FYI Linux, I hear (no experience), has support for blind users, e.g. connecting a braille display and its voice recognition (I also guess) must be adequate too. Making a voice interface to your project must be feasible.

Options (1), (2) (I have no experience with microcontrollers) are valid depending on where you want to end up, i.e. how far to expand it. This can easily turn into a useful product with lots of capabilities unless re-inventing the wheel.

SSH, i.e .accessing the remote unit (uncle's) from your home (re:not sure yet how to access the remote unit): hmm you need to sort out uncle's IP somehow as ISPs tend to arbitrarily change it for home users. The problem is solved if the unit (uncle) accesses your servers (the website you have) to download script+data updates once a day - i think this is what you are suggesting. But then you must make sure that this works perfectly as you will be away. You can always install a back-door, it seems now-a-days it's a requirement in order to be MI5-certified :) There are various techniques to enable incoming SSH with minimal risk. But the risk is there none-the-less.

The RPi has lots of memory. You could preload a year's(or 10 years) worth of sunrise sundown times and reduce the need for as many updates.

James

... year's(or 10 years) worth of sunrise sundown times ...

The Earth's rotation is slowly slowing and days are getting longer, but the year-to-year change over ten or twenty years is small. If one were only concerned with 1-2 minute resolution, one could store, say, 62 or 183 sunup/sundown pairs (the day-to-day variation is also small). Since sunup and sundown only happen during certain periods of the day, these times might be stored as one byte each. This is a very small table.

Be that as it may, I'm not convinced one should be concerned with time as much as with light. What does it matter if, in midwinter, the curtains open at "sunup" when the sky is so overcast that it's like the middle of the night? A photocell/light level interface seems more important.

I agree with stevieb: These considerations and others suggest a microcontroller solution. A system running Linux seems like overkill indeed.

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Give a man a fish:  <%-{-{-{-<

These considerations and others suggest a microcontroller solution. A system running Linux seems like overkill indeed

If I were starting this now and the only outcome was to open and close curtains then I would be using a microcontroller.

I first heard about the Raspberry Pi many years ago and have been meaning to experiment with one periodically ever since so this is a good 'excuse'. Plus, it forces me to improve my Linux skills which in and of itself is a good outcome.

Besides, when this project was started, microcontrollers were not on my radar...

You could preload a year's(or 10 years) worth of sunrise sundown times and reduce the need for as many updates

Yes indeed that could be done. It is not especially difficult to calculate them either.

A side benefit of having the RPi call in is that the last state it put the curtains into can be seen on the web interface. Some family members are rather concerned that these curtains will never work correctly because of the poor experience we have had with the timer that is controlling them presently. Being able to see the time they last closed or opened might relieve some worry.

There is also the issue of opening at 8:30am and not at sunrise. My blind uncle's guide dog enjoys barking loudly at the children going to the school opposite...by 8:30am most of the children are safely installed. It is quite possible that the curtains might be required to open earlier during school holidays so keeping it flexible seems sensible.