Interference solution for safety light curtains: positioning and coding

Safety light curtain application

The application of ESPE electro-sensitive protection devices in the safety system of the manufacturing industry has shown a strong momentum. The large-scale work stations of some high-end manufacturing plants have fully applied two-dimensional or even three-dimensional protection systems.

More production equipment, in the occasion of frequent intervention, fully consider the material spill, spark, dust and other divergent risks, almost always choose to use the safety light curtain as a solution. The benefits of using a safety light curtain are:

1. The technical chain of the electro-sensitive protection device technology is mature, the product classification is clear, and various resolutions and safety performance levels can meet the requirements;

2. The development of safety technology is fast, and the improvement technologies in all aspects have continuously broken through the bottlenecks and formed norms, and the road to standardization in the future is clear;

3. As a technology of active defense, the safety light curtain allows automatic reset in most cases, which can effectively solve the problem of landing in the manufacturing process, greatly reduce the complexity of operation and improve production efficiency.

PILZ's safety light curtains and scanner products

Signal interference from safety light curtains

As a safe electro-sensitive protection device, the safety light curtain brings convenience and the signal interference problem is also one of the issues that must be paid attention to.

The signal interference of a safety light curtain usually comes from two aspects:

Light curtain and environmental interference:

If there is a reflective surface near the beam emitted by the safety light curtain, the passive reflection will cause the light curtain receiving end to receive an incorrect reflection signal, and the invasion in the protected area cannot be recognized.

Mutual interference between adjacent light curtains:

Since the safety light curtain is used in a large number of adjacent areas, and the protection distance of the light curtain element itself is relatively long, it is easy to generate mutual misalignment between the transmitting end and the receiving end of the light curtain.

Mutual interference between adjacent light curtains

Safety light curtain interference resolution

In order to effectively avoid the above types of interference, we can resist by physical positioning and technical means.

Light curtain positioning associated with the reflective surface

[1] Reflective surface

[2] Safety light curtain transmitter

[3] Safety light curtain receiver

[4] One-half scanning angle

[5] Minimum distance from the safety light curtain to the reflecting surface

Physical positioning:

The light curtain itself has a fixed scanning angle, and the specific parameters can be inquired through the light curtain technical manual; at the same time, the positioning of the light curtain transmitting end and the receiving end can also be confirmed according to working conditions. According to the above two types of parameters, the minimum distance to prevent reflection interference can be obtained by trigonometric tangent (tan or tg).

If for the use of multiple sets of adjacent light curtains, the mutual signal interference between the light curtains can be solved by means of an additional physical barrier or an inversion of the installation order of the receiving end and the transmitting end.

Use of multiple sets of adjacent light curtains

Technical means:

In addition to physical means, some types of safety light curtains have integrated coding functions, even if they are physically close to each other.

The encoding function allows the grating to work properly when other gratings interfere with it. This is especially true when the transmitting ends of the first pair of gratings are directly transmitted to the receiving end of the second pair of gratings, as long as the two pairs of gratings are configured to be differently encoded, the problem of mutual interference between them is solved.

PIER's V2.0 version of the PSEN opII safety light barrier can be set to three codes (code A, code B and no code). The grating encoding is configured by the wiring of the 5-pin connector at the transmitting end and the receiving end, so that the physical arrangement of the grating is more flexible.

The physical arrangement of the light curtains is no longer unlimited!

PSEN opII safety grating coding