This project is a simple pest control upgrade for your loved backpacks.

The ultrasonic sound waves emitted is safe to humans and may offend pest such as rodents, mosquitoes and cockroaches.

Please see following instructions to see how the project was done.

Step 1: The Circuit

The circuit is basically a 555 timer configured as astable multivibrator.

Frequency calculated based from R1, R2 and C1 values is around 43-kHz (above human threshold of 20kHz).

The output of 555 timer is fed to a piezoelectric buzzer creating the ultrasonic effect. The circuit is powered by two CR2032 button cells connected in series providing 6V supply.

Step 2: Materials and Tools

Here are the tools and materials I used to complete this project:

Materials:

- 555 timer (IC1)

- 15k Ohms resistor (R2)

- 3.3k Ohms resistor (R1)

- 10nF mylar capacitor (C2 and C4)

- 1nF mylar capacitor (C1)

- 0.47uF electrolytic capacitor (C3)

- SPST Switch (SW1)

- Piezoelectric Buzzer (PS1)

- Key Chain (optional)

- Universal PCB

- Wires

- IC holders

- CR2032 Button cell and Holder

Tools:

Soldering Iron

Wire Stripper

Soldering lead

Hack saw (optional)

Step 3: Dry Fit the Components

Assemble the parts to the universal PCB. The circuit layout is dry fitted to maximized space that allow it to look like a small back pack tag.

Step 4: Assemble Components and Start Soldering

Solder the leads once installed to the PCB. Start with the small parts since it will be difficult for it to be soldered if the big parts comes first. Cut the excess leads of each component.