OUT, BUT NOT IMMEDIATELY

OFF, BUT NOT IMMEDIATELYOne of the inconveniences in the design of many cars is that the interior light goes out immediately when closing the doors. There are, however, a special device to delay the power light on 5-15 that the driver had time to explore the dashboard controls and to insert the ignition key. But these developments are usually complex and expensive. And reliability often leaves much to be desired.

Recommend to equip the car home, a circuit diagram is shown in illustrations, and problems, as they say, no.
 
When the doors are closed here contacts button ЅА1 — ЅА4 open. And because the interior lamp of car D1.1 is not lit. The capacitors C1 and C2 are charged via the circuit VD1 VD1 R3 and R2, respectively. At pin 3 of the chip DD1 has voltage logical “O”, and the transistors (VT1, VT2) are in the closed state.
When opening any of doors will close the corresponding contact (button ЅА1 — ЅА4). Lamp in the cabin immediately go into glow mode. When capacitor C1 begins to discharge through the circuit VD3R1SA, and the capacitor C2 through the circuit VD2R1 SA.
 
When closing the doors of the car open contacts ЅА1 — ЅА4. As a result, begin to charge the capacitors C1, C2 through the previously mentioned chain. But as the time of the charge at C2 much smaller than C1, at pin 1 of the chip will be logic level “1” and output 2 is logic “O”. So, at terminal 3 from DD1 to “1”. Transistors VT1 and VT2 are in the open state. And through the second continues to maintain the glow lamp НL1.
 
 
After charge of capacitor C1 on both the input circuits DD1 will be attending the logical levels “1” and output 3 to logical “O”.
 
As a result, the transistors VT1, VT2 are closed, the lamp goes out НL1.
during which lamp in the vehicle remains illuminated when the door is closed, is determined by the timing chain VD1R3С1. And it is about 10.5 s. the Desired time delay is achieved by selection of resistor R3 and capacitor C1.
 
When the doors are closed car, our home consumes several units of µa. Mounting it is simple. Moreover, due to the small number of parts used in the installation can be mounted. Types of resistors MLT; capacitors КЗ0-16 is designed for a voltage of 16 V. Special settings and adjustments the home requires.
 
V. PROKOPENKO,
Minsk

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