[mh] Psuedo IP Thermostat

[John M. <jo...@wy...>]

I have a 9 zone radiant heat system.  Rather than replace all my thermostat=
s
with proliphix IP thermostats, at ~$250 each, I'd like to "hack on" etherne=
t
interfaces.  I'm am trying to see if I can reverse engineer a serial I/O
capability in my current thermostats, which are
simple WHITE-RODGERS non-programmable thermostats.  If that fails, I have
located power, ground, temp up, temp down, and heat/cool digital signals on
the thermostat PCB.  The thermostat settings (on the LCD) run from 45
degrees to 90 degrees.

I was thinking of using the 3 digital I/O pins that are on the gridconnect
Xport (http://www.gridconnect.com/xport.html) to monitor the heat/cool
switch (the thermostats are only used for heating) and the up/down
pushbuttons.  When the gridconnect detected a pushbutton closure, it could
keep a shadow counter to know what the temperature on the LCD display is se=
t
to.  Since the GPIO pins can be input or output, if I wanted to set the
temperature via ethernet, the pin could be reconfigured as output and then
pull the switch input low to change the thermostat setting.  Each night,
say, at midnight, the xport could drive the down button to 45, then send
pulses to get the temp back to what the "believed" temperature was.  I coul=
d
see the temp getting off a degree or so, if a button press was missed, but
overall it would give me two capabilities I'd like to get from my
thermostats:
   Ability to command 1-2 degree setbacks (without my wife's knowledge :) )=
,
   Ability to command "heat ups" to store extra heat in my thermal mass whe=
n
it is available (via active solar), or to turn on heating my garage (too
cheap to turn the heat on, but it's there) if solar heat is available...

Thoughts, pitfalls?  Or should I just swap out for the proliphix units?

I have ibuttons in all of my slabs, but don't feel like wiring up 18 relays
to get me override and ignore, while keeping my wife happy and having thing=
s
keep running if MH had a problem.

Thanks,
John