Axel Berger  wrote:
> Mans Nilsson wrote:
>> On the actual issue you've got, I did google a bit to see if this was
>> easy. Apparently it is not.
>
> You seem to be absolutely right. I have just started a thread on the
> openHAB community (and through a snafu, fault is mine, can't contribute
> or reply there any more) and from what I see nobody there has an inkling
> what a thermostat is or does.
>
> All they can come up with is
>
> If temp
> which is bound to male you life hell in a slow reacting floor heating
> environment. They seem to think the smarts are in the rules for turning
> up a bit in the morning and down in the evening and in creating a jazzy
> GUI.
>
> The plus side is, I can easily forego all that bloat then. If I do get
> down to it and tech myself digital regulation algorithms I can just as
> well put on a simple command line interface as is preferable anyway and
> be done with it.
>
> This leads to two questions: What programming language should I use? I
> haven't done any real programming in ages and the languages I used to
> know are obsolete. I have done (or rather used) a simple test routine
> for my solenoid output card in python, which seems to be the accepted
> standard for the pi, but I don't like it. Are there any better
> alternatives (except c, which I hate)?
>
> The second problem is hardware. The ducts leading to my current
> thermostats are strictly a star configuration, so one wire is not the
> obvious choice. What ohter kinds of sensors are there and how can I
> connect at least 8 to the Pi? Part of the GPIO, 8 output pins, is
> already taken by the solenoid card.
>
> Danke
>  Axel
>

Some years ago, I lived in a house with radiant floor heating. Surprisingly
(to me) it was controlled by a simple thermostat--negligible hysteresis, no
anticipator.

As you might imagine, it would switch on in the afternoon and typically run
until about 5am, after which the temperature would continue to climb until
almost noon, necessitating opening doors and windows to stay comfortable!

My solution was to install a simple timer switch in the thermostat circuit
that switched on about 4pm and off about midnight. The effect of this
arrangement was that on cooler days, the heat came on earlier, but not
before 4pm, and turned off at midnight. This provided a "pulse width
modulated" heat input to the house with a daily period.

The result is that the house was beginning to warm as the night got colder,
and the heat in the slab was sufficient to keep the house comfortable until
the afternoon (on a cold day) or the evening (on a not-so-cold day). A
further benefit was that it cut our heating fuel cost in half.

For heating systems with lags of hours, it is important to anticipate a
future need for heat as well as anticipating the considerable overshoot
that will occur after the heat is switched off. I found this simple PWM
approach quite effective.

--
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

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