Simple ultrasonic piezo humidifier disk driver

Thread Starter

vahidasadi

Joined May 21, 2010
13
Hi everyone
I have a piezo humidifier disk that work with 24v, 1.7mhz
Because i didn't have a 24v supply i decided to use a desktop pc power supply, as you know we can have a 24v dc with using the blue and yellow wires of pc power
Blue wire =-12
Black wire =gnd
Yellow wire= +12
To achive 1.7 mhz i use 555 astable ic as digram shows and a NPN transistor number 13005
Every things is. Correct but i don't know why my humidifier not working
 

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bertus

Joined Apr 5, 2008
20,319
Hello,

You do not have a base resistor in your schematic.
Without the base resistor, the transistor will get the full current from the 555 (ca. 200 mA for a Bipolair version and 100 mA for the Cmos version).

Bertus
 

KeithWalker

Joined Jul 10, 2017
665
Are you sure the 555 is giving you a 1.7 MHz output? I have never seen one run at that high a frequency. I re-read the specs several times but could not find any recommendation for maximum frequency in astable operation. The quick calculator timing charts do not show operation beyond 1MHz.
Keith
 

pmd34

Joined Feb 22, 2014
503
Normally the piezos are driven with a self resonating circuit as the actually frequency varies slightly, and can overload the driver off resonance. The newer MIC1557 MIC1555 ics can go up to 5MHz.
 

Thread Starter

vahidasadi

Joined May 21, 2010
13
Hello,

You do not have a base resistor in your schematic.
Without the base resistor, the transistor will get the full current from the 555 (ca. 200 mA for a Bipolair version and 100 mA for the Cmos version).

Bertus
Thanx all of you for respons
I forgot to add resistor to schematic but in test board i had added one

Well about 555 specs, i used two or three apps to calculate the circuit and they all suggested me the same Components so i ordered them
I'm not sure about the exact frequency but i'm using variable resistor to be able to change the frequency but still no success
 
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