The circuit
Apart from the CloudWatcher itself, the only additional component required is a roof-open limit switch — that is, a switch that is closed (active) when the roof is open and open (inactive) when the roof is closed.
The roof motor push button is connected, in series, to the limit switch and the CloudWatcher relay. This means the CloudWatcher can only trigger the motor when the limit switch reports that the roof is open. If the roof is already closed, the circuit is open and the CloudWatcher relay cannot activate the motor — making it physically impossible for the system to try to close an already-closed roof or to open a closed one.
Compatible limit switches
Any limit switch that provides a normally-open contact can be used. Common options include:
- Rugged mechanical limit switch (e.g. Omron)
- Distance/proximity sensor with relay output
- Magnetic proximity switch
Choose a switch rated for outdoor use with appropriate IP protection for your climate.
Before relying on this in production: Test the circuit with the roof motor before leaving the observatory unattended. A small minority of roof motors require the push button to be released before movement begins; for those motors, this wiring approach will not work as described. Test to confirm yours responds correctly.
Safety by design
The series connection ensures that the system can only close the roof, never open it. The CloudWatcher determines when to trigger the relay (based on weather conditions), and the limit switch determines whether the triggering is physically possible. If either condition is not met — CloudWatcher says safe, or roof is already closed — nothing happens.
This is a simpler and more cost-effective approach than full observatory automation with a DragonFly controller, suitable for setups where only emergency roof closure is required and no other automation is needed.
For full roll-off roof automation including remote opening, status monitoring, and multi-sensor integration, see the DragonFly observatory controller.