Courtesy Light Extender


Posted on Feb 5, 2014

In essence, this circuit is a 15 to 20-second courtesy light extender for cars. It is activated in the usual way by opening a door but it also samples the negative lock/unlock signals from a car alarm or central locking and does two more things. First, when an unlock signal is received, it turns on the courtesy light for 15-20 seconds before you o


Courtesy Light Extender
Click here to download the full size of the above Circuit.

pen the door. Second, when a lock signal is received, it turns off the courtesy light immediately, with no fade-out. This is done to eliminate false triggering of the burglar alarm through current drain sensing. When a car door is open or the unlock relay is activated, the 33 µF capacitor discharges through diode D1 and this keeps transistor Q1 turned off. This allows Q2 and Q3 to turn on and the courtesy lamp is activated. When the door is closed, the courtesy lamps stay illuminated and the 33 µF electrolytic capacitor starts charging through the associated 1MO resistor. As the voltages rises, Q1 turns on slowly, turning off Q2 and Q3 which gradually fades out the courtesy lamp. If a lock signal from the central locking system is received, relay 1 closes and charges the capacitor instantly, so the lamp turns off immediately. Relays were used to interface to the central locking/alarm system as a safety feature, to provide isolation in case something goes wrong.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Closed-loop-motor-speed-control
    simple microphone preamplifier
    water activated alarm
    24V Battery Charger Schematic
    Audio Mixer Circuit
    Night Light schematic
    LS7263 Application Circuit Example
    CW117 CW217 CW317 charger has a current-limiting protection configuration
    HD a 3A limit energy-saving three-phase power protection circuit



    Top