The resistance value of LDR (Light dependent resistor) will change with light intensity about it or around it. In dark conditions the resistance of approximately 200KΩ and LDR in bright Around 500Ω. LDR is made from semiconductor materials such as cadmium sulfide. With this material the energy of the light that falls cause more load to the electric current is released or increased. This means that the material resistance has decreased.
LDR can be easily tested by using a multimeter. because the resistance of an LDR varies according to the light falling on it. At bright light, the LDR resistance will be around 500Ohms and at darkness the resistance will be around 200K. For a proper diagnosis we need to measure the resistance of the LDR at bright light and at darkness.
Gambar Cara Menguji LDR menggunakan Multi MeterKeep the multimeter at Ohms mode. The LDR must be subjected to a bright light source (day light is enough).Connect the LDR leads to the multimeter terminals as shown in the figure. Now the multimeter will show a low resistance reading around 500 Ohms.
When dark
Keep the multimeter at Ohms mode. The LDR must be subjected to darkness by covering it with an opaque paper. Connect the LDR leads to the multimeter terminals as shown in the figure. Now the multimeter will show a high resistance reading around 200K.
