sarahtelayrii
New Member
Hi all,
I'm working on an ultrasonic rangefinder and I have the transmitter working just fine and my receiver circuit looks something similar to the below:
**broken link removed**
On the oscilloscope it's receiving (the ultrasonic receiver between 50-115mV, that is, when I connect the ends of receiver to the oscilloscope and it being placed about an inch away from the transmitter (at 40KHz 5V p-p) both facing directly at me, I was able to see sine wave responses on the oscilloscope via holding a chair and moving it forwards and backwards about 2-2.5 meters away.
The thing is the receiver circuit is supposed to amplify the received signal to a few volts and then use a schmitt trigger to smooth out the sine wave with noise) to a square wave as much as possible.
It worked for a few moments but not at the voltage I expected (still was in very low volts), with alot of noise being detecting (thick line on the top of the received square wave) however since pressing auto-set on the oscilloscope the whole thing just went berserk. Now, there's no received square wave and all I get at the end of the schmitt trigger is sine waves that doesn;t responsd to an object moving at all. Even after re-trying several times.
So any ideas? I know it's hard to say without looking at a screen shot (i have no access to oscilloscope until monday) however I'm thinking the cirucit I have above (im using the same components) might not be suitable in my case.
So I was thinking of one of these 2 solutions:
**broken link removed**
a)
Use the above concept (which is basically my transmitter circuit) but have V+ (pin 8) at 5V and on Pin 3 have the resistors instead of at 1K each have R1 at 10K and R2 at 1M Ohm, so the reference shall be instead of 2.5V it would be at about 50mV. The output of Pin 7 can then go through a schmitt trigger to convert the sine wave to an approximate square wave via upper/lower Threshold voltages. This would then be fed back into the microcontroller pin to be read by the software to calculate distance etc...OR
b) Use a "LM8272 is a Rail-to-Rail input and output" OpAmp.
https://www.electro-tech-online.com/custompdfs/2009/05/LM8272.pdf
The pin 2, inverting Input A shall receive the main signals from the ultrasonic receiver, V+ reference I guess at 5V, V- at GND. Correct me here if I'm wrong I don't have much practice with OpAmps here. The main Output A can then go through a Schmitt trigger and then to micro...
Thanks everyone, I'm getting progress in this project albeit Im working on all of it my own.. and am happy with that but bit by bit.
PS: I have the transmitter working after testing on the oscilloscope, it's sending to about approximately 2-2.5 meters there's a sine wave response on the receiver transducer. I switched to the Murata ultrasonic transmitter (the MA40B8R) and the distance increased by a lot.
I'm working on an ultrasonic rangefinder and I have the transmitter working just fine and my receiver circuit looks something similar to the below:
**broken link removed**
On the oscilloscope it's receiving (the ultrasonic receiver between 50-115mV, that is, when I connect the ends of receiver to the oscilloscope and it being placed about an inch away from the transmitter (at 40KHz 5V p-p) both facing directly at me, I was able to see sine wave responses on the oscilloscope via holding a chair and moving it forwards and backwards about 2-2.5 meters away.
The thing is the receiver circuit is supposed to amplify the received signal to a few volts and then use a schmitt trigger to smooth out the sine wave with noise) to a square wave as much as possible.
It worked for a few moments but not at the voltage I expected (still was in very low volts), with alot of noise being detecting (thick line on the top of the received square wave) however since pressing auto-set on the oscilloscope the whole thing just went berserk. Now, there's no received square wave and all I get at the end of the schmitt trigger is sine waves that doesn;t responsd to an object moving at all. Even after re-trying several times.
So any ideas? I know it's hard to say without looking at a screen shot (i have no access to oscilloscope until monday) however I'm thinking the cirucit I have above (im using the same components) might not be suitable in my case.
So I was thinking of one of these 2 solutions:
**broken link removed**
a)
Use the above concept (which is basically my transmitter circuit) but have V+ (pin 8) at 5V and on Pin 3 have the resistors instead of at 1K each have R1 at 10K and R2 at 1M Ohm, so the reference shall be instead of 2.5V it would be at about 50mV. The output of Pin 7 can then go through a schmitt trigger to convert the sine wave to an approximate square wave via upper/lower Threshold voltages. This would then be fed back into the microcontroller pin to be read by the software to calculate distance etc...OR
b) Use a "LM8272 is a Rail-to-Rail input and output" OpAmp.
https://www.electro-tech-online.com/custompdfs/2009/05/LM8272.pdf
The pin 2, inverting Input A shall receive the main signals from the ultrasonic receiver, V+ reference I guess at 5V, V- at GND. Correct me here if I'm wrong I don't have much practice with OpAmps here. The main Output A can then go through a Schmitt trigger and then to micro...
Thanks everyone, I'm getting progress in this project albeit Im working on all of it my own.. and am happy with that but bit by bit.
PS: I have the transmitter working after testing on the oscilloscope, it's sending to about approximately 2-2.5 meters there's a sine wave response on the receiver transducer. I switched to the Murata ultrasonic transmitter (the MA40B8R) and the distance increased by a lot.
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