What Is a PLC Connection Module? Types and Selection Criteria
A PLC connection module distributes the 24 V DC, 0 V or earth potential of sensors and actuators to many connection points at an I/O station.
A PLC connection module is a potential distribution module that multiplies the 24 V DC, 0 V or earth potential needed by sensors and actuators at an I/O station across many connection points. The brown (+24 V) and blue (0 V) wires of a three-wire sensor go to this module and the signal wire to the digital input module, so there is no need to line up a separate row of terminal blocks next to the I/O module.
Types of connection modules
| Type | Potential distributed | Typical use |
|---|---|---|
| 24 V DC module | Supply positive | Sensor supplies, common positive of actuators |
| 0 V module | Supply negative (return) | Sensor negatives, return of output loads |
| Mixed 24 V + 0 V module | Both potentials, half each | Supplying a few sensors from one module |
| Earth module | Earth | Cable shields and housing earthing |
Selection criteria
- Potential: Count how many sensors or actuators need which terminal. Three-wire sensors need both 24 V and 0 V; two-wire contacts that only give a signal need only 24 V.
- Number of points: The modules in the catalog have 16 points (24 V or 0 V), 8+8 points (mixed) and 14 points (earth). Leave spare points.
- System compatibility: AX-5 connection modules are part of the Delta AX-5 station and are used in the same row as the I/O modules. In another system, potential distribution is done with DIN rail terminal blocks and jumpers.
- Total current: The current through the module is the sum of all connected sensors and loads. Check the permitted limit and how the potential is fed to the station in the Delta AX-5 hardware manual. If consumption is high, the I/O supply is reinforced with power modules; the catalog has 24 V DC 2 A and 10 A models.
- Sensor type: The signal wire of a PNP or NPN sensor must match the source or sink type of the digital input module; the connection module does not change this choice.
Common mistakes
- Mistaking a connection module for an I/O module: This module does not read signals or drive outputs; it only distributes potential.
- Using the earth module as the 0 V return: Earth is not the return path of the circuit; sensor negatives go to the 0 V module.
- Swapping the 24 V and 0 V wires: A sensor whose brown and blue wires go to the wrong potentials does not work; check the module code and label.
- Not calculating the total current: When many sensors and valves are supplied from one module, the limit can be exceeded.
Connection modules in the catalog
Welibaba lists 4 active Delta Electronics AX-5 connection modules:
| SKU | Potential | Points |
|---|---|---|
| `AX-516PC10-0A` | 24 V DC | 16 |
| `AX-516PC20-0A` | 0 V DC | 16 |
| `AX-516PC30-0A` | 24 V DC + 0 V DC | 8 + 8 |
| `AX-514PC40-0A` | Earth | 14 |
Frequently asked questions
What does a PLC connection module do?
It lets you connect the supply and common terminals of sensors and actuators together next to the I/O station, so you do not need a separate terminal block and jumper for each sensor.
When should I choose the mixed 24 V + 0 V module?
If there are only a few three-wire sensors, one module covers both the positive and the negative terminals. The AX-516PC30-0A has 8 points at 24 V and 8 at 0 V and supplies up to 8 three-wire sensors; with more than 8 three-wire sensors, separate 24 V and 0 V modules (AX-516PC10-0A and AX-516PC20-0A) provide points for up to 16 sensors.
Does a connection module replace a digital input module?
No. The sensor signal always goes to the digital input module; the connection module only multiplies the supply and return terminals.
Can Delta AX-5 connection modules be used with other PLCs?
These modules are designed for the AX-5 station. In a system of another brand, the same job is done with DIN rail terminal blocks and jumpers.