This little device is a fun tool for pranking your friends and coworkers. Every few minutes it emits a brief, high-pitched beep. The beeping gets annoying after awhile, but what is really frustrating is not being able to find it. If you choose a good hiding spot, it can take hours to figure out where it is.
Step 1: Materials
3 Button cell Batteries (I used LR932 cells but other sizes will work)
Printed Circuit Board (RadioShack #276-159)
3-16V Piezo Buzzer (RadioShack #273-074)
100μF 10V Capacitor
555 Timer IC (RadioShack #276-1723)
The values of the capacitor and resistors are not critical. You can easily replace them with capacitors and resistors of similar values. The only effect will be that it changes the time between beeps. See Step 2 for a better explanation.
The PCB can also be replaced with any other PCB with enough holes to fit all the components.