Recently Developed Reflex Light Barrier Offers Reflector-free Detection

The Wenglor Sensoric Group has expanded its catalog with a new and improved light barrier system. The P1PM light barrier is a reflectorless light system that measures return time and backscattered light intensity. Wenglor's compact, rugged sensor is designed for use in a variety of settings, including part detection and fill-level monitoring.

 

A digital portrayal of the P1PM reflex light barrier detecting small parts on an aluminum surface. Image used courtesy of Wenglor

 

Detecting Distance and Intensity

Light barriers are used to detect the distance between objects and thicknesses of coatings. A light barrier system emits light and looks for the reflection as a source of information. For calculating distances, pulses are emitted, and the time it takes to receive the reflection is measured. The distance can then be calculated because the time is measured, and the speed of light is known. 

Safety interlocks also use light barriers to determine whether foreign objects, such as a worker’s hand, are in a protected space. In this case, the distance is either shorter than expected or some characteristic of the reflection has changed. In some cases, the light is returned from a highly reflective barrier, so the return signal's intensity is reduced if this barrier is broken. More often than not, the reduction in distance is the trigger to open the interlock. 

 

Ambient lighting and varied object surfaces can pose a challenge for typical light barrier systems. Image used courtesy of Wenglor

 

Light Barrier Challenges

Designing a light barrier system is not fool-proof. Some applications are more challenging than others. Because the system relies on reflected light, anything interrupting the reflected light can cause problems. Bright ambient indoor lighting or changing sunlight through a window or skylight can wreak havoc on the calibration and use of a light barrier system. Furthermore, non-reflective, transparent, or translucent objects can be difficult to detect. Even reflective objects, which might catch changing light from normal movement in a factory, can lead to issues.

 

The Wenglor P1PM reflex light barrier has four available models for static or moving backgrounds and PNP or NPN switching outputs. Image used courtesy of Wenglor

 

The P1PM Reflex Light Barrier

Wenglor addresses the challenges faced by standard light barriers with its new P1PM reflex light barrier. As part of the PNG // Smart Reflex system, Wenglor's P1PM sensors do not require a return reflector but are instead “trained” by the operator. In doing so, ambient light conditions can be subtracted out, leaving behind a sensitive detection method that does not require the alignment and space needed for most reflected systems.

Also, reflectors tend to get dusty in the manufacturing environment, which may lead to downtime for cleaning. A reflector-free design eliminates that hassle. The P1PM is capable of working in dusty, dirty environments and on reflective, non-reflective, glossy, and semi-transparent surfaces, making it versatile for most production facilities. It is also rugged and suitable for use in environments with high vibration.

 

Reliable Processing and Detection

Wenglor’s P1PM light barrier has the potential to improve safety and quality in manufacturing environments. The ease of installation, calibration, and operation make it an attractive alternative to legacy light barriers that can suffer from inaccuracy in distance measurements, false positives, AND false negatives for safety interlocks.