HomeVision Controls my Central
Heating!
14 December
2001
Submitted By: Mark
McCall
I've finished (eventually) the pics
and write-up of Keith
Doxey's
interface
between my central heating and HomeVision...
"The switch mounted LED's are fed from the 12 volt
supply via resistors R1 (Downstairs Zone) and R2 (Upstairs Zone).
HomeVision
pulls Port A3/A4 low when the heating is OFF which short the LED side of
the
resistor to ground, this extinguishes the LEDs. The relays are fed from the
12
volt supply and are grounded by Port A1/A2 going low to operate the relay.
This
turns the heating ON. The mains side of the relays
are
wired in parallel to the existing programmer contacts and the programmer is
set
to OFF. In the event of HomeVision or Relay failure the existing programmer
can
be switched on and conventional heating control is instantly available. As
the
relays are connected to 240V AC is important that all connections are
insulated
using heat shrink sleeving and the enclosure containing the relays is only
accessible by means of a screwdriver."
Click here to see all the pics,
circuit diagram and write-up.
http://www.automatedhome.co.uk/homevision_heating.html
M.