How to distinguish source and drain of PLC

1, the source type and drain type, generally for the transistor-type circuit, it can be directly understood as the IO circuit to the outside / current (source or source) or absorption / inflow current (leakage or sink). For DO, the general PNP transistor output is a source type, the output module has been connected to the power supply, the current flows out through the DO, do not need any external power supply DO can directly drive the relay. Siemens 300/400 series or European PLCs are accustomed to using such outputs. Japanese, Taiwanese, and Siemens Series 200 and most domestically produced PLCs generally use a leaky type DO, which is an NPN type, and requires an external connection to be pulled up to a 24V power supply. Current flows from an external relay to an output module.

2. For DI, the reason is the same, that is, to determine whether the current flows out of the DI terminal or inflow, to distinguish whether it is a source type or a drain type. In general, DI's public COM terminal is connected to 24V, input 0V is valid, and the current flow is from DI. This is the source type. And COM connects 0V, 24V is effective, the electric current flows into DI at this moment, this is leak type.

It should be noted that some Japanese PLCs (such as the three X) understand the DI input part as "the type of output that can be accessed." Specifically, if the DI can access the source DO, the DI is referred to as "source input" and vice versa as "sink input."

Source and sink DIDOs can be directly wired if paired together. That is, DI (source) - DO (leakage), or DI (leakage) - DO (source). If DI and DO of the same nature are interconnected, reverse polarity measures such as pull-up resistors are generally required.

Siemens source (PNP) or drain (NPN).

1, Sinking logic: When the signal input terminal flows out of the current, the signal turns ON, which is a drain logic.

2, source logic: When the signal input terminal into the current, the signal becomes ON, for the source logic.

Take positive power supply as an example:

When the signal terminal issues an "ON" signal, if the voltage at this time is a low level (0V), it is a sink logic;

When the signal terminal sends "ON" signal, if its voltage is high level (PLC, frequency converter, etc. is generally 24V), it is source logic.

The source input is active high, meaning that current flows in from the input point, and the sink input is active low, meaning that current flows from the input point.

Mitsubishi's current FX3U can choose source and drain type

1. Source (source): The current flows from the terminal and has the output characteristics of the PNP transistor. The sink (sink), the current flows in from the terminal, and has the NPN transistor output characteristics.

2, s7-200plc can be connected to drain type, can also be connected to the source type, and 300plc is generally the source type, Europe and the United States is generally the source type, the input is generally used pnp switch, high input. In Japan and South Korea, it is easy to use a drain type. Generally, an npn type switch is used as a low-level input.

3. The source output refers to the DC positive output, and the sink output refers to the DC negative output. So Siemens PLC output, both active and leaky output, but generally is the source type.

4, Mitsubishi PLC, the input is both active and leaky, but mostly leaky. The proximity switch connected to the sink input is an NPN PLC.