Overview: Why IR LEDs matter for projects
Infrared LEDs are the invisible workhorses behind common maker projects: proximity sensors, night-vision illumination, remote control transmitters, gesture detection, and short-range data links. For South African students, technicians and procurement teams, choosing the right IR LED changes a prototype into a reliable product - especially when availability, lead times and practical wiring matter.
Common applications and real-world examples
Use an 850nm LED for robust reflectance sensing in dusty industrial labs; pick a 940nm LED to avoid visible glow in consumer-facing devices. Example: a VEX-style robot arm with an 850nm array for close-range object detection will be easier to tune under shop lights than a 940nm array used solely with a matched photodiode and IR filter.
Standards, specifications and how to read a datasheet
Datasheets provide the few numbers you actually need: peak wavelength (nm), forward voltage Vf (V), maximum continuous forward current If (mA), radiant intensity or radiometric power (mW/sr or mW), and viewing angle (degrees). Use those to check electrical and optical compatibility with drivers, sensors and optics in your design.
| Spec | What it tells you | Practical tip |
|---|---|---|
| Peak wavelength (nm) | Sensor sensitivity match and visible glow | 850nm = slight purple glow; 940nm = nearly invisible |
| Forward voltage Vf (V) | Volt drop to size resistor or driver | Common Vf ~1.2V-1.5V for IR LEDs |
| Radiant intensity / mW | How bright IR illumination will be | Compare by viewing angle - narrow angle concentrates energy |
| Viewing angle (°) | Beam spread for illumination or sensing | Wide angle for flood illumination, narrow for spot sensing |
Practical spec comparison
| Type | Wavelength | Vf (typ) | If (max) | Use case |
|---|---|---|---|---|
| Through-hole IR LED | 940 nm | 1.2 V | 100 mA | Remote control, covert indicators |
| High-power IR emitter | 850 nm | 1.5 V | 500 mA | Night-vision illumination, machine vision |
| IR LED array (8×) | 940 nm | 1.2 V (per LED) | 30 mA (per LED) | Flood reflectance sensing |
Selection criteria: choose for compatibility and supply
Start with the sensor or camera: many CMOS cameras have peak sensitivity around 850nm-950nm, but response falls past 1000nm. Match your LED wavelength to the detector. Then match electricals: ensure your MCU, driver or transistor can supply the If you want, or use a constant-current LED driver for stable output and dimming.
Availability and local sourcing
Stock levels and lead times affect project timelines. Communica keeps a broad range of LEDs and arrays across categories you can browse in our buy-ir-leds-south-africa and the complete category index at ir-leds-in-stock-south-africa. For urgent pickup, check availability at the Samrand head office or view branch hours on the ir-leds-johannesburg page.
Electrical basics and formulas
Use Ohm's law to size a series resistor when driving an IR LED from a microcontroller pin or supply.
Basic formulas:
- R = (Vsup - Vf) / If
- P = V * I (for power dissipation in resistor or LED)
Example: 5 V supply, Vf = 1.2 V, desired If = 20 mA: R = (5 - 1.2) / 0.02 = 190 ohms. Choose nearest standard resistor and ensure resistor power rating P = Vdrop * I = 3.8 V * 0.02 A = 0.076 W (use 0.25 W or higher for safety).
