The concept: hardware-level safety

Most observatory automation systems close the roof via software: the weather sensor triggers a signal, the automation software reacts, and a command goes to the roof controller. This chain works well, but it has a weak point: if the automation PC crashes or freezes, the software cannot react.

Wiring the CloudWatcher relay directly into the roof motor circuit provides a hardware-level backup that operates independently of any PC. When CloudWatcher detects unsafe weather—regardless of what the computer is doing—the relay opens and the roof can no longer remain open.

What you need

  • CloudWatcher with relay output (all models include this)
  • Your roll-off roof motor and its existing push button
  • A roof-opened limit switch—activated when the roof reaches the fully open position
  • Wiring between these three components (in series)

Available limit switch options include rugged mechanical switches (Omron), proximity sensors, magnetic switches, and USB-controlled switches for integration with automation software.

The wiring principle

The three components—the roof motor's push button, the roof-opened limit switch, and the CloudWatcher relay—are connected in series in the motor's control circuit.

Series circuit—simplified wiring diagram

Push
button
Roof-opened
limit switch
CloudWatcher
relay
Roof
motor

How it works in practice

  • Normal operation: all three components are closed → pressing the push button runs the motor in either direction (open or close).
  • When weather is unsafe: the CloudWatcher relay opens → the motor circuit is broken → the roof cannot be driven open, even if the push button is pressed.
  • The limit switch: when the roof reaches the fully open position, the limit switch activates → this also breaks the circuit → the motor cannot accidentally over-drive into the open direction.

This design allows the relay to close the roof but prevents it from opening automatically. The roof can only open when the push button is manually pressed. Safety always defaults to closed.

Before you wire it permanently: test your motor first

A small number of roof motors require the push button to be released before they will start moving. For these motors, this wiring scheme will not work: the relay closure triggers as a momentary pulse, and if the motor needs the button released to start, it will not respond. Test your motor before committing to this design. In practice, the vast majority of motors are compatible.

Combined hardware + software approach

The relay-based approach works best as a hardware safety layer underneath a software automation system. Your automation software handles normal sequencing (park mount → close roof), while the relay provides a fallback that works regardless of PC state. Both approaches complement each other and neither prevents the other from working.