Photoelectric Sensors

How Does a Photoelectric Sensor Work?

Generally a photoelectric sensor consists of the following:

• Transmitter - emits the light beam
• Receiver - detects the light beam and converts it to an electrical signal

Photoelectric sensors detect changes in the light beam caused by the presence/absence, movement or properties of an object.

Types of Photoelectric Sensors:

• Through-Beam (Thru-Beam)
  • Transmitter and receiver are two separate units that are directly opposite of each other. The sensor detects when an objects breaks the light beam
  • Great for long distance detection
  • Ideal for conveyors, counting or monitoring door openings
• Retroreflective (Reflective Mode)
  • Transmitter and receiver are in one housing; light beam is reflected back by a reflector. Detection is triggered when an object breaks the beam.
  • Medium range detection and easier to install than a through beam
  • Ideal for package detection and pallet positioning
• Diffuse (Proximity Mode)
  • The transmitter and receiver in one housing; the sensor detects light reflected directly off the target object (no reflector needed)
  • Best for short range applications
  • Ideal for detecting objects on assembly lines, verifying presence or checking fill level
• Specialized Types:
  • Background Suppression: Can ignore objects beyond a set distance, focuses close range
  • Color or Contrast Sensors: Detects specific colors or contrast differences
  • Distance Measuring Sensors: Mesaure the distance to an object

Categories Related to Photoelectric Sensors:

• Stack lights - signal towers visually communicate the data or alerts that the photoelectric sensors are generating
• Smart relays - photoelectric sensors provide input signals which can process the data and control outputs
• Pushbuttons and estops - if your sensor detects a fault, an operator can use a pushbutton to reset the system
• HMIs - HMIs can dispay the data from the photoelectric sensor which allows you to monitor processes