Ldr is a type of resistor whose value changes depending on the light. The resistance value changes depending on the amount of light it is exposed to, that is, it gives a data output as a result of an external effect, therefore we can say that it is a passive sensor. When used with Arduino, you can use it in many projects such as a light-oriented robot, light detection or not, light-oriented solar panel, etc. Its width is 5mm.
The images above show how LDRs change their resistance value with light intensity and an example LDR circuit diagram. Below is an example connection diagram on how to use it with Arduino. It is the connection diagram of the LED flashing process with the data received from LDR.
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