The Advantages and Disadvantages of the LDR Sensors

 Owning very strong R&D Center, Senba can research and develop the passive infrared sensor independently. Among those motion sensor companies, Senba Sensor has become the first owner of this special technology enterprise in China. We are awarded as "Henan high-tech enterprises" in 2006 and awarded as "Notional high-tech enterprises" in 2012.

 

The Advantages and Disadvantages of the LDR Sensors

The working principle of LDR sensors is based on internal photoelectric effect. Difference between LDR and photodiode is formed by installing electrode leads at both ends of a semiconductor photosensitive material and encapsulating them in a shell with a transparent window. In order to increase the sensitivity, the two electrodes are usually made into combs.

 

Semiconductors such as metal sulfides, selenides and tellurides are the main materials used to manufacture LDR sensors. Usually, thin LDR sensors and comb-shaped ohmic electrodes are fabricated on insulating substrates by coating, spraying and sintering methods. Leads are connected and encapsulated in sealed shells with transparent mirrors to avoid dampness affecting their sensitivity.

 

When the incident light disappears, the electron-hole pairs generated by photon excitation will recombine, and the resistance of the LDR sensors will return to its original value. When the metal electrodes at both ends of the LDR sensors are applied with voltage, there will be current passing through them. When irradiated by a certain wavelength of light, the current will increase with the increase of light intensity, thus realizing photoelectric conversion.

 

The LDR sensor has no polarity. It is purely a resistor device. It can be used with both DC voltage and AC voltage. The conductivity of a semiconductor depends on the number of carriers in the conduction band.

 

Advantages of LDR Sensor

① The linearity of photoelectric conversion under strong illumination is poor.

 

② Photoelectric relaxation process is long, and the relaxation phenomenon of photoconductivity will happen: that is, after illumination, the photoconductivity of semiconductor increases gradually with illumination time, and reaches the steady state value after a period of time. The photoconductivity decreases gradually after the illumination stops.

 

③ The frequency response (the ability of the device to detect the fast changing optical signals) is very low.

 

The internal photoelectric effect has nothing to do with the electrodes (only photodiodes do), that is, DC power supply can be used.

 

Sensitivity depends on the semiconductor material and the wavelength of the incident light.

 

It is coated with epoxy packaging, and has good reliability, small volume, high sensitivity, quick response and good spectrum characteristic.

 

Disadvantages of Photoelectric Effect

① The linearity of photoelectric conversion under strong illumination is poor.

 

② Photoelectric relaxation process is long, and the relaxation phenomenon of photoconductivity will happen: that is, after illumination, the photoconductivity of semiconductor increases gradually with illumination time, and reaches the steady state value after a period of time. The photoconductivity decreases gradually after the illumination stops.

 

③ The frequency response (the ability of the ldr light dependent resistor to detect the fast changing optical signals) is very low.

 

It is affected heavily by the temperature and has a low response speed. The delay time between MS and S is affected by the illumination of the incident light (photodiode has no shortcomings, and photodiode sensitivity is higher than LDR sensor), which is a consumable material.

 

If you want to know more information including advantages and disadvantages of PIR sensor, you can click our official website.