Precautions and technical indicators for the use of photoelectric switches

Keywords: photoelectric switch photoelectric switch manufacturer photoelectric switch model photoelectric switch price photoelectric switch wiring diagram photoelectric switch principle photoelectric switch type photoelectric switch application

Photoelectric switch:

The photoelectric switch is the abbreviation of the photoelectric proximity switch. It utilizes the shielding or reflection of the light beam by the detected object, and the circuit is connected by the synchronization loop to detect the presence or absence of the object. Objects are not limited to metal, all objects that can reflect light (or block light) can be detected. The photoelectric switch converts the input current into a light signal on the transmitter, and then the receiver detects the target object according to the intensity or presence of the received light. The common photoelectric switch smoke alarm in the security system is often used in the industry to count the number of movements of the robotic arm.

Photoelectric switch model:

The photoelectric switch is a kind of sensor, which converts the change of the intensity of light between the transmitting end and the receiving end into the change of current to achieve the purpose of detection. Since the output circuit and input circuit of the photoelectric switch are electrically isolated (ie, electrically insulated), it can be used in many occasions. A new generation of photoelectric switch devices manufactured using integrated circuit technology and SMT surface mounting technology has intelligent functions such as delay, widening, external synchronization, anti-interference, high reliability, stable working area and self-diagnosis. This novel photoelectric switch is an active photoelectric detection system electronic switch that adopts pulse modulation. The cold light sources it uses include infrared light, red light, green light and blue light, etc., which can be non-contact and rapid without damage. And control the state and action of various solids, liquids, transparent bodies, black bodies, soft bodies and smoke. It has the advantages of small size, multiple functions, long life, high accuracy, fast response speed, long detection distance and strong resistance to optical, electrical, and magnetic interference.

Photoelectric switch manufacturers:

Use optical elements to change the light beam in the middle of the propagation medium; use the light beam to reflect the object; make the light beam return instantaneously after being emitted over a long distance. The photoelectric switch is composed of three parts: transmitter, receiver and detection circuit. The transmitter is aimed at the target to emit a beam, and the emitted beam generally comes from a light emitting diode (LED) and a laser diode. The beam is emitted continuously, or the pulse width is changed. The radiation intensity of the pulsed beam has been selected many times in the launch, and it runs towards the target without indirectly. The receiver is composed of a photodiode or phototransistor. In front of the receiver, optical components such as lens and aperture are installed. Behind it is the detection circuit, which can filter out the effective signal and apply the signal.

Working principle of photoelectric switch:

After the modulated pulse generated by the oscillation circuit passes through the reflection circuit, the light pulse is radiated from the luminous tube GL. When the measured object enters the range of the light receiver, the reflected light pulse enters the photosensitive transistor DU. The photoelectric switch demodulates the optical pulse into an electrical pulse signal in the receiving circuit, and then is amplified by the amplifier and synchronized gating and shaping, and then the interference is eliminated by digital integration or RC integration, and finally the driver is triggered by a delay (or no delay) Output photoelectric switch control signal. Photoelectric switches generally have good hysteresis characteristics, so even if the detected object shakes in a small range, it will not affect the output state of the driver, so that it can be kept in a stable working area. At the same time, the self-diagnostic system can also display the light receiving status and stable working area to monitor the work of the photoelectric switch at any time.

Types of photoelectric switches:

The amplifier separation type is to separate the amplifier and the sensor, and is made with a dedicated integrated circuit and a mixed installation process. Because the sensor has the characteristics of ultra-small and multi-variety, the amplifier has more functions. Therefore, this type adopts the terminal block connection method and can be used for both AC and DC power supplies. With on and off delay function, you can set the light and sound switch, can control 6 kinds of output states, and have two output modes of contact and level.

The built-in type of amplifier integrates the amplifier and the sensor. It is made by ASIC and surface mounting technology, and it works with DC power supply. Its response speed situation (there are two kinds of 0.1ms and 1ms), can detect small and high-speed moving objects. Changing the polarity of the power supply can switch between bright and dark movement, and can set a self-diagnostic stable work area indicator. Both voltage and current output modes can prevent mutual interference, which is very convenient in system installation.

The built-in power supply unit integrates the amplifier, sensor and power supply device, and is made with a dedicated integrated circuit and surface mount technology. It generally uses AC power and is suitable for replacing contact type limit switches at the production site, and can be directly used for strong current control circuits. You can also set self-diagnostic stable working area indicator lights by yourself. The output is equipped with SSR solid state relay or relay normally open and normally closed contacts, which can prevent mutual interference and can be installed tightly in the system.

