Basic Knowledge of Photoelectric Sensors

Control Output of Photoelectric Sensors

Control Output

There are 2 polarities of transistor output, NPN and PNP.
A current flows from the Collector to Emitter on a NPN transistor.
On a PNP transistor, a current flows from the Emitter to Collector.

NPN

  • NPN Open-Collector Output Circuit Diagram

A load to NPN output can be connected to a power supply to the sensor or a separate power supply.

PNP

  • PNP Open-Collector Output Circuit Diagram

A power supply to load of PNP output must be the same with one to the sensor.
Therefore, a separate power supply with a different voltage from one for the sensor cannot be used.

Transistor Voltage Output

Example of NPN

  • NPN Voltage Output Circuit Diagram

With a NPN transistor, a voltage output flows through a pull-up resistor between a Collector and +V.
Unlike the open collector output, it does not require to connect an external resistor to have a voltage output.

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