Fun and easy to build buzzer circuit

Posted on Feb 6, 2014

This circuit is an oscillator, and is able to generate a sound wave, a tone. The tone`s frequency (if it`s a high or low sound) is controlled by the variable resistor. The sound volume of this circuit is considerable so, don`t put your ear too close to the speaker on the first run The circuit can be used as a bell, a sound warning, small alarms, simple sirens, etc (leave your application

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ideas on the comments section at the bottom). When I was in high-school I made a game as a project for the Electricity course. I made that game where you have a twisted wire that runs inside a metal ring; the goal is to take the ring from one extreme of the wire to the other, without ever touching the wire with the ring. If the wire and ring touched, a bulb lamp would turn on. This was what my teacher allowed me to do, but a few hours before project delivery I built this circuit inside a cheese box and connected it in parallel with the lamp, adding a quite audible buzz to any game playing failure. My teacher didn`t comment on my work, but he spent about 15 minutes looking inside the cheese box :). The circuit is quite simple, consisting of only 7 components, including the loud-speaker (FTE1). The speaker must have an impedance of at least 8ohm (it is usually written in the speaker itself). You can get one of these speakers easily, but also scavenge them from old small pocket radios (maybe even found on the street) or a PC speaker  taken from an old PC. The speaker you can see in the photo below was taken from a toy given with a MacDonald`s Happy Meal! It`s a nice speaker, 8 ohms and 0. 25 W maximum power, excellent for small projects as this one. The values of variable resistor P1, capacitor C1 and resistor R1 define the tone`s frequency and are not critical. You can try other values for C1, bigger or smaller than...

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