Photoelectric switch price:

Strong light source: The photoelectric switch can generally work stably when the ambient illuminance is high. However, it should be avoided that the optical axis of the sensor faces strong light sources such as sunlight and incandescent lamps. When the angle between the optical axis of the sensor (receiver) and the strong light source cannot be changed, a light-shielding plate or a long light-shielding tube can be installed around the sensor.

Mutual interference: MGK series of new photoelectric switches usually have the function of automatically preventing mutual interference, so there is no need to worry about mutual interference. However, when several groups of HGK series through-beam infrared photoelectric switches are installed in parallel and close to each other, the adjacent groups and mutual interference should be prevented. The most effective way to prevent this kind of interference is to set the emitter and the receiver crosswise, and open the group distance when more than 2 groups. Different frequency models can also be used.

The effective way of HGK series reflective photoelectric switch to prevent mutual interference is to open the interval. And the farther the detection distance is, the larger the interval should be, and the specific interval should be determined according to the debugging situation. Of course, models with different operating frequencies can also be used.

Photoelectric switch wiring diagram:

The slot photoelectric switch is usually a standard U-shaped structure. The transmitter and receiver are located on both sides of the U-shaped groove and form an optical axis. When the detected object passes through the U-shaped groove and blocks the optical axis, the photoelectric switch The detected switch signal is generated. The slot photoelectric switch is safer and more suitable for detecting high-speed changes and distinguishing transparent and semi-transparent objects.

Optical fiber photoelectric switches use plastic or glass optical fiber sensors to guide light, so as to realize the detection of objects not in the vicinity. Generally, fiber optic sensors are divided into through-beam type and diffuse reflection type.

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Photoelectric switch article:

Photoelectric switches can be used in various applications. In addition, when using the photoelectric switch, you should also pay attention to the environmental conditions, so that the photoelectric switch can work normally and reliably.

(1) Matters needing attention:

1) Avoid photoelectric switches with strong light sources, which generally work stably when the ambient illuminance is high. However, it should be avoided that the optical axis of the sensor faces strong light sources such as sunlight and incandescent lamps. When the angle between the optical axis of the sensor (receiver) and the strong light source cannot be changed, a light-shielding plate or a long light-shielding tube can be installed around the sensor.

2) Preventing mutual interference The most effective way to prevent mutual interference is to cross the emitter and the receiver, and open the group distance when there are more than 2 groups. Of course, using models with different frequencies is also a good way.

3) The influence of the mirror angle When the measured object is shiny or encounters a smooth metal surface, the reflectivity is generally very high, and it has the effect of a mirror surface. At this time, the projector and the detected object should be installed at an angle of 10-20°. So that its optical axis is not perpendicular to the detected object, thereby preventing malfunction.

4) Eliminate the influence of background objects. When using a reflective diffuser, sometimes the detected object is close to the background, the photoelectric switch or the background is smooth and other objects with high reflectivity, which may make the photoelectric switch unable to detect stably . Therefore, you can switch to distance-limited projectors and receivers, or use methods such as staying away from the background object, removing the background object, painting the background object in matte black, or trying to make the background object rough and dark.

5) When the self-diagnostic function is used during installation or use, sometimes due to the influence of the table or background and the use of vibration, there may be problems such as slight deviation of the optical axis, lens contamination, dust, external noise, and ambient temperature out of range. . These problems may cause the photoelectric switch to deviate from the stable working area. At this time, the self-diagnosis function of the photoelectric switch can be used to notify the user through the STABLITY green stability indicator to remind the user to adjust it in time.

6) Eliminate the influence of the table surface. When the projector and the light receiver are installed close to the table surface, part of the light beam reflected by the table surface may illuminate the light receiver and cause unstable operation. In this regard, the light receiver and the light projector can be separated from the table at a certain distance and a light shield can be installed. Do not use chemicals such as thinner to avoid damage to the plastic lens. The wiring of the high voltage line, power line and photoelectric sensor should not be placed in the same wiring duct or wire slot, otherwise it will cause (sometimes) malfunction or damage of the photoelectric switch due to induction, so in principle, they must be wired separately.

The following places may generally cause the photoelectric switch to malfunction, and should be avoided as much as possible:

①Places with a lot of dust;

②Places with more corrosive gas;

③Places where water, oil and chemicals may splash directly;

④ Outdoors or places where there is strong direct sunlight without shading measures.

