How light curtain sensors work
The optoelectronic safety device emits infrared rays to generate a protective light curtain. When the light curtain is blocked, the device sends out light-shielding signals to control potentially dangerous mechanical equipment to stop working to avoid safety accidents. The installation of photoelectric safety protection devices can effectively avoid the occurrence of safety accidents, avoid the danger of workers and third parties, reduce the overall cost of the accident, and benefit the company itself, the workers and society. Light curtain sensors are mainly used in forging machine tool factories, automobile manufacturers, motorcycle manufacturers, electrical appliance manufacturers, hardware processing plants, plastic machinery plants, paper cutter applications and other industries.
Light curtain sensor features
Compliant with IEC61496-1 / 2
Synchronized violet or infrared scanning with mature technology, excellent optical performance and divergence angle of 2.5 °, easy to align and maintain
Small size, with aluminum alloy shell, very strong and light
20 / 40mm resolutions
Wide range of protection height: 4-128cm
Electrical connection. 4-pin M12 connector
Compact size OTDGM, the cross-sectional area of the series is only 25 × 25mm
Customizable resolution and protection width, as well as various other interfaces and extended functions
How light curtain sensors work
As shown in the figure above, it is a schematic diagram of the test principle structure using a safety light curtain to detect the entry of an object (such as a hand). In the figure, one side of the light curtain is equipped with multiple infrared transmitting tubes at equal intervals, and the other side has the same number of infrared receiving tubes in the same arrangement. Each infrared transmitting tube corresponds to a corresponding infrared receiving tube and is installed in the same On a straight line. When there are no obstacles between the infrared transmitting tube and the infrared receiving tube on the same straight line, the modulation signal (light signal) from the infrared transmitting tube can smoothly reach the infrared receiving tube. After the infrared receiving tube receives the modulation signal, the corresponding internal circuit outputs a low level. In the case of obstacles, the modulation signal (optical signal) sent by the infrared transmitting tube cannot reach the infrared receiving tube smoothly. At this time, the infrared receiving tube The tube cannot receive the modulation signal, and the corresponding internal circuit output is high. When there is no object in the light curtain, the modulation signal (light signal) from all infrared transmitting tubes can smoothly reach the corresponding infrared receiving tube on the other side, so that all internal circuits output low level. In this way, by analyzing the state of the internal circuit, information on the presence or absence of an object can be detected.
The maximum number of infrared transmitting and receiving channels of a safety light curtain can theoretically be 215. Considering the height of the actual light curtain and the distance between the upper and lower channels, it generally does not exceed 48.
The safety light curtain is divided into linear scanning mode and cross scanning mode. Under the linear scanning mode, the single-chip microcomputer sends the same path selection signal to the transmitting end and the receiving end each time, that is, the first way sends the first way and the second way sends the second way. Road collection, ... Fifteenth road sends 15th road collection, 16th road sends 16th road collection. In the cross-scan mode, the microcontroller sends different path selection signals to the transmitting end and the receiving end each time. That is, the first route sends the second route, the second route sends the first route, ... the fifteenth route sends the sixteenth route, and the sixteenth route sends the fifteenth route. In contrast, the cross-scan mode is more accurate in measuring the height of an object and has the highest detection accuracy at the center 1/3 of the detection area. The minimum detection height can be reduced to 2/3 in linear scanning mode. However, in consideration of practical needs, the linear light scanning safety light curtain is commonly used now.
How to use the light curtain sensor (example)
· Check whether the safety light curtain is firmly fixed on the equipment to be equipped, whether the transmitter and receiver of the TB series light curtain sensor are in the same plane, and the protection area bordered by the transmitter and receiver should be in the plane Of a rectangle
· Check whether the transmitter and receiver of the safety light curtain are accurately assembled with the respective cables and whether the cable terminals are accurately and firmly connected to the power supply and control unit
· Power on the safety light curtain sensor. At this time, the light curtain sensor starts self-test, synchronization and self-calibration. After about 1 second, the yellow indicator light on the transmitter is stable and the receiver indicator lights are all off, indicating that the light curtain sensor has entered normal work status
Safety light curtain sensor in working condition
1 . When there is no intrusive object in the protection area, the receiver of the sensor is in the light receiving state. At this time, the communication indicator (red light) of the receiver should be off, and the emission indicator (yellow light) should be on. Work switch, equipment can run normally
2. When an object (not less than the smallest detectable object or resolution) intrudes into the protection area, the red indicator light of the receiver will be lit (maybe the receiver is in a light-shielded state or the optical communication is blocked). The protected equipment is under control and in a forced halt state.
3. When the intruding object exits the protection area, the light curtain sensor will return to 1. state, and the device will continue to work.