Re: Software for Central Heating Control

["Steve S" <incog@xxxxxxxx>]

"John Rumm" <see.my.signature@xxxxxxxxxxxx> wrote :


<mega snip>>
> Have a look at some of the many X10 and home automation sites.
>
>> What is the best hardware?
>
> Define best?
>

You need to be very careful with projects like this, especially when you
have loads of sensors and functions. They introduce very many corner cases
and single points of failure. You will need to do a lot of very methodical
testing. What happens when a sensor fails? Can you detect it and act
appropriately? In the system I am designing (using C, by the way) it is
designed to fail passive, reverting to the old control system.

Most SBC solutions use cooperative multitasking. This requires careful
coding in order not to break it.

Also, plan what to do if you decide to move house. A homebrew heating
control system is not likely to add to the value of the house. In my case I
shall be able to revert to a normal if somewhat outdated control system at
the drop of a hat.

Dallas 1-wire sensors are OK, but bear in mind that for any significant
distance you'll need twisted pair cabling. Also think carefully about the
interface to them. If interfacing directly to an SBC the timing is critical,
and you'll need interrupts turned off for much longer than is desirable on a
multitasking SBC. Use the 18S20's via an I2C interface chip instead.

I'd advise looking carefully at risks versus benefits wrt the complexity of
your project. Does taking wind speed and direction into account (for
example) result in measurable benefit and what is the risk in terms of
software complexity?

If you want to go ahead, get yourself an evaluation kit and start playing
and learning. This will help you understand the magnitude of the task ahead.

HTH,
Steve S