RE: Homevision Relay boards ... Interested?

["Keith Doxey" <ukha@xxxxxxx>]

Why not design a small PCB with 4 relays on it and use a PIC12C508 to dirve
the relays.

The PIC could be programmed with a base address at programming time that
way
you wouldnt need any address pins just a few different PIC's programmed
with
different addresses. The PIC could be programmed for either serial(1 wire)
or clocked data (2 wires). That would leave 4 pins for driving the relays.

PIC12C508 is about a quid.(or less)

Serial data would allow any device capable of RS232 or RS485 to drive it.
Clocked data would allow almost anything that could waggle a couple of data
lines to drive it at almost any speed. (Homevision, Comfort, Parallel Port)

Serial or Clocked could be chosen by the PIC that was fitted.

People could order "GP Relay Board <a-nn>"
where a = C (Clocked) or S (Serial)
nn = Base address.

When you program the PIC to put in the kit you just choose a different
program to load into it.

By using RS485 line drivers/receivers you could put upto 256 of these
boards
on one cable. By using a PIC you can also do clever things like use
different codes to do do different thing eg codes 1,2,3,4 turn the
appropriate relays ON whereas 5,6,7,8 would turn the relays off. 9,10,11,12
could pulse the relay for 1 second so the board can be used for either
momentary or latching purposes.

It would make the board more flexible because it wouldnt just be limited to
HomeVision.

Just a few thoughts....keep us informed.

Keith

-----Original Message-----
From: Phil Harris [mailto:phillip.harris1@xxxxxxx]
Sent: 12 October 2001 18:53
To: ukha_d@xxxxxxx
Subject: [ukha_d] Homevision Relay boards ... Interested?



Hiya Guys,

Ian B and myself have been sitting here this afternoon trying to design a
relay board to control my electric curtains ... we thought that instead of
a
purpose built board to do exatcly what I need it might be useful to have a
general purpose relay board.

Throwing around ideas we have come up with the following "rough
description"
and are wondering whether there would be much interest from the group for
this as either a PCB or a built unit.

The board will take up a complete output port on HV. Four of the port lines
will be "relay select" lines, a fifth would be a
"status" line (On/Off) and
a sixth would be used as a "set" line to get the relay board to
read the
output port and perform the requested setting.

For example to turn on relay 4 you'd set the bottom four lines on the port
to OFF,ON,OFF,OFF (Binary Coded Decimal for 4), the "status" line
to ON and
then the "set" line to ON to action the command.

This would give you sixteen individually addressable relay outputs that
would retain their state until changed again or until the power went off.

It was discussed that the remaining two output lines could be used as
"board
select" lines which would enable up to 64 individually addressable
relays to
be controlled from a single HomeVision output port with the boards planned
as being stackable or daisychainable units.

Now, we haven't looked too deeply into this so we have no idea what kind of
costs would be involved or even at the moment what the programming for the
output ports would be like but we were wondering what kind of interest
there
would be from the group for such a board if we were to get it working.

Anyone interested if we decide to progress this further?

Phil



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