In the fast paced world of education one often finds oneself with a burning hatred towards one or more teachers or fellow students. This article on Variable-Pitch Frequency Generator will describe how to build a little device that will emit a very high frequency noise that is -extremely- annoying to most people and it will wreck concentration and can cause some nasty headaches.
R1: 100k ohm Trimmer potentiometer
R2: 47k ohm resistor (5% tolerance)
C1: 4.7 uF Polarized electrolytic capacitor
C2: small disc capacitor (.001 uF or less)
SP: 8 ohm speaker. Piezo buzzers work best but you can use most any speaker for this job.
IC: 555 timer Integrated Circut.. Availible at Radio shack or any decent electronics store
Schematics for Variable-Pitch Frequency Generator:
Let’s start with a schematic of the device..
Okay. Now that we have the schematic out of the way we can discuss construction.. It’s best to use an 8-pin socket for soldering before you put the IC in.. You can put it on a small PC board or perfboard.. Use R1 (the potentiometer) to adjust the frequency from a high whistle to an instant migrane. If you find that the freqency is not as high as desired use a smaller capacitor for C2. The Idea here is to bring the frequency just below the highest frequency that can be perceived by the human ear. You will definetly know when you have acheived this! Once finished mount it in a project case with an on/off switch and you’re ready.
One particularly nice thing about this device is that if you set it to a high enough frequency it is almost impossible to locate once hidden.. So once you’ve found a suitible location put it anywhere were it can’t easily be seen and turn it on.. Guaranteed results! .. One little problem with this thing is that some teachers don’t seem to hear it (generally older teachers).. but anyone with a good set of ears will be driven crazy by it!! Including you if you place it in a room that you are planning to be in for any length of time.. So DONT. Now you know that building a Variable-Pitch Frequency Generator is not hard as it seems.. Have fun!