Embedded temperature controller...

[Geir Holmavatn]

Hi,

I'm looking for a way to control the temperature in various rooms in a
community building. One should be able to program 'events' where the
temperature in the room (channel) in question should be altered for a
period of time.

I imagine that such a device would be simple to implement using an
embedded controller with flash memory and a TOD clock. I could run
linux with a webserver and a simple database.

Anyone here having heard about such devices or have comments on this
scenario?

Thanks a lot for feedback

regards Geir

 

[linnix]

Hi,

I'm looking for a way to control the temperature in various rooms in a
community building. One should be able to program 'events' where the
temperature in the room (channel) in question should be altered for a
period of time.

I imagine that such a device would be simple to implement using an
embedded controller with flash memory and a TOD clock. I could run
linux with a webserver and a simple database.

Anyone here having heard about such devices or have comments on this
scenario?

Thanks a lot for feedback

regards Geir

Controller is the easy part. Wiring all the sensors and actuacters is
the difficult part. How do you plan on commuicating between sensors,
actuacters and the controller?

 

[Geir Holmavatn]

linnix skrev:

Controller is the easy part. Wiring all the sensors and actuacters is
the difficult part. How do you plan on commuicating between sensors,
actuacters and the controller?

1-wire or X10.

I focus now on finding a good embedded controller with at least 4
channels and a good data base and intuitive webinterface.

regards

geir

 

[linnix]

linnix skrev:


1-wire or X10.

I focus now on finding a good embedded controller with at least 4
channels and a good data base and intuitive webinterface.

regards

geir

There are X10 modules for passing digital on/off data. I have not
seen any module for analog data such as temperature sensors.

 

[linnix]

There are X10 modules for passing digital on/off data. I have not
seen any module for analog data such as temperature sensors.

OK, find one. No sure how it works with the rest.

http://www.smarthome.com/3049B/X10-Bi-Directional-HVAC-System/p.aspx

 

[Geir]

linnix skrev:

OK, find one. No sure how it works with the rest.

http://www.smarthome.com/3049B/X10-Bi-Directional-HVAC-System/p.aspx

This allows the threshold to be altered by anyone. I want to control
everything from the computer, a dual display for current and preset
temperature would be nice though, but no requirement

geir

 

[John G.]

Hi,

I'm looking for a way to control the temperature in various rooms in a
community building. One should be able to program 'events' where the
temperature in the room (channel) in question should be altered for a
period of time.

I imagine that such a device would be simple to implement using an
embedded controller with flash memory and a TOD clock. I could run linux
with a webserver and a simple database.

Anyone here having heard about such devices or have comments on this
scenario?

Thanks a lot for feedback

regards Geir

Centrally controlled air cons are crap.

Thermostats in each room are the only successful way and many aircon
companies make them and have done for 50 or more years.
Stop reinventing the wheel and let an expert help you.

John G.

 

[John G.]

But such systems aren't just simple duct work. At the very least a
multi-room controller involves controllable registers.

I would bet that Geir doesn't have a lot of money to burn.

...Jim Thompson
--

Whatever way you look at it, central control will never provide the comfort
of distributed thermostats and both require duct work of some sort to
actually change the temperature.
I agree the OP is likely tring to save money but should realize it may be
the wrong way to achieve a good result.
And professional A/C suppliers are likely to be better value in the end.

John G.

 

[Charlie E.]

Whatever way you look at it, central control will never provide the comfort
of distributed thermostats and both require duct work of some sort to
actually change the temperature.
I agree the OP is likely tring to save money but should realize it may be
the wrong way to achieve a good result.
And professional A/C suppliers are likely to be better value in the end.

John G.

John,
I take it you have never investigated the cost of those duct and
register controls. I have. you can figure about an order of
magnitude in cost increases over a standard set of ducting.
Electronics (as in thermostats and controls) are cheap, but
mechanically operating duct controls are expensive!

The system I was looking at would basically divided my house into
three 'zones.' Trying to do it room by room is just expensive
insanity!

Charlie

 

[Charlie E.]

There are retrofit systems that create multiple zones from one central
heat a/c source. They involve installing some sort of damper for each
zone. This is going to be the big cost item (if individual zone controls
don't already exist).

From that point, the zone thermostats, central controller, etc. are
simple and existing technology. They come loaded with features that will
guarantee your scratching your head and pouring over operating manuals
for months.

One interesting system I saw on a home improvement show involved
controlling the air to each room with a system of inflatable bladders
that were pulled into the ductwork. Each had an air line that was routed
back to a pressure/vacuum control manifold. Upon a command from a
wireless zone t'stat, the controller would start the furnace or a/c and
then deflate or inflate the bladders depending on whether a particular
zone needed or did not need air flow.

You also need to add a 'diverter' to the system, that diverts extra
air flow not needed by the fewer ducts, back to the supply side of the
fan. Otherwise, you blow those balloons right out the duct!

Charlie


PS: Those balloons aren't cheap, either!

 

[Charlie E.]

With it likely that Obama's "development of alternate energy sources"
is going to double my electric bill, I think I'd better be looking
into replacing my 15-year-old "heat pumps" with something more
sophisticated/efficient.

Servo-controlled registers shouldn't be all that hard to implement on
your own... unless you're as dumb as AlwaysWrong or Slowman.

Fortunately my house is already well-insulated... I make it thru the
Winter with rarely more than a night or two of heat required.

"Diversion to supply side" sounds like it could be implemented simply
with another duct with a controllable register??

Of course my system would not utilize a single uP ;-)

And maybe we _will_ have global _cooling_, beneficial to us
CONSERVATIVE desert rats ;-)

...Jim Thompson

Hi Jim,
The diverters I studied were all mechanical. Basically, as the
pressure reached some value, it forced open a damper between the two
sides. It functioned pretty much as a pressure regulator.

Of course, all this stuff is real sheet steel, so it isn't really
cheap. When you add the motorized dampers for zone control, that is
when the real expense kicks in.

Some of them were basically on/off, which consisted of a spring loaded
flap and a latch. When you wanted it closed, it released the latch.
Air flow raised the flap to block that register or zone. It only
would re-latch if you stopped the air flow. Not good if your system
wants to add flow to a zone that is already stopped. You have to shut
down, wait for the presure to drop, the spring to catch, and then you
could start up again with the new load setup.

Sounds like an MCU sort of operation to me!

Charlie

 

[John G.]

John,
I take it you have never investigated the cost of those duct and
register controls. I have. you can figure about an order of
magnitude in cost increases over a standard set of ducting.
Electronics (as in thermostats and controls) are cheap, but
mechanically operating duct controls are expensive!

The system I was looking at would basically divided my house into
three 'zones.' Trying to do it room by room is just expensive
insanity!

Charlie

Hey,
I never said how small or how to divide the AIR system, all I suggested in
the beginning was that central control by a computer was not too clever and
a better way would be local thermostats that actually knew what area was hot
or cold.

However the decisions are made there will be similar costs involved in
controlling the air delivery.

My house is 3 zones and one thermostat and if I think I need a change, I
change a zone switch. That's the way it was when I came here and it works
fine ,for us.

John G.

 

[Charlie E.]

How about a couple of solenoids to open/close dampers,
thermostatically controlled, OR all thermostats to the central unit
(AND'd with pressure sensor... exists already on my big systems.)

...Jim Thompson

Exactly, that is the level of complexity that comes across. Of course
a solenoid takes real power to operate, it has got to move that
'heavy' damper...

Charlie

 

[krw]

Not a "vane" type.

Weenies blow with the wind.