Let us take care of your production needs !
Is the safety light curtain frequently causing temper tantrums? 6 common faults and solutions, explained in one article!
Aug 01,2025
As the "safety guard" of industrial equipment, once a safety light curtain malfunctions, it will either frequently shut down and affect production, or "fail" at critical moments and lay hidden dangers. Many factory workers have encountered this headache: why did the light curtain suddenly sound an alarm when they had just replaced the new equipment?
Today, let's take a look at the 6 common faults of safety light curtains, from symptoms to causes and solutions. We will teach you step-by-step how to quickly troubleshoot and make the production line less shut down and safer!
Fault 1
After power on, there is no response and the indicator light does not light up
1、 Phenomenon:
After connecting the power, the indicator lights of the transmitter and receiver do not light up, and the device cannot enter the protective state.
2、 Possible reasons:
Power supply issues: unstable power supply voltage (such as 15% below rated voltage), broken power lines or loose connectors;
• Fuse blown: The internal circuit short circuit caused the fuse to blow;
• Mainboard malfunction: The core control board is damaged (such as lightning strikes, strong electrical shocks).
3、 Solution:
1. Use a multimeter to measure the output voltage of the power supply, ensuring it meets the rated value of the light curtain (usually 24V DC);
2. Check if the power cord connector is oxidized and replace the damaged cable;
3. If the fuse is blown, first check for a short circuit (such as cable breakage), and then replace it with a fuse of the same specification;
4. Are all of the above okay? Perhaps the motherboard is damaged, please contact the manufacturer for repair or replacement.
Fault 2
Frequent false alarms when unobstructed
1、 Phenomenon:
There is no object blocking the beam of light, but the light curtain repeatedly triggers protection signals (indicator light turns red, equipment stops).
2、 Possible reasons:
Environmental interference: direct sunlight, strong arc welding light, and other interference receivers;
• Lens contamination: Dust and oil stains cover the lens, causing beam attenuation to be misjudged as obstruction;
Alignment deviation: The transmitter and receiver are installed askew, and some beams are not received;
Electromagnetic interference: Electromagnetic radiation interference signals from nearby motors and frequency converters.
3、 Solution:
1. Wipe the lens with a dust-free cloth and clean it at least once a week (recommended once every 3 days for high dust workshops);
2. Install a shading board to block strong light, and separate the light curtain cable from the power line for wiring (spacing ≥ 30cm);
3. Use a laser alignment device to calibrate the installation angle, ensuring that the transmitter and receiver are completely parallel (deviation ≤ 1 °);
4. Cover the light curtain cable with a shielding layer and ground it (grounding resistance ≤ 4 Ω) to reduce electromagnetic interference.
Fault 3
No alarm or protective action after obstruction
1、 Phenomenon:
When using an object to block the beam of light, the light curtain indicator light does not change color, and the device still operates normally, completely "unresponsive".
2、 Possible reasons:
The beam is completely blocked: the transmitter or receiver lens is completely blocked by thick oil stains or metal shavings;
• Component damage: The LED of the transmitter is burnt out (some beams do not emit light), and the photosensitive component of the receiver is malfunctioning;
Output circuit fault: Relay contacts are stuck and output cables are disconnected, resulting in the inability to send protection signals.
3、 Solution:
1. Thoroughly clean the lens (stubborn oil stains can be lightly wiped with an alcohol swab) to ensure that there is no complete obstruction;
2. Observe the transmitter in a dark environment to see if there is a missing beam (or detect with an infrared camera), and replace the damaged LED;
3. Use a multimeter to measure the output terminal. If the signal does not change when obstructed, it may be due to a faulty relay and the output module needs to be replaced.
Fault 4
Protect signal delay and respond slowly
1、 Phenomenon:
After blocking the beam, the equipment takes 1-2 seconds to shut down, which is significantly slower than before.
2、 Possible reasons:
• Component aging: transmitter LED brightness attenuation, receiver sensitivity decrease;
Algorithm redundancy: Some old models have too many light curtain verifications, resulting in long processing times;
• Load delay: Downstream equipment (such as contactors and frequency converters) operates slowly and is mistakenly identified as a light curtain issue.
3、 Solution:
1. Use an oscilloscope to measure the response time of the light curtain (normally ≤ 50ms). If it exceeds the standard, check if the components are aging and need to be replaced;
2. Contact the manufacturer to upgrade the firmware and optimize the signal processing algorithm (some new models can reduce redundancy checks);
3. Test the action time of downstream equipment separately and replace the high-speed contactor (response ≤ 10ms).
Fault 5
Some areas are insensitive and have 'blind spots'
1、 Phenomenon:
Blocking the upper part of the light curtain triggers a normal alarm, but blocking the lower part does not respond, indicating a detection blind spot.
2、 Possible reasons:
Local component damage: One row of transmitter LEDs or receiver photosensitive components is damaged;
Latest News
![[Exhibition Preview] Seaga invites you to the SIA Shanghai International Industrial Automation and Robotics Exhibition](https://omo-oss-image.thefastimg.com/portal-saas/pg2025053016052611495/cms/image/02d2b254-9b75-4d19-ae43-83b93ea22dac.jpeg "[Exhibition Preview] Seaga invites you to the SIA Shanghai International Industrial Automation and Robotics Exhibition")
Leave your email address
WE GET YOU THE NECESSARY PARTS QUICKLY
Get A Quote
Our sales team will provide you with a detailed quotation within 24 hours.
Whether your needs are for a single product or a complete customized solution, we will provide a tailored quotation and technical support based on your specific requirements.
|
Deputy General Manager |
 |
|
Deputy General Manager |
 |
| Overseas Marketing Manager Lucia Jiang Phone: +86 18616850611 WhatsApp: +86 18616850611
|
 |