THE OPTOELECTRONICS BEHIND FACTORY AUTOMATION
Factory automation is rapidly transforming industries worldwide, marking a new era of efficiency, precision, and innovation. As we advance deeper into Industry 4.0, the integration of advanced automation technologies has become a cornerstone of modern manufacturing. From automotive manufacturing to electronics assembly, these systems are key to enhancing productivity and reducing operational costs.
The key role of photoelectric sensors in automation
At the heart of this automated revolution are photoelectric sensors, which play a crucial role in enabling precise, safe, and reliable operations. Optical sensors, also known as optical switches, are indispensable in various industrial applications, such as presence detection, fill level measurement, and safety protection. In addition, they can offer relatively long operational distances for presence detection compared to other technologies, making them ideal for challenging environments.
How optical switches work: configurations and applications
In the basic configuration, optical switches consist of a light emitter and a receiver. The emitter, usually a light- emitting diode( LED), produces modulated pulses, while the receiver, a photodiode, converts incoming light into electrical signals. These signals are then amplified and processed before being sent to the controller. The versatility of optical switches lies in their various configurations, each suited for specific applications in factory automation.
1. Transmissive configuration: long-range sensing
In the transmissive configuration, the transmitter and receiver are housed separately. When an object interrupts the light beam between them, the receiver’ s output changes, indicating the presence of an object. This configuration is highly effective in environments with fog, dust, and dirt and is commonly used to monitor production and packaging lines, measure fill levels through transparent containers, and safeguard hazardous areas.
2. Retro-reflective configuration: detecting shiny objects
The retro-reflective configuration houses both the transmitter and receiver together. Objects are detected when they break the light beam between the sensor and a reflector. These sensors excel at sensing glossy or shiny objects, making them particularly useful in the packaging and printing industries.
Photosensor
Light emitter
3. Diffuse reflection configuration: versatility in object sizing
In the diffuse reflection configuration, the emitter and receiver are also housed together but without a reflector. Here, the sensor is triggered when the light reflected by an object reaches the photosensor. When a linear image sensor is used instead of a single photodiode, the distance to the object can be measured using triangulation. This method is particularly useful for determining the size of packages on a conveyor belt for sorting applications.
Photosensor
Light emitter
Reflected light
Object to be detected
Object to be detected
Reflected light
Transmitted light
Transmitted light
4. Measuring light curtains: broad area detection
Measuring light curtains utilize infrared light to detect and measure objects across a large field. These devices operate using multiple through-beam sensors, each with an individually evaluated output signal. Available in various sizes and beam distances, they are suitable for diverse measurement tasks.
Regressive reflection plate
Figure 2: Retro-reflective configuration( also called regressive reflection)
Photosensor A
A’
Light emitter
Figure 3: Diffuse reflection configuration Object to be detected
Reflected light
A
Figure 4: Triangulation distance measurement
A’
Object to be detected
Light emitter Transmitted light
Photosensor
Figure 1: Transmissive Configuration
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Figure 5: Safety light curtain