Light Sensor LDR (Light Dependent Resistor) is one type of resistor that can experience changes in resistance when experiencing changes in light reception. The amount of resistance value on the LDR Light Sensor (Light Dependent Resistor) depends on the size of the light received by the LDR itself. LDR is often called a device or sensor in the form of resistors that are sensitive to light. Usually LDR is made of cadmium sulphide which is a semiconductor material whose resistance varies according to the amount of light (rays) that hit it.
The LDR resistance in dark places typically reaches about 10 MΩ, and in the light of the LDR has resistance down to about 150 Ω. Like a conventional resistor, LDR mounting in a circuit is exactly the same as a regular resistor installation. The LDR symbol can be seen as in the following figure.
Application of LDR Light Sensor (Light Dependent Resistor) LDR Light Sensor (Light Dependent Resistor) can be used as:
- · Sensors on light switch circuit
- · Sensor on automatic light
- · Sensor on safe alarm
- · Sensors on the sun light tracker
- · Sensors in the direction of solar cell control
- · Sensor on line follower robot
And many more electronic circuit applications that use LDR (Light Dependent Resistor) as light sensor.
a. Characteristics of LDR (Light Dependent Resistor)
The LDR Light Sensor (Light Dependent Resistor) is a component form that has a change in resistance depending upon the amount of light. Characteristics of LDR consists of two kinds: Recovery Rate and Spectral Response as follows:
b. LDR Light Sensor Recovery Rate
When a “Light Dependent Resistor” LDR sensor “is brought from a room with a certain level of light power into a dark room, we can observe that the resistance value of the LDR will not immediately change its resistance to the dark room state. Na-mun LDR will only be able to reach the price in the dark after a certain time lapse. The recovery rate is a practical measure and an increase in the value of resistance within a certain time.
This price is written in K / sec. For LDR the current type is greater than 200K / sec (during the first 20 minutes starting at the 100v light level), the speed will be higher in the reverse direction, ie moving from dark to light takes less than 10 ms to achieve the appropriate resistance with 400 lux light levels.
c. Spectral Response of LDR Light Sensor (Light Dependent Resistor)
The LDR Light Sensor (Light Dependent Resistor) does not have the same sensitivity for every wavelength of light that falls on it (ie color). Materials commonly used as conductor of electric current that is copper, aluminum, steel, gold and silver. Of the five materials copper is the most abundant, used because it has a good hantaryang power.
d. Working Principle of LDR Light Sensor (Light Dependent Resistor)
The LDR Light Sensor Resistance (Light Dependent Resistor) will change with the change in the intensity of light that surrounds it or the surrounding. In a dark state the LDR resistance is about 10MΩ and in a bright state of 1KΩ or less. LDR is made from semiconductor binders such as cadmium sul-fida. With this material the energy from falling light causes more charge to be released or increased electrical current. This means that the resistance of the material has decreased.