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    This circuit project automatically turns on a night lamp when bedroom light is switched off. The lamp remains ON until the light sensor senses daylight in the morning. A super-bright white LED is used as the night lamp. It gives bright and cool light in the room. When the sensor detects the daylight in the morning, a melodious morning alarm sounds.

    The automatic night lamp circuit utilises light-dependant resistors (LDRs) for sensing darkness and light in the room. The resistance of LDR is very high in darkness, which reduces to minimum when LDR is fully illuminated. LDR1 detects darkness, while LDR2 detects light in the morning.

    Night lamp circuit how it works

    When LDR1 is illuminated with ambient light in the room, its resistance remains low, which keeps trigger pin 2 of IC2 at a positive potential. As a result, output pin 3 of IC2 goes low and the white LED remains off. As the illumination of LDR1’s sensitive window reduces, the resistance of the device increases.

    In total darkness, the specified LDR has a resistance in excess of 280 kiloohms. When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2 of IC2 via resistor R2 (150 kiloohms). This activates the monostable and its output goes high, causing the white LED to glow.

    LDR2 and associated components generate the morning alarm at dawn. LDR2 etects the ambient light in the room at sunrise and its resistance gradually falls and transistor T1 starts conducting. When T1 conducts, melody-generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts producing the melody. The musical tone generated by IC3 is amplified by single-transistor amplifier T2. Resistor R7 limits the current to IC3 and zener diode ZD limits the voltage to a safer level of 3.3 volts.

    The night lamp with alarm circuit can be easily assembled on a general-purpose PCB. Enclose it in a good-quality plastic case with provisions for LDR and LED. Use a reflective holder for white LED to get a spotlight effect for reading. Place LDRs away from the white LED, preferably on the backside of the case, to avoid unnecessary illumination. The speaker should be small so as to make the gadget compact.

    Night lamp with alarm circuit diagram

    night lamp alarm circuit schematic

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    26 Responses to "Automatic Night Lamp with Morning Alarm"

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    1. these are to good for lerning basics of electronics

    2. what is the use of 4 diodes forming a bridge?can we use IN4007 instead ofIN4001?

    3. jigar ladhani says: on January 26, 2011 at 6:43 pm

      Its too easy for me to find such extraordinary projects as i am a student.

    4. cyrell catequista says: on November 17, 2011 at 10:29 am

      your device is great though the circuit is quite simple.
      can we use solar power to supply the circuit?

    5. hey………its not working on pcb… as ldr is very sensitive, i tink it can b damage….can u tell me, how to check ldr working or not
      nw??

    6. why we use zener diode to limit voltage to 3.3volts???? Cant we use any ordinary diodes????

    7. bittoo sharma says: on March 25, 2012 at 10:08 pm

      becaus. the zener diode works in revers bias nd breakdown voltage. so the ckt. req. zener nt. silicon diode

    8. saurabh says: on April 7, 2012 at 12:59 pm

      I want block diagram of automatic night lamp with morning alarm

    9. Arnav Bansal says: on June 28, 2012 at 3:17 pm

      Can we use 560 ohm resistor instead of 580ohm?????????

    10. can we use circuit without transformers..

    11. what is the use of 4 diodes forming a bridge,, without that can be construct the circuit…

      • d 4 diodes forming a bridge can b avoided…. look at IC 7806… it gives d o/p voltage of around 6V…. so, we can do is jst connect 6 volt battery..

    12. whether the circiut can work for bulb with out any changes in the circuit

    13. What is the real value for IC1? says: on August 2, 2012 at 11:45 pm

      What is the value for IC1?

    14. Sir, IC UM66 is not avialable, can i found it inside a doorbell or melodous toy? says: on August 10, 2012 at 1:54 am

      Can i found IC UM66 inside a doorbell or any melodous toy?

    15. i need some explanation regarding to project automatic night dimmer with morning alaram. is there any website to search about this matter

    16. richard kabadi says: on July 17, 2013 at 10:19 pm

      can you tell me draw back of this project

    17. Hi,
      Can we use dc supply between 6 to 9 volts instead of using transformer and bridge rectifier?

    18. can i get the design specifications of all the components used

      • sorry joan..can you check in the market if um66 is available in your place..is it hard to find,,before you try to make it,,check it first,,ill do the same but it is hard for me to find that ic/..

    19. what ic or components can replace the um66 ic??this ic is not available in the market already,,can anyone help me to replace hat ic??thanks alot,,it will help me alot..

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