On Tue, 23 Nov 2010 21:59:14 -0600, "Jane_Galt"
wrote:

John Fields wrote :

On Mon, 22 Nov 2010 01:01:01 -0600, "Jane_Galt"
wrote:

John Fields wrote :

On Fri, 19 Nov 2010 13:58:09 -0600, "Jane_Galt"
wrote:

Does anyone make a programmable appliance controller that can handle
fluorescent lights?

I want to be able to program lights so that they always go off at 10
PM but match the number of hours in the local day.

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I'm not sure I understand.

Do you mean that you want the controller to always turn the lights on
at something like "sunrise plus one hour" and always turn them off at
10 PM?

What about daylight savings time?

No, I want them to always go off at 10 PM and be on the length of the
local daylight. So, for example, if we have 7.25 hours of local daylight
that day, I want them to come on 7.25 hours before 10 PM and go off at
10 PM.

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So how do you plan to determine the amount of local daylight on an
ongoing daily basis??

Good question. If I were a programmer ( I'm not ) I'd use an ephemeris
table to pick the number of daylight hours each day and subtract them from
10PM.

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An ephemeris is used to locate objects in the sky; what you'd use
would be a sunrise/sunset table:

http://www.usno.navy.mil/USNO/astron...rs-one-year-us


In response to your original question, I don't believe there are
appliance timers out there that do what you want.

It sounds like what you're trying to do is mimic the duration of
natural daylight, indoors, with sundown being hard-wired to 10 PM.

If you're interested I can tell you how to do that.


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JF