Application examples of photoelectric sensors

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:

Application 1: Barcode Scanner

When the scanning pen head moves on the bar code, if it encounters a black line, the light of the light-emitting diode will be absorbed by the black line, and the phototransistor will not receive the reflected light, presenting a high impedance and being in a cut-off state. When encountering the white interval, the light emitted by the light-emitting diode is reflected to the base of the photosensitive triode, and the photosensitive triode generates a photocurrent to conduct. After the entire barcode has been scanned, the phototransistor deforms the barcode into individual electrical pulse signals, which are amplified and reshaped to form a pulse train, which is then processed by the computer to complete the identification of the barcode information.

Application 2: Product counter

When the product is running on the conveyor belt, it continuously shields the light path from the light source to the photoelectric sensor, so that the photoelectric pulse circuit generates an electrical pulse signal. Every time the product is shaded, the photoelectric sensor circuit generates a pulse signal. Therefore, the number of output pulses represents the number of products. The pulse is counted by the counting circuit and displayed by the display circuit.

Application 3: Photoelectric smoke alarm

When there is no smoke, the light emitted by the light-emitting diode travels in a straight line, and the phototransistor does not receive a signal. When there is no output, when there is smoke, the light emitted by the light-emitting diode is refracted by the smoke particles, so that the triode receives the light, has a signal output, and sends an alarm.

Application 4: Measuring speed

Coated with black and white on the rotating shaft of the motor. When rotating, the reflected light and non-reflected light alternately appear. The photoelectric sensor correspondingly intermittently receives the reflected light signal, and outputs the intermittent electrical signal, which is amplified by the amplifier and the shaping circuit. The square wave signal is shaped and output, and finally the motor speed is output by the electronic digital display.

Application five: photoelectric detection and automatic control

When photocells are used as photodetectors, their basic principles are the same as photodiodes, but their basic structures and manufacturing processes are not exactly the same. Since the photovoltaic cell does not require an external voltage when working; it has high photoelectric conversion efficiency, wide spectral range, good frequency characteristics, low noise, etc., it has been widely used in photoelectric readout, photoelectric coupling, grating ranging, laser collimation, film sound recovery, etc. , UV monitors and flameout protection devices for gas turbines, etc.

Application 6: Applied to laser weapons

Since the photoelectric sensor is particularly sensitive to infrared radiation, or visible light, or both, it is easier to become a target of laser attacks. In addition, the electronic system and the sensor itself are extremely susceptible to the interference of thermal noise and electromagnetic noise generated by the laser and cannot work normally. The laser weapons on the battlefield attack the photoelectric sensor mainly in the following ways: Use a laser beam of appropriate energy to "blind" the sensor so that it cannot detect or continue to track the target that has been detected. Or, if the sensor is guiding the weapon towards the target, blinding will cause it to lose the target. In summary, because sensors play an increasingly important role on the battlefield, and at the same time are vulnerable to laser attacks, they have become the preferred target of low-energy laser weapons.

Application 7: Used to monitor smoke pollution

The photoelectric sensor is a small electronic device, which can detect the change of the light intensity it receives, and realize the control function by converting the change of the light intensity into the change of the electrical signal. Because photoelectric sensors have the characteristics of non-contact, fast response, reliable performance, etc., they are widely used in industrial automation devices and robots. We can use the characteristics of photoelectric sensors to detect smoke and dust, so the output signal of photoelectric sensors is strong or weak. It can reflect the change of flue turbidity.