Hi
i am working on yet another motion security unit that uses a smoke alarm beeper, however i did a stupid thing and threw the smoke alarm circuit away thinking i only needed the beeper (i was scared to keep the radioactive unit) i know they cant penetrate your skin but i was just cautious, anyway dose anyone know how much Voltage and Current they need to operate, i figured maybe 9V but i put a 9V battery on the +red and -black pos neg and it made a quick short "tik" then i take it off and put it back on and same thing.

Please help

Thanks, Chris

 

That's not a "beeper", it's most likely a piezo "speaker". You will need to drive it with an oscillator circuit.

Ken

 

Oh sorry i know it is a piezio electric sound generator and i may have thought it would need an oscillator, could you explain in more detail what kind, a 555 Timer, but with what time constant resistance X Capacitance

Thanks Chris

 

Here's one. http://www.geocities.com/tomzi.geo/whistle/whistle.htm. Thought it's designed for ultrasonic piezo transducers, by changing some component values you can use it with yours at audible frequencies.

2k2 > 1000Ω
1k2 > 1000Ω
4k7 > 20kΩ
10nF > 0.1uF

Ken

 

A piezo transducer (speaker) has a sharp resonant frequency that is affected by the size of the cavity of its enclosure. The oscillator must be tuned to the peak of the resonant frequency for the loudest sound or the most sensitive microphone.

 

OK Thanks heaps both of u now i dont only know how to use it i also know what it is, will try that circuit

Chris