Hi there,

I'm currently trying to build an ultrasonic ranging module using two ultrasonic sensors Ultrasonic Tx and Rx. I've attached the schematic for the transmitter and receiver circuits as well as a photo of the actual circuit built on a breadboard. The transmitter is based round a 555 timer in astable mode. The receiver is based around an LM324n op-amp.

The issue I am having is based around the receiver. The first stage of the receiver involves a non-inverting amplifier with a gain of 11. I'm having two issues with this as the receiver is picking up ultrasonic waves from the transmitter before anything is reflected, im not sure how to solve the issue of this noise? The second issue is that the oscilloscope output is not the same as the multisim simulation.

The noise is so bad on the second amplifier that I can't really sense anything as the picked up waves from the receiver are amplified straight away.

I've attached screenshots of the multisim oscilloscopes and oscilloscope traces from the Rx signal before amplification, after 1st stage and 2nd stage.

C

 

Without having actually looked at your circuits, I would suggest a few recommendations.

1) The receiver is very frequency selective. You need to provide a means of adjusting the transmitter frequency so as to match the peak response of the transmitter/receiver pair.

2) You need to gate the transmitter signal so that only a short chirp is transmitted, i.e. 10-20 cycles of the transmitted frequency.

3) The receiver is very sensitive to direct pickup from the adjacent transmitter. The two transducers should be separated physically. Even a physical barrier between the two might provide some improvement.

4) Watch out for gain-bandwidth limitations of the op-amp. 40kHz is getting up there where there is little gain available. You want to make sure that you are not inadvertently amplifying 60Hz instead of the desired 40kHz.

 

Try an HC-SR04. All the work is done for you, they are tried and tested, and cheaper than buying the parts to make your own.
https://www.amazon.co.uk/Xiton-Ultr...28&hvtargid=aud-857761465096:pla-817220254953

 

Try an HC-SR04. All the work is done for you, they are tried and tested, and cheaper than buying the parts to make your own.

True. But there is so much more one can learn by building it yourself.

 

True. But there is so much more one can learn by building it yourself.

I actually have a HC-SR04, I just want to build this project myself! I've got a nano controlling the 555 which turns the transmitter on for 10 pulses of 40 kHz.