Driving a 120W Piezoelectric Transducer: Voltage, Impedance, Frequency Control?

Hi All who can help me? i am trying to drive a Piezoelectric Transducer , but there are 2 question. first, in many document i read,mentioned that for driving this transducer and for getting 120 watts power, we have to use high voltages about 400 volt,and my question is how we can use 400 volts for radiation resistance about 20 ohms??i thing one thing is wrong here,what is wrong???? 2nd, in these documents mentioned that the frequency is changing because of changing impedance,is it necessary to use a frequency control circuit or we can drive the transducer without using this circuits??? please help me

Have a look at these links Also see uploaded PDF file

http://www.ultra-piezo.com/ultrasonic-cleaning/55.html

http://jumperone.com/2012/02/ultrasonic-cleaner-re/

http://www.picproje.org/index.php?topic=45268.0

thank you amigo
god bless you

De Nada Amigo

Amigo
do u know what is consideration for driving this transducer?
i found ou that we need to use a transformer after power amplifier and in last step for increasing voltage and isolation.
acctually i wanna produce a pulse signal by AVR and then use that for driving transducer, but i dont know what i need for doing this work
can u help me , plz?

Have another look this page all the way down

http://www.picproje.org/index.php?topic=45268.0

It shows you how to wind the transformer for achieving this application then apply the coding that you would in a pic micro to atmel cpu or in your case what you call the arduino Its All roughly the same thing


So you want pwm out one channel driving one of the fets and inverted on the other output driving the other Fet for a signal frequencey of 42khz to 47khz depending on what ever your piezo element is rated at

Lets see how you would work this out
If you know your instruction time then one port will be high for x cycles instruction time and the other port pin will be low during that period

To complete one cycle the you would have to use period = 1/f which is 1/ 42000

So lets see period for 42khz is 23.81us which constitutes one cycle 11.9 us On 11.9us OFF

You would use possibly a timer interupt and then invert the state of the ports every 11.9us

Preloading the timer with a value so that every 11.9us it overflows and calls the on interrupt routine

The on interrupt routine would simply alter the state of the ports ie if Invert port pin state ie low to high or high to low

i.e Port.pin = NOT (port.pin ) // invert state

C syntax would be something like this

Inside your interrupt call back
PORTD = PORTD ^ B00100100; // invert bit 5 , 3 (digital pin 5, digital pin 4), leave others untouched

Or not having worked with ardiuno reading through it appears you may do this
ISR(TIMER1_COMPA_vect)
{
digitalWrite(PORTPINA, !digitalRead(PORTPINA));
digitalWrite(PORTPINB, !digitalRead(PORTPINB));
}


Thats how I would approach this Then if you need to check your output with a simulator or a Scope

You would have to alter the value in the timer to account for other instyruction times to get far greater accuracy on your final frequency out

See here for more info on timers Arduino
http://www.engblaze.com/microcontroller-tutorial-avr-and-arduino-timer-interrupts/

Far better explanation of this here
http://www.hobbytronics.co.uk/arduino-timer-interrupts

The answer here lies in your understanding of instuction time which is also determined by your cpu clock frequency

a question will apear?
why we need to use PWM and current controlling(frequency controlling)?
is it necessary?

You are using a form of pwm by changing the pin sates with the use of a timer interrupt although not true pwm it is essentially a square wave oscillator with two pins You could use real pwm to ensure correct V out stabilized if you were using adc to check output voltage sampled from your secondary of the TX but you don’t really need to be that accurate Your frequency out how ever does need to be reasonably accurate so that it lies within the tolerance of your Piezo transducers that is 42khz to 47khz

There is nothing to stop you using for example a 555 timer IC Or a Cmos oscillator with nand gate attached to the output to give you inverted and non inverted drives to the fets although you do need to observe your drive voltage to the gates of the Fets typically this shouldnt exceed 5 volts for given fets

thx
ur helps is usefull
but in the web links that u put,( http://www.picproje.org/index.php?topic=45268.0 )(turkish)
i thing one thing is wrong,
because in that circuit, he use transfirmer in last step an after amplifying,and in this situation if we want to have 120 watt power ,in output we have to have 50 volts voltage and 2.5 amps current and actually in primary stage of transformer by turns (12/50) then we have to have 2.5*4=10 amps current,isnt it???or i think wrong???

I calculate 67 volts secondary

( Number of turns in secondary/Number of turns in primary) =(Voltage in secondary/ Voltage in primary )

transposing ES = EP* NS / NP = 67.5 volts
(12 * 45/ 8 )

Cant see how you calculated your current though dont forget the primary acts as open circuit at 42 khz so current I would have thought would be about 0.75 amp or so for 50 watts in secondary at 67.5 volts

so if i wanna have 120 watt in secondary(output) and input of transducer,how much voltage need current i need in secondary???????
why primary act as open circuit?????
can i use IRFZ840 istead of two transistors(MOSFETs)???
ty again

I calculate 1.75 amp which means halve the gauge on the secondary winding looking at the data sheet cant see why not IRF 840 should be ok Id = 8 amps and max vgs = +- 20 volts you are only using 5 volts gate drive which gives 3 amps max Ids acc the graph

Current rating of the gauge in primary is 25 mm = 30 gauge using tables http://www.powerstream.com/Wire_Size.htm is rated at 0.86 amps

So you will have to make the gauge in the primary side
23 gauge giving you 4.7amps keep turns the same

The secondary will still be the same turns so we look at what we need current wise is 1.79 amp at 65 volts

P = VI = 1.79 * 65 = 116 watts ( Close enough )

So you want 26 gauge in the secondary rated at 2.2 amps

IS / IP = NS/ NP = VS/VP

how do u calculate???what is the value of theNP and NS???
what is ur mean about halve the gauge???
that is mean we need 68.5 volts in secondary???

Someone else might have a far better answer to this but thats what i would do

Only one way to find out I suppose Try it and see I'd be interested to see how close my answers are last time round i did this It worked out A ok

Im sure there are many other points that you would have to take into account like the type of core etc but for these purposes I think It may just work You may have to take one or two turns off or on thats to get resonant frequency correct but to all intensive purposes It will work ( thats what matters at the end of the day Does it work or not )

thank you so much
your helps were usefull
and i hope u be lucky
gracias amigo

De Nada Amigo Espere que esto le ayude

dear Mark
i have a question
i saw that in some made circuits , some producer use PWM controlling for controlling frequency because of chnaging frequency during running,
do you know do i have to use frequency controlling for driving algae removal circuits or this technique is optional and is not necessary???
do you have any information about Lp-Bs(Low Power Bright Signal) Technolgy??does it electronical technique or Mechanical type??
how can i use this technique for my circuits?
can i use this circuits as my driver?(attached file)
thanks mi mejor amigo