# Using a 555 timer to generate 144 kHZ square Wave for a transducer

#### danielkaroly

Joined Sep 4, 2019
6
Hi Everyone,

Im a chemistry masters student who is currently about to finish his project. I have a problem although, Im trying to design an driving circuit to drive an Ultrasonic vibration micro nozzle, which will be used to generate droplets on demand. The main porblem I have is that I tried several different circuits and none of them seems to be working. The micronozzle ( product number: M2313500 Prowave electronics) has a Resonant frequency of 143±5 kHz, to achive this frequency I tried using a 555 ic timer (first picture), but sadly its not working. I found a different driving circuit which uses coils, and two different kinds of transistors to drive this transducer(second picture), but again its also not working. To my suprise I found yet an another driving circuit (third picture) which is also used to drive the very same transducer, but it is entirely different to the others. The weird thing that according to this datasheet the resonant frequency is 135±kHz. I havent yet made the third one as I dont have all the parts for it.
I have no formal education in electronics this is something I picked up lately so Im not sure if Im doing something wrong. The circuits that I linked here were all made as a prototypes on separate breadboards ( except number 3, which I have not attempted to build yet)

If anyone could steer me in the right direction it would be much appreciated.
Thanks,
Dan

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#### crutschow

Joined Mar 14, 2008
23,314
Did the second circuit oscillate?

You could try the 555 oscillator with the output circuit of the bottom circuit which uses an inductor to resonate with the nozzle capacitance in a tank circuit.
Note that the LED appears to be reversed.

You could also try a push-pull emitter follower driver circuit using an NPN and a PNP transistor.
Connect the NPN collector to V+, the PNP collector to common, and the two emitters tied together is the output.
Drive the two bases tied together from the 555 output.

Joined Mar 10, 2018
3,577
The manufacturers circuit in the datasheet should be a very good
choice. Normally this is the "golden" standard for a part, as quite
often the part may have been characterized with their recommended
circuit.

Regards, Dana.

#### Externet

Joined Nov 29, 2005
1,410
Drivers working at 5V and 12V supply will not create much action from the transducer. They like to work at higher voltages if piezoelectric, more current if solenoid types. Check specifications for the transducer requierements.
Is it like a fuel injector type of transducer ?

#### BobTPH

Joined Jun 5, 2013
2,021
Why the transistor with a 2K collector resistor in the first circuit? The direct output from the 555 would provide more drive current.

What are the specs of the transducer?

Bob

#### Bordodynov

Joined May 20, 2015
2,389
Here's the idea of using a transformer. However, the driver used is outdated. You need to use dual gate drivers that contain both direct and inverse outputs.

#### danielkaroly

Joined Sep 4, 2019
6
Thanks all for the replies guys. Im processing all the information you have given me, and will update.

#### danielkaroly

Joined Sep 4, 2019
6
Why the transistor with a 2K collector resistor in the first circuit? The direct output from the 555 would provide more drive current.

What are the specs of the transducer?

Bob
Im not sure why the 2k resistor. I found this circuit online. They used it to drive a transducer with a resonant frequency of 40kHz. I changed the values of R1(2 K ohm), R2( 6 K ohm) and C2 ( 1 nF) so that the output on pin 3 is 144 kHZ, since theres an equation of f=1.44/(R2+2R1)*C1.
Im was assuming that the transistor is there to amplify the current ?
I attached the specs of the transducer. My biggest problem is that I have two separate datasheets for the sampe product number, and they differ in the resonant frequency

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#### danielkaroly

Joined Sep 4, 2019
6
Drivers working at 5V and 12V supply will not create much action from the transducer. They like to work at higher voltages if piezoelectric, more current if solenoid types. Check specifications for the transducer requierements.
Is it like a fuel injector type of transducer ?
So if it wont work using 5 or 12 V what voltage am I supposed to use. Im not sure what type. Its a 50 micron thcik Ni-Co alloy with 7 micron holes on it. I attached the datasheet.

Note: For some reason it has 2 different datasheets, where the product number matches, but the resonant frequency is different.

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#### danielkaroly

Joined Sep 4, 2019
6
Did the second circuit oscillate?

You could try the 555 oscillator with the output circuit of the bottom circuit which uses an inductor to resonate with the nozzle capacitance in a tank circuit.
Note that the LED appears to be reversed.

You could also try a push-pull emitter follower driver circuit using an NPN and a PNP transistor.
Connect the NPN collector to V+, the PNP collector to common, and the two emitters tied together is the output.
Drive the two bases tied together from the 555 output.
What do you mean by did it oscillate ? Do you mean if i checked it with a led if its blinking ?

#### danielkaroly

Joined Sep 4, 2019
6
Here's the idea of using a transformer. However, the driver used is outdated. You need to use dual gate drivers that contain both direct and inverse outputs.
View attachment 185642
This looks well complicated for me. Have you got some rescources on this so I can read a bit about it ?

Thanks

#### Bordodynov

Joined May 20, 2015
2,389
Here's the circuit without the transformer. Current through a piezo resonator 800 mA. This is much more than with a single-stroke driver.

#### Bordodynov

Joined May 20, 2015
2,389
Here is an example with two weekends - a gate driver and a transistor with high current amplification. C2 and C4 are two piezo emitters. The diagram shows the current through the piezoelectric emitters.

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