Maybe OT: Save fuel with a setback thermostat?

The actual input range of the A/D is 0 to +4V or +5V. You can change
the full scale range to increase the sensitivity by removing the
offset and attenuating resistors.
http://www.solid-motion.com/support/dataq_mod.html

jsw

Hello, Jim.

The input range of this DAU is 0-10 volts on the outside of the box.
I added the 10k pot so I could reduce the current a lot more than just
applying the whole  9 v across the the thermistor, since I was 1)
originally using a 9 v battery and 2) to minimize the heating of the
thermistor.  I saw no need to mess with the DAU circuitry, as long as I
could get a useful excursion.
   For determining the actual on and off points, I import the raw
readings into an Excel spreadsheet and mess with them there.
Of course, all of this is really overkill, because I could easily enough
just take the signal from the gas solenoid, or something in that area.
I just wanted to do it this way for the heck of it.  It is kinda
interesting, though, to see the rate of change of the temp as it all
happens.
   The graphs I show have been considerable compressed.  There are a
little over 900 samples taken per day.

I really have been delighted with this inexpensive Dataq DAU.  I used it
a couple of years ago to run a 1 1/4 year solar energy test  with one of
those HF 45 watt PV kits.

Pete Stanaitis
-------------------

Jim Wilkins wrote:

An inexpensive thermocouple amplifier for it:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3DAD8495AR=
MZ-ND
The high temperature limit is a bit low for some of my projects but I
may buy a few to play with. The Small Outline package can be spider-
webbed to a DIP component platform.

jsw

Interesting.
What do you do for cold junction compensation with a device such as this?

Are you aware of the Arduino?  The woodgas guys at allpowerlabs have
fitted one out with LOTS of stuff like this.  Looks like a really neat
almost general purpose process controller.

http://www.gekgasifier.com/gasification-store/instruments-and-test-equipment /

Pete Stanaitis
----------------------
Jim Wilkins wrote:
<snip>

-
After posting I read the full data sheet. The device reads its own
temperature to compensate, or if you short the t/c inputs it outputs
its temperature, at 5mV/C.

I've considered learning the PIC because I've seen them embedded in
quite a few products, like Lithium battery pack monitors. But for
logging data an old ~15 Watt laptop on AC makes more sense to me
because I can write substantial programs in QBASIC and have access to
the Windows file system, at least for 8:3 filenames.

An engineer I worked for encouraged me to use the parallel port for
general purpose I/O on his projects and it worked very well.

The data format from the DI-194 is messy but not THAT difficult to
capture and untangle. I also wrote a driver for the Radio Shack serial
data output multimeter, which is opto-isolated and useful to capture
AC voltage or current. With QBASIC I can read data from both.

The Dell Diagnostics partition on some older machines is FAT32 and
runs DOS7 from Win98. I edited the autoexec.bat with Knoppix to remove
all the reboots so it works as a DOS + Basic partition, and they are
incredibly fast on a >2GHz PC. An integer FOR loop takes one
nanosecond. Unlike Windows, DOS has almost no overhead, just the clock
tick every 55mS.

jsw

Jim Wilkins wrote:

That info gives an upper limit of about 1000C for a 5V supply but it has
a much higher supply capability so it implies the temperature limit can
go higher. Some of my interests include glass blowing so being able to
monitor temperatures upto 1300C would be good but that also typically
requires a R or S type thermocouple (platinum + platinum rhodium) for
longevity. As they have a lower output/ degree C then maybe they will
work OK with a 5V supply which would be easy. Do you have any idea if
they can be used directly with non K or J thermocouples?. Maybe a
software map to do any correction required.

Since you don't need extremely fast response times for glass, why not
just go with a stainless steel sheathed C/A TC?  IIRC, you can get them
with the TC junction welded to the end of the sheath or insulated from it.

Pete Stanaitis
-------------------

David Billington wrote:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AD8495ARMZ-ND

spaco wrote:

By C/A do you mean chromel alumel, if so that would be a K type IIRC.
The trouble is they don't live long at temps in the range 1300C and
neither do stainless sheaths, even the high grade ones especially with
certain glasses such as leaded glass. The normal thermocouple used would
be R or S and in a ceramic sheath as they can stand the temperature for
long periods.


http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AD8495ARMZ-ND

On Mon, 06 Dec 2010 09:23:41 +0000, the renowned David Billington


In Europe, IME, type R or S (Platinum-Rhodium) thermocouples are
common in this kind of application. In the US it's common just to use
a big fat (eg. AWG 8) cheap open thermocouple and replace it every now
and then.



Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Yes, Type R was a favorite in the high temp (2200 F to 3000+ F) Vacuum
heat treating furnaces.  But we still used C/A (type K) in the workhorse
machines---- 1800F to 2300F vacuum furnaces.  Of course we didn't have
the corrosion problems unless we were experimenting with partial
pressures of various gases.

Pete Stanaitis
-----------------------

Spehro Pefhany wrote:

On Sat, 4 Dec 2010 17:30:10 -0800 (PST), Jim Wilkins

Spaco is using a thermistor, not a thermocouple.


What does "spiderwebbed" mean?  Is that when you stick the SMT part on
a board upside down with glue and then solder #30 wires to its leads?

