Safety Light Curtain Troubleshooting: Common Faults and Solutions
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- Issue Time
- Jun 14,2025
Summary
Solve safety light curtain problems with our expert guide. Learn to fix power issues, cable connections, beam obstructions, and more to ensure workplace safety.
In the industrial production process, safety light curtain play a vital role. They can effectively protect the personal safety of operators and prevent accidents. However, even the most advanced equipment may have some faults during operation. This article will introduce the common faults of safety light curtains and the corresponding solutions to help you with safety light curtain troubleshooting and ensure the normal operation of the equipment.
Power Issues
Check the power supply: First, confirm whether the power supply of the machine safety light curtains is normal. Use a multimeter to measure the power output voltage to ensure that it meets the voltage range required by the equipment. For example, the light curtain safety system of DADISICK usually requires a power supply voltage of about 24VDC.
Check the power cord: Check whether the power cord is loose, damaged or aged. If the power cord is damaged or has poor contact, replace it or repair the connection in time.
Check the power supply device: If the power output voltage is abnormal, the power supply device itself may be faulty and the power module or related components need to be replaced.
Cable Connection Problem
Check whether the cable connections are firm: Check whether the cables between the muting safety light curtain and the safety light curtain controller and power supply are tightly connected one by one, and whether there are any loose or detached connectors. If any looseness is found, re-plug the cable to ensure a firm connection.
Check the integrity of the cables: Check whether the cables are damaged, broken or aged. If there are damaged cables, they need to be replaced in time to avoid interruption or interference of signal transmission.
Light Curtain Transmitter and Receiver Issues
Check for beam obstruction: Check whether there is dust, oil, debris or other obstacles on the beam path of the type 4 safety light curtain. If there is any obstruction, use a clean soft cloth dipped in an appropriate amount of detergent and gently wipe the lenses of the transmitter and receiver to remove the obstruction.
Check alignment: Make sure the light beam between the optical transmitter and receiver is aligned correctly. Readjust the position of the transmitter and receiver to align the beams If the optical axis is offset. You can use specialized tools or manual fine-tuning, observe the indicator lights, or use detection equipment to determine the alignment.
Check the safety light curtain emitter and receiver components: Use tools such as photoelectric detectors and oscilloscopes to test whether the optical emitting and receiving devices are working properly. If the light emission intensity is insufficient or the receiving sensitivity is reduced, it may be that the photoelectric device is aging or damaged, and the corresponding parts need to be replaced.
Environmental Interference Issues
Check for light source interference: Check whether there are interference sources such as strong direct light, welding arc, reflective objects, etc. around the safety light curtain. If so, you can avoid strong light interference by adjusting the installation position and angle of the light curtain, or adding hoods, baffles, etc.
Check electromagnetic interference: Check whether the electrical equipment near the light curtain, such as motors, inverters, welding machines, etc., generates strong electromagnetic interference. If necessary, use shielded cables for the signal lines of the infrared safety light curtain and ensure that the shielding layer is well grounded to reduce the impact of electromagnetic interference.
Safety Light Curtain Controller and Parameter Setting Issues
Check the controller connection: Confirm whether the output signal line of the safety light curtain is correctly connected to the input port of the controller, and whether it is loose or damaged. If there is a problem with the connection, reconnect or replace the signal line.
Check parameter settings: Check whether the safety light curtain parameter settings in the controller are correct, such as sensitivity, response time, measurement mode, etc. Adjust the parameter settings reasonably according to the device's instruction manual and actual application requirements.
Restart the controller: Sometimes the controller may fail or be in an error state, causing the safety light curtain to not work properly. Try restarting the controller to reinitialize the system and see if it can return to normal.
Detection range: 0.3-6m
Detection: Fingers, Hands
Security Level: IP65
This safety light curtain uses optical synchronization technology, featuring a compact design, easy installation, and tidy wiring. It has intelligent design and user-friendly features, with a comprehensive self-check function. It ensures no incorrect signals are sent in case of safety sensor malfunctions, ensuring operational safety. It is cost-effective and offers high safety, customizable for specific needs in terms of height, length, and resolution.
Misalignment of the Light Curtain Causes Trigger Signal Errors
The safety light curtain’s transmitter and receiver need to be accurately aligned. If the alignment is inaccurate, it may cause a false trigger signal. For example, if the light beam from the transmitter is not completely received by the receiver, the light curtain may mistakenly think that an obstacle has been detected, and send out a false trigger signal.
Solution:
1.Recalibrate the light curtain: You can use a special debugging tool or manually fine-tune the position of the transmitter and receiver until the light beam is aligned. For example, some light curtains are equipped with an alignment indicator light, and the state of the indicator light can be observed to determine whether the light beam is aligned, such as QSA safety light curtain of DADISICK. During the adjustment process, ensure that the installation position and angle of the light curtain meet the equipment requirements so that it can accurately detect objects in the protection area.
2. Check the installation position: Make sure that the installation position of the light curtain is not offset and the transmitter and receiver of the light curtain are on the same horizontal line. If the installation position is deviated, you need to readjust the mounting bracket to ensure that the light curtain is correctly installed and aligned.
Environmental Interference Causes Trigger Signal Errors
Strong light, reflective objects, interference signals and other factors in the surrounding environment may affect the normal operation of the safety light curtain and cause trigger signal errors. For example, strong light sources such as direct sunlight and welding arc light may interfere with the light beam of the light curtain, causing it to mistakenly think that an obstacle has been detected; while electromagnetic interference may affect the signal transmission of the light curtain, causing abnormal trigger signals.
