On Mon, Aug 27, 2001 at 09:09:40PM +0300, Markus Vuori wrote:
> Hi, all!
>
> I'm planning to build a home automation system of my own.
> I've been told that PICs would be great for this.

It looks like a PIC could be usefule in this application.

>
> I plan to use RS-485 bus to connect PICs together. Is this
> a good choice?

Yes. Just a couple of comments though:

1) You may not want to do polling. First off it loads your primary controller.
Secondly the application environment is relativly static. Lastly when you
really need to get an event (FIRE! Burglar!) the dectector of the event will
have to wait to be polled to respond. Probably not a big deal with only
a few nodes. But I'll bet that once the infrastructure is in place, that
you'll add a whole bunch of nodes.

As an alternative consider adding an interrupt line that any node can signal
on. Making it wire-or means that multiple nodes can tug on the line without
contention. This line can interrupt the primary. The only issue that's left
is how to resolve contention when multiple nodes want to report.

2) Consider a PIC per station/detector as opposed to one per room. Two
reasons. The first is that you get more flexibility with automatic control.
Consider the situation where you want different groups of lighting in the
same room. By having a PIC per socket, you can simple readdress the group
without having to change the state of the PIC. Also you're going to have
to have a wire at the target socket anyway, so why not put the intelligence
as close to the socket as you can.

3) Send power through your wire. I believe that CAT5 can support up to 3.3A
of current. That should certainly be enough.



> For several weeks I have tried to document
> my ideas and today I started translating the document into English.
> It can be found at http://www.plopcrew.net/vuori/talo/ha.html
>
> However, I'm _new_ to PICs and electronics, so I would
> like to ask if anyone of you has done something similar.
> I would be pleased if you had some ideas or appropriate
> links (especially for circuits). Any kind of help would be
> greatly appreciated. I hope I'll some day get this finished
> and documented so that others can benefit, too.
>
> I think the programming is not that bad for me, as I know C and
> have done some Z80 asm programming, too.

Consider JAL (http://www.xs4all.nl/~wf/wouter/pic/jal) as another alternative.
Easy to learn, Compilers for Windows and Linux, significant libraries.

>
> Sorry for my bad English. Please ask, if this email or
> the web page mentioned is unreadable or not understandable.

How about this. I wish I could write Finnish as well as you write English.
It's not bad at all.

BAJ

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