How to create Schematic Circuit of Insect Repellant

 Some continuous sounds can repel insects (and also attract). The frequency

and intensity depends upon the application and type of insect and can be

found through experimentation.

The circuit shown here generates a continuous sound that can be used to

repel (or attract) some types of insects, or in scientific experiments involving

animals.

Our insect repellent can be powered by 9V batteries, two M cells or four AA

cells, and its low current requirements will extend the life of those cells or

batteries.

Figure I shows the schematic diagram of the lnsect Repellent. The heart of

the circuit is a 7555 lC, a CMOS timer wired as an audio oscillator and driving

a piezoelectric transducer.

The components placement on a homemade printed-circuit board is shown in

Figure 2. Exact placement is not that critical.

All the components and the power supply can be housed in a small plastic box.

Transducer BZ is a crystal earpiece or a piezoelectric transducer, such as the

Radio Shack 273-073.

Position of the polarized pieces, such as c2 and the power supply, must be

carefully observed.

Using the insect repellent is very easy. You only need to adjusthe trimmer

potentiometer P1 to produce a sound with the same pitch as the insect you

intend to repel. Experimentation should be made until you find the best sound

to repel a specific insect.

Parts List - Insect Repellent

c1     - TLC7555 CMOS integrated-circuit timer

   - Crystal or piezoelectric transducer

BZ       Radio Shack 273-073 or equivalent

R1       - 10,000 ohm, 114W,5% resistor

R2      - 4,700 ohm, 114W,5% resistor

P1      - 100,000 ohm trimmer potentiometer

C1     - 0.047 uF metal film or ceramicapacitor

C2     - 10 uF, 12 WVDC electrolytic capacitor

S1  - SPST slide or tdggle switch

B1  - 3V (2 AA cells), 6V (4 M cells), 9V (battery

Replace R2 by an LDR.The circuit now becomes a light-dependent

oscillator. Experiments with light and sounds can now be conducted

using the device.