LDR stands for the light-dependent resistor or a photoresistor is basically a resistor whose resistance decreases with an increase in incident light intensity(photoconductivity).
A photoresistor is made up of high resistance semiconductor material. If the light falling on the LDR is of high enough frequency and energy density, photons get absorbed by the semiconductor give’s band electrons enough energy to jump to the conduction resulting in free-electron conduct electricity lowering resistance.
LDR is made of Semiconductor materials with high Resistance like Silicon or Germanium. It is a light-sensitive device, so this resistor has a different resistance value in day and night as given below
Features:
- It requires less power to operate
- Quick Response
- Easy to use
- Generate high current
- Miniature open frame package.
- Epoxy coated.
- Moisture resistant.
- Spectral response is similar to the human eye
- Operating temperature: -30˚C ~ +70˚C
- Response time: 20ms (Rise), 30ms (Down)
Application:
- Camera Exposure Control
- Colorimetric Test Equipment
- Densitometer
- Automatic Gain Control
- Automated Rear View Mirror
- Automatic Headlight Dimmer
- Night Light Control
- Oil Burner Flame Out
- Street Light Control
- Position Sensor
- Auto Slide Focus – dual cell
- Photocopy Machines – density of toner
- Magnetometer
- Electronic Scales – dual cell
Parameters:
| Max power dissipation |
100mW |
| Max voltage at 0 lux |
150V |
| Peak wavelength |
480nm |
| Min. resistance at 10lux |
~8kΩ |
| Max. resistance at 10lux |
~15kΩ |
| Typ. resistance at 100lux |
~1kΩ – 3kΩ |
| (Dark) resistance after 1 sec |
~1MΩ |
| (Dark) resistance after 5 sec |
~2MΩ |
