![]() ![]() The difference between the two wirings is that in the PNP type wiring, the relay is always connected to 0V, and +24V is switched by the sensor. ![]() Let’s have a look at a relay-type circuit, where a relay is operated directly by a proximity sensor. a PNP sensor can be either N/O or N/C as can an NPN be either N/O or N/C) This is dependent only on the application. Two of the wires are used to provide the sensor with power to operate, while the other wire is the output from the sensor.Īt this point, t’s worth mentioning that being a PNP or NPN type sensor, does not imply if the sensor output is normally open (N/O) or normally closed (N/C). They use PNP or NPN type transistors to switch the output when an object is detected. The most popular type of proximity sensor is the 3-wire type. ![]() PNP vs NPN for 3 wire connection of a sensorĪlmost all the industrial proximity sensors are solid-state devices, meaning that they do not have moving parts inside. But, in the NPN sensor wiring, the load is always connected to Positive, and the Negative is switched when an object is detected. The Positive is switched when the proximity sensor detects an object. In the PNP sensor wiring, the load is always connected to Negative. Therefore, they must always be connected to a 24V power source to function. To easily remember the wiring of a 3-wire DC proximity sensor, we can use the following analogy: A Way to Remember NPN and PNP Sensor Wiring PNP proximity sensors are also known as ‘ sourcing’ sensors. When connected to a PLC input, it detects this as a logic HIGH signal. When an object enters the detecting range of the sensor, the output of the sensor is connected with +24V. PNP proximity sensors provide an active HIGH output. This type of sensor is also known as ‘ sinking’ sensor. This means that when an object enters the detecting range of the sensor, the output of the sensor is connected with the ground. NPN proximity sensors provide an active LOW output. This article aims to provide an outline of the two main output types and a guide on how to connect a proximity sensor to a PLC. Selecting the correct type of proximity sensor for a particular application can ensure the correct operation of a system. There are two main types of proximity sensors based on their output type: NPN and PNP. There are 2-wire and 3-wire proximity sensors, and 3-wire proximity sensors are more popular. We are non-native english speakers, and technical terminology is even more difficult to get right.Proximity sensors are used to detect objects without making physical contact. I'm sorry if we are using 'incorrect terminology'. Since electronics isn't his specialty I convinced him that the internet might help him with these issues. What he's bumping into is that one issue with the incompatibility between the encoder and the generator. (He's a retired bending machine architect/engineer). My dad is the one who has replaced the old 1970's circuits by a PLC, and reprogammed the entire thing. It's while trying to get everything connected again, that this problem showed up. The counter can count up to 30 kHz, so speed is also important.Īs was guessed in the comments, this is indeed for industrial machinery.Īn old bending machine's (iron pipes) logic is broken and is being replaced by something completely new. How can I convert the encoder signals, so the counter can use them.īoth encoder and counter have a supply voltage of 24VDC. I have a high speed counter that needs PNP signals. I have a signal generator (shaft encoder) that has 2 NPN outputs. As a follow-up of my previous too generic question ![]()
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