An Good Thread Here On Wiring For Day vs Night Scenes?

I've been thinking about day and night with 3 ganged variacs, clock wise, clockwise, and counter clockwise, day and nite are cw & ccw;dusk and twilight the third variac, with all variacs appropriately "tape insulated" for sequencing of day-dusk-nite-twilight-day. Nite would be the stars and moon with Aurora borealis ,perhaps. Still a concept and not yet a reality... but...

As you ask for any ideas, 

As I see it, the Variac is sunlight.  In the 1:1 world, light sensors are used to turn lighting on/off at dusk/dawn.  So how about a light-sensitive relay?  These are just a few bucks.  A relay turns on or off depending on the light level at the sensor - adjustable "trip" threshold.  Since the relay is of the SPDT type, it can turn some circuits ON at night (dark) and other circuits ON during day (light).

Otherwise, wire in an SPDT toggle switch to manually switch between day and night.

The relay idea is a good one. But I'd still want the ability to over-ride it. So I'd still end up with a switch controlling a separate power bus for....just as an example...the billboards. So the relay could sense a lack of light and turn on the billboards. But if I wanted them to stay off, I could hit my over-ride switch.

The triple-ganged variacs and the aurora borealis is an amazing idea. It is well out of my scope--heck I am not sure I can get this layout running before I kick the bucket. But for someone modeling the Northern roads, imagine the reaction that would draw from visitors!

Don

@Don Merz 070317 posted:

 

... But I'd still want the ability to over-ride it. So I'd still end up with a switch controlling a separate power bus for....just as an example...the billboards. So the relay could sense a lack of light and turn on the billboards. But if I wanted them to stay off, I could hit my over-ride switch.

A 3-position toggle switch could select between OFF-ON-AUTO.