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Ultrasonic Lighting

web-craftWeb Craft wrote 10/09/2020 at 02:22 • 3 min read • Like

This article shows an ultrasonic sensor lighting system:

You can see my circuit working in this video:

I created this circuit after reading those articles:

https://www.instructables.com/Ultrasonic-Alien

https://www.instructables.com/Sound-Light-Robot



Step 1: Design the Circuit

I have drawn the circuit in the old PSpice simulation software (student edition version 9.1) to reduce drawing and simulation time.

The Rv potentiometer controls the brightness of the bright LED. The LEDs I used in my circuit might need a current of 20 mA. A typical LED consumes a current of 10 mA and has a potential voltage of 2 V across its terminals. High currents might burn the LED or reduce the LED's lifetime.

Although microphone circuits are always biased, most ultrasonic circuits do not bias the ultrasonic sensor. In my circuit, the DC current across the sensor is very small.

The Ri1 resistor is needed because the potential voltage across the ultrasonic sensor could be minimal (below 0.7 V) due to low resistance/impedance.

The LED will turn ON and OFF when the ultrasonic signal is applied.



Step 2: Simulations

Simulations show that my design is correct:

Time Domain Simulations:

Frequency Spectrum:



Step 3: Make the Circuit

You do not need to use the high-power resistors that I used. I used 1-watt resistors. You can use 1/4-watt resistors. However, you must admit that the circuit appears more professional with bigger resistors.

Second photo:

Step 4: Testing

I connected the ultrasonic transducer to Dick Smith Electronics FG-30 3 MHz Function Generator.

I adjusted the signal for maximum resonance and recorded the input signal applied to the ultrasonic transducer. I used a Hantek 6022BE USB Oscilloscope:

The measured frequency was 40.8 kHz and the peak-to-peak voltage was 9.6 V.

Testing showed that the circuit is receiving reflected and direct signals.


Conclusion

The circuit presented in this article is an ultrasonic detector. This circuit is not the best method of detecting ultrasonic signals. A better way would be to implement AC amplifiers rather than DC amplifiers. This way would can significantly increase the receiving range of the circuit (maximum distance from the transmitter to the receiver for detection).

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