Message:23089 In: TECH.WW
From: G8MNYDate: Tue, 26 May 26 06:42:00 Z
Newsgroups: TECH.WW
Subject: Delayed Interior Car Lamp
Message-ID: <60786_GB7CIP>
Path: N2MH4|GB7BED|GB7YEW|GB7CIP
R:260526/0652Z 31670@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260526/0651Z 11952@GB7BED.#21.GBR.EU LinBPQ6.0.25
R:260526/0651Z 18891@GB7YEW.#79.GBR.EURO LinBPQ6.0.24
R:260526/0642Z @:GB7CIP.#32.GBR.EURO #:60786 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
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
is armed.
ÂÄ+12V
Lamp
³ 1A
ÚÄÄÄÄ1MÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄ>Ä´
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
_³_ _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 and 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 and
T2 turned off. The addition of the 3K3 makes this a snappier action keeping
T2's heating down.
If either the Ignition or Alarm circuits are powered while C is less than 1.2V
it will very quickly charge up and the light extinguished.
LOCATION
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, and 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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