Monday, October 20, 2014

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How to Build Timer with Musical Alarm

The timer with Musical Alarm  use famous CMOS oscillator/divider IC (IC1 ). Although this circuit operates in 9V its standby current drain is very low. The time delay of timer circuit can be adjusted by adjusting the preset VR1. The base of npn transistor T1 is connected to pin 3 of IC1 through resistor R4 and its emitter terminal is connected with pin 2 of melody generator IC­ (IC2) in order to provide positive supply when adjusted time delay is over.

Timer with Musical Alarm Circuit Diagram

Here the zener diode ZD1 is used as regulator which reduce power supply to required for operation of IC2 i.e. 3.3V. Lastly for music output the output from pin 1 of IC2 is fed to loud speaker via driver transistor and its volume is controlled by preset VR2. For starting the timer power is supplied by pressing switch SW1. Link

Parts list

Resistor (all ¼-watt, ±5%)
R1 = 1.2 MΩ
R2 = 2.2 MΩ
R3 = 56 KΩ
R4, R5, R6 = 1 KΩ
VR1 = 1 MΩ
VR2 = 1 KΩ

C1 = 0.01 µF
C2 = 0.22 µF
C3 = 1 µF/25V

IC1 = CD4060 (CMOS oscillator /divider IC)
IC2 = UM66 (melody generator)
T1, T2 = BC547

SW1 = on/off switch
9V battery
LS1 = 8Ω, 0.5W speaker

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