LDR circit | Student Projects https://studentprojects.in Microcontroller projects, Circuit Diagrams, Project Ideas Sat, 02 Apr 2022 12:07:39 +0000 en-US hourly 1 https://wordpress.org/?v=6.1.7 Automatic Street Light Control System using LDR https://studentprojects.in/electronics/basic-electronics/automatic-street-light-control-system-using-ldr/ https://studentprojects.in/electronics/basic-electronics/automatic-street-light-control-system-using-ldr/#respond Sat, 02 Apr 2022 11:52:34 +0000 https://studentprojects.in/?p=8874 Here is a simple dark sensor circuit that is useful to switch ON and OFF any appliances automatically depending on the Light. As an output device, we’ll utilise a street lights/bulb in this example. If you are looking for LED as an output device, check this article. To detect the light, we will use an

The post Automatic Street Light Control System using LDR first appeared on Student Projects.

]]> Here is a simple dark sensor circuit that is useful to switch ON and OFF any appliances automatically depending on the Light. As an output device, we’ll utilise a street lights/bulb in this example. If you are looking for LED as an output device, check this article. To detect the light, we will use an LDR (Light-dependent Resistor). As the name says, when the light intensity on LDR is high, the resistance through it decreases; when the light intensity on LDR is low, the resistance through it increases and becomes extremely high. It’s a kind of variable resistor, but the resistance varies based on the light.

You must use a relay if you want to connect any heavy load. The Relay connection with the Dark Activated automated Light switch is shown in the circuit diagram below.

Circuit diagram

LDR Dark Sensor Circuit with Relay
LDR Dark Sensor Circuit with Relay

Components required

LDR
100k Ohm Potentiometer
BC547 Transistor
9V Battery
9V Relay
1N4007 Diode
Bulb with holder
Bulb with a holder

100k Ohm Potentiometer is a variable resistor that is used to change the trigger point for the LED. That is, how much light is needed for the LED to turn ON and OFF. You can also use a 50k Resister in the place of a variable resistor.

BC547 is an NPN transistor that is used to amplify the current. When there is a small current at its base, it controls the large current at its collector and emitter end.

BC547 Pin details

1N4007 is a PN junction rectifier diode. This allows only the flow of electrical current in one direction only. So, it can be used for the conversion of AC power to DC.

A relay is an electrically operated switch.

How does it work?

During the daytime when there is a light, the LDR has very low resistance and all voltage coming through R1 dropped with the ground. This makes the voltage at the base of the transistor very low and it will not switch ON the transistor. Because the transistor is OFF, the current will not flow through the transistor. As a result, the relay will not be switched ON and the bulb remains OFF.

At night when there is no light, the LDR has high resistance and very less power dropped with the ground. This makes the voltage at the base of the transistor high to turn the transistor ON. Because the transistor is turned ON, current flows through the transistor. It flows from the positive battery terminal, through R2, the relay, and the transistor down to the negative battery terminal. As a result, the relay turns ON and hence the bulb turns ON.

The same circuit can be used for a variety of purposes.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post Automatic Street Light Control System using LDR first appeared on Student Projects.

]]> https://studentprojects.in/electronics/basic-electronics/automatic-street-light-control-system-using-ldr/feed/ 0 Automatic night light using LDR https://studentprojects.in/electronics/basic-electronics/automatic-night-light-using-ldr/ https://studentprojects.in/electronics/basic-electronics/automatic-night-light-using-ldr/#respond Sat, 02 Apr 2022 11:20:45 +0000 https://studentprojects.in/?p=8847 Here is a simple dark sensor circuit that is useful to switch ON and OFF any appliances automatically depending on the Light. As an output device, we’ll utilise an LED in this example. To detect the light, we will use an LDR (Light-dependent Resistor). As the name says, when the light intensity on LDR is

The post Automatic night light using LDR first appeared on Student Projects.

]]> Here is a simple dark sensor circuit that is useful to switch ON and OFF any appliances automatically depending on the Light. As an output device, we’ll utilise an LED in this example. To detect the light, we will use an LDR (Light-dependent Resistor). As the name says, when the light intensity on LDR is high, the resistance through it decreases; when the light intensity on LDR is low, the resistance through it increases and becomes extremely high. It’s a kind of variable resistor, but the resistance varies based on the light.

Circuit diagram

LDR Dark Sensor Circuit

Components required

LDR
100k Ohm Potentiometer
BC547 Transistor
LED
1K Resistor
9V Battery

100k Ohm Potentiometer is a variable resistor that is used to change the trigger point for the LED. That is, how much light is needed for the LED to turn ON and OFF. You can also use a 50k Resister in the place of a variable resistor.

BC547 is an NPN transistor that is used to amplify the current. When there is a small current at its base, it controls the large current at its collector and emitter end.

BC547 Pin details

How does it work?

During the daytime when there is a light, the LDR has very low resistance and all voltage coming through R1 dropped with the ground. This makes the voltage at the base of the transistor very low and it will not switch ON the transistor. Because the transistor is OFF, the current will not flow through the transistor. As a result, LED will not turn ON.

At night when there is no light, the LDR has high resistance and very less power dropped with the ground. This makes the voltage at the base of the transistor high to turn the transistor ON. Because the transistor is turned ON, current flows through the transistor. It flows from the positive battery terminal, through R2, the LED, and the transistor down to the negative battery terminal. As a result, the LED turns ON.

The same circuit can be used for a variety of purposes. Check out the Automatic Street Light Control System using LDR application. Instead of LED, bulbs are used using a relay.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post Automatic night light using LDR first appeared on Student Projects.

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