# Car central Light Dimmer

Posted on Jan 8, 2013

A useful operation for the cars is delayed extinguishing internal lighting cabin of passengers, after close some door of car. Certain cars allocate this operation from their constructor. Oldest sure do not allocate such operation. This delay makes this circuit. In the scheme appears the delay circuit as well as a typical circuit of connections of lamp L1, usually 12V 10W, with the switch S1 choice of lamp operation. In place A the lamp L1 remains continuously turned on, because the switch is in the place of 0V. In place B the lamp it remains off and in place C the lamp it turns on and she remains turned on all hour some door is open, hence somebody from the switches that are found in each door have closed have given the 0V in the lamp. If now the door close, the corresponding switch go open, but the C1 is already charge, discharge by the Q1 and makes the Q4 close.

Thus lamp its load anymore in the Q4 that follows the rhythm of C1 discharge. The time discharge of C1 depends from the resistance of TR1, with that we can change the time that will remain turned on the lamp L1 afterwards the close of some door of car. In a lot of cars the lamp L1 found in parallel connection with the indicative lamp, open door that is found in the automotive dashboard. Thus you will observe this indicative lamp remains also turned on afterwards the door close and follows the course of lighting of lamp L1. This is a " failing" of circuit. Transistor Q4 should be placed on one small piece of aluminum and it will be supposed insulated from this. The circuit after it is regulated with the TR1 in the time that you wish should insulated well, so that short-circuit his some point with the chassis of automotive and it is placed with small length of cables somewhere near in the unit of lamp L1. Q1-2=BC547B D2=1N4002 C1=47uF 25V Q3=BD140 R1-2=2.2Kohms 1/4W F1=Fuse 2A Fast Q4=BD243C R3=33Kohms 1/4W J1=2PIN Connector D1=1N4148 TR1=47ohmsK trimmer

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