Dog stopping: Finding a Piezo buzzer/transducer? - Page 2 - Electronic Circuits Projects Diagrams Free

audioguru · 6th March 2007, 07:57 PM

You don't need a coil to drive a high capacitance piezo, you need a bridge amplifier made with two complimentary pairs of emitter-followers to supply the high charging and discharging currents.

DigiTan · 6th March 2007, 08:26 PM

Okay, I think I will have room for that. Since distortion won't be a factor, can I use a single emitter-follower stage but with really high gain or will that cause a new problem?

audioguru · 6th March 2007, 11:32 PM

The piezo transducer needs to be driven push-pull. They have a max signal voltage of 24V so a bridge driver could be used with a 12V supply to get about 21V p-p output like this:

DigiTan · 8th March 2007, 02:07 AM

Are there 24 Volts between the "+" symbol and ground or is it like a charge pump situation where I can use 12V? I can can probably start testing this with my 40kHz transducers. In the meantime, I'll just order a circuit off ebay, I can't find a single transducer with the right transfer function.

audioguru · 8th March 2007, 02:44 AM

My circuit has the transducer in a bridge. The bridge nearly doubles the voltage across the transducer. Use a 12V supply because the Cmos IC has 18V max.

mvadu · 8th March 2007, 11:27 AM

And what is the OP-Amp IC used in that circuit?

audioguru · 8th March 2007, 02:56 PM

Quote:

Originally Posted by mvadu

And what is the OP-Amp IC used in that circuit?

My circuit doesn't use opamps. It uses two of the 6 inverters in a CD4069 hex (6) inverters Cmos logic IC.

**Nigel Goodwin** · 8th March 2007, 03:21 PM

Quote:

Originally Posted by audioguru

My circuit doesn't use opamps. It uses two of the 6 inverters in a CD4069 hex (6) inverters Cmos logic IC.

It's also clearly labelled on the circuit!.

Hero999 · 8th March 2007, 10:31 PM

Also a coil in parallel can increase the power factor and therefore the efficeincy by effectively recycling the wasted capacitve current.

audioguru · 9th March 2007, 12:23 AM

One time I had a 240VAC fan that wouldn't run on my 120VAC mains. So I tuned it to my mains frequency with a capacitor in series and it ran fine. It developed about 190VAC.

I have never tried "tuning" a piezo transducer with a coil in series to increase its power.

A coil in parallel would not allow the piezo transducer to draw much current because then it would be in a high impedance tuned circuit, wouldn't it?

DigiTan · 9th March 2007, 07:54 AM

Sounds like this coil is worth looking into then. Is the voltage-doubling still likely to work the same after the circuit is tuned?

audioguru · 9th March 2007, 01:49 PM

If the AC source impedance is very low and the resistance of the coil is also very low then the coil in series with a capacitor will be a very low impedance at resonance and a very high current will flow in them.

mneary · 10th March 2007, 03:18 AM

I have a water-powered ultrasonic transducer in my yard: the sprinkler system. Very loud high pitched hissss while the air is being flushed out. Advantage is that if they don't respect the sound they'll respect the water.

Hero999 · 10th March 2007, 10:39 AM

Quote:

Originally Posted by audioguru

One time I had a 240VAC fan that wouldn't run on my 120VAC mains. So I tuned it to my mains frequency with a capacitor in series and it ran fine. It developed about 190VAC.

Good idea.

Quote:

A coil in parallel would not allow the piezo transducer to draw much current because then it would be in a high impedance tuned circuit, wouldn't it?

It wouldn't make any difference to the piezo, but it would to the driver; the driver will see a higher impedance load but still supply the same current to the piezo. Just like the parallel power factor correction capacitor in a fluroscent ube fitting; the tube might draw 1A but the with the capacitor the totaly load on the supply might only be 0.4A.

mneary · 11th March 2007, 07:56 AM

You need to measure the reactance of the piezo at the output frequency and put a series reactance to counteract this, forming a low impedance load.

This could result in a high output, an overloaded driver, or a shattered piezo.

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6th March 2007, 07:57 PM	#16
audioguru	You don't need a coil to drive a high capacitance piezo, you need a bridge amplifier made with two complimentary pairs of emitter-followers to supply the high charging and discharging currents. __________________ Uncle $crooge

6th March 2007, 08:26 PM	#17
DigiTan	Okay, I think I will have room for that. Since distortion won't be a factor, can I use a single emitter-follower stage but with really high gain or will that cause a new problem? __________________ The most-hated young engineer in America. * AVR Projects * Robot War: TI * About

6th March 2007, 11:32 PM	#18
audioguru	The piezo transducer needs to be driven push-pull. They have a max signal voltage of 24V so a bridge driver could be used with a 12V supply to get about 21V p-p output like this: Attached Thumbnails __________________ Uncle $crooge

8th March 2007, 02:07 AM	#19
DigiTan	Are there 24 Volts between the "+" symbol and ground or is it like a charge pump situation where I can use 12V? I can can probably start testing this with my 40kHz transducers. In the meantime, I'll just order a circuit off ebay, I can't find a single transducer with the right transfer function. __________________ The most-hated young engineer in America. * AVR Projects * Robot War: TI * About

8th March 2007, 02:44 AM	#20
audioguru	My circuit has the transducer in a bridge. The bridge nearly doubles the voltage across the transducer. Use a 12V supply because the Cmos IC has 18V max. __________________ Uncle $crooge

8th March 2007, 11:27 AM	#21
mvadu	And what is the OP-Amp IC used in that circuit?

8th March 2007, 10:31 PM	#24
Hero999	Also a coil in parallel can increase the power factor and therefore the efficeincy by effectively recycling the wasted capacitve current. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

9th March 2007, 12:23 AM	#25
audioguru	One time I had a 240VAC fan that wouldn't run on my 120VAC mains. So I tuned it to my mains frequency with a capacitor in series and it ran fine. It developed about 190VAC. I have never tried "tuning" a piezo transducer with a coil in series to increase its power. A coil in parallel would not allow the piezo transducer to draw much current because then it would be in a high impedance tuned circuit, wouldn't it? __________________ Uncle $crooge

9th March 2007, 07:54 AM	#26
DigiTan	Sounds like this coil is worth looking into then. Is the voltage-doubling still likely to work the same after the circuit is tuned? __________________ The most-hated young engineer in America. * AVR Projects * Robot War: TI * About

9th March 2007, 01:49 PM	#27
audioguru	If the AC source impedance is very low and the resistance of the coil is also very low then the coil in series with a capacitor will be a very low impedance at resonance and a very high current will flow in them. __________________ Uncle $crooge

10th March 2007, 03:18 AM	#28
mneary	I have a water-powered ultrasonic transducer in my yard: the sprinkler system. Very loud high pitched hissss while the air is being flushed out. Advantage is that if they don't respect the sound they'll respect the water.

11th March 2007, 07:56 AM	#30
mneary	You need to measure the reactance of the piezo at the output frequency and put a series reactance to counteract this, forming a low impedance load. This could result in a high output, an overloaded driver, or a shattered piezo.