Reading 40 KHz analog signal using Arduino

I am designing a 40 kHz Ultrasound detector. I used a piezoelectric transducer to detect the Ultrasound after that I used a bandpass filter centered around 40 kHz. I want to know how can I read this 40 kHz bandpassed signal using Arduino.

Exactly what information about the 40kHz signal are you interested in reading?
Paul

I just have to sense if 40Khz Ultrasonic Frequency is present or not. If present the send a SMS alert

Put the 40 kHz through a low-pass filter and use a comparator or opamp to get a "present" signal.

You can copy the circuitry from the receive side of the HC-SR04

http://www.pcserviceselectronics.co.uk/arduino/Ultrasonic/electronics.php#circuit

try NE567

If you are "rolling your own" ultrasonic detector one would assume you are going to "ping" the transducer (i.e. energize with 40Khz for a short period of time. Then stop, wait some milliseconds then listen for the return.

Is this what you are doing?

If so, you have to decide how much 40Khz return signifies a positive returned signal. Then the schematic @johnwasser provided would be your best bet.

I am designing a 40 kHZ Ultrasound detector using a Piezoelectric Transducer. I have used amplifier and Bandpass filter centered around 40 kHz. Now I want to convert this 40 kHz , 5V signal to DC signal to glow an LED and feed it to the analog pin of Arduino.

I want to know how to Convert 40 kHz , 5V signal to DC signal.

Hi @vassu_jaiswall.
Please, read How to get the best out of this forum

Give more details, you inform the frequency of the signal, but not the voltage level of this signal.

RV mineirin

hi @ruilviana
5V peak voltage AC Signal having frequency 40 kHz

I thought COVID was supposed to be associated with much higher frequencies than 40kHz.

(Edit: the new forum software seems to have swallowed my sarcasm tags)

1 Like

Hi @vassu_jaiswall

You can use a diode as a rectifier (or a bridge rectifier), an electrolytic capacitor maybe 10uf, and a 5V regulator like LM7805.
5V VAC rectified = ~ 7.01 VDC

RV mineirin

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Hi @ruilviana
What is the name of the 5V regulator component. That I can order online

Use a LM7805 .
What current will be drawn from this 5V DC?

I will use this 5V in Digital Pin of arduino to send an alert SMS

Ok so you can even use the LM78L05 which is small then LM7805.

@ruilviana
So from BandPass 40 kHz , 5V peak signal , I will use a Bridge Diode Rectifer and a electrolytic capacitor 10uf then LM7805 to get 5V DC to feed the Digital Pin of Arduino.
If 40 kHz frequency is present I will get 5V input to Digital Pin of arduino and if 40kHz frequency is not present then 0V is input to arduino.
Can you name the diode component so that I can buy that online.

Hi
A very common diode found anywhere is 1N4007.
But you can use any of these:
https://www.mouser.com/datasheet/2/149/1N4007-888322.pdf

RV mineirin

Before you get too far into ordering stuff, you might describe how many seconds the 40 kHz will last. With what you seem to be designing, it would have to exist for quite a few seconds to charge a 10 uf capacitor and the bypass capacitors for the LM7805.
Then it might take several seconds for the capacitor to discharge to the point that the regulator cannot maintain 5 volts.
Paul

thanks @ruilviana
I wanted to ask if there is a low voltage like 1V if 40 kHz frequency is not present then will LM7805 give voltage around 0V. So that I can use this logic in Digital Pin of Arduino