What is the role of photoelectric sensors?
Photoelectric sensor is a kind of small electronic equipment. It is the key element to realize photoelectric conversion in various photoelectric detection systems. It mainly uses various properties of light to detect the presence or absence of objects and changes in surface state. Photoelectric sensors are widely used in industrial automation devices and robots because of their non-contact, fast response and reliable performance.
Photoelectric sensor is a kind of sensor that uses photoelectric elements as detection elements. It transforms optical signals (infrared, visible and ultraviolet radiation) into electrical signals. It is the key element to realize photoelectric conversion in various photoelectric detection systems. Photoelectric sensor is generally composed of light source, optical path and photoelectric components. It first converts the measured changes into changes of optical signals, and then further converts optical signals into electrical signals by means of photoelectric components. A kind of
Photoelectric detection method has the advantages of high accuracy, fast response, non-contact, and many measurable parameters. The sensor has simple structure and flexible forms. Therefore, photoelectric sensors are widely used in detection and control. A kind of
It can be used to detect the non-electric quantity which directly causes the change of light quantity, such as light intensity, illumination, radiation temperature measurement, gas component analysis, etc. It can also be used to detect other non-electric quantity which can be converted into the change of light quantity, such as the diameter of parts, surface roughness, strain, displacement, vibration, speed, acceleration, shape and work of objects. State recognition, etc. Photoelectric sensors are widely used in industrial automation devices because of their non-contact, fast response and reliable performance. Recently, it has been widely used in laser weapons, automatic meter reading system, smoke and dust turbidity monitor, bar code scanning pen, product counter, photoelectric smoke alarm, speed measurement, photovoltaic cell application in photoelectric detection and automatic control, etc.
Photoelectric sensor is a sensor which uses photoelectric devices as conversion elements. It can be used to detect non-electrical physical quantities which directly cause the change of light quantity, such as light intensity, illumination, radiation temperature measurement, gas component analysis, etc. It can also be used to detect other non-electric quantities which can be converted into light quantity change, such as the diameter of parts, surface roughness, strain, displacement, vibration, speed, acceleration, and the shape of objects. Identify the working state, etc.
According to the different phenomena of photoelectric effect, photoelectric effect can be divided into three categories: external photoelectric effect, internal photoelectric effect and photovoltaic effect. Photoelectric devices include phototubes, photomultipliers, photoresistors, photodiodes, phototransistors, photovoltaic cells and so on.
In general, photoelectric sensors are composed of three parts: transmitter, receiver and detection circuit.
The transmitter aims at the target to emit the beam, which generally comes from semiconductor light source, light emitting diode (LED), laser diode and infrared emitting diode. Beams emit uninterruptedly, or change the pulse width. The receiver consists of a photodiode, a phototransistor and a photoelectric cell. In front of the receiver, optical elements such as lenses and apertures are installed. Behind it is the detection circuit, which can filter out the effective signal and apply the signal.
Application of Photoelectric Sensor
- Smoke and Dust Turbidity Monitor
In order to eliminate industrial smoke pollution and know the amount of smoke and dust emissions, it is necessary to monitor, display and alarm the sources of smoke and dust automatically. The smoke turbidity in flue is measured by the change of light in the process of transmission in flue. If the flue turbidity increases, the light emitted by the light source is absorbed and refracted by the dust particles, and the light arriving at the photodetector decreases. Therefore, the intensity of the output signal of the photodetector can reflect the change of flue turbidity.
- Barcode Scanner
When the scanning pen moves on the bar code, the light of the light emitting diode will be absorbed by the black line if it encounters the black line, and the phototransistor will not receive the reflected light, showing high impedance and being in the cut-off state. When encountering a white interval, the light emitted by the light emitting diode is reflected to the base of the phototransistor, which generates photocurrent and conducts.
After the whole bar code is scanned, the phototransistor transforms the bar code into an electric pulse signal, which forms a pulse train after amplification and shaping, and then is processed by computer to recognize the bar code information.
- Product counter
When the product runs on the conveyor belt, the light source is continuously blocked from the light path of the photoelectric sensor, so that the photoelectric pulse circuit generates an electric 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.
- Photoelectric Smoke Alarm
In the absence of smoke, the light emitted by the light emitting diode travels in a straight line, and the phototransistor receives no signal. No output, when there is smoke, the light emitted by the light emitting diode is refracted by the smoke particles, so that the transistor receives the light, has signal output, and gives an alarm.
- Measuring Speed
When the motor is rotated, the reflected light and the non-reflected light alternately appear. The photoelectric sensor receives the reflected signal of the light and outputs the intermittent electric signal. Then the square wave signal is amplified and shaped by the amplifier and shaping circuit. Finally, the electronic digital display outputs the s peed of rotation ofmotor.