How to Make LDR Darkness Sensor Circuit Simple DIY

Hello Friends

In this post we will see how to use LDR to make a Darkness sensor circuit.

Basically a darkness sensor circuit turn on a light in darkness and turn off light in brightness.

Step 1: VIDEO

Watch the video to know full procedure

Step 2: Component Required

1) LDR—–1No. http://amzn.to/2rNr33i

2) 50KOHM RESISTOR———1No.

3) 1KOHM RESISTOR———1No.

4) BC547 TRANSISTOR———1No. http://amzn.to/2rNxpjm

5) 9V BATTERY———1No.

Step 3: Circuit Diagram

Step 4: What Is LDR ?

LDR is a photoresistor is a light-controlled variable resistor.

The resistance of a photoresistor decreases with increasing incident light intensity,

in other words, it exhibits photoconductivity.

A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-activated switching circuits.

Step 5:

A photoresistor is made of a high resistance semiconductor.

In the dark, a photoresistor can have a resistance as high as several megohms (MΩ),

while in the light, a photoresistor can have a resistance as low as a few hundred ohms.

Step 6: BC547 Transistor

BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current. A small current at its base controls a larger current at collector & emitter terminals.

BC547 is mainly used for amplification and switching purposes. It has a maximum current gain of 800. Its equivalent transistors are BC548 and BC549. data sheet

Step 7: Procedure

Follow the step as shown in the Video

50K ohm resistor one end is connected with Positive (9V) of battery and other end is connected in series with LDR and LDR another point is connected with negative of battery

here in video I have used 2 100Kohm resistor in parallel because i dont have 50K one.

1K OHM resistor one end is connected with Positive (9V) of battery and other end is connected with anode (positive) of LED

Cathode (negative) of LED is Connected with C (collectr) of BC 547 Transistor

Emitter (E) of transistor is connected with the negative of battery

Base (B) is connected Junction point of the 50K resistor & LDR

it is a simple and powerful concept , which uses transistor ( BC 547 NPN) as a switch to switch ON and OFF the LED LIGHT automatically .
It automatically switches ON lights when the light goes below the visible region of our eyes. ( e.g in evening after Sunset ). it automatically switches OFF lights when light fall on it ( e.g in morning ) , by using a sensor called LDR (Light Dependent Resistor) which senses the light just like our eyes.

Comments

[Saalim bhat]

What if we have to increase the no. of led
Like if I add 2-3 more led .Do I have increase voltage of battery accordingly?
Please help

[Connor17S]

If I wanted to use a solar panel to charge the battery, what voltage solar panel should I use?

[Peter N]

How can I apply this to a grid support solar installation. To switch battery charging from solar panels source to grid source when sunlight is low and battery voltage down to low limits.

[bnmiweaver]

if you had a relay with the coil resistance of 1000 ohms use it in place of the resistor and the common to battery with normally closed to grid charger and normally open to
solar panels

[franksparacio]

what does circuit look like

[almamater]

Hello, thanks for your information. Just one question, there is any possibility to ADD one more Led at your circuit? but just for stay ON when there is light, when it darks then goes OFF and the other LED turns ON. Thanks

[Circuits Galore]

You can, but it will have to be using another photoresistor. You also must use another transistor.

[minionsraven]

What is the forward voltage and mA of the LED?

[st70891]

there is no 50k reistor

[shivanshnegi241]

Photoresistor's resistance get lowered when light of adequate freguency strikes on it.But in this circuit photoresistor is in reverse function.Why and how?

[Tanyike]

The direction you connect your resistor will determine if it will detect light or darkness
ie connecting a resistor before or after the LDR will give different results

[Crs17]

This job is done by the transistor.

[dipin.adk]

sir in replace of two 50kohm resistor i used 100kohm resistor it didnot work

[wayamanpaypal36922]

Sir it didnt Work.When it dark led is on And if we give a light led Off.Give Me what is the my mistake

[djsnowman06]

The circuit as drawn is a darkness sensor. Swap the position of the 50kohm resistor and LDR and it should light the led when it detects light.

[Samiksha.]

I want to connect a buzzer to the circuit such that when the LED glows the buzzer makes a sound.Where should I connect the buzzer in this circuit?

[MDM76]

I want LDR bout

[Omega35]

Listen , led as well as buzzer has both positive and negative pins , so in order to make them turn on at the same time just connect positive leg of the buzzer to where the positive leg of led is connected and do same with the negative leg also. You will get it working .

[sarims3]

can i have the block diagram

[Samiksha.]

In the components required please mention LED,Breadboard and connecting wires so that people can use it as a list while buying the components.