Sensors can be divided into two main categories based on their output type: NPN (sometimes called source sensor) and PNP (sometimes called sink sensor). Both types of sensors have three pins, which are connected to 24V, 0V, and Out (signal output). So, what types of sensors does the Siemens S7 series PLC support?
>>>Sensor types supported by Siemens PLCs and modules
1. What types of sensors does Siemens S7-200 support?
The S7-200 series inputs support both source and sink types, so it can be connected to both NPN and PNP sensors (see step 2 for specific wiring instructions). For other models, please refer to the product manual (as shown in the figure below):
2. What types of sensors does the Siemens S7-200smart support?
Like the S7-200, the S7-200smart supports both sinking and sourcing inputs, so it can be connected to both NPN and PNP sensors (see step 2 for specific wiring instructions). For other models, please refer to the product manual (see diagram below).
3. What types of sensors does the Siemens S7-1200 support?
The S7-1200 inputs support both sinking and sourcing types, so it can be connected to both NPN and PNP sensors. (Please refer to step two for specific wiring instructions). For other models, please refer to the product manual (as shown in the image below).
4. What types of sensors does the Siemens S7-300 support?
The S7-300 has many DI modules. To find the specific parameters, you need to check the hardware configuration (please refer to step two for the specific connection method).
(1) Most DI modules of the S7-300 are sinking type (PNP type sensors should be selected). During hardware configuration, there is no indication of whether it is source or sinking type, meaning it defaults to sinking type. For example: 321-1BL00 :
(2) Source-type DI module of S7-300 (NPN sensor should be selected), such as: 6ES7321-1BH50-0AA0:
(3) Dual-purpose DI module for source/drain (can be used with both NPN and PNP type sensors): e.g., 6ES7321-1BP00-0AA0
5. What types of sensors does the Siemens S7-1500 support?
The S7-1500 series currently offers DI modules with a sinking design for connecting PNP type sensors (please refer to step two for specific wiring instructions). For example: 6ES7523-1BL00-0AA0
There is a DI module that supports source-type sensors, which can be connected to NPN sensors (please refer to step 2 for specific connection instructions). For example: 6ES7131-6BF60-0AA0
Wiring methods for NPN and PNP sensors
1. First, understand the types of PLC input terminals.
Definition of source and sink input types for Siemens PLCs: Source and sink are distinguished based on the direction of current flow at point I on the PLC terminal block (the definition is opposite to that of Mitsubishi PLCs, where source and sink are distinguished based on the direction of current flow at the COM terminal).
Source type: When current flows out from point I, it means the source of current;
Leakage type: When current flows in from point I, it means the direction in which the current flows.
2. Connecting the NPN sensor to the PLC (for Siemens PLCs, this is a source input connection method)
Current flow: 24V+----COM terminal---- I0.0 (current flows out from point I)----sensor out terminal----sensor 0V terminal----0V, as shown in the diagram below:
3. PNP sensor connected to PLC (for Siemens PLCs, this is a sinking input connection).
Current flow: 24V+---Sensor 24V----Sensor out terminal---- I0.0 (current flows into point I)----COM----0V, as shown in the diagram below:
Sensor Classification
1. NPN (Source Type): Outputs a low level when on.
When the signal is turned on, the signal output line OUT is connected to the 0V line, which is equivalent to outputting a low level: 0V.
NPN type sensors are divided into three subcategories based on their installation logic.
NPN-NO (Normally Open): No output when not connected; outputs a low level when connected;
NPN-NC (Normally Closed): Outputs a low level when not connected; no output when connected.
NPN-NC+NO (normally open and normally closed common type): two out output terminals (one open and one closed).
2. PNP (Sinking): Outputs a high level when on.
When the circuit is on, the signal output line OUT is connected to the power supply line VCC, which is equivalent to a high-level power supply line, 24V.
PNP type sensors are divided into three subcategories based on their installation logic:
PNP-NO (Normally Open): No output when not connected; outputs a high level when connected;
PNP-NC (Normally Closed): Outputs a high level when not connected; no output when connected.
PNP-NC+NO (normally open and normally closed common type): Two out output terminals (one open and one closed).
