PAGE 023 OF 150 · COLOURS, SIZES & TYPES
Infrared LEDs
Infrared light is invisible to the eye but visible to many cameras.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Invisible light
Infrared LEDs emit light beyond human vision, commonly at 850 nm or 940 nm. Their forward voltage is low, about 1.2 to 1.6 V.
Uses
- TV and device remote controls, usually 940 nm
- Proximity and object sensors
- Night-vision illumination for security cameras, often 850 nm
Testing one
Point a remote at a phone camera in a dim room and press a button. Many phone cameras show a purple-white flash. An 850 nm LED may also show a faint red glow to the eye, while 940 nm is essentially invisible.
Use a resistor as with any LED, and avoid staring at strong infrared sources.
REMEMBER
Colour is set by the semiconductor material, not by the plastic lens.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
Explore LED clocks, stopwatches and electronics at cosycom.com.