Examples of applications of photoelectric sensors

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 to the target, blinding will make it 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.