Titania remote I/O power planning starts by separating two loads that are easy to combine incorrectly: the module’s own electronics and the current drawn by external devices connected to its outputs. The controlled Titania datasheet specifies a 24 VDC nominal supply, a 19.2 to 28.8 VDC operating range, and 2 to 3 W maximum system consumption excluding external digital-output load current. That exclusion is the important part of the calculation.
A supply sized only for the module may power the logic and communications while collapsing when valves, relays, lamps or sirens energise. A supply sized by simply adding eight channel ratings can be unnecessarily large and still miss the real problem if several loads have high inrush or the enclosure is hot. A defensible design uses an operating-state load schedule, measured or manufacturer-specified inrush data, conductor voltage drop and thermal assumptions.
Titania remote I/O power planning starts with two current paths
The Titania Super I/O family combines isolated inputs, protected high-side outputs and Modbus RTU integration. For the Modbus DI-8 DO-8 variant, the power budget has two distinct parts:
- Module demand: the electronics, isolation and communications functions, specified at 2 to 3 W maximum.
- Field-load demand: the current delivered through DO1 to DO8 to the connected 24 VDC loads.
At the nominal 24 VDC supply, 3 W corresponds to 0.125 A. That conversion is useful for a current-based load schedule, but it does not include any output load. Each active output must be added separately using the current that its field device actually draws.
Titania’s eight outputs are high-side sourcing channels. The controlled specification states 0.7 A continuous per channel with all eight channels active, subject to ambient and thermal conditions. It also states approximately 1.1 A for short-duration surge and overload limiting. The higher figure describes driver behaviour around surge and overload; it should not be treated as a continuous design current or as a substitute for qualifying load inrush.
Turn operating states into a 24 VDC load schedule
A useful load schedule is organised by machine state, not only by terminal number. Record the normal current, starting or pull-in current, duration of the transient and whether each load can be active at the same time as the others.
Example: four controlled loads
Consider a hypothetical cabinet in which four 24 VDC solenoid coils each draw 0.30 A after pull-in. If all four can remain energised together, their steady field-load demand is 1.20 A. Adding Titania’s maximum module demand at nominal voltage gives a combined steady demand of about 1.325 A before allowing for other devices on the same supply, wiring loss, supply derating or design margin.
The steady calculation is only the first line of the schedule. If the coils have a higher pull-in current, use the coil manufacturer’s data or a controlled measurement. Record whether the machine sequence can start them simultaneously. A software interlock that normally staggers operation is useful, but the electrical design should also consider power-up, communications-loss and fault-recovery states that could produce a different combination.
Do not hide diversity assumptions
If only two of eight outputs are permitted to be on together, document where that restriction is enforced and what happens after a controller reset. Titania provides programmable power-up and communications-loss values per channel. Those states belong in the power study because they can become the worst simultaneous-load case even when normal production logic is carefully sequenced.
Where a load approaches the channel rating, has uncertain inrush or carries substantial inductive energy, use an interposing relay, contactor or external driver selected for the application. The internal output protections are safeguards, not permission to design at an undefined boundary.
Check delivered voltage at the load
The supply terminal can remain inside its stated range while a distant load sees too little voltage. Titania’s output specification allows up to 1 V maximum ON-state drop relative to the field supply. Cable resistance, terminals, protective devices and shared return paths add further loss.
Check the lowest credible supply voltage, output drop and cable drop against the load’s pick-up and hold requirements. This is especially important for long cable runs, high-current coils and loads with a narrow operating window. Measure at the load during the actual switching event; a multimeter reading with every output off does not prove adequate dynamic voltage.
The same check applies at the upper end. Confirm that the field device remains within its permitted voltage and dissipation limits when the supply is high. Titania’s module range does not automatically establish the acceptable voltage range of the connected load.
Simultaneous current becomes a thermal question
Electrical current and enclosure temperature must be reviewed together. The Rev 08 datasheet explicitly makes the 0.7 A-per-channel continuous figure subject to ambient and thermal conditions and instructs engineers to assess all eight channels together. Conductor routing, terminal density, adjacent heat-producing equipment, enclosure size and airflow all affect margin.
A panel calculation should therefore identify:
- the maximum credible number of active outputs;
- steady current and transient current for every active load;
- enclosure ambient at the intended installation;
- power-supply temperature derating;
- cable and terminal ratings at that temperature;
- heat from neighbouring supplies, contactors and drives; and
- the effect of an output held on by a power-up or communications-loss state.
For an enclosed or high-ambient installation, verify the final arrangement under representative load. A bench test with the door open and only one channel active does not reproduce an eight-channel cabinet condition.
Branch protection belongs in the load design
The controlled datasheet calls for external overcurrent protection sized for the conductors, supply and connected loads. Select protection from the complete circuit, not from the module alone. Consider the available fault current of the 24 VDC supply, cable ampacity, load inrush, discrimination between branches and the behaviour required after a fault.
Separate branch protection can make a field fault easier to isolate and reduce the chance that one damaged load removes power from the I/O electronics and every other channel. Whether the logic supply and output-load supply are arranged as separate protected branches depends on the released terminal drawing and cabinet design. Confirm the terminal legend on the delivered hardware revision before wiring.
Commission the worst credible state
After the paper calculation, reproduce the states that challenge the supply and wiring most severely. Record supply voltage at Titania, voltage at the farthest or highest-current load, field current, enclosure conditions and the commanded output pattern.
- Verify polarity, protective devices and conductor sizes before connecting automatic loads.
- Check the output-load current with the expected simultaneous combination active.
- Capture inrush with equipment suitable for the transient duration.
- Cycle power and verify the programmed startup pattern.
- Stop Modbus polling under controlled conditions and verify the communications-loss pattern.
- Confirm that output fault indication and the required recovery policy behave as documented.
- Repeat the voltage and temperature checks after the system reaches a representative operating condition.
For fault interpretation after energisation, the companion guide to Titania output fault diagnostics explains how commanded state, load measurements and supported driver status should be read together.
Selection and design review inputs
This planning method is relevant to machine builders, panel designers and system integrators using Titania with solenoids, relays, indicators, annunciators and other 24 VDC loads. It is particularly useful where multiple outputs may operate together, cable runs are long, ambient temperature is high or the safe-state pattern differs from normal operation.
Use the product selector to compare the field-I/O requirement, then review the industrial automation solutions and controlled resources. Final design work must use the matching terminal drawing, installation guidance, firmware release and register map for the delivered revision.
Need a quick engineering check? Send the load list, steady and inrush currents, simultaneous-output pattern, cable lengths, supply model and enclosure temperature. Tachyonic can review the main power-budget assumptions before panel design is frozen.
Technical basis: Titania Modbus DI-8 DO-8 datasheet TTN-DS-2026-001, Rev 08, issued 22 July 2026. Image: ranjeet . via Pexels, used under the Pexels licence.
