How it works Light Sensor

                 One type is the light sensor LDR (Light Dependent Resistor). With this sensor, we could create a tool that deals with light like a clothesline automatic, tracking toward the source of light, automatic light (for the house, aquarium, etc), or as a regulator of light intensity to tananaman in the room, and much more. In the market there LDR measuring 4 mm and 11 mm. In Figure 6.1 are LDR with a size of 11 mm.

LDR 11mm 

                 LDR also called photoresistor because these tools will have a resistance that will change with changes in the intensity of the light that hits. In dark conditions, the resistance of LDR can reach 10 M ohm, but in bright conditions, LDR resistance down to 1 K ohm even smaller number (Figure 6.2 and 6.3). Nature is what makes LDR can be used as a light sensor.

                 LDR disc made of a semiconductor such as cadmium sulfide with two electrodes on its surface. At the time of the intensity of light incident on the LDR slightly, the material of the disc LDR generates free electrons with a relatively small amount. So there are only a few electrons to carry electric charge. This means that when the intensity of light incident on the LDR LDR bit will have a large resistance.

LDR resistance lighted

LDR resistance when the lights hindered paper

                 Meanwhile, when the light conditions, the intensity of the LDR lots. Then the light energy absorbed will make the electron move quickly so loose from the atoms of the semiconductor material. With so many free electrons, the electric charge is easier to pour. This means that when the intensity of light incident on the LDR LDR many will have a small resistance and become a good conductor.

                 The above image is the LDR resistance in conditions of light and dark conditions. In bright conditions, the resistance is still a range of 1K ohm, and when the little light is blocked so it was a bit dark, then the resistance increases to tens of kilo ohms. Characteristics of this is that we can use to activate the relay and turn on the lights.

Subscribe to receive free email updates: