Device integrations
Technical specifications
Technical specifications of the Volt DIO: digital inputs, relay outputs and what they can switch, network and Modbus details, power, environmental limits, certifications and failsafe behaviour.
The data of the Volt DIO that you need to design and wire the cabinet.
At a glance
| Item | Specification |
|---|---|
| Channels | 6 digital inputs (DI) + 6 relay outputs (DO) per module |
| Relay switching, max | 5 A resistive / 2 A inductive per channel, at 250 VAC or 30 VDC |
| Contact type | Form A (normally open) power relay, potential-free |
| Communication | Modbus TCP (server/slave) over Ethernet, TCP port 502 |
| Ethernet | 2 × 10/100 Mbps RJ45 switch ports (daisy chain), 1 MAC address |
| Power supply | 24 VDC nominal (12 to 36 VDC), 188 mA @ 24 VDC (≈ 4.5 W) |
| Mounting | DIN-rail or wall, 27.8 × 124 × 84 mm, < 200 g |
| Ambient temperature | −10 to 60 °C (standard) or −40 to 75 °C (wide-temperature model) |
| Isolation | 3 kVDC / 2 kVrms, field to logic |
Relay outputs and maximum switching capacity
Each of the six outputs is a potential-free Form A (normally open) contact with two screw terminals of its own: R0_NO and R0_C up to R5_NO and R5_C (see Terminal block). There is no NC terminal, so the actuation modes that assume normally-closed contacts (NC-ON, NC-OFF) only describe an installation where an interposing relay provides that contact. This is the hard limit of what one output can switch:
| Parameter | Value |
|---|---|
| Maximum switching current | 5 A resistive, 2 A inductive, per channel |
| Maximum switching voltage | 250 VAC or 30 VDC (also rated at 110 VAC) |
| Maximum switching power | ≈ 1150 W at 230 VAC or 150 W at 30 VDC (5 A resistive) |
| Contact type | Form A (N.O.) power relay, potential-free |
| Relay on/off time | 1500 ms (max.) |
| Maximum switching rate | 0.3 Hz at rated load (pulse mode) |
| Mechanical endurance | 5,000,000 operations |
| Electrical endurance | 100,000 operations @ 5 A resistive load |
| Field wiring | I/O cable max. 14 AWG (≈ 2.5 mm²), screw terminal block |
These ratings are per channel, not a budget for the module, and they are switching limits, not continuous-duty design targets. The inductive rating (2 A) is less than half the resistive one, and motors, pumps, fans, transformers, contactor coils, capacitor banks and LED drivers draw an inrush current several times their nominal current, which erodes the contacts quickly. Size on inrush, not on nominal power, and switch anything substantial through an interposing contactor.
What you can wire directly, and what needs a contactor
| Load | Directly on the relay output? |
|---|---|
| 230 VAC resistive load ≤ 5 A (≈ 1.1 kW), e.g. small heater | Yes |
| 230 VAC resistive load > 5 A (> ≈ 1.1 kW) | No, switch an interposing contactor |
| 400 VAC (three-phase) load, any size | No, contacts are rated 250 VAC max; use a contactor |
| Inductive AC load ≤ 2 A (small coil, small pump) | Possible; add an RC snubber across the contact |
| Inductive AC load > 2 A (motor, fan, transformer) | No, use a contactor, sized for the load's inrush |
| DC load ≤ 30 VDC and ≤ 5 A resistive (≤ 150 W) | Yes, for inductive DC loads keep to 2 A and add a flyback diode |
| DC load above 30 VDC | No, outside the contact rating |
In practice: use the relay output as a command contact for switchgear (contactor coil circuit, an EPO/stop input, an enable input) rather than as the power switch of the load itself. A separate contactor also keeps the cabinet's power wiring away from the module.
A wiring example is on Placement and cabling.
Digital inputs (DI)
| Parameter | Value |
|---|---|
| Channels | 6, sharing one common (6 points per COM) |
| Sensor type | Dry contact, or wet contact (NPN or PNP) |
| Dry contact | On = short to GND, Off = open |
| Wet contact (DI to COM) | On = 10 to 30 VDC, Off = 0 to 3 VDC |
| Isolation | 3 kVDC or 2 kVrms |
| Field wiring | I/O cable max. 14 AWG (≈ 2.5 mm²), screw terminal block |
What the EMS does with an input depends on the function you assign to it, see Assigning ports. A wiring example with a wet contact is on Placement and cabling.
Terminal block
The inputs and relays share one removable 20-pin screw terminal block, numbered top to bottom:
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | COM 0 | 11 | R1_NO |
| 2 | DI0 | 12 | R1_C |
| 3 | DI1 | 13 | R2_NO |
| 4 | DI2 | 14 | R2_C |
| 5 | DI3 | 15 | R3_NO |
| 6 | DI4 | 16 | R3_C |
| 7 | DI5 | 17 | R4_NO |
| 8 | GND | 18 | R4_C |
| 9 | R0_NO | 19 | R5_NO |
| 10 | R0_C | 20 | R5_C |
Each relay channel has exactly two terminals, NO and C (common), and no NC terminal. The 24 VDC supply and the ground pin sit on a separate terminal block on the top panel. Screw torque 3 lb-inch.
Network and protocol
| Parameter | Value |
|---|---|
| Ethernet ports | 2 × 10/100BaseT(X) RJ45, built-in switch (daisy chain), 1 MAC address |
| Protocol used by the EMS | Modbus TCP (the module is the server/slave), TCP port 502 |
| Addressing | Fixed (static) IP address required; note IP, port and Modbus slave ID |
| Factory default | IP 192.168.127.254, netmask 255.255.255.0, no gateway |
| Configuration | Browser-based web console on the module's IP address |
Keep the Modbus addressing at its factory setting: the EMS uses the default addresses.
Failsafe behaviour and watchdog
| Function | Behaviour |
|---|---|
| Power loss | All relays de-energize; the normally-open contacts open. This needs no configuration: the contacts cannot stay closed without coil power. |
| Communication loss, watchdog disabled (factory default) | Every output holds the last value the EMS gave it. A controller crash or a broken network therefore changes no relay at all, as long as the module stays powered. |
| Communication watchdog | Optional, disabled by default. When enabled with a timeout, the module enters safe mode after that long without Modbus TCP communication. The EMS polls the module every control cycle, which keeps the watchdog satisfied while the controller is alive. |
| Safe status per output | Each output has its own safe state (Hold Last, ON or OFF), applied when the module enters safe mode. It has no effect at all while the communication watchdog is disabled. |
| Safe status latch | Once a channel has entered safe mode, its safe status stays latched until it is cleared. The EMS polls the module's watchdog alarm flag, reports it as a device error and clears it once the module is reachable again. |
Enable the communication watchdog and the per-channel safe status for every output that carries an emergency stop, whatever its actuation mode. Without them, only a loss of the module's own supply drives the relay to a defined state; a controller or network failure simply leaves the relay where it was. Set the channel's safe status to the value that means stop: OFF for a de-energize-to-stop mode (NO-ON, NC-OFF), ON for an energize-to-stop mode (NO-OFF, NC-ON). With an energize-to-stop mode the watchdog is the only thing that can enforce the stop when the link is down. See Safety and requirements.
The module is not a certified functional-safety device: it carries no SIL or performance-level (PL) rating, and its relays are not safety relays. Where a rated safety circuit is required, the relay output should command a safety relay or contactor that provides that rating, and the safety function must be assessed against the applicable standards (for example EN 60204-1 and EN ISO 13850).
Power supply
| Parameter | Value |
|---|---|
| Power input | 24 VDC nominal, 12 to 36 VDC |
| Power consumption | 188 mA @ 24 VDC (≈ 4.5 W) |
| Connection | Screw terminal block on the top panel, with ground pin |
| Earthing | Connect the ground pin to the cabinet earth |
Size the 24 VDC supply for all modules in the cabinet, and keep the emergency-stop chain in mind: if the stop relies on the module being powered, the supply is part of that chain.
Mechanical and environmental
| Parameter | Value |
|---|---|
| Dimensions (W × H × D) | 27.8 × 124 × 84 mm |
| Installation | DIN-rail or wall mounting |
| Operating temperature | −10 to 60 °C (standard model) or −40 to 75 °C (wide-temperature model) |
| Ambient relative humidity | 5 to 95%, non-condensing |
The relays may malfunction in condensing environments below 0 °C. In unheated or outdoor cabinets, provide heating or dehumidification, and choose the wide-temperature model.
Sizing and design notes
- Switching latency. The EMS re-evaluates outputs every control cycle (≈ 1 s) and the relay itself takes up to 1500 ms, so allow roughly 2.5 s from decision to contact change. The outputs are not suitable for fast or continuous cycling: the maximum switching rate is 0.3 Hz at rated load.
- Contact life. 100,000 operations at full load is the electrical limit. For a load that is cycled often (a controllable load following PV surplus), the minimum runtime per activation setting protects the relay as much as it protects the load. See Controllable loads.
- Keep the relay a command contact. Interposing contactors keep load current, inductive loads and 400 V circuits out of the module.