Saturday, June 22, 2024

Dual-Tone Horn

This circuit generates two different frequencies and mixes these to produce a balanced ringing tone, which can be used in burglar alarms or call bells.

Fig. 1: Circuit for dual-tone horn
Fig. 1: Circuit for dual-tone horn

The circuit uses a dual-timer IC LM556 (IC1) and penta-watt audio power IC TDA2003 (IC2) (refer Fig. 1). Both the timers of LM556 are wired as astable oscillators to generate square waves. The first timer is configured to generate a 400Hz audible tone and the second timer for a 550Hz tone. The frequencies of both the oscillators are mixed and amplified by IC2. A higher frequency would result in shrill and unpleasant sound.

Fig. 2: Pin configuration of TDA2003
Fig. 2: Pin configuration of TDA2003

For better performance, the speaker should have a good-quality woofer with coil impedance of 4 ohms. Use a proper heat-sink for IC2. Adjust potmeters VR1 and VR2 to achieve a pleasant sound. Potmeter VR3 is used for volume control.

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Refer Fig. 2 for pin configuration of TDA2003. Connect the switches at the front panel and the speaker at the back side of the cabinet.



Unique DIY Projects

Electronics News

Truly Innovative Tech

MOst Popular Videos

Electronics Components