Advantages of Photoresistor | disadvantages of Photoresistor

This page covers advantages and disadvantages of Photoresistor. It mentions Photoresistor advantages or benefits and Photoresistor disadvantages or drawbacks.

What is Photoresistor?

• It is a passive component which varies its resistance in response to the light.
• It is a disc shaped component with two leads as shown in the figure-1.
• When the light falls on the surface of the disc, resistance between the leads diminish (or reduce). In darkness, resistance as high as 10 MOhms and in bright light, resistance as low as 500 Ohms can be achieved.
• It is a passive component with no polarity.
• It represents equal resistance in both the directions and it can be used either with AC or DC.

Photoresistor construction

One of the applications of photoresistor is shown in the following circuit. Here it acts as variable resistor based on light intensity falling on it. The resistance of a photoresistor decreases with increasing incident light intensity. In other words, it exhibits photoconductivity. There are various circuit symbols of the photoresistor. Photoresistors of various sizes are available ranging from smaller one (5 mm in diameter) to larger one (25 mm in diameter). It can be used to generate variable voltage.

Photoresistor circuit

The term photocell was used formerly for photoresistor. The other names used for photoresistors are photoconductive cell, LDR (Light Dependent Resistor) etc.

Benefits or advantages of Photoresistor

Following are the benefits or advantages of Photoresistor:
➨It is replacement of variable resistance and also has dependency on the light. It's resistance decreases when light falls on it and increases in the dark.
➨Photo resistors are cheap and available in various shapes and sizes.
➨They require very small power and voltage for its operation.
➨It can be used to create simpler circuits.
➨It is bi-directional and hence can be connected in any direction.

Drawbacks or disadvantages of Photoresistor

Following are the drawbacks or disadvantages of Photoresistor:
➨Photoresistor is less sensitive to light compare to photodiode or phototransistor.
➨Cadmium sulfide used in photoresistor construction is hazardous to environment. Hence they are available only in selected countries.
➨If applied voltage exceeds rated maximum voltage of a photoresistor for short duration, it will cause irreversible damage to the photoresistor.
➨It is very accurate but it has very slow response time of about 10s or 100s of milliseconds.
➨It is temperature sensitive and bulky in size.
➨It has nonlinear characteristics.

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