This project produces sound like an ambulance siren. This can be attached to your car or by-cycle. This is a very low cost project and widely used in cars while reversing.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
This project employs the timer IC555. The project produces the sound like an ambulance siren. The current consumption of the project is very low. Two IC555 are utilized here in an astable mode. The output of the first IC is connected to pin no. 5 of other IC. As the first IC is in an astable mode, a clock pulse is released through its multivibrator action. This clock pulse is applied to pin no. 5 of other IC [It serves as control voltage input]. The first IC adjusts the reference level across the thureshold pin no. 6 and trigger pin no. 2. This level goes on varying in the other IC because of the multivibrator action of the first IC. As a result, the sound, like an ambulance siren is produced from the speaker. Its tone can also be varied through the preset.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*Check polarity of electrolytic condenser while assembling.
*Check polarity of condenser mike while mounting.
*Check the polarity [ Anode & Cathode] of Diodes before fitting.
*First of all check all the components as per circuit.
*Ensure that the transister BEL 187 connection [C,B &E]are proper and not altered.
*Use IC base for mounting of IC 555.
IC 555 = 2
IN4148 = 1
10MFD/25V = 1
220MFD/25V = 1
47MFD/25V = 1
820K = 1
4.7K = 1
1K = 2