Right side up, on one of these:
http://media.digikey.com/photos/Aries/08-600-10.jpg

jsw

An 8 pin, 600 mil .1" between pin header.
Martin

On 12/6/2010 7:12 AM, Jim Wilkins wrote:

spaco wrote:

Would be interesting to know the outside temperatures.

First question is, "why do you care?".
If you care about cost, you should measure what you pay for.
Eyeballing a temperature graph has insufficient resolution.
While the "loss" is relative to temperature difference, you
don't know the temperatures where the loss happens.

You should always set the thermostat as low as you can tolerate,
but no lower.  It costs what it costs.  If your measurement
leads you to lower the thermostat to save cost, you weren't honest
about setting it as low as you could tolerate.

Assuming you're comfortable and you care about what it's costing
you...beyond what it says on the gas bill...measure that.

Faced with a similar question, I put a flapper on a microswitch,
set it on a register
and stuffed the signal into the serial port of an old Palm IIIc.
After some quality time with a stopwatch, the furnace and the gas meter,
I know the relationship between fan on-time and gas consumed.
I graph gas consumed.

I've been struggling to understand why my gas consumption
doesn't track outside temperature.  After doing the math, I discovered
a possible explanation.  The graph resolution is equivalent to 17 watts
of electricity converted to heat.  That's WELL below the noise level
of the measurement, but does seem to explain the anomalies.

Gas consumption tracks "inversely" the added 200W of heat while I
watch TV.  Go figger.
Outside temperature is around 40F this time of year.

So, what have I learned from all this?

1) I turned off the setback and run the house at 65 degrees 24/7
in winter.  I'm home 24/7 and sleep when I feel like it.  YMMV.

2) Air movement is EXPENSIVE.   My furnace fan runs 1.5 minutes longer
than the typical 6 minutes of heat.  You get some of that back in winter,
but it's still a significant electricity consumption and 3x the cost of
gas.
That's the dirty little secret of high efficiency furnaces.  Fans run
longer and that doesn't figger into the efficiency numbers.
Summers in Oregon are cool enough to open the windows at night.
I'd been running a big circulation fan all night.  I learned that
I could run the air conditioner all night for not much more $$.

3)Floor insulation may not be all it's cracked up to be.
Temperature in my crawl space was 55F when it was 20F outside.
After adding floor insulation and heating duct insulation,
it's still 55F under there.  Heat loss thru the floor insulation should
be proportionally better, but the deltaT isn't much.

4) The better your insulation, the less "anything you do inside" matters.

5)I managed to consume a bunch of time working on this, but in the
end, the answer is simple.  Use as little energy as you can tolerate.
I really didn't need any measurements to determine that.

Are we having fun yet?

Thanks for your insight.
The graph is simply the visaul representation of the data.  I represents
about 900 samples per day.  I calculate the "percent on" for each day
from that.  I can also get the on length  on each cycle that way to
determine the difference between setback and no-setback.

It'll be below zero every night for the next 4 or 5 here and it isn't
even "winter" yet.  If I had your warmer climate, I wouldn't worry much,
either.   Our propane bill went from $2400 to $4400 in one year, so it's
a real issue for us.

Pete Stanaitis


mike wrote:
  <snip>

Yikes!  $4400 would be hard to swallow. We have been heating our modest 1100
SF home in Northern Minnesota with off peak electric for about $90.00 a
month. We used to keep our day and evening temp at 70 but this year I
lowered the temp from 70 to 65 in the late afternoon and evening with a
short bump up to 65 at 6:30 in the morning. I keep it at 60 at night and
during the day when my wife and I are out in the shop. On sunny days the
south facing windows help immensely. We often see temps up to 80 in the
living room because of the sun. I should try a steady 65 to see if it would
affect the electric bill.
Steve

wrote:


Holy Shit, Maynard!  I'd say it's time to buy a more efficient
furnace, triple up on the insulation, install triple-glazed winders,
put dampers in the kitchen & bath fans, and caulk, caulk, caulk!

--
You can't wait for inspiration. You have to go after it with a club.
                                                      --Jack London

(Gasp) 74°? What, do you sit around in your skivvies? If you can
afford to splurge so prodigiously on heating your house, why do you
care how much it costs? Even when NG was cheap years ago, I never had
mine over 68°.
My setback is 60° in the evening, and 50° at night. in the bedroom, an
extra comforter on the bed, a  1500 watt heater on about 30% duty
cycle, and the night temp doesn't matter. In the morning, by the time
the t-stat gets up to 60°-because of where it's located, the majority
of the house is warm enough. In the evening, we hang out in the den,
where the fireplace easily keeps it at 65° or so with a small fire,
and the infared warms the room objects significantly more Plenty warm.
JR
Dweller in the cellar
gee, 68° would be positively luxurious now...

wrote:


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I can suggest a couple of tweaks that will save you some money.  We
also heat by propane which is about as expensive as electric resistive
heating ( at least it is here ).  So we have the thermostat set to
switch to a much lower temperature several hours before we go to bed.
And use a space heater to keep the room where we are warm if needed.
So my guess is that you could set the thermostat to setback at about 9
pm instead of midnight.

I also do not set the temperature as high as you do.  Just wear warm
clothes and have the thermostat set to about 68 degrees.

In the mornings I wait as long as possible before cranking up the
heat.  If the weather is sunny, I will shut the furnace off while the
house is still pretty cool.
We get a lot of solar gain.

                                                      Dan