LDR(Light dependent resistor) | Code | Circuit | Pin configuration

LDR- LIGHT DEPENDENT RESISTOR 

LDR can be called by different names such as a photoresistor, Photocells, Photodiode. But some other light detecting devices are also called with these synonyms, it is familiar with LDR. LDR’s are used to detect light intensity or measure the levels of light intensity. LDR is made from the Cadmium material (cds) because the spectral response curve closely matches the spectrum range of the human eye and even it can be controlled by normal light sources.

Model: LDR-5mm

Other names: Photodiode, Photo Resistor, Photocells, Light sensor.

Other devices: TSL2591, TEMT6000, TCS3200,SMD LDR. 

Light Dependent Resistor

LDR

Light source	Illumination(LUX)
Moon light	0.1
60w bulb at 1m(one meter)	50
1w MES bulb at 0.1m	100
Fluorescent lamp	500
Bright sunlight	30000

LDR types

LDR are sensors are available in different packages such as

5mm LDR, 10mm LDR, 20mm LDR, Photoresistor.

LDR pin configuration

In general, LDR is an analog sensor, It has two terminals and they have no polarities just like a general resistor that means you can connect in any direction. In the figure shown below the arrow mark inside direction indicates the light-absorbing property.

LDR_IEC_Standard_TechnoElectronics44

    

LDR_Symbol_TechnoElectronics44

                 

Technical specifications

Model	GL5528
Operating voltage	3.5 – 5v
Operating current	15ma
Light resistance at 10 Lux (at 25 ͦ C)	10 -20KΩ
Dark resistance at 0 Lux	1MΩ (min)
Temperature range	-30 ͦ C to 70 ͦ C
Material	Cadmium (cds)
Power dissipation	100mw
Maximum withstand voltage	150V  DC

How LDR works

The nature of LDR is it provides a large change in resistance with respect to the Light intensity.

                                    Light intensity α 1/Resistance of LDR

Light intensity and LDR resistance are inversely proportional if the light intensity decreases LDR’s resistance will Increases in the Darkness LDR has maximum resistance, range of several megaohms so it is called a light variable resistor.

DOWNLOAD:  DATA SHEET

How to use LDR

We know that it is just like a resistor, we called a photoresistor. So we can use in many ways in circuits like a resistor, but in application point of you, these are interfaced with microcontrollers, op-amps, and 555 timers.
            To perform the switching action(ON/OFF) of any load  LDR alone is not used, because it is an analog sensor the output voltage continuously varies with respect to light. So you have to convert analog to digital or use ADC(analog to digital converter).

• Design a digital output circuit, to give output either logic-0 or logic-1

LDR_circuit_TechnoElectronics44

LDR circuit

          Torch -ON     LED-OFF                      Torch -OFF     LED-ON

This type of interface is used to control the devices without a program or microcontroller, otherwise directly LDR modules with analog output and digital outputs are available.

LDR module is very easy to interface with any device because we can get digital data.

                                                                            

Pin configuration: LDR Module

• Vcc- power supply(5v pin)
• Gnd - Gnd
• A0-Analog output
• D0- Digital output

LDR Sensor Module has D0, A0 pins, we can use any of these two pins, if we want digital data D0 is used and if we want analog data A0 is used.  

LDR with Arduino

you can interface LDR with ADC pin(A0) of a microcontroller then you can use as shown below.

ARDUINO LCD CLICK HERE 

LDR_Arduno_Interface

LDR_Arduno_Interface_TechnoElectronics

Code

/***************************************************** # ADXL335 Example sketch follow us: www.technoelectronics44.com ******************************************************/ #include<LiquidCrystal>> const int rs = 2, en = 3, d4 = 4, d5 = 5 , d6 = 6, d7 = 7; LiquidCrystal lcd(rs, en, d4, d5, d6, d7); #define ldr A0 ///LDR CONNECTED TO A0 PIN #define led 13 int ldrvalue; void setup() { lcd.begin(16, 2); pinMode(ldr,INPUT); pinMode(led,OUTPUT); digitalWrite(led,LOW); lcd.print("LDR PROJECT"); lcd.clear(); lcd.print("LDR:"); } void loop() { ldrvalue=analogRead(A0); lcd.setCursor(4,0); lcd.print(ldrvalue); if(ldrvalue<900) { digitalWrite(led,HIGH); lcd.setCursor(0,1); lcd.print("LED ON "); } if(ldrvalue>900) { digitalWrite(led,LOW); lcd.setCursor(0,1); lcd.print("LED OFF"); } }

 

DOWNLOAD CODE

DATASHEET

Applications

• Mobiles automatic brightness control
• Home automation
• Streetlight automation
• Solar tracking

DATASHEET

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