Photoelectric sensor is a small electronic device, a key element to end the photoelectric conversion in various photoelectric detection systems. It is a sensor that uses the various properties of light to detect the presence or absence of objects and changes in the surface state. Photoelectric sensors are non-contact, fast responding, and reliable, so they are widely used in industrial automation equipment and robots.
First, the principle of photoelectric effect
Optoelectronic components are the most important components of photoelectric sensors, and their central operating principle is the different types of photoelectric effects. According to wave-particle duality, light is composed of photons moving at the speed of light, and when an object is irradiated by light, the electrons inside it absorb the energy of the photons and change their state, and their electrical properties will also change, which is called the photoelectric effect.
2. Classification of photoelectric sensors
Photoelectric sensors are divided into diffuse reflection type, reflective plate type, and through-beam type according to the detection method, and there are the following photoelectric sensors with different structures according to the corresponding detection methods:
1. Fork photoelectric sensor
Placing an optical transmitter and a receiver face to face at the opposite ends of a slot is a fork photonics. The luminaire announces infrared or visible light, and the light receiver receives the light unobstructed. However, when the detected object passes through the trough, the light is blocked, and the photoelectric switch is activated. Output a switch control signal, block or turn on the load current, and then end a control action. The detection distance of the slot switch is generally only a few centimeters due to the constraints of the overall structure.
2. Through-beam photoelectric sensor
If the luminaire and receiver are separated, the detection distance can be increased. The photoelectric switch composed of a light emitter and a light receiver is called a through-beam split photoelectric switch, referred to as a through-beam photoelectric switch. Its detection distance can reach several meters or even tens of meters. When using, the luminaire and the receiver are respectively installed at the two ends of the detector path, and the detector blocks the optical path during the passage period, and the receiver outputs a switch control signal on the action.
3. Reflector type photoelectric switch
The light emitter and the light receiver are installed in the same device, a reflector is installed in front of it, and the reflective principle is used to end the photoelectric control effect, which is called the reflector reflection (or mirror reflection type) photoelectric switch. Under normal conditions, the light announced by the luminaire is reflected back by the reflector and received by the receiver; Once the optical path is blocked by the detector and the receiver cannot receive light, the photoelectric switch will act and output a switch control signal.
4. Dispersion reflection photoelectric switch
It also has a light emitter and a light collector in the detection head, but there is no reflector on the front. Under normal conditions, the luminaire announces that the light receiver cannot be found. When the detected object blocks the light and partially reflects the light back, the receiver receives the light signal and outputs a switching signal.
The basic characteristics of the photoelectric sensor include the contact curve between the output current and the voltage at both ends of the receiver, the contact curve between the output current and the input current of the transmitter, the contact curve of the output current with temperature, and the impulse response characteristic curve. |
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