Photo-Electric Switch

A photo-electric switch (also known as a photoelectric sensor or photo sensor) is an electronic device used to detect the presence or absence of an object, or to measure the distance to it, by using a beam of light.

How It Works:

It typically operates on the principle of light interruption or reflection:

• A light emitter (like an LED) sends out a beam of light.
• A light receiver detects the beam.
• When an object interrupts or reflects the light, the sensor detects this change and sends a signal to a controller.

Common Types:

1. Through-beam (Opposed mode):
   • Emitter and receiver are placed opposite each other.
   • Object interrupts the beam = detection.
2. Retro-reflective:
   • Emitter and receiver are in the same housing.
   • Requires a reflector.
   • Object breaks the reflected beam = detection.
3. Diffuse-reflective:
   • Emitter and receiver are in the same housing.
   • Light reflects off the object itself.
   • Good for detecting light-colored or shiny objects.

Applications:

• Automatic doors
• Conveyor systems
• Counting items
• Safety devices (e.g., elevator door sensors)
• Street lighting control (auto on/off)