Driving a ultrasonic piezo transducer (atomizer/mist maker)

Thread Starter

TrmickCO

Joined Oct 9, 2016
72
I've got a mini tree that needs more humidity during the day when I'm not there. Was looking at using a ultrasonic piezo atomizer (mist maker) I pulled out of a small personal humidifier and building a simple frequency generator to drive it for mist. I've got some small solar panels that work well and thought it would be fun to construct something that does not require batteries, MC's or mains, but simply increases humidity(small amounts) according to the sun's position. I suspect current will be an issue.
These piezo discs usually require 1KHz to 2MHz. I played around with my 555's a bit, but realize it depends which 555 you have. Recently saw a chip- Maxim 038- which produces a huge range of frequency. It's discontinued apparently.
Is what I'm thinking about even doable with solar, and any recommended simple high frequency oscillator circuits?
One thing I need to look up is if a certain type of waveform is required for these piezos.
 

sghioto

Joined Dec 31, 2017
5,368
A cmos 555 or TS555 will go to 3 mhz. How much voltage do you need to power the piezo and the waveform?
The job seems feasible once you figure out some of the specs.
SG
 

Thread Starter

TrmickCO

Joined Oct 9, 2016
72
A cmos 555 or TS555 will go to 3 mhz. How much voltage do you need to power the piezo and the waveform?
The job seems feasible once you figure out some of the specs.
SG
Yeah, apparently the 555's I had don't reach higher, and there are some that can- as you pointed out. I see these being powered from 5-15V + .....This is my first try at powering one if these piezos. My impression is- it works if it hits its designed frequency on its two leads. In water.
Looking into waveform.
 

Externet

Joined Nov 29, 2005
2,181
Perhaps a resonant circuit makes a much higher peak to peak driver for the capacitive load of the piezo transducer.
 

Thread Starter

TrmickCO

Joined Oct 9, 2016
72
From what I have read a square is fine so the 555 is OK as the oscillator. The next question is how much power or current is required to operate. May need a transistor or FET after the oscillator to drive the piezo.
SG
I hope to have the time to it figure out. Current is the thing I wonder about. I've reached 18 volts on the little panels. I've only tried some 555 stuff so far.
 

Thread Starter

TrmickCO

Joined Oct 9, 2016
72
Perhaps a resonant circuit makes a much higher peak to peak driver for the capacitive load of the piezo transducer.
It's definitely some type of LC oscillator. Out of my expertise range. Don't have the driver circuit anymore. The question more leans to- Anybody ever buy or aquire one of the ultrasonic transducers that produce mist and drive it with simple components and mini solar panels?
 

Externet

Joined Nov 29, 2005
2,181
Bought them, with its intended resonant driver. Which suspect pumps it to more than 100Vp-p. at ~2MHz
The oscillator could be a 555, but the resonant amplifier is the key. And 5W or more peak. The output transistor shown in the schematic is capable of 60W.
Mini solar panels won't do it, the transformer is rated near 20 Watts:
----> https://www.ebay.com/itm/AC-110-220...h=item4d8ce6d606:g:Zn0AAOSwPhdU1jh0:rk:2:pf:0

Once I read the patent of the circuit, cannot find it now.
 
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Thread Starter

TrmickCO

Joined Oct 9, 2016
72
Bought them, with its intended resonant driver. Which suspect pumps it to more than 100Vp-p. at ~2MHz
The oscillator could be a 555, but the resonant amplifier is the key. And 5W or more peak. The output transistor shown in the schematic is capable of 60W. Mini solar panels won't do it.
Once I read the patent of the circuit, cannot find it now.
Pure and simple. Not enough current?
 

Externet

Joined Nov 29, 2005
2,181
Am trying, we are trying; but we do not know what is a 'small' tree - 10 feet ? 10 inches? and 'mini' panels; how many, what voltages, what current capabilities ?

If you imagine the board on post #14 as a dream chip that you feed small solar panels, will probably cost less than the dream chip you wish exists.
 
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Thread Starter

TrmickCO

Joined Oct 9, 2016
72
Am trying, we are trying; but we do not know what is a 'small' tree - 10 feet ? 10 inches? and 'mini' panels; how many, what voltages, what current capabilities ?
10 inch range- tree, and the voltage on the three panels in series is Max 20V....Haven't experimented with them enough to talk current capabilities.
 

Externet

Joined Nov 29, 2005
2,181
Come back whenever you find the power/current specifications for the panels. The Max chip is an oscillator; like the 555 is. But it is about driving power, not frequency. your 3 panels in parallel for 6V may do it for the item on post #14 if they are 0.7W each.
I do not think you will get a better deal without knowing what panels you have.
 

pmd34

Joined Feb 22, 2014
527
Hi Trimick, you really need to drive the piezos with a high voltage sine wave, this nearly always done using a self resonant circuit so it always finds the resonant most efficient frequency of the piezo. Using something like a 555 is liable to over heat something. There are lots of examples on the net for resonant driving of a piezo, but unless you want to do something more complex with it your best just buying a driver off the net, and then incorporating it into your project.
 
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