⑤Places where the ambient temperature changes beyond the specified range of the product;

⑥ Locations where vibration and shock are large, but shock-absorbing measures are not taken.

Photoelectric switch-technical indicators

Photoelectric switch plastic or metal housing, cylindrical, square, fork-shaped, glass or plastic optical fiber and other direct radiation systems, long detection distance, maximum 100m, accurate and reliable detection of opaque objects, good resistance to harsh conditions (dust, scattered light guide) reflection system detection The distance is medium, the maximum is 15m, and it is easy to install. It can detect opaque objects or non-reflective transparent objects; the polar reflection system can detect reflective objects. The diffusion system has a short detection distance, up to 2m, depending on the reflection coefficient of the object. It is easy to install and set up. Detection of transparent, reflective or semi-transparent objects requires a clean environment. The diffusion system with background suppression function is not sensitive to background objects. The detection distance has nothing to do with the color of the object. There are two methods: relay or solid-state output, and analog (4- 20mA) The optional functions of the special series of output products: time delay, separation amplifier, sensitivity adjustment and other three wiring methods: screw terminals, connectors, and cable leads. The highest protection level is IP67Design18, the most widely used standard in the market. The first generation Ø18 has a background suppression function.

Electric switch-related comparison

The difference between light control switch and photoelectric switch:

1. First of all, it can be determined that the light control switch is not a photoelectric switch.

2. The photoelectric switch realizes the control by converting the change of light intensity into the change of electric signal. It utilizes the shading or reflection of the infrared beam (distinguish point) of the detected object, and the presence or absence of the object is detected by the synchronization circuit. The object is not limited to metal, and all objects that can reflect light can be detected. In general, the photoelectric switch is composed of three parts, which are divided into: transmitter, receiver and detection circuit. According to different detection methods, infrared photoelectric switches can be divided into: (1). Diffuse reflection type photoelectric switch (2). Retro reflection type photoelectric switch (3). Through-beam type photoelectric switch (4). Slot type photoelectric switch (5) ). Optical fiber photoelectric switch

3. The light control switch, its "on" and "off" are realized by the conduction and blocking of the thyristor, and the conduction and blocking of the thyristor is affected by the brightness of natural light (differentiation point) (Or artificial brightness) controlled by the size. The device is suitable for street, dormitory corridors or other public places to control the lighting, so as to save electricity.

4. The environment in which the photoelectric switch is applied is an important condition that affects its long-term reliability. When the photoelectric switch is working at the maximum detection distance, the optical lens will be stuck by the dirt in the environment, and even be corroded by some strong acid substances, which will reduce the use parameter characteristics. But the light control switch is not affected by the index of "detection distance".

The difference between photoelectric switch and photorelay

The electric switch is a light pulse radiated by the luminous tube GL after the modulation pulse generated by the oscillating circuit passes through the reflection circuit. When the measured object enters the range of the light receiver, the reflected light pulse enters the photosensitive transistor DU. And in the receiving circuit, the optical pulse is demodulated into an electrical pulse signal, and then amplified by an amplifier and synchronized gating and shaping, and then the interference is eliminated by digital integration or RC integration, and finally after a delay (or no delay), the driver is triggered to output the photoelectric Switch control signal.

Photoelectric switches generally have good hysteresis characteristics, so even if the detected object shakes in a small range, it will not affect the output state of the driver, so that it can be kept in a stable working area. At the same time, the self-diagnostic system can also display the light receiving status and stable working area to monitor the work of the photoelectric switch at any time.

The working principle and characteristics of photoelectric relay. A relay is an electronic control device, which has a control system (also called an input loop) and a controlled system (also called an output loop). It is usually used in automatic control circuits. In fact, it uses a smaller current to control a larger An "automatic switch" of electric current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

The difference between photoelectric coupler and photoelectric switch

Photocoupler is what we call optocoupler. Its principle is to illuminate the transistor through the light-emitting diode so that the transistor is turned on and off short, and the luminous intensity is adjusted by adjusting the voltage of the diode, so that the current flowing through the transistor is changed, and light is often used. The lotus root is for feedback.

The principle of the photoelectric switch is similar, but it is only used as a switch, that is, when the light-emitting transistor is turned on, it needs a light-blocking thing, but it does not need to adjust the current size. It is generally used for general control. Precise hands.