Tag Archives: photoresistor

Seg 2: Characteristics of photoresistor

7.3 Characteristics of photoresistor

Before doing the experiment, we should understand the properties and principle of photoresistor. So, in the section, we will focus on the introduction to the characteristics of photoresistor.

  1. photoconductive effect

It is also called as photoelectronic effect, or photosensitive effect, and introduced by the Semiconductor materials conductivity change. That is, when the material absorbs the photon energy, which can generate the intrinsic absorption or impurity absorption. This would cause the change of the carrier concentration, and thus make the material conductivity change. This phenomenon is called the photoelectronic effect.

  1. express of photo resistor

The photoresistor is a resistor, whose value would be changed by the change of the strength of the incident light by use of the photoelectronic effect. Thus, it is also named as the photoconductive detector. More stronger of the incident light, the resistor value decreases; while weaker, the value of resistor increases. In addition, there exists another contrary change resistor, as shown in Figure 7-1. Generally speaking, its letter label can be written as “RL”, “RG”, or “R”.

  1. photoresistor (b) express of photoresistor

Figure 7-1 photoresistor and its express

  1. photoconductive material

Some materials have the photoconductive effect, such as Si, Ge, CdS, CdSe, PbS, and so on. The products generated from these materials can change the electrical conductivity along with the strength of the incident light.

Seg 1: How to use Arduino make a controllable LED light?

7.1 Problem: How to use Arduino make a controllable LED light?

In this experiment, we will use an Arduino board to make a controllable LED light, which let LED light bright and/or dark by the strength of light. This experiment is very usable. For example, when night is coming, we should let the street lamp light, and the lamp should be dark in the daytime for the energy saving. So, with respect to this experiment, we can make a light controllable lamp in our home. Similarly, we can also make voice controllable LED light.

7.2 The required materials

The required materials are also very simple in this example. On the basis of experiment, we just use photoresistor to replace the nixie tube, which are shown in Table 7-1.

The required materials


Name Quality Function Note


Arduino software 1 suit Provide ide New ver 1.05


Arduino UNO board 1 Control board Many


USB data line 1 Connect board distribution


Dupont line 2 Connect elements optional


Photoresistor 1 control optional


Bread board Connection optional