The RELO IO8 provides eight independent SPDT (single-pole double-throw) relay outputs on removable screw-terminal blocks. Each relay can switch loads of up to 10 A at 250 V AC (or 10 A at 30 V DC), making them suitable for switching mains-voltage devices, low-voltage control signals, and dry-contact interfaces.
Electrical specifications
| Contact type | SPDT (Form C) |
| Maximum switching voltage (AC) | 250 V AC |
| Maximum switching voltage (DC) | 30 V DC |
| Maximum switching current | 10 A |
| Maximum continuous current | 8 A |
| Minimum switching load | 100 mA at 5 V DC |
| Contact resistance | < 100 mΩ initial |
| Insulation resistance | > 1,000 MΩ at 500 V DC |
| Mechanical life | 10,000,000 operations |
| Electrical life (rated load) | 100,000 operations |
| Operate time | < 10 ms |
| Release time | < 5 ms |
Do not exceed the rated contact current. For loads above 10 A, use an appropriately rated external contactor and wire the RELO IO8 relay to the contactor coil. Always follow local electrical codes when switching mains-voltage loads.
Terminal block pinout
Each relay output uses a 3-pin removable screw-terminal block. The terminals are labelled on the PCB silkscreen and on the rear panel. The order from left to right for each relay is:
| COM | Common: connect the supply or input side of the load here |
| NO | Normally Open: open when relay is de-energised, closed when energised |
| NC | Normally Closed: closed when relay is de-energised, open when energised |
Default state and power-on behaviour
All relays default to de-energised (NO contacts open, NC contacts closed) on power-up and after any factory reset. The power-on state for each relay can be configured individually in the device settings: de-energised (default), energised, or "last known state" (the device stores relay states in flash memory and restores them on boot).
Controlling relays from a flow
In the flow editor, use the following Action node types to control relay outputs:
- Relay Set: force a relay to a specific state (ON or OFF)
- Relay Toggle: flip the current state of a relay
- Relay Pulse: energise a relay for a defined duration then de-energise it (minimum 50 ms)
- Relay Set All: set all eight relays to a defined bitmask pattern in a single operation
Controlling relays over the network
Relay outputs can also be controlled directly via HTTP without writing a flow. This is useful for testing or for quick integration with third-party systems.
# Set relay 1 ON
GET http://192.168.1.50/api/relay/1/on
# Set relay 1 OFF
GET http://192.168.1.50/api/relay/1/off
# Toggle relay 1
GET http://192.168.1.50/api/relay/1/toggle
# Pulse relay 1 for 500 ms
GET http://192.168.1.50/api/relay/1/pulse?ms=500
# Read all relay states (returns JSON)
GET http://192.168.1.50/api/relay