Light Barriers, Photocells & Proximity Switches
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Useful information about light barriers
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What was a light barrier?
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Structure and operation
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Types and models of the light sensors
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Pros and cons at a glance
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Questions and answers
What was a light barrier?
A light barrier consists of a beam, which is mostly invisible to the human eye, with a previously defined range. If this barrier is interrupted by an object, a machine body or a person entering it, this triggers an effect. This way, for example, a gate or a door can be opened automatically. In addition, the invisible light grids are used in the field of safety technology. If a burglar falls within the range of the barrier, an alarm is triggered or a floodlight is activated depending on the system.
Structure and operation
The light sensor has a receiver, which is also referred to as a "sensor". It perceives the interruptions of the light beam and then triggers a signal. The receiving element is a photodiode, a photo transistor or a so-called light-dependant resistor. A light source is added to the receiver, which can be a light bulb or an LED lamp. Some barriers have all individual parts in the same element, others are installed with several elements.
What types of light barriers are there?
You have to decide whether you want to purchase a so-called one-way model or a reflection light sensor.
One-way light barrier
The transmitter and receiver are located in separate components. The installation requires a well-planned structure in which the light beam can hit the receiver at a certain distance. The sensors maintain the invisible light curtain between the elements until an object enters. Mounting is usually more difficult than with a diffuse mode sensor, but the range is larger.
Reflection light barrier / reflection light sensor:
This is a light barrier whose transmitter and receiver have been combined together in one component. The light emitted by the object is evaluated, a special reflector is not necessary. Especially in photo technology, reflective light sensors are often used. Due to their simple installation, they are also popular with light barriers for company security.
Good to know
Special filters belong to the typical accessories of a light sensor. Because often other light sources and the direct sunlight disturb the reliable function. Filters such as background suppression can be used to compensate for this.
Advantages and disadvantages at a glance
| Type of light barrier | Advantages: | Disadvantages: | |
|---|---|---|---|
| One-way light barrier | Long range | Time-consuming installation | |
| Very precise trigger point, especially with laser light | Often difficult to assemble because the position of the parts is important to each other | ||
| High reaction speed, therefore also suitable for use in cameras | High susceptibility to interference: Difficulty in changing position; a storm is sufficient for this | ||
| Reflex light barrier | Regardless of color and shape triggering sensor | The range is usually less than two to ten meters, depending on the size | |
| Reliable even in very bright background | Slower response times of up to one millisecond | ||
| Hardly susceptible to interference, as a change in position has no influence on the quality of the sensor | |||
| Simple assembly by a single component | |||
Questions and answers
What should you pay attention to when using a light barrier?
Once you have chosen the one-way version or the Reflection Light Switch, you should take a look at the quality features. This includes reliable object recognition, which should be independant of the color, surface finish and shape of the incoming object. In the best case, the light barrier even manages to detect reflective or almost transparent objects and to trigger the function even with these machines entering the invisible beam. You can always find the relevant information in our product descriptions.
How can the barrier be built/mounted?
There are various instructions with which you can build your own light barrier. We offer kits and components for safe detection as well as the advantage of a long range. If a component is missing or needs to be replaced over time, please contact us for the appropriate supply. But attention: The inspection and repair may only be carried out by a specialist. Of course, you can also purchase ready-made retro-reflective light barriers that allow easy installation even in places with little available space. If you have any questions about the areas of application and variants, please contact our service team.
Who can check the function of the light barrier?
The transmitter and receiver are checked by measuring the voltage in volts. Therefore, functionality may only be checked by experienced specialist personnel.