Simple Ultrasonic Mosquito Repellent Circuit

Mosquitoes are often seen as annoying little pests and they can be a big health threat because they spread diseases like malaria and dengue fever.

The main idea behind this circuit is that certain sound frequencies especially ultrasonic ones (which are above 20 kHz) can keep insects like mosquitoes away.

One effective way to repel these bugs is by using ultrasonic sound waves that disrupt their surroundings.

This simple Ultrasonic Mosquito Repellent Circuit is made to create ultrasonic sounds that mosquitoes find really uncomfortable making them want to leave the area.

The key part of this circuit is the CD 4047 integrated circuit, which generates high frequency sounds.

These sounds are then boosted by transistors which help a piezo buzzer produce the annoying noise that drives mosquitoes away.

Circuit Working:

Parts List:

The circuit diagram for a Simple Ultrasonic Mosquito Repellent Circuit shows some important parts like an oscillator, a transistor amplifier and a piezo buzzer that makes sound.

The main part of this circuit is the CD 4047 integrated circuit which is set up to work as an astable multivibrator.

This setup helps create a frequency that is in the ultrasonic range which is above 20 kHz.

This is done by choosing specific timing components VR1 preset and C1.

You can figure out the output frequency using the formula below.

To boost the signal from the CD 4047 pairs of transistors are used specifically Q1-Q2 and Q3-Q4.

The first pair Q1 BD139 and Q2 BD140 , works together in a push-pull setup while the second pair Q3 BD139 and Q4 BD140 does the same.

These transistors are really important because they make sure the frequency is strong enough to power the piezo buzzer.

The stronger ultrasonic signal then goes to the piezo buzzer which changes the electrical signal into sound waves.

The capacitor C2 included in the circuit to help keep the power supply steady and reduce any extra noise.

This whole circuit is made to work well when it gets power from a 12V DC source.

Formulas with Calculations:

Formulas with calculations for Simple Ultrasonic Mosquito Repellent Circuit is mentioned below:

Frequency Calculation:

The frequency of the astable multivibrator using CD 4047 is given by:

The output frequency can be approximately calculated using the formula:

f = 1 / (4.4 × R1 × C1)

Substituting the given values:

f = 1 / (4.4 × 10k × 4.7nF) f = 22.8 kHz

This frequency falls in the ultrasonic range, which is irritating to mosquitoes.

Capacitor Charging Time:

The charging time constant (τ) for capacitor C1 is given by:

τ = R1 × C1

Substituting values:

τ = 10k × 4.7nF τ = 10,000 × 4.7 × 10^-9 τ = 47 µs

Current through Transistors:

The transistor current can be approximated as:

I = V / R

If the supply voltage is 12V and assuming a load resistance of 1kΩ:

I = 12V / 1000Ω I = 12mA

How to Build:

To build a Simple Ultrasonic Mosquito Repellent Circuit following steps need to be followed to design you own circuit:

• Gather all the components mentioned in the above circuit diagram
• Connect pin 1 of IC1 CD 4047 to one end of C1 capacitor, and other end of C1 to one leg of VR1 preset resistor.
• Connect pin 2 of IC1 to center leg of VR1 preset resistor.
• Connect pin 3 of IC1 to third leg of VR1 preset resistor.
• Connect pin 4, 5, and pin 6 of IC1 to positive supply of 12V DC
• Connect pin 7, 8, 9 and pin 12 of IC1 to GND.
• Connect pin 14 of IC1 to positive supply of 12V DC.
• Connect pin 10 of IC1 between the base of transistors Q1 and Q2
• Connect pin 11 of IC1 between the base of transistors Q3 and Q4.
• Connect the collector pin of transistor Q1 and Q3 to positive supply and connect the collector of Q2 and Q4 transistor to GND.
• Connect the base of transistor Q1 to Q2 base, and connect the emitter of Q1 to Q2 emitter.
• Connect the base of transistor Q3 to Q4 base, and connect the emitter of Q3 to Q4 emitter.
• Connect one pin of piezo buzzer between emitter of Q1 and Q2 transistor, and second pin of piezo buzzer connect between emitter of Q3 and Q4 transistor.
• Connect a positive of capacitor C2 to positive supply and negative of capacitor to GND.

Conclusion:

This Simple Ultrasonic Mosquito Repellent Circuit is a easy but powerful way to keep mosquitoes at bay.

It uses ultrasonic sounds that are safe for both people and pets while making mosquitoes uncomfortable.

You can adjust the resistor and capacitor values to change the frequency, which helps make it even better at repelling mosquitoes.

This project is great for use in homes, offices and outside areas where you want to control mosquitoes.

References:

DESIGNING-AN-ELECTRONIC-MOSQUITO-REPELLENT-CIRCUIT