Φ7mm light dependent resistor sensor LDR for street lights control

Description:

Photo resistors, also known as light dependent resistors (LDR), are light sensitive devices most often used to indicate the presence or absence of light, or to measure the light intensity. In the dark, their resistance is very high, 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.

LDR sensor is a resistor which made of semi-conductor material, and the conductance changes with luminance variation. LDR sensor can be manufactured with different figures and illuminated area based on this characteristic. LDR sensor is widely used in many industries, such as toys, lamps, camera, etc.

Specifications:

Working principle:

when light falls on LDR i.e. when photons fall on LDR, valence band electrons get sufficient energy to get excited to the conduction band. Incident photons must have energy greater than the forbidden energy gap of the semiconductor. When light having enough energy falls on the device, more electrons will get excited to conduction band. As the number of free electrons increases, more current flows through the circuit. Hence it is said that, as light falls on LDR, resistance decreases.

Application:

There are many applications for Light Dependent Resistors. These include:

• Lighting switch

The most obvious application for an LDR is to automatically turn on a light at a certain light level. An example of this could be a street light or a garden light.

• Camera shutter control
LDRs can be used to control the shutter speed on a camera. The LDR would be used to measure the light intensity which then adjusts the camera shutter speed to the appropriate level.

Test condition:

• Light resistance: Irradiated by 400-600Lux light for two hours, then test with 10Lux under standard light source A (as colour temperature 2856K)
• Dark resistance: Refer to the resistance 10 seconds after the 10Lux light is shut up.

• γ value: Logarithm of the ratio of the standard resistance value under 10 Lux and that under 100Lux.
• R10, R100 are the resistances under 10Lux and 100Lux respectiverly.
• Max. power consumption: Maximum power at the environmental temperature 25℃.
• Max. external voltage: Maximum voltage to be continuously given to component in the dark.

Dimension:(mm)

Temperature-Property:

Spectrum Response Characteristic:

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