Car reversing Horn

             Here is a simple circuit that starts playing the car horn whenever your car is in reverse gear. The circuit (refer Fig. 1) employs dual timer NE556 to generate the sound.  One of the timers is wired as an astable multivibrator to generate the tone and the other is wired as a  monostable multivibrator

To prepare a car reversing horn we need

• ON/Off switch 
• IC NE556
• Diodes
• Resistor
• Capacitor
•  load speaker (don't take loadspeaker of high rang ..take one which consume lower power and sound great )

           Working of the circuit is simple. When the car is in reverse gear, reverse-
gear switch S1 of the car gets shorted and the monostable timer
triggers to give a high output. As a result, the junction of diodes D1and D2 goes
high for a few seconds depending on the time period developed
through resistor R4 and capacitor C4. At this point, the astable
multivibrator is enabled to start oscillating. The output of the astable
multivibrator is fed to the speaker through capacitor C6. The speaker,
in turn, produces sound until the output of the monostable is high.
            When the junction of diodes D1 and D2 is low, the
astable multivibrator is disabled to stop oscillating. The output of the astable
multivibrator is fed to the speaker through capacitor C6. The speaker, in
turn, does not produce sound. Assemble the circuit on a general purpose
PCB and enclose in a suitable cabinet. Connect the circuit to the car
reverse switch through two wires such that S1 shorts when the car gear
is reversed and is open otherwise. To power the circuit, use the car
battery.


The want the circuitry of Flasher then see this " Flasher "

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