Here is a simple car reverse horn circuit that starts blowing the car horn whenever your car is in reverse gear. This circuit will produce a musical sound when ever your car is in reverse direction to alert the other vehicles.
As most of the people have their own vehicle so I suppose this circuit is very useful for them. This circuit will also avoid the chances of accident at blind turn, as speeding vehicle get a alert by hearing the musical sound that a car is taking reverse and he will slow its speed.
Fig. 1: Prototype of Car Reverse Horn Circuit on Breadboard
This simple circuit is based on melody generator IC UM66, transistor and few more components.
This car reverse horn circuit can be used with any vehicle having 12V battery.
Whenever user reverses its car, brake switch gets connected to power supply and circuit will get power supply for its working. And the transistor T4 connected through a diode gets power supply and start conducting.
We have to use diode D1 to protect the battery if connected with reverse polarity. And we have used a zener diode ZD1 to provide a regulated power supply to circuit as transistor T4 is a medium power npn transistor (excess voltage may destroy SL100). Now this will made the transistor T2 and T3 into conduction which is wired as a-stable multi-vibrator to generate the beeping sound which in turn amplify by transistor T1 and provided to a melody generator IC UM66 and a musical sound is heard.
For checking the circuit momentarily provide 12V from battery and if you are getting sound than your circuit is working properly. So when you reverse your car circuit gets 12V supply required for the operation of circuit.