One of the disadvantages in the design of many cars is that the light in the cabin immediately goes off when closing the doors. There are, however, a special device for shut-off delay lighting 5-15 with that the driver had this is the time to view the dashboard, controls and insert the key the ignition. But these developments are typically complex and expensive. Yes and reliability often leaves much to be desired.
I recommend to equip the car with homemade, circuit diagram which is shown in the illustration, and problems, as they say, no.
When the doors are closed here button contacts SА1 - SА4 open. But because the lamp the interior light of the car H1.1 is not lit. Capacitors C1 and C2 are charged through circuit VD1 R3 VD1 and R2, respectively. At pin 3 IC DD1 there is a voltage logical "0", and the transistors (VT1, VT2) are in the closed state.
When opening any of the doors will close the corresponding contact of a button SА1 - SА4). The lamp in the cabin immediately go into a mode of illumination. Thus the capacitor C1 will be discharged through the circuit VD3R1SA, and the capacitor C2 through chain VD2R1 SA.
When closing the door of the car opens contacts SА1 - SА4. As a result begin charging the capacitors C1, C2 through the previously mentioned circuit. But as the charging time at C2 is much smaller than C1, then at pin 1 of the chip will be to present a logic level "1", and the output 2 is a logical "0". So at pin 3 DD1 is "1". Transistors VT1 and VT2 are in the open state. Moreover, through the second continues to be supported by the glow lamp НL1.
After charging the capacitor C1 on both input circuits DD1 will be present the logical levels "1" and the output 3 to a logical "0".
As a result, the transistors VT1, VT2 are closed, lamp НL1 goes out.
The time during which the lamp in the vehicle continues to glow after the door is not closed, is determined by the timing chain VD1R3С1. And this is about 10,5 C. the Desired delay time achieved by selection of resistor R3 and capacitor C1.
When the doors are closed car our homemade consumes a current of the order of several units μa. Its simple installation. Moreover, due to the small number used details of the Assembly can be mounted. Type resistors MLT, capacitors CS-16 designed for a voltage of 16 V. Special settings and adjustments not art project requires.
Author: Vladimir Prokopenko