Sensor is a most useful thing in industry and robotics applications. When designing a industrial machine we cannot think without sensor. There are various types of sensors for different purpose use. Sensor’s output widely used two types: npn and pnp.
Different Between PNP and NPN Sensor:
PNP Sensor:
For PNP type sensor the output is Positive (+24Volt), and need negative (0volt) to make output working. so in the circuit I pull down (sinking) output sensor.
NPN Sensor:
For NPN type sensor the output is Negative (0Volt), and need positive (+24Volt or whatever voltage supply) to make output working. so in the circuit I Pull up (sourcing) output sensor.
Physical Diagram:
PNP is Common Negative meaning what ever is pulling the load (sensor or light, etc…) is grounded always and needs the positive to complete the circuit (on/off switch on the positive side).
NPN is reversed so it is always connected to positive and needs a on/off switch to connect the ground to complete the circuit.