How a Hotel RCU Drives a Motorized Curtain: Wiring and Control Logic
One-touch motorized curtains look effortless to a guest, but the behavior is defined entirely by the Room Control Unit (RCU) behind the wall. In this demo we wire a tubular curtain motor to the RCU’s motor-control output and walk through the open / pause / resume / close logic. This article breaks down what’s actually happening on the board, the signal path, and how the same logic plugs into a wider guest room management system (GRMS).The hardware in this demo
The bench setup has three parts: a guest wall panel, the RCU mainboard with its relay outputs, and a tubular curtain motor on a powered track. The curtain motor in this example is a mains-voltage tubular motor with built-in limit switches, so it stops itself at the fully-open and fully-closed positions. That means the RCU only has to command direction and run/stop — it does not need continuous position feedback for basic operation.
The signal path: panel → RCU → motor
The wall panel does not switch mains power directly. Instead it sends a momentary command over the room bus to the RCU. The RCU’s firmware interprets that press and energizes the appropriate output. For a curtain, that output is a pair of mechanically interlocked relays — one for the “open” (up) direction and one for “close” (down). The interlock guarantees both directions can never be energized at once, which protects the motor windings.
Why one button does open, pause, and resume
The “press to start, press again to pause, press again to resume” behavior is not in the motor — it lives in the RCU firmware as a simple state machine driven by momentary presses:
- First press (Open): RCU latches the open-direction relay; the motor runs until the next press or until the motor’s own limit switch trips at full open.
- Second press: RCU drops the relay — the motor stops at its current position.
- Third press: RCU re-latches the same direction — the motor resumes.
- Close follows the identical state machine on the down-direction relay, running until fully closed.
Because the logic is firmware-based, the same physical key can be re-mapped to other loads, and pause positions are arbitrary — a guest can stop the curtain at any opening they like.
Integrating curtain control into the GRMS
Keeping the curtain logic in the RCU rather than the motor is what makes it scriptable at the property level. Once the RCU is on the GRMS bus (typically RS-485 or IP to a room gateway), curtain open/close becomes a command the system can issue as part of a scene: a “Goodnight” scene that closes curtains and dims lights, a “Wake-up” scene on a timer, or an automatic close at check-out to cut solar heat load. The front desk or BMS can trigger these without anyone entering the room.
Frequently asked questions
Does the RCU need position feedback to stop the curtain?
Not for basic open/close. The tubular motor’s internal limit switches halt travel at both ends; the RCU only commands direction and run/stop. Motors with encoder feedback can be used where precise intermediate positioning is required.
How are the two directions protected from running together?
The open and close relays are interlocked, so only one direction can be energized at a time — a standard safeguard for AC tubular motors.
Can curtains be controlled remotely as well as from the panel?
Yes. Once the RCU is part of the GRMS, the same curtain commands can be sent from a scene, a timer, the front desk, or the building management system.
Bring one-touch curtain control to your rooms
Motorized curtains are one of many loads a single hotel RCU manages alongside lighting, HVAC, and service signs. For wiring diagrams, supported motor types, or a full GRMS specification, see more at smartguestroom.com or contact our engineering team.