• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

ultrasonic sensor

Status
Not open for further replies.

anand.usic

New Member
Hello,
I am trying to construct one ultrasonic distance measurement circuit which uses 40KHz signal input. I used wein bridge oscillator in this circuit and AND gate for giving the input. In one terminal of the input the oscillator is connected and the other terminal for user control and the output of the and gate is given to the sensor.
In the reverse action the output of the sensor is amplified and taken for processing.
My question is whether the circuit will work or not.
if not please guide me in this regard. the circuit is attached.
 

Attachments

ericgibbs

Well-Known Member
Most Helpful Member
Hello,
I am trying to construct one ultrasonic distance measurement circuit which uses 40KHz signal input. I used wein bridge oscillator in this circuit and AND gate for giving the input. In one terminal of the input the oscillator is connected and the other terminal for user control and the output of the and gate is given to the sensor.
In the reverse action the output of the sensor is amplified and taken for processing.
My question is whether the circuit will work or not.
if not please guide me in this regard. the circuit is attached.
hi,:)
The Wein sine wave osc is not neccesary as you are driving a 7408 gate.
A simple square wave osc would be easier.

On the RX side, the 741 is powered by +/-12V, so the output will exceed the rating of the 7408.
You need to clamp the voltage output levels.

Also the feedback on the 741's have been connected to the non inverting input pin!
 
Last edited:

bjorn.juul

New Member
The circuit will work, but you need two measure points to process the signal.

To measure a "time-of-flight" for your ultrasonic signal, you need to have a signal that represents the time elapsed from the signal was transmitted to the moment you recieve it again.
Simply connect the output of your transmitter flip-flop V1/1 to an external counter function, and use this to start the count, and then the output of your reciever ends the count.
Divide the result by two, and you should end up with a time, representing the distance of the nearest reflection point.
 

audioguru

Well-Known Member
Most Helpful Member
Your Wien Bridge generator uses a lousy old 741 opamp that operates poorly above only 9kHz. Use a modern opamp (TL071 single, tL072 dual or TL074 quad) that works perfectly up to 100kHz.
Your generator does not have an amplitude-limiting circuit so its output will be clipped into a square-wave.

you CANNOT gate an analog signal with a logic gate.
The high input voltages (positive and negative 10V) to the logic gate will destroy it.

Use an analog transmission gate (CD4066) to gate the analog signals. Its max total supply voltage is 18V so reduce the power supply voltages for the opamps and for it.

Your two opamp amplifiers have a very low input impedance of only 1k ohms because they are inverting. Make them non-inverting so that their input impedance is high.

I think a max gain of only 10 for your receiver is much too low. The analog transmission gate should be at its input, not at its output so that it is not overloaded during transmit.

The output of the transmitter opamp is always connected to your single ultrasonic transducer so it will not receive a signal. A few analog transmission gates might be paralleled so that they can gate the transmit signal into the ultrasonic transducer.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top