Solution:
1. Avoid direct strong light: If there is strong light interference around, you can use a sunshade to prevent strong light from directly hitting the light beam of the light curtain. Choose a suitable sunshade and install it correctly around the light curtain to ensure that the light beam can be transmitted normally.
2. Adjust the installation position: According to the source of environmental interference, adjust the installation position of the light curtain to keep it away from the interference source. If the installation position cannot be changed, consider using a shielding cover or shielded cable to reduce the impact of electromagnetic interference. At the same time, ensure that the shielded cable is well grounded to improve anti-interference ability.
The Obstruction on the Surface of the Light Curtain Causes Trigger Wrong Signal
If the surface of the light curtain's transmitter and receiver is blocked by dust, oil, debris or other obstacles, it will affect the normal transmission of the light beam and cause trigger signal errors. For example, oil attached to the surface of the light curtain may weaken or scatter the light beam, making it impossible for the receiver to accurately receive it. You can use a soft cloth and a cleaning agent such as anhydrous alcohol to clean the surface of the light curtain, gently wipe the transmitter/receiver window, and remove dust, oil and other obstructions. During the cleaning process, be careful to avoid scratching or damaging the surface of the light curtain.
Light Curtain Signal Connection and Controller Setting Issues
If the output signal of the safety light curtain installation is not correctly connected to the equipment control system, or the program setting of the controller such as PLC is wrong, the trigger signal may not be transmitted normally or correctly recognized by the controller. For example, incorrect signal line connection and incorrect light curtain parameter setting in the controller may cause trigger signal errors.
Solution:
1. Check the signal connection: verify the signal link, and detect the signal on and off step by step from the light curtain output end to the control cabinet. Check whether the signal line is connected correctly and whether it is loose or damaged. If there is a problem with the wiring, reconnect or replace the signal line.
2. Check the safety light curtain controller settings: confirm whether the safety light curtain parameter settings in the controller are correct, such as sensitivity, response time, measurement mode, etc. According to the equipment's instruction manual and actual application requirements, adjust the parameter settings reasonably. At the same time, check whether the safety light curtain controller program can correctly read the light curtain signal and trigger the corresponding action.
No Response When Alarm Occurs
Alarm system problem: Make sure the alarm system is working properly, check the alarm interface and line connection, and confirm whether the alarm system is turned on. If the alarm system fails, repair or replace the corresponding parts in time.
Reset the safety light curtain: Sometimes resetting the safety light curtain can solve the problem of unresponsive alarm. Perform the reset operation according to the instructions in the device manual, but be sure to back up the relevant configuration parameters before resetting to prevent data loss.
Detection Accuracy Decreases
Beam blocking problem: Check whether there is dust, oil or other obstacles on the beam path of the light curtain. If so, use a clean soft cloth to dip in an appropriate amount of detergent, gently wipe the surface of the light curtain, and remove the obstruction to ensure the normal transmission of the light beam.
Installation position deviation problem: If the installation position of the safety light curtain deviates, the detection accuracy may be reduced. Recheck and adjust the installation position and angle to ensure that the relative position between the light curtain and the object being detected meets the design requirements to improve the detection accuracy.
Aging or damage of light curtain components: Due to long-term use or environmental factors, the photoelectric device of the light curtain may age or be damaged, resulting in insufficient light emission intensity or decreased receiving sensitivity, thereby affecting the detection accuracy. Tools such as photoelectric detectors and oscilloscopes can be used to test whether the light transmitting and receiving devices are working properly. If the photoelectric device is found to be aged or damaged, the corresponding components need to be replaced in time.
Improper controller settings: Improper settings of the safety light curtain parameters in the controller, such as sensitivity, response time, measurement mode, etc., may lead to a decrease in detection accuracy. Users can reasonably adjust the parameter settings in the safety light curtain controller according to the device's instruction manual and actual application requirements to improve detection accuracy.
Environmental factors: Harsh environmental conditions such as high temperature, high humidity, and smoke may affect the normal operation of the light curtain, resulting in a decrease in detection accuracy. Try to install the light curtain in an area with good environmental conditions and avoid using it in harsh environments such as high temperature, high humidity, and smoke. If it must be used in a harsh environment, appropriate protective measures can be taken, such as installing a cooling device, dehumidification equipment, and a dust cover.
Other Faults
The light curtain does not respond and does not output the measured value: Check whether the power is on and the voltage is stable; re-plug the communication cable and confirm that the connector is not damaged; check whether the interface definition matches the manual; restore the factory settings or reconfigure the communication protocol parameters.
The data large fluctuates and the measurement is unstable: try to avoid direct strong light and add a light shield; check whether the transmitter and receiver are parallel and firm; for workpieces of special materials, adjust the measurement sensitivity or use a model with anti-interference function.
Some areas cannot be measured or blind spots appear: gently wipe the light curtain window with a clean cotton cloth; use the alignment indicator or laser to recalibrate the position; replace damaged parts or contact the manufacturer for inspection and repair.
Beam spacing: 2.5mm
Number of optical axes: 32
Protection height: 77.5mm
Beam spacing: 30mm
Number of optical axes: 42
Protection height: 1230mm
Safety light curtain outputs (OSSD)2 PNP
Beam spacing：40mm
Number of optical axes：20
Protection height：760mm
Safety sensors for machines output (OSSD):2 PNP
Beam spacing：20mm
Number of optical axes: 10
Protection height: 180mm
Safety Curtain outputs (OSSD):2 PNP
Beam spacing: 80mm
Number of optical axes: 10
Protection height: 720mm
Safety Curtain outputs (OSSD):2 PNP