[MOVED] how to deliver 23 Khz freq

[aliyesami]

I will be generating 23Khz digital 5v frequency signal via arduino board . I want to amplify it to 1W using some
audio amplifier but how can I out put it .. use normal audio speakers or use ultrasonic transmitter ?
I know 23KHz is ultrasonic freq but iam confused if I can feed it to a normal speaker .

thanks

 

[jiripolivka]

I will be generating 23Khz digital 5v frequency signal via arduino board . I want to amplify it to 1W using some
audio amplifier but how can I out put it .. use normal audio speakers or use ultrasonic transmitter ?
I know 23KHz is ultrasonic freq but iam confused if I can feed it to a normal speaker .

thanks

A "normal" speaker will emit the 23 kHz ultrasound but with a poor efficiency. You can try ultrasonic transducers but they are usually resonant, adjusted to 24 kHz. If you need 23 kHz to be emitted, try piezo "tweeters", loudspeakers designed for a high frequency above ~10 kHz. The best idea is to have two such tweeters, one used as the emitter with your 1 W amplifier, the other as a microphone connected to an oscilloscope for fine tuning adjustments.

The piezo tweeters are high-impedance devices, so use a ferrite-core transformer from the ~8 Ohm amplifier output, to ~ >1 kOhm for the tweeter. I used this procedure to optimize my ~1W dog repeller device at 24 kHz, and it works. Tuning the transformer to resonance gave the best output.

As the tweeters are typically not specified for the response above 20 kHz, you could test two or more different pairs for best results.

 

[aliyesami]

hi Jiripolivka !

I found this piezo tweeter that says impedence range of 4-8 ohm so can I use this and not use the ferrite core transformer ?
and the 8 ohm amplifier out is characteristic of a particular amplifier chip I will buy or do I have to do something to achieve this ?

sorry I am new to analog circuit design and learning .

 

[jiripolivka]

hi Jiripolivka !

I found this piezo tweeter that says impedence range of 4-8 ohm so can I use this and not use the ferrite core transformer ?
and the 8 ohm amplifier out is characteristic of a particular amplifier chip I will buy or do I have to do something to achieve this ?

sorry I am new to analog circuit design and learning .

If your tweeter has 4-8 Ohm impedance, then you can use a LM386 half-watt amplifier or another type. I have used a 24 kHz ceramic transducer and it was best when fed from a transformer, some 100 V p-p. Please try to test your tweeter as specified, and for adjustments use another one as a receiver, connected over ~30 cm distance to an oscilloscope. This can make sure the best efficiency is achieved to transmit 23 kHz.

 

[aliyesami]

iam trying to build a device to scare my cats away from couch which they like to destroy , so what watt amplifier would I need for indoor usage that would be effective ?
I am not very clear on how to achieve the best efficiency but I will ask once I get the basic circuit working.

 

[jiripolivka]

iam trying to build a device to scare my cats away from couch which they like to destroy , so what watt amplifier would I need for indoor usage that would be effective ?
I am not very clear on how to achieve the best efficiency but I will ask once I get the basic circuit working.

I am not sure about cat deterrent, I had never a cat at home. Those who do use special cat furniture to save theirs ). I used 24 kHz transducers by Murata to make a dog deterrent and it works. I used a 555 to generate 24 kHz, with a fine tuning potentiometer. Then a Japanese power transistor as the final-stage switcher, and a ferrite-core transformer, tuned by a set of capacitors to get a maximum output indicated by another sensor of the same type connected to an oscilloscope.
The oscilloscope indicated several volts p-p over several meters, the transducers are pretty directional and fine tuning is needed. The peak voltage across the transmit device is ~130 Vp-p (one can use a neon to indicate the tuning,too).
Barking dogs of my neighbors hate the ultrasound and either stop barking or go away. I think mice escape, too, but I have none around to test. Many years ago I built an oscillator with a piezo plate from a watch, fed with 5 Vp-p at > 15 kHz (above my hearing). Intended as a mosquito deterrent it did not work but I made several for my friends who used the devices to get rid of mice. A 4.5 V battery lived over several months ( less than 5 mA needed) and mice simply moved away.

 

[aliyesami]

hi Jiripolivka !
can you look at my new thread at https://www.edaboard.com/threads/297179/ and give your valuable comment?

thanks