The Photo resistor module sometimes up to 1MΩ, but when the LDR sensor is exposed to light, the resistance drops dramatically, even down to a few ohms, depending on the light intensity. LDRs have a sensitivity that varies with the wavelength of the light applied and are nonlinear devices. They are used in many applications but are sometimes made obsolete by other devices such as photodiodes and phototransistors. Some countries have banned LDRs made of lead or cadmium over environmental safety concerns.
Widely used in cameras, solar garden lights, lawn, detectors, clock, music, cups, gift boxes, miniNight light, light voice switches, lights automatically switch toys and a variety of light control, light control lighting, lamps and other light automatic opening OFF control field.The photoresistor module is used to measure light intensity. It can determine
the presence or absence of light.
This module consists of a photoresistor and a 10 kΩ in-line resistor.
The photoresistors resistance will decrease in the presence of light and
increase in the absence of it. The output is analog and determines the
intensity of light.
Features of Photoresistor module
1. The photosensitive resistances can be divided into three type by their spectral
properties: UV resistance, infrared photosensitive resistance, visible light photosensitive resistor;
2. Main specifications are as follows:
2.1. Dark current and dark resistance: When photosensitive resistance is under a certain applied voltage and there is no light, the flowing current through it is called dark current. The ratio of the applied voltage and the dark current is called dark resistance;
2.2. Sensitivity : sensitivity is refer to the relative changed value from the resistance value off the light (dark resistance) to the resistance value under the light (light resistance).
2.3.V-A character curve: the volt ampere characteristic curve is used to describe the relationship between the applied voltage and the photo current of the photosensitive resistance. For the photosensitive elements, the photo current increases with the increase of applied voltage.
2.4. Temperature Coefficient: The temperature has a great influence on the photoelectric effect of the photosensitive resistance, photoelectric sensitivity of a part of the photosensitive resistances is high at low temperature, while it is low at high temperature.
2.5. Rated power: Rated power refers to the power allowed to be consumed in a certain circuit with the photosensitive resistor. When the temperature increases, its consumed power will reduce.
- dark current, dark resistance: photosensitive resistance at a certain applied voltage, when the light is not irradiated when the flowing Current is called dark current. Applied voltage and dark current ratio as the dark resistance;
- Sensitivity: Sensitivity is irradiated by light sensitive resistor, the resistance value (dark resistance) when irradiated with light Resistance value (light resistance) the relative change in values.
- volt-ampere characteristic curve. Voltage characteristic curves are used to describe the resistance of the applied voltage and the photosensitive photocurrent relationship, On the photosensitive devices, the light current with applied voltage increases.
- temperature coefficient. Photoelectric effect photoresistor affected by temperature, at a low temperature portion photoresistor photoelectric Sensitive high sensitivity at high temperatures is low.
- rated power. Photosensitive resistor rated power is allowed for certain lines in the power consumed when the temperature rise High, its power consumption is reduced.
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