Sunday, May 26, 2024

Musical Alarm Timer

A timer is a specialised type of clock for measuring time intervals. Here we present a simple musical alarm timer that can be used for that purpose. This low cost musical alarm timer can be used for introducing a delay of one minute to two hours. After the timing period is over, a musical song is heard.

Musical alarm timer circuit

The circuit is built around popular CMOS oscillator/divider CD4060 (IC1). It works off a 9V PP3 battery and its standby current drain is very low.

Fig. 1: Pin configuration of melody generator ICUM66
Fig. 1: Pin configuration of melody generator IC UM66

By adjusting preset VR1, the time delay can be adjusted. After time delay is over, output pin 3 of IC1 goes high and npn transistor T1 conducts to provide positive power supply to melody generator IC UM66 (IC2) at its pin 2. Zener diode ZD1 reduces this power supply to 3.3V required for operation of IC2.

The output of IC2 is fed to the loudspeaker (LS1) via driver transistor T1. Preset VR2 is used to control the volume of the loudspeaker.

Fig. 2: Musical alarm timer
Fig. 2: Musical alarm timer

The timer gets activated when power is supplied by pressing switch S1. To switch off the alarm, you need to switch off the power supply.

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The article was first published in October 2004 and has recently been updated.


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