Photoelectric Sensor Explained by RealPars

Video: https://youtu.be/l1rjErRvbgw

↩️ Go Back

Table of Contents:

A) Introduction to Photoelectric Sensors

In this video, I’ll cover the three main types of Photoelectric Sensors:

• Through-Beam, (Barrera)
• Retroreflective, (Réflex)
• and Diffused. (Difuso)

A Photoelectric Sensor uses light to detect the presence or absence of an object.

A.1) Applications of Photoelectric Sensors

Photoelectric Sensors can be used in many different ways and industries.

For example,

• they can be used to detect objects on a production line,

• they can be used to count,
  

• and they can also be used to stop an automatic closing door.
  

These sensors have a wide range of applications across different industries, including:

• automotive,
• food,
• transportation,
• and material handling.

Photoelectric Sensors can detect various materials such as:

• metal,
• plastic,
• wood,
• and even transparent items like glass and liquids.

B) Basic Operation of Photoelectric Sensors

A Photoelectric Sensor works by sending out a light beam from the part called the emitter.

This beam travels to a part called the receiver.

Note: Depending on the sensor type, the light either goes directly to the receiver or reflects off an object or reflector before reaching the receiver.

B.1) Through-Beam Sensors

• How They Work: In Through-Beam sensors, the emitter and receiver are separate components that must be aligned.

When the light path is unobstructed, the sensor’s output remains on.

If an object blocks the light, the output turns off.

• Output Signals (PNP and NPN)
  The sensor’s output signal can be positive (PNP) or negative (NPN), which needs to match the type of input card on the PLC.
  • A PNP sensor connects to a sinking input card,
  • while an NPN sensor connects to a sourcing input card.

• Light-On and Dark-On Modes : Many Through-Beam sensors have a mode selector switch.

• In Light-On mode, the output is on when the light reaches the receiver.
• In Dark-On mode, the output is on when the light is blocked.
  

• Detection Range and Disadvantages
  Through-Beam sensors offer the longest detection range, as the light travels directly from the emitter to the receiver.
  

  However, they cost more, require more space, and may struggle with detecting thin, clear objects.
  

B.2) Retroreflective Sensors

• How They Work: Retroreflective sensors combine the emitter and receiver in one unit. They require a reflector to send the light back to the receiver.

When light is blocked, the sensor’s output changes state.

• Light-On and Dark-On Modes
  Like Through-Beam sensors, Retroreflective sensors can switch between Light-On and Dark-On modes.

• Detection Range and Disadvantages
  These sensors have a shorter range than Through-Beam sensors because the light has to travel to the reflector and back.
  

  They may also trigger falsely on shiny objects, which can reflect light unintentionally.
  

Adjusting the sensor and reflector angles can help reduce this effect.

B.3) Diffused Sensors

• How They Work
  Diffused sensors also combine the emitter and receiver.
  

Instead of using a reflector, they rely on light reflecting off an object to reach the receiver.

• Light-On and Dark-On Modes
  Diffused sensors have a mode selector for Light-On and Dark-On options, similar to the other types.
  

• Detection Range and Disadvantages
  Diffused sensors have the shortest detection range. Their performance may vary depending on the object’s shape, size, and color, which can affect the light's ability to reflect back to the receiver.
  

C) Summary

In this video, you learned about the three main types of Photoelectric Sensors:

• Through-Beam,
• Retroreflective,
• and Diffused.

Each type uses light to detect objects and can be configured to work with a PLC using either PNP or NPN signals.

Or between Light Mode or Dark Mode:

We also discussed each sensor’s detection range and disadvantages.

Z) 🗃️ Glossary