RE: Sending and receiving addressable contact closures.

["Hawes,Timothy Edward \(GEG\)" <haweste@xxxxxxxxxxxxxxx>]

Alan,

There's a number of "brick" PLCs that may do the job, from
manufacturers
such as Mitsubishi (model = Alpha 2), Siemens (LOGO), Telemechanique
(Zelio), Moeller (Easy500, 700, 800) and Crouzet (Millenium 2 Plus).
See RS for examples (http://rswww.com) and
Google for more detailed info
:-)

The only drawback I see with these is that 70 I/O will be a bit of a
challenge. Most brick PLCs stop at 30-40 I/O, so you could use two (or
more) separate systems. Any more and you may be better off buying a
"proper" PLC e.g. Allen Bradley, Mitsubishi and others, but then
the
price starts to go up quite considerably.

Also see page 9 of the Crouzet brochure from the link below. The top
picture ("Network") indicates that you can link 2 Crouzet units
together
for a total of (20+6)+(20+6)=52 I/O points.
http://www.crouzet-usa.com/downloads/millenium/m2_brochure_usa3.pdf
Using RS's prices you're looking at nearly GBP 500+vat (1 starter kit,
one additional XT20 controller, two expansion modules and a power
supply). I don't know all the ins & outs of the Crouzet range so you
may
need additional parts. What budget do you have?

I guess you could also do it all with CBus if you wished, via Bus
Couplers (inputs) and relay modules (outputs) with suitable interposing
relays between the mains voltage on the module and the 12V / 24V for
your relays. IIRC the input switches to bus couplers are volt-free, the
coupler itself drawing power from the CBus network, but I'm not sure of
that.

Hope that helps, if you want to pursue the PLC route further then drop
me a line (it's my day-job :-)  ).

Cheers,

Tim H.


> -----Original Message-----
> From: Alan Ainslie
>
> Some clever guy on our group must know the answer to this.  I
> have been looking in all the wrong places I guess.:-
>
> I need to send instructions to a number of switches to close or open:
> accessed by address.
>
> I also need to read the status of other switches as inputs.
>
> This is all ON/OFF so no proportionality and I do not want to
> use a PC, but am happy to make up a central controller and
> then to make up the devices that go onto the control bus.
> Ideally control bus would be two wires plus the heavy 12V
> supply to power relays and things.
>
> Anyone any ideas for chip set to do this robustly and
> economically.  Devices will be outdoors.  Everything is 12V
> only.  Numbers?  Less than 50 of the addressable switches and
> less than 20 of the input contacts closures.
>
> Application?  Well, almost an automated home: in truth this
> is to control signals and to read status of various devices
> on a 7 1/4 gauge large steam railway located-----in an automated home.
>
> Any railway nuts out there welcome to a day on the Spinney
> light Railway in Surrey.  Fully signalled at present using
> authentic 1930s railway technology.  new stuff is for a large
> extension and I really don't want to be running more miles of
> cables for the mice to eat.
>
> Alan