G8MNY > TECH 11.12.18 11:00l 55 Lines 2279 Bytes #5 (0) @ WW
BID : 48944_GB7CIP
Subj: Delayed Interior Car Lamp
Sent: 181211/0952Z @:GB7CIP.#32.GBR.EURO #:48944 [Caterham Surrey GBR]
To : TECH@WW
By G8MNY (Correction Jan 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Here is a circuit I used, originally based on a Maplin kit.
WHAT IT DOES
It holds on the interior light for 20-30 seconds after opening the door, but
immediately turns it off if the Ignition Switch is turned on, or the car Alarm
D1 ³ ³ ³ ³
Arm Alarm +>Ä´>ÃÄ¿ ÃÄÄÄ´>ÃÄÄÄ´ ³ ³
ÃÄ4k7Ä´ D3 4k7 ³ ³
Ignition +>Ä´>ÃÄÙ ³ ____³ ____³ ³
D2 ³ ³/ ³ ³/ T2 ³ ³
ÃÄÄÄ´ T1 ÃÄÄ´ TAB ³ o /Door
3k3 ³\e ³/ ³\e ³/ / Switch
C ³+ ÀÄ´ ÀÄ´ ³
47u=== ³\e ³\e ³
6V ÀÄÄÄÄÄÄÄÄÄÁÄÄÄÂÄÄÄÄÙ ³
HOW IT WORKS
C is normally charged up to 1.2V & T1 darlington held on by the current through
the 1M, T2 power darlington (or VMOS FET) is held off.
Opening the door the lamp lights & C is discharged through D3 turning off T1.
Now on closing the door T2 is held mostly on (1.5V drop) through the 4k7 until
the C is charged up to 1.2V via the 1M. At C = 1.2V T1 is again turned on & T2
turned off. The addition of the 3k3 makes this a snappier action keeping T2's
If either the Ignition or Alarm circuits are powered while C is less than 1.2V
it will very quickly charge up & the light extinguished.
This circuit does not need power itself, only an earth, so the location is not
too critical. If switched power lines like the Ignition & Alarm are at risk
with this addition, consider putting a 4k7 in series with each wire so that
accidental shorts to earth can't harm anything.
Note this circuit draws about 2.2mA all the time, & although a very small
current it may add to other loads on a parked car battery!
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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