Several circuits of musical car horn have been published in BEP but “Double tune car reverse horn” can generate two types of sounds- one a pleasant ‘ding-dong’ bell sound and the other a sweet chiriping sound of a bird.
Here the sound generator IC HT82D (IC1) whose operating voltage range is 2 to 5 volts. DPDT switch SW1 in the circuit selects the sound. When it is in top position, pin 9 of IC1 is connected to power supply (common poles of the witch are connected to each other), and a bird’s sound is generated. When SW1 is in bottom position, pin 10 is grounded, and a ‘ding-dong’ sound is generated.
After moving selector switch SW1, the push-to-on switch SW2 has to be operated .When SW2 is released the circuit switches off. Any low-voltage, 8-ohm speaker can be used. By using a 9-volt or 12-volt battery eliminator, the circuit can be used as a door-bell.
Readers are advised to ask for the ‘dual melody generator IC’ from the component shops to make this circuit because some dealers may not recognize it from its number HT82D.
Resistor (all ¼-watt, ± 5% Carbon)
R1 = 180 KΩ
R2 = 270 KΩ
R3 = 820 Ω
C1 = 100 µF/12 V (electrolytic)
C2, C3 = 0.1 µF (ceramic disc)
IC1 = HT82D (dual melody generator IC)
IC2 = 7805 (voltage regulator )
T1 = BC548B
T2 = SL100B
D1 = 1N4001
SW1 = DPDT switch
SW2 = Push-To-On switch
B1 = 12V car battery
LS1 = 8Ω, 0.5W loud speaker