The safety light curtain is also the photoelectric safety protection device (also called safety protector, punch protector, infrared safety protection device, etc.). In modern factories, humans and machines work together on some potentially dangerous mechanical equipment, such as stamping machinery, shearing equipment, metal cutting equipment, automated assembly lines, automated welding lines, mechanical transmission and handling equipment, hazardous areas (toxic, High pressure, high temperature, etc.), it is easy to cause personal injury to operators.
Introduction to Safety Light Curtain
The safety light curtain is a safety-certified light curtain product, which consists of two parts. The emitter emits modulated infrared light, which is received by the receiver to form a protection net. When an object enters the protection net, when light is blocked by the object, through the internal control circuit, the receiver circuit immediately responds, that is, the output Part of the output is a signal for emergency braking of machine tools such as punches and presses. Light curtains have a very wide range of applications. For example, if a contact safety protection door is installed on a stamping equipment that requires continuous feeding and reclaiming, the operator needs to open and close the protection door frequently, which not only increases the workload of the operator, but also reduces Increased production efficiency. In this case, the use of gratings and light curtains is the best choice. When the operator is sending and reclaiming materials, as long as any part of the body blocks the light, it will cause the machine to enter a safe state without causing injury to the operator.
Safety light curtain detail drawing and bracket cable
The density of the light beam determines how large the body part can be detected through the light curtain. According to ergonomic data, the diameter of the fingers of an adult should be no less than 14mm, the thickness of the palm should be no less than 30mm, and the diameter of the wrist should be no less than 40mm. 20mm, its resolution is 40+20=60mm, then fingers, palms, wrists and arms may pass through the light curtain without being detected. Therefore, if you want to obtain higher security, you need to use a higher resolution light curtain.
When using gratings and light curtains, there are certain requirements for installation. People are not allowed to bypass the gratings and light curtains and enter the dangerous area, and it is also not allowed to have surfaces that reflect light near the gratings and light curtains so that the receiver can receive The safety switch signal cannot be output due to the reflected light. In addition, there are certain requirements for the use environment of gratings and light curtains. If the dust in the environment is too large, it will affect the emission of light, thereby affecting the use of gratings and light curtains.
Introduction to the working principle of safety light curtains
Introduction to the working principle of safety light curtains
As shown in the figure, it is a schematic diagram of a test principle structure that uses 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 emitting tubes at equal intervals, and the other side has the same number of infrared receiving tubes in the same arrangement. Each infrared emitting tube corresponds to a corresponding infrared receiving tube, and they are installed in the same In a straight line. When there is no obstacle between the infrared emitting tube and the infrared receiving tube on the same straight line, the modulation signal (light signal) sent by the infrared emitting tube can reach the infrared receiving tube smoothly. After the infrared receiver tube receives the modulated signal, the corresponding internal circuit outputs low level, and in the case of obstacles, the modulated signal (light signal) sent by the infrared transmitter tube cannot reach the infrared receiver tube smoothly, then the infrared receiver The tube cannot receive the modulation signal, and the output of the corresponding internal circuit is high. When there is no object in the light curtain, the modulation signal (light signal) from all the infrared emitting tubes can reach the corresponding infrared receiving tube on the other side smoothly, so that all the internal circuits output low level. In this way, the presence or absence of an object can be detected by analyzing the state of the internal circuit.
The number of infrared transmitting and receiving channels of the safety light curtain can theoretically be countless at most. Taking into account the height of the actual light curtain and the distance between the upper and lower channels, generally it will not exceed 48.
The safety light curtain is divided into linear scanning mode and cross scanning mode. In the linear scanning mode, the single-chip microcomputer sends the same path selection signal to the transmitter and receiver each time, that is, the first channel sends the first channel to receive, and the second channel sends the second channel. Road to receive… the fifteenth route to send the fifteenth route to receive, the sixteenth route to send to the sixteenth route to receive. In the cross scan mode, the single-chip microcomputer sends different channel selection signals to the transmitter and the receiver each time. That is, the first channel sends the second channel to receive, the second channel sends the first channel to receive,…the 15th channel sends the 16th channel to receive, the 16th channel sends the 15th channel to receive. In contrast, the cross scan mode is more accurate in measuring the height of the object, and the detection accuracy is the highest in the center of the detection area. The minimum detection height can be reduced to 2/3 of the linear scan mode. However, considering the actual needs, linear scanning safety light curtains are commonly used now.
Safety light curtain type
The light curtain is divided into optical synchronization and line synchronization. Optical synchronization means that the receiving and transmitting of the light curtain do not need any communication line connection. The emission emits infrared light according to the prescribed law, and the receiver receives the light signal and compares the emission. If the signals emitted by the transmitter are consistent, it means that the light curtain is not blocked at this time, and a light signal is output.
Safety light curtain selection
Step 1: Choose the safety level of the safety light curtain according to the degree of danger your equipment poses to people (in short: for major casualties, select level four or select level two for major casualties). The following figure shows the selection criteria of the security level
Step 2: Choose a foreign brand or a domestic brand according to your customer needs (or choose Level 4 or Level 2, which is a large portion of imported light curtains whose price is higher than that of domestic light curtains.)
Step 3: Determine the size of the safety distance (the vertical distance from the protective wall formed by the safety grating to the source of danger)
Step 4: Select the optical axis spacing. To protect fingers, generally choose 10mm spacing; to protect palms, generally choose 20mm; to protect feet or body, generally choose 40mm spacing. Of course, the above principles do not apply when the safety distance is large. The principle is that the equipment can be stopped before the human body reaches the source of danger.
Step 5: According to your protection height, select the appropriate number of optical axes (even numbers greater than 4) and then select the signal output (there are multiple signal outputs, PNP*2, NPN*2, relay, etc.)
Step 6: Choose the opposite beam distance (the cross-sectional size of the light curtain is small, and the beam beam distance is generally shorter, less than 3 meters; if the light curtain has a large cross-sectional size, the beam beam distance is generally longer, greater than 3 meters.
Step 7: Select the synchronization method between the emitter and the receiver (optical synchronization: there is no connection between the transmitter and the receiver, line synchronization: there is a wire connection between the emitter and the receiver.)
Step 8: Choose the structure type of the safety light curtain, whether to choose a larger or thinner one, and whether a safety light curtain without blind spots is required.
Step 9: Choose the installation method (multiple installation methods, L-shaped side installation, L-shaped top and bottom installation, steel pipe bracket method, end cover comes with installation holes, etc.)
Step 10: According to the environment in which your equipment is used, consider whether the safety light curtain needs to be anti-electromagnetic interference, anti-arc and laser interference, and sunlight interference, as well as waterproof and dustproof.
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