Industrial and Consumer Applications for IR LEDs
投稿人:DigiKey 北美编辑
2025-07-02
Infrared waves are part of the electromagnetic spectrum, situated between the longer wavelengths of visible light and the shorter ones of microwaves. Invisible to the human eye but detectable as heat, infrared radiation (IR) covers the range between 760 nm to 1 mm. The IR band splits into additional components, including the near-infrared (NIR) range from 760 nm to 1400 nm (Figure 1).
Figure 1: The electromagnetic spectrum with the infrared region highlighted. The near-infrared spectrum occupies wavelengths between 760 - 1400 nm and is used in a variety of applications. (Image source: Broadcom)
How NIR applications work
NIR is especially useful because it facilitates wireless communication. In most applications, non-contact sensing using NIR works by pairing an IR emitter with a receiver.
A television remote control, for example, uses NIR radiation. When a button on the remote is pressed, internal circuitry converts the action into binary code and relays it to the IR transmitter. The transmitter then emits the encoded information as pulses of NIR light. At the other end, the paired sensor on the television receives the pulses and converts them back into binary code to execute specific commands.
The method by which applications use the transmitter-receiver combination can vary. As in the remote control example, the receiver decodes signals from the transmitter. In other cases, it can set off a trigger when the radiation gets blocked. Such interruption-based patterns find use in applications that detect persons or objects.
To avoid external signal interference, a receiver is designed to detect a specific wavelength, necessitating the need for the radiation transmitted by an emitter to have a matching, precise wavelength and sufficient intensity. The HSM8-C120 IR ChipLED Emitter (Figure 2) from Broadcom is an example of an NIR LED that can be used in various applications, including consumer electronics, smart meters, and more.
Figure 2: The HSM8-C120 ChipLED IR LED emitter from Broadcom offers a peak wavelength of 850 nm and has a compact footprint, making it well-suited for dense PCB circuitry. (Image source: DigiKey)
The HSM8-C120 is a side-emitting surface mount IR ChipLED with a small package footprint of 1.6 mm by 0.93 mm, making it suitable for a wide range of space-constrained applications.
It has an 850 nm peak wavelength, a 150° viewing angle, and is compatible with industry-standard automatic machine placement and IR reflow soldering.
Applications for NIR LEDs
Photoelectric smoke detectors - IR LEDs use the basic principle of object intrusion to detect the presence of smoke, utilizing an emitter and a photodetector in the same unit. Under routine operating conditions, the LED emits infrared radiation which causes the detector to produce an electrical current. The presence of smoke, however, disrupts the path of the radiation and scatters it. As a result, the net current registered by the photodetector decreases and triggers an alarm. IR LEDs are especially useful in this application due to their ability to penetrate smoke and detect smaller and denser particles.
Photoelectric smoke detectors are not the only kind in this category, such as those that measure air ionization levels. However, these are notorious for false positives. Triggers from cooking smoke are especially problematic, so smoke alarms in residential buildings must pass the “hamburger test,” which means they should not be triggered by the smoke from cooking. IR LEDs are resistant to the effects of kitchen smoke particles and therefore cause fewer false alarms. IR LEDs can also integrate with other systems, such as heat, gas, and airflow detectors, yielding more real-time information on hazardous situations.
Home appliances - In addition to their use in remote controls, IR sensors in washing machines can detect water levels, while robotic cleaners utilize IR sensors to avoid obstacles in the mapped path. Similar sensors in microwaves can detect an open door and issue alerts. Automatic faucets, soap dispensers, and hand dryers can all use the obstacle and proximity sensing capabilities of IR LEDs.
Safety light curtains - Worker safety is always critical when working with large or hazardous industrial equipment on the manufacturing floor, in warehouses, construction sites, or other industrial environments. Physical barriers can be bulky and laborious to set up, so IR LEDs—which are much lighter and more portable than physical barriers—offer an effective alternative. They can also be set up to accommodate a range of shapes and sizes, depending on the area that needs to be covered.
The IR LED safety light curtain (Figure 3) works on the principle of object detection to prevent mishaps. It consists of an array of IR LED emitters with photodiodes serving as receivers. The LEDs emit synchronized and parallel IR light beams, covering the entire area that needs to be monitored. As a result, the grid is bathed in IR light, which is modulated to a specific and unique frequency that the photodiodes detect. When the IR curtain has an object in its field, it likely indicates an unsafe situation and can trigger warnings. For example, if a hand or an arm enters the beam field, the machine can shut down automatically to prevent injury.
Figure 3: Safety light curtains, when operating without object interruption, emit and receive IR signals as shown on the left. When IR beams get disrupted by an object as shown on the right, an appropriate response can be initiated. (Image source: Broadcom)
Smart utility meters - The goals for energy conservation and responsible use include consuming only as much electricity as necessary. Smart utility meters play a significant role in such outcomes by enabling consumers to see their electricity usage in real-time, allowing them to adjust it accordingly. They also help detect leaks and faults more quickly, and assist in pricing utilities on a sliding scale according to peak-hour consumption patterns.
In smart meters, IR LEDs are used for bidirectional data transmission over short distances. IR LEDs transmit encrypted infrared light pulses, which are received by a photodiode on the data collection device. The pulses can relay a range of digital information, from energy consumption readings to diagnostic data. For added security, the IR pulses have a special signature that the detectors use for verification.
Conclusion
Whether it’s consumer appliances or relaying diagnostic data, the HSM8-C120 is particularly well-suited for designs that require a high-performance IR emitter. Its many advantages include a small footprint, efficient energy use, and a stable output.

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