preset time period.

The circuit is using two ICs and few discrete components. It can be easily fixed in the place of the car doom light. The circuit is also energy saver and eats less battery as compare to the doom lamp used in the cars. The project can also be used in any vehicle that uses a 12v car battery.

Working of the circuit

Working of the circuit is simple when the push button S1 is pressed the 555 timer is triggered for a preset time period, when the IC is triggered the output goes high due to which the transistor BD139 will become actuated and provides current to the LM2940CT-12 voltage regulator IC. This IC then provides stable 12v to the LEDs.

The preset time of the circuit or LEDs activation time can be increased by increasing the value of 47uf capacitor and adjusted by the 1M variable resistor.
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We often forget to turn off our car doom light that continuously eats battery and as a result the battery goes flat and till we come back its too late and the car doesn't start. The circuit shown here will solve this problem by disconnecting the doom light LEDs automatically from the car battery after a
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