What Is the Difference Between LDR and Photodiode?

LDR (photoresistor) and photodiode are two types of light sensors commonly used. When the LDR is exposed to light, its resistance changes. The photodiode, on the other hand, produces current when exposed to light. This is the main difference between LDR and photodiode.

What Is the Difference Between LDR and Photodiode?
11.03.2023
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LDR (photoresistor) and photodiode are two types of light sensors commonly used. Although the purpose of use is similar, both sensors have their own advantages and disadvantages.

LDR (Light dependent resistor) is a passive component used to detect the presence and level of light. The resistance of the LDR changes according to the intensity of the light falling on it. The amount of light falling on the surface of the LDR is inversely proportional to its resistance. In high light the resistance of the LDR is minimized, in the dark it is maximized. LDR has no polarity, equal resistance is measured in both directions.

Photodiode is a type of light sensor that can convert light into current. The photodiode allows current to flow when exposed to light. The current is directly proportional to the amount of light reaching the clear lens of the photodiode. In high light the current is maximum, in the dark it decreases to a minimum. The photodiode is directional as it works as a diode.

When the LDR is exposed to light, its resistance changes. The photodiode, on the other hand, produces current when exposed to light. This is the main difference between LDR and photodiode.

Photodiode is more sensitive to light than LDR. LDR is sensitive to light from all directions. The photodiode, on the other hand, is sensitive to light coming from a certain direction. The photodiode can measure very small changes in light intensity. A photodiode can also be used to detect different colors of light.

Photodiode is faster than LDR. It can react more quickly to light intensity changes.

LDRs are generally used in street lighting, night lights, solar powered systems, mobile phones, cameras. Photodiode is mostly used in smoke and fog detection devices, security systems, medical devices, optical communication equipment.

Emre Yılmaz, the founder of Lighting Portal, graduated from Atılım University Department of Electrical and Electronics Engineering in 2013, and since then has been involved in the management and product development activities of state-supported projects in the lighting industry. He completed his master's degree at Gazi University Industrial Design Engineering Department and continues his education in the doctorate program of the same department.
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