Automatic Door Lamp Timer Circuit

The article explains a simple automatic door light timer circuit which activates every time the door is opened, and switches OFF after a predetermined time if the door is kept open for too long. The circuit was requested by one of the avid readers of this blog, Mr. Juan. Let's learn more.

The Circuit Request:

I always find your blog very interesting.

I want to know if this would be possible

I have a cabinet in with I put a magnetic switch with normally closed and normally open contacts. (today, I only use one of them)

Today, when you open the door, the light that is on top turns on

I would change the circuit so that:

1. Open the door once so the circuit is ON, after a given time, the light turns off (although the door hasn't been closed and is opened). If I ever want to turn on the light, I have to close the door and reopen it.

2. add a LDR to turn on the light ONLY if there isn't sunlight in the room. With LDR in series with the load is enough?

The system is 12V. Should I use the famous 555? (all I've seen is with tiggers (push buttons), which is not my case)

Thank you.

 

The Circuit Design

Instead of 555 IC, a 4060 IC has been used here due to it's better accuracy.

The IC 4060 is configured in its standard delay timer mode, where the 1M pot and 0.68uF decides the length of the time delay.

The door switch is set in such a way that it closes when the door opens.

The 10uF capactor at the supply resets pin#16 so that the timer initiates the counting process from zero.

During this period pin#3 stays at logic zero, keeping the first BC547 switched off, which in turn switches ON the relay driver and the lamp.

If the door stays open until the timer delay lapses, pin#3 goes high switching ON the first BC547 and consequently switching OFF the relay driver and the lamp.

Also, at the same time the positive from pin#3 reaches pin#11 of the IC via the connected 1N4148 diode which latches the entire circuit.

This renders the lamp permanently ON,

In order to switch OFF the lamp, the door will need to be closed now.
An LDR at the base of the first transistor makes sure that this transistor switches ON when there's ample ambient light.

In the above situation the relay driver transistor is held switched OFF, which in turn keeps the lamp switched OFF.



20 thoughts on “Automatic Door Lamp Timer Circuit

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. Good Morning Sir, i have query, we have lift in our flat and the light in it always NO, can you give us a circuit to ensure the light is ON only when it is in use and switch off automatically when not in use, with little time delay for passenger to off load form the lift after reaching the floor.

    • It can be implemented through a simple relay driver stage having its own DC power supply, however triggering this circuit may be the difficult part, because the trigger input will be required to be derived from the lift electrical system…..from a point corresponding to the switching of the lift motor.

    • Yes, suggest a relay to be switched on by a darlington pare of transistor to be triggered from the DC voltage supplied to LED indicator light which would be on while the lift is in use. we can add an Capacitor for time delay in switching off.

      Pranav BM

    • You can make the circuit shown in the following link:

      https://www.homemade-circuits.com/2012/01/how-to-make-relay-driver-stage-in.html

      The input trigger can be taken from any of the lift LEDs which switches off when the lift is not in use.

      You will have to connect a 1000uF/25V capacitor across the outer free end of the transistor base resistor and ground for getting the desired time delay.

      The relay N/O contact should be wired in series with the mains AC and the associated lamp.

  3. Hi swagatam
    can you please design a circuit for me using 555 ic for 12v 7amp battery, i want 12 and 24volts, 1 and 2 amp that should last for about 4-5 hours
    regards

    • Make a coil of 10 turns of 22 SWG wire over a radio antenna ferrite rod, or any other similar ferrite core.Measure the voltage across the coil after powering the circuit with 12V, adjust the number of turns by increasing or decreasing it until it produces 24V.

      12V can be directly taken from the battery.

      You may clear your doubts here and learn gradually….

      Regards.

  4. Yes but i only want 12v and 1 amp how can i limit the current to 1 amp out of a 12v 1 amp battery without any or less loss plz help me
    regards

  5. sir, can yo give a circuit using 555 as a timer to switch on after 5 minutes from the time the power is connected. not a push button type



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