Day and Night Indicator using IC 555

Day and Night Indicator using IC 555

Added by: Sydney

On: 12 Nop, 2018

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Category: Circuit

Day and Night Indicator using IC 555 Rating:
83 out of 100 based on 426 user ratings

The main aim of the Day and Night Indicator circuit is to help us to turn on the lights as the night falls automatically and as the dawn sets in the Day and Night Indicator automatically gets switches off the light and plays a musical morning wake...

The main aim of the Day and Night Indicator circuit is to help us to turn on the lights as the night falls automatically and as the dawn sets in the Day and Night Indicator automatically gets switches off the light and plays a musical morning wake up alarm. Another feature of the project is that at the time of no light in the room during night the night lamp gets turned on automatically. The main advantage of the project is that with the help of the circuit you are not required to switch on or off the lights in nights or in the morning. Isn’t it a stress free idea? Besides the above you also do not need to set morning wake up alarms. The only requirement of the project is to keep the circuit in a room where you get good amount of sunlight and then see the magic of Day and Night Indicator enfold.

The circuit of Dark and Light Indicator is  quite easy to understand. At the time of darkness, the output of LDR1 goes to high. And these high inputs are applied to IC1 NE555 at pin2 which shifts resistance of pin 2 of IC1 at high state. Due to this the resistance of pin 3 of NE555 switches to high. As a result of it, LED attached with pin 3 of IC1 glows. At the same time resistance of LDR2 is also at high state. Due to this reason transistor T1 whose base is connected with LDR2 remains in ideal. As a result of it IC2 UM66 which is connected with the collector of transistor T1 remains in the off state and no sound will be heard from the speaker.

But at the time when the room is full of light resistance of LDR1 move to low condition. Pin 2 of IC1 NE555 shifts into high state. Due to these high resistance outputs from pin 3 of IC1 NE555 moves to low state. Because of these low resistances, LED linked to pin 3 of IC1 LED would not blink. In the same condition when the room is full of light LDR2 resistance is also low. Due to these small resistances transistor which is coupled with LDR2 through its base begins it conduction. Transistor T1 gets power through power supply of 6V via its power supply. And the output of transistor T1 is given to IC2 UM66 via its collector terminal. IC2 UM 66 is a sound generating IC. The sound produced by IC2 is supplied to transistor T2. Transistor T2 is used to amplify the sound generated by IC2. Now these amplified sound signals is supplied to Speaker Sp which is connected with transistor T2 collector terminal. Resistor R6 in the circuit is used to limit the current passing into the IC3 while the zener diode of 3.3V is used to limit the flow of current.

The circuit works on 6V of power supply. Any color of LED can be used in the circuit depending upon its use.

You can connect a switch with speaker to switch off or switch on the alarm as per your need.

Components Used


IC1 (NE555)1

IC1 (UM66)1


T1, T2 (BC548)2




R1, R4 150K 2

R2 120K 1

R3 220E 1

R5 580E 1

R6 1K 1

R7 560E 1


C1, C2 0.01u 2

Zener Diode

Zd (3.3V, 0.5W)1


Sp (8E, 4.5W) 1


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