Ahh Lighting Control... The ultimate tweak
(AKA: What Else Can We Make It Do!)
This is an area where Control ideas can be simple, complex, or just beyond the fine line drawn at "Crack-Pot"
Anyhow, with that disclaimer mentioned, here are several approaches to your particular scenario, and a few "Ideas" to consider.
Each example has a valid use, and I will stay away from the "Crack-Pot" zone stuff!
Simplest control method is to use a Photocell by its self. The PC could control the Lights directly (one lighting circuit through the Photocell), or the PC could control a Contactor - which would control 2 or more circuits
(the Contactor is an "Amplifier" - but in the first example, the Photocell is also an "Amplifier". A little trivial FYI for the heck of it!).
This method is rather crude, and is limited to "On At Dusk / Off At Dawn" ( ±20 minutes tolerance ).
Next approach would be to bring the Lights on at Dusk, and turn them off at certain set Time(s). ("Times" being an even more advanced approach. - see "Multichannel Clocks" below)
For the most basic setups, controlling the lights using a very simple and basic program schedule(such as "On at Dusk, Off at 10:00 PM - Mon. thru Sun. - All Areas")
incorporate a Basic Time Clock with a Photocell.
The Power Source - which feeds to both devices, would be "Unswitched"; so they operate constantly and do not effect each other's "Time Of Day" Feature.
Time Clock Motor is connected to constant power, and so is the Photocell's "Line" side.
The "Load" side lead from the Photocell (typically the Red wire), would run through the Time Clock's Contacts only - not to the T.C. Motor (or timing element).
This could drive a Contactor for any combination of circuits, or if only one lighting circuit is used, drive the lights directly.
This setup gives the "On At Dusk" function
(set the Time Clock for "On" Event at around 3:00 PM, so the contacts will be closed once the Photocell closes its contacts, and allows the "Load" side to become active),
and allows for a "Fixed Off Schedule"
(set "Off" Event for something like 10:00 PM).
***Advanced Timeclock Approach: Multichannel Clocks
An advanced approach to the above scheme, is to use a 2 channel Time Clock for two separate "Off Events" - like all "On" at Dusk, one area "Off" at 10:00 PM, the other area "Off" at 12:30 AM.
Choices of 1, 2, 4, 8 and even 16 channel clocks bring these functions into a new idea of "Advanced"!
An additional "Dusk To Dawn" function may be incorporated with these also - just drive a Contactor directly from the Photocell's "Load" output.
Now, we have gone from "Basic Controls" into "Advanced Controls", simply by adding a few basic functions to a scheme.
With the "Electronic" versions of Time Clocks (suggest using these if possible), even more control ideas may be achieved.
These clocks add to the "Advanced" approaches with Flexibility of schedules:
- meaning they can be programmed to have certain events occur on certain days, and normal events on others;
plus they can allow for manual overriding by the user, and in addition to the manual override, they can be set to "Sweep" the schedule, which assures the Lights return to "Off" status by a certain time.
Very handy and useful when doing advanced control techniques, or if users will be using an override feature at random times.
As an alternate component, the "Astronomical Timer" is nice. They also come with multi channels and advanced features.
These eliminate the need of a Photocell, and allow for more precise "Sun Tracking" (if needed), and nicer transition to Daylight Savings / Standard Time changes.
Most Electronic Time Clocks have automatic time adjustments for Spring / Autumn.
Also, they have "back-up clock power" - in the event of a power loss, they do not lose their program or RTC program (they won't go back to "12:00 AM" if power is momentarily lost).
For the really big tweaks, incorporate Sun Tracking abilities - either with a Photocell, an Astro Clock, or both -, along with some "Decade Timers", Motion / Zone Detectors, an RTC (Real Time Clock) function, some manual overrides, a programmable sequencing controller, and even toss in some simple Dimming Schemes (like Lutron's Graphic Eye stuff).
Now you have a complex approach to Lighting Controls, and are still far away from the "Crack-Pot" realm!!!
All functions mentioned above are simple to design, install and use.
The "Complex Tweak" is - of course - much more difficult to design, install and use - but it still can be done in a simple all-around way.
Edit: edited to clarify the information in a few places
[This message has been edited by Scott35 (edited 04-27-2005).]