quartz controlled bedroom automatic light switch circuit schematic

Clock Alarm Controlled Light Switch

Here is an ultra simple automatic light switch circuit for bedrooms.
After construction, connect the input terminals of this circuit in parallel to the internal buzzer terminals of a Quartz-Alarm Clock. When the clock alarm is activated at a time set by the user, electromagnetic relay in the circuit is energised for a short duration, controlled by the timer IC 555.

Contacts of the relay can be used to switch on a bedlamp, table lamp or similar electric light loads. The circuit works off unregulated 12V.U se any12VDC/500mA rated standard ac mains adaptor.

When the clock alarm rings, input pulses are fed to the trigger input point (T1+Pin2) of IC1, through an RC filter (C1, R1&C2).

Here IC1 is wired as a monostable and dc voltage at its output (Pin 3) terminal goes high instantly after receiving a trigger,and remains in the condition for about 10 seconds, as configured by the components values of R3 and C3. Output from IC1 directly drives the low current relay RL1 through diode D1.

Note that diode D2 is here used as a freewheeling diode to suppress the counter emf generated during relay switching.

Clock Alarm Light Switch Circuit Schematic

quartz controlled bedroom automatic light switch circuit schematic


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  • Cassie

    It seems the diagram is for turning on the light. I need a circuit diagram that turns off the light. Can you please help me out? I’m doing a DIY project where I can turn off my lamp at a time set by my clock…, This diagram is useful, but the relay might not work on what I really wanted to have. Please help. Thank you.

  • Darren

    What is the meaning of rl

  • Timmy

    It was realy helpful

  • Timmy

    This is realy wonderful this website what i have being looking for.Sir i am a final year student doing my project but finding some difficulties in the circuit design, please sir if is not going to be too much troble can u help design a circuit that can close a relay for 8seconds and delay it for 52minute or 1hour the circuit should continue work for 12hour and stop.Thank u i wil be expecting your respond.

  • arya809

    It is a very useful circuit. But it is not working for me. I am using a common ‘Orpat’ alarm clock for input signals. How do i test my circuit with a multimeter?
    I have connected the cathode of diode D1 to pin 3 of IC, is it right?
    The ground connected to pin 1 is the negative terminal of adapter, right?
    Thanks in advance!

  • Bharath

    The circuit is so useful, congrats, but the there is no detail about how long the light will glow.

  • anoosha

    Is the output occur efficiently?

  • anoosha

    Is the output occur for this clearly?

  • ALI

    Thanks for ur contribution but plz iam using digital clock pezzo buzzer output for this circuit input but they can not worked plz tell me how this is possible that using digital clock pezzo output as input for circuit.


    Sir I want telivision circuits please

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