Beeper & Buzzer Schematics

Posted on Feb 7, 2014

24v DC is a very popular voltage used in industrial settings. The circuit below was designed to accept four different 24v DC alarm input signals, which are then used to drive a single low power beeper. The beeper is a magnetic type with its own oscillator/driver. The four diodes form an OR  gate so

Beeper & Buzzer Schematics
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any one of the four inputs will cause the beeper to make noise. A CMOS version of the popular 555 timer is used to strobe the beeper on and off at about 1Hz. 3V Sweeping Siren Alarm - The circuit uses a LTC1799 precision frequency generator from Linear Technology. A 74HC14 hex Schmitt trigger from Texas Instruments is also used to perform several other functions. One section is wired as a simple 7Hz square wave oscillator. 555 Tone Generator 8 Ohm Speaker - This is a basic 555 square wave oscillator used to produce a 1 Khz tone from an 8 ohm speaker. In the circuit on the left, the speaker is isolated from the oscillator by the NPN medium power transistor which also provides more current than can be obtained directly from the 555 (limit = 200 mA). A small capacitor is used at the transistor. American Police Car Siren (linscott) - Scroll down to locate this circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is wired as a low frequency astable timer which generates a ramp waveform of about 6 seconds that is buffered by the transistor and again used to frequency modulate the tone generator. The transistor is used to help strengthen the signal to the speaker. Another Very Loud Piezo Alarm Beeper - This is yet another beeper circuit that really draws attention. It sweeps the drive frequency slightly to produce a very annoying sound. It uses a transformer to increase the drive...

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