Wednesday, November 23, 2011

Ready for Christmas

One of the jobs I want to hand over to the WebCell is turning the Christmas lights & decorations on and off. I’ve been using mechanical timers, which is fine until there’s a power outage and they fall behind.

I spent three days last week creating the web pages needed to enter the Insteon control devices and the times to turn them on and off. It was very similar to the thermostat pages and I used them as a starting point. All the underlying scheduling features of the WebCell were supposed to ready, but one of the days was spent debugging new bugs the pages exposed.

I wasn’t satisfied when I was done, because I was still skipping over one of the last unimplemented features in the CellScript specification: the ability to schedule relative to sunrise and sunset. It made a lot of sense to do this now, since I would want the lights to go on about sunset. So I attacked that problem this week.

I did a web search to find the equations, and used a spreadsheet to enter test values and see all the intermediate values. The equations use a lot of trig functions, but they’re all in the C runtime library for the AVR. It took two days to get “sun-based” scheduling fully implemented, and one more day to rework the scheduling web page to accept entries. I put one set of decorations on a sunset-to-midnight schedule so I can watch and make sure it seems to be working right.

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