Subject: From: Date:

Temp items - format question Wayne Sun, 13 Sep 1998 15:32:39 -0400

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  Mark G and I have been working on adding support for the HAI RC-xx series
of thermostats.  I am (We are?) not sure what format the temperature items
and set-points should be presented in.  Most of the dilema has to do with
the 'stat serial protocol, as it is geared towards Celsius.  Here is part of
the protocol chart:

OmniUnits   C       F   (from Appendix A of serial6.doc)
121	 20.5	 68.9
122	 21.0	 69.8
123	 21.5	 70.7
124	 22.0	 71.6
125	 22.5	 72.5
126	 23.0	 73.4
127	 23.5	 74.3
128	 24.0	 75.2
129	 24.5	 76.1
130	 25.0	 77.0  ***
131	 25.5	 77.9  ***
132	 26.0	 78.8
133	 26.5	 79.7
134	 27.0	 80.6
135	 27.5	 81.5  ***
136	 28.0	 82.4  ***
137	 28.5	 83.3
138	 29.0	 84.2
139	 29.5	 85.1
140	 30.0	 86.0
141	 30.5	 86.9

   The left column is the register values, the Celsius is a simple, direct
conversion ( (register-80)/2 = Celsius ).  Fahrenheit is the mathematical
conversion of the Celsius, so it is not nice round numbers.  Notice that
there are two register settings that compute to 77, if it is truncated to
whole numbers.  If you round things, then there is a double entry at 82!
   The physical thermostat displays WHOLE F degrees (ie 79) or HALF degrees
C (ie 26.5).  As an engineer, it kinda goes against my nature to display a
number such as 79.7, when the next increment is 80.6, rather than 79.8.  It
implies a precision/accuracy that isn't really there!  Am I being too nerdy
here?
   At the moment, Mark has items showing as '79.7 F / 26.5 C', we have also
considered '79.7 / 26.5' (no labels) or '79 / 26/5' (no decimal).
   At one time, it simply displayed '79' and you had another item that would
toggle all displays to Celsius mode.  This version had a problem where the
ECS item didn't always match the stat display (due to rounding?).
   I am not sure if it is better to use whole numbers (rouunded or
truncated?) or show the true number (including decimal)?  I think that
somewhere/somehow, we need simple numbers for speaking and testing in events.
   Since I have only been testing on a spare Win machine without my 'stat
actually hooked up to the A/C, I haven't written any real events to handle
this stuff.

   What do y'all think of this?  What would be the preferred format?  What
are those of you with weather devices or other 'stats using?  This situation
really applies to many temperature devices, not just this 'stat.  This would
be so simple if my wife spoke Celsius!

c'ya,
Wayne

   waynew 'at' magicnet 'dot' net,   Orlando, FL
   http://www.magicnet.net/~waynew

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