogger/mister I have right now! - ... I also saw these other $$$-like devices, from what I gather it forces the liquid tightly through a nozzel to create the 'fog' that was said to be MUCH finer than a ultrasonic device, however, as I recall it produced minimal amounts more for coating nano objects.. ANYWAYS! PeterWhite seems do know his stuff. I eagerly await your next post, Peter! ... Please make a explaination/guide for the dummies too: I'm epic noob :p
     
  17. gelecg

    gelecg New Member

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    Hello

    I've got 2 questions
    1)
    why the capacitor 1.5n and 33n is high voltage?(the circuit voltage is

    40v rms but the capacitors is 400 or 600 volt)?
    2)
    can you tell me about the oscillator?(how does it work?)
     
  18. atferrari

    atferrari Well-Known Member

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    Last edited: Mar 27, 2011
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    You don't need to filter a square-wave into a sine-wave. The resonance of the transducer is the filter.
    I think you must operate the drive at the resonant frequency of the transducer, not at a harmonic.

    You use PWM to reduce the amount of drive (why?) but reducing the supply voltage of the driver circuit does the same thing.
     
  20. arvinfx

    arvinfx Member

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    Sorry, but this device with about 2Mhz and 40W isn`t dangerous for human body?
    How about radio radiation?
     
  21. Triode

    Triode Member

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    Wattage doesn't necessarily tell you if it will do you any harm. Voltage pushes amps through the resistance of a conductor like pressure pushes mass through the constriction of a pipe. But who said anything about 40W?
     
    Last edited: Jun 8, 2012
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