Infrared (IR) communication is a simple and widely used wireless method for short-range control. It is commonly used in TV remotes, air conditioners, audio systems and many DIY electronics projects.
IR is especially relevant for embedded systems because it is inexpensive, easy to implement and works reliably over short distances without radio interference.
What Is Infrared Communication?
Infrared communication uses light in the infrared spectrum to transmit data between a transmitter and a receiver.
A typical IR system includes:
- An IR LED transmitter
- An IR receiver module
- A microcontroller to encode and decode signals
IR signals are invisible to the human eye but can be detected by specialized receivers.
How IR Communication Works
IR remotes do not send a constant light signal. Instead, they use modulated pulses.
- A carrier frequency (commonly 38 kHz)
- Bursts of IR light represent data
- The receiver filters out ambient light
This modulation makes IR communication robust against normal lighting conditions.
Line-of-Sight Requirement
IR communication typically requires line of sight.
- Signals do not pass through walls
- They can reflect off surfaces
- Range depends on angle and obstacles
This is different from RF-based wireless systems like WiFi or Bluetooth.
Common IR Protocols
IR remotes use standardized protocols.
Common examples:
- NEC protocol
- RC5 and RC6 (Philips)
- Sony SIRC
These protocols define how bits are encoded into pulse sequences.
IR Receiver Modules
Most projects use integrated IR receiver modules.
Typical features:
- Built-in demodulation (e.g. 38 kHz)
- Digital output signal
- Noise filtering
Common modules include TSOP-style receivers.
IR vs RF vs Bluetooth
| Feature | Infrared | RF | Bluetooth |
|---|---|---|---|
| Range | Short | Short to medium | Short |
| Line of sight | Required | Not required | Not required |
| Interference | Low (filtered) | Medium | Medium |
| Typical use | Remote controls | Wireless switches | Device connectivity |
Typical Applications
- TV and media remotes
- Air conditioner control
- DIY remote control projects
- Learning IR codes from existing remotes
Using IR with Microcontrollers
Microcontrollers can easily decode IR signals.
Typical setup:
- IR receiver connected to a GPIO pin
- Library to decode protocols
- Optional IR LED for transmitting signals
This allows:
- Reading remote control buttons
- Controlling devices via IR
- Building universal remotes
Common IR Problems
- Wrong carrier frequency (e.g. 36 vs 38 kHz)
- Poor alignment between transmitter and receiver
- Strong sunlight interference
- Weak IR LED output
When to Use IR
- Short-range remote control
- Low-cost communication
- Line-of-sight operation is acceptable
When Not to Use IR
- Communication through walls is required
- Long-distance communication is needed
- Two-way communication is required
Conclusion
Infrared communication is a simple and effective method for short-range control systems. It is inexpensive, reliable and widely supported in consumer electronics.
For DIY electronics and embedded systems, IR is a great way to add remote control functionality with minimal hardware.