RE: Thermostat Hysterysis

["Dean Smith" <ukha@xxxxxxx>]

Currently I've stuck with the DS1820's own scheme for the temp i.e. store
i=
t
as double the real value (therfore last bit =3D 0.5 or 0.0). I match my
required temps and hystersis etc to that scheme so keep the 0.5 degree
resolution. - and use "Byte" throughout for that side.

Some of my string handling I think is too blame a little. Too much bad
practice from VB coming through ;) I think I need to explore storing a few
bytes in eprom or something.

Currently I've had to drop checking for negative numbers to get it to fit.
Hopefully that would never be an issue though :o

Dean

-----Original Message-----
From: Dave McLaughlin [mailto:dave@xxxxxxx]
Sent: 07 October 2003 09:52
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Thermostat Hysterysis


Hi Dean,

I use a 2 degree hysterisis. At present it is only used to operate an
electric heater in my loft, where my computer and HA system lives. To save
code space, I didn't use an LCD and stored the temp as an integer times 10.
The DS18S20 only changes by 0.5 degrees anyway so this is ideal. The CAN
Bu=
s
interface code is quite compact as it uses the filters built into the CAN
controller to receive any new messages for the setup etc. Haven't really
done much more than this at present. The relay output is fed into Homeseer
via Justin's gameport plugin.

I programme in C using the excellent Codevision compiler so I can't really
comment on code optimisation other than ask how you store the value in the
software and if maybe using integers might compact it up more?

Regards
Dave...
PS.. My embeddedcomputer.co.uk website is back up now if you want to have a
look at the CAN bus stuff. I am looking at doing some simple room
thermostats using the ATMega16 and a 2 digit LED display as I wanted an
excuse to use the new blue seven segment displays from Farnell :o)
---
Very funny Scotty, now beam down my clothes!!!
---


-----Original Message-----
From: Dean Smith [mailto:ukha@xxxxxxx]
Sent: 06 October 2003 20:38
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Thermostat Hysterysis


Dave

Do you implement any hold time on the heating on/off state ? i.e. It can
only change 1 a minute etc. or do you rely on the general hysteresis of
the
house to ensure the thermostat cant cycle on/off too quickly ?

I have working code for :- Reading the DS1820 and displaying to a 2 line
LCD
+ RS232 Comms for Parameter Setup/Temperature interogation

Which is now 99% of the available flash on a 2313 using BASCOM-AVR. Any
hints and tips for code optimisation !

Thanks
Dean
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