[SOLVED] Ultrasonic Transmitter/Receiver Circuits

[amirahmadian]

Hi everybody.
I need to build a ultrasonic transmitter and a receiver for my project (The ultrasonic wave must be at a frequency about 30kHz). I wonder if I make a simple circuit that generates a 30kHz sine wave and I feed a typical loudspeaker with this signal, will it transmit ultrasonic waves? Or I have to use some special devices as the transmitter?
And what about the receiver? Can I use a typical microphone as the sensor of my receiver (And I would use a bandpass filter to detect my desired signal)?
Please help.

 

[carpenter]

I thing typical loudspeaker not work on 30kHz. What you do not use uktrasonic transducen on 40kHz, for example.

 

[amirahmadian]

Thank you,
But for the sensors that you suggested, the datasheets specify a Nominal Frequency (Center Frequency). If the nominal frequency of the sensor is 40kHz, can't I use it to transmit/receive ultrasonic signals with 30kHz frequency?

 

[carpenter]

Unfortunately not. ultrasonic transducers are closely tuned and men use the nominal frequency count.
30kHz transducers are manufactured, but are harder to find him
Commonly used ultrasonic frequencies are 25kH (28kHz) 40kHz, 60kHz, for exaple **broken link removed**
Why do you insist on 30kHz?
For what it is to serve?

 

[amirahmadian]

Ok, Actually 30kHz is not really crucial. But could you answer another question,please?
Can you estimate the maximum range of my ultrasonic transmitter/receiver system? Suppose I feed the trasducer with the maximum power that is possible. Approximately what should be the maximum distance from the transmitter to receiver? Does it depend on the frequency? (For instance, estimate it for 25kHz and then 40kHz frequency.)

 

[kripacharya]

no it doesn't depend on frequency.
It depends on the following:

amplifier output power
transmit transducer efficiency / gain
gain of any "antenna" (e.g. parabolic reflector) attached to your tx
impedance match/ mismatch between 'antenna' and the medium (free air i suppose?)
receiver sensitivity
gain of any antenna (e.g. parabolic....) on your rx
impedance match/ mismatch between rx antenna and free air
receiver amplifier gain vs noise floor

Note that power of any signal falls off proportional to the square of the distance

 

[amirahmadian]

Please note I'm talking about ultrasonic systems (Not RF systems).
What is a typical range for a ultrasonic transmitter/receiver system? Is 20 meters possible,for example?

 

[kripacharya]

Please note.... whether it is ultrasonic's or RF, the concepts are the same.

And yes, 20mtrs is possible. I have made doppler systems @40kHz for that range and higher

 

[asim_123]

please can you add the circuit diagram of ultrasonic receiver and transmiter???

 

[Audioguru]

If this is a homework school assignment then the student should do his own research or design.