Trying to create a Piezo Transducer circuit for a mist maker.

[ntgcleaner]

Hello everyone!

My current goal is to make a simple cigar humidor tender.  Something that will turn on a humidifier to run into the box.  (note: There's a lot of fluff in here, scroll down to read the question)

The circuit to use two humidity sensors (HIH-4000) and a circuit averager, with an op-amp comparator works like a charm.  I can now send power to another circuit - hopefully the  humidifier.  My first attempt was to use this simple circuit to turn on an air pump and pump water through a simple water reservoir with a sponge, which would then run the air into the humidor.  After doing testing, I found that this humidifier only produced 60% humidity.  For my purpose, I need 72%.  So I took a look into ultrasonic piezoelectric transducers.  I ordered a bottle cap small room humidifier to see how it works. 

After ordering a newer multimeter that read frequency, and reading up as much as possible on everything, I found that this bottle cap humidifier was sending 222Khz to the transducer.  I don't know exactly the serial number or anything, but I've read that you can use anything up to 2Mhz transducers to create mist. 

I then ordered a CMOS 555 timer which could produce up to 3Mhz frequency and 2 sets of piezo transducers (one is 1.66Mhz, the other 190Khz).  I got all of the parts on the same day and started to build my 555 timer circuits.  One of them produced 1.66Mhz, the other 190Khz.  Happy as can be, I hooked them up directly to the timer output and....  Nothing... 

I read the specs again on both of them and asked some questions on stackexchange and found out that I need to feed these things between 30 and 50v!!!  I'm trying to drive this from a 5V usb plug! 

"Ok, great." I said... 

Now, I'm looking up boost converters, but I need a sine wave, and transducers and transformers and inductors.  There's about 10 ways to multiply voltage but none of them are working for me! 

After looking again at the bottle cap humidifer, I noticed that it has a small transformer with 5 pins, only 4 of them being used and it has a shielded axial inductor on it.  I'm still trying to figure out what wires to what, but I see right there that it's possible and I only purchased this thing for $9.00!

So - What am I missing? I'm not sure how to produce 1.66Mhz frequency at 48V!  I've been looking for 10:1 transformers, but I know I need to generate a since-wave frequency for them to work.  The 555 generates a different type of frequency.  I got a simple voltage doubler circuit to work, but when I make an 85hz signal with 5v, it drops to voltage to around 2.5v.  Double that and I'm back to where I started.

I can't seem to figure out how to drive this piezo transducer properly.  Does anyone have any suggestions? Schematics?

[David Hess]

Piezo transducers are pretty high Q so driving them and not getting a sine wave is pretty difficult and probably not worth worrying about.  The efficient designs I have seen use the transducer as part of a resonate circuit so the frequency of operation ends up being the resonate frequency including the mechanical load but stepping up the output of a fixed oscillator is certainly feasible.

[anshu]

 I am also trying to make a humidifier circuit similar to bottle cap humidifier.Could anyone help in this matter? Circuit diagram would be helpful.

[lapm]

Problem with those ultrasonic humidifiers is you need distilled water with no impurities.. Otherwise your cigar box will soon enough be full of white chalk from water... These devises were short lived hit in my country few years ago, but soon disappeared from market reason mentioned above..