# Placement and cabling

> Where to place the Volt DIO and how to wire a relay output and a digital input.

Source: https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/placement-and-cabling/

Put a Volt DIO in the cabinet where it has to switch a relay or read a contact. The controller reaches the module over the network, so the wiring to the relays and contacts stays short and inside the cabinet.

## How many modules do you need?

-   One module per cabinet where you need inputs or outputs.
-   An extra module in the same cabinet when you need more than 6 inputs or 6 outputs there.

```mermaid
flowchart TD
  CTL["Voltmasters controller"] --> NW["installation network (Modbus TCP)"]
  NW -->|"network cable"| KA["Cabinet A: Volt DIO"]
  KA --> RA["relays and contacts"]
  NW -->|"network cable"| KB["Cabinet B: Volt DIO"]
  KB --> RB["relays and contacts"]
```

One module per cabinet: the number of modules follows the layout of the installation.

## Wiring

![Wiring example of a Volt DIO. Input: the plus of a 24 VDC supply runs through a normally closed contact to terminal DI0, the minus goes to terminal COM 0. Output: phase L of 230 VAC goes to terminal R0_C, terminal R0_NO goes to A1 of the coil of a contactor, A2 goes to neutral N. The contactor switches the load.](https://voltmasters.io/assets/docs/volt-dio-wiring-en.svg)

*An input with a wet contact, and a relay output that switches the coil of a contactor.*

-   **Relay output.** Each output is a potential-free, normally open contact between the terminals `C` and `NO`. Use it as a command contact, in the coil circuit of a contactor or in a stop or enable circuit. The contactor switches the load. What an output may switch directly is in the [technical specifications](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/technical-specifications/#relay-outputs-and-maximum-switching-capacity).
-   **Input with a wet contact.** Feed 24 VDC through the contact to the input, and connect the minus to `COM 0`. A closed contact reads high, an open contact low.
-   **Input with a dry contact.** Connect the contact between the input and `GND`.

The terminal numbering is under [Terminal block](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/technical-specifications/#terminal-block).

## Network and power

-   Connect every module to the installation network, the same network the controller uses.
-   Give every module a fixed IP address and note the IP address, the port and the Modbus slave ID. You need them to add the module on the platform.
-   Power the module from the cabinet’s 24 VDC supply.

> **Note**
>
> Each module has **two Ethernet ports** that act as a small switch, so you can **daisy-chain** modules. A daisy chain is a single path though: a module that loses power also cuts off the modules behind it. Connect a module that carries an emergency stop directly to the switch.

## Next steps

[Volt DIO](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/): Add the module on the platform and assign its ports.

 

[Technical specifications](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/technical-specifications/): The switching capacity, the terminals, the network and the power supply.