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    Safety Light Curtain Troubleshooting

    Safety light curtain is a powerful safety laser sensor for machine guarding and personal safety. It is rather convenient and flexible in wiring and installation. The safety light curtain is equipped with flexible and relevant software, which can easily change the shielding and blanking effect according to the customers' various on-site requirements. It greatly reduces the time for re-arrangement and re-wiring. However, due to the complexity of the production process, the on-site product models often change, the settings for the safety light curtain also change accordingly. There are still some common problems in installation and maintenance. Today, ATO will tell you how to solve these problems.

    I. How to deal with the optical alignment of safety light curtain in unstable states?

    1. The distance between light emitter and light receiver has exceeded the limit distance (protection length) of the light curtain itself. It should be readjusted.
    2. The light emitter and light receiver are not at the same level, it will be very difficult to do beam-focusing when the difference in lights angle between the light emitter and light receiver is plus or minus 5 degrees. It also needs to be readjusted.
    3. The safety light curtain has been used for too long, which has accumulated too much dirt or dust inside that may cause instability. In this case, it is better to buy a new safety light curtain.
    4. The safety light curtain is interfered by the outside. It needs to be connected with the shielding wire.

    II. How to solve the various external interference problems of safety light curtain?
    If the safety light curtain is still interfered after connecting with the shielding wire, the interference sources of safety light curtain should be find out.
    The interference is generally caused by the followings:

    • Interference from the light source.
    • Interference from VFD.
    • Interference from the paratactic positions.
    • Interference from external high-strength signal.


    First, the light source interference is divided into strong light interference and reflection interference, these two interferences are easy to resolve. Replace the glare light with the ordinary light of where the light curtain light curtain sensor is being used. The reflection interference is due to the bright objects near the light curtain, such as a shiny object or mirror, put it outside the light curtain protection area, then the problem can be solved.

    Second, the interference from VFD, this is a common problem for almost all safety light curtains, there are several ways to solve the problem in such cases.

    1. Is there a shielding cable with the light curtain communication cable that is being used? If so, it must be connected well (preferably shielding cable of good quality).
    2. Avoid wiring in the places where a VFD exists.
    3. Connect an intermediate relay on the signal line of the safety light curtain, isolate the interference signal. There are some safety light curtains that cannot use the power supply on the machines, so an independent switching power supply needs to be added. The advantage is also to prevent the interference signals from passing on the light curtain through the power supply.
    4. If all the above methods cannot solve the problem, the safety light curtain manufacturers could come to the site, test according to the actual situation and modify the internal circuit of safety light curtain based on the interference source.

    Third, interference from the paratactic positions means that the two machines that have installed light curtains are close to each other or one of the machines has two sets of safety light curtains. The signal sent by the light emitter of the first set of safety light curtain is also received by the light receiver of the second set of safety light curtain. It will result the paratactic interference. This problem can be solved easily. As long as slightly move the two safety light curtains away from each other or exchange the position of the emitter and the receiver of one of the safety light curtains, this problem will be solved.

    Fourth, the interference from external high-strength signals, this case occurs rarely, the safety light curtain can be interfered in some factories where wifi or some pass-frequency transmitters and other signals are being used. So be away from these signals or turn them off.

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