Infrared photoelectric sensor principle - Solutions - Huaqiang Electronic Network

The transmitter is directed at the target, emitting a beam typically sourced from a semiconductor light source, such as an LED, laser diode, or infrared emitting diode. The beam can be emitted continuously or in pulses with varying widths. On the receiving end, the system includes components like a photodiode, phototransistor, or photocell. Before the receiver, optical elements such as lenses and apertures are often installed to focus and control the incoming light. After that, a detection circuit processes the signal, filtering out noise and amplifying the valid information for further use.

In addition to these core components, the photoelectric switch may also incorporate structural elements like a launching plate and optical fiber, which help in directing and managing the light beam more effectively.

The triangular reflector serves as a reliable and durable launcher. It features a small triangular pyramidal reflective material that ensures the beam is accurately returned to its source. This design is highly practical and allows for adjustment of the emission angle within a range of 0 to 25 degrees relative to the optical axis. As a result, the beam can return either along the same emission path after reflection or from the same reflective surface.

Classification and Working Methods

(1) Slot-Type Photoelectric Sensor: A slot-type photoelectric sensor is mounted on one side of a slot where the emitter and receiver are aligned face-to-face. The emitter sends out infrared or visible light, and the receiver detects it when the path is unobstructed. However, when an object passes through the slot, it blocks the light, triggering the photoelectric switch. This causes the switch to output a control signal, either cutting or activating the load current to perform a control action. Due to the physical constraints of the slot design, the detection range is usually limited to just a few centimeters.

(2) Through-Beam Photoelectric Sensor: When the emitter and receiver are separated, the detection distance can significantly increase. This type of sensor, known as a through-beam or off-beam photoelectric switch, consists of a separate emitter and receiver positioned on opposite sides of the detection area. When an object interrupts the light path, the receiver detects the absence of light and generates a switching signal. These sensors can detect objects from several meters up to tens of meters away, making them ideal for long-range applications.

(3) Reflective (Mirror) Type Photoelectric Switch: In this configuration, both the emitter and receiver are housed within the same unit, with a reflector placed in front of them. The sensor operates based on the principle of reflection. Normally, the light from the emitter is reflected by the reflector and received by the detector. However, if an object blocks the light path, the receiver no longer gets any light, causing the switch to activate and send a control signal.

(4) Diffuse Reflective Photoelectric Switch: This type of sensor also has both an emitter and a receiver in the same housing, but there is no reflector in front. Under normal conditions, the receiver does not detect any light because it is not reflected back. However, when an object enters the detection zone, it reflects part of the light back toward the receiver, which then triggers the switch to generate a control signal. This method is commonly used in applications where a reflector is not available or practical.

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