ldr-simple tutorial

LDR - light dependent resistor or photo resistor

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A typical ldr looks like it

What is a Light Dependent Resistor?

An LDR or light dependent resistor is also known as photo resistor, photocell, photoconductor.It is a one type of resistor whose resistance varies depending on the amount of light falling on its surface. When the light falls on the resistor, then the resistance changes. These resistors are often used in many circuits where it is required to sense the presence of light. These resistors have a variety of functions and resistance. A typical light dependent resistor has a resistance in the darkness of 1MOhm, and in the brightness a resistance of a couple of KOhm.

• ldr will be apllicable for all light projects
• ldr will have so many types size
• you can buy it from your local electronic shops or online

The basic circuit diagram for ldr

Components :

1. resistor- 1k for handling LED  
2.  BC547 transistor 
3. preset 4.7 k or less than 1 k resistor (either preset or resistor)
4. preset will give flexibilty to adjust the resistance based on input 

it needs a minimum 3v or 9v power supply  

      Using microcontroller we can controll or take decision based on your projects.

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