[Noisebridge-discuss] Termperature sensor datalogger

[Mikolaj Habryn]

Do you need realtime data or just logging? If you're just logging, and have
$40 to spend on a solution, look at the DalSemi^WMaxim thermochron iButton:
http://www.maxim-ic.com/products/ibutton/ibuttons/thermochron.cfm

m.

On Sat, Apr 10, 2010 at 11:34 PM, Lee Sonko <leelist at lee.org> wrote:

> >     This is excellent. Thank you for the help. I don't mind
> > recharging batteries often - but will they operate properly
> > for a day, explode, cause aliens to visit my home, or
> > anything else weird?
>
> The batteries won't explode or anything dreadful. I'm pretty sure they'll
> deliver a low voltage and wear out quickly. I'll hazard a wild guess and
> say
> you'll get 60% of what would be a full charge out of them. You could
> compensate by using more batteries in series and recharging more often.
>
> You want a very stable voltage source for the thermister's voltage divider
> so you should go through the onboard regulator and be sure to have more
> than
> 6.0 volts of batteries.
>
> The Arduino draws about 40ma.. maybe another 10ma for the thermistor. It
> would normally run for about 20 days on 1,000ma of batteries. Maybe you'll
> get 12 days of battery at low temperature.
>
> I found this datasheet
>
> http://www.panasonic.com/industrial/includes/pdf/Panasonic_NiMH_Overview.pdf
> page 10 shows the batteries having low voltage (maybe 0.1 volts low) and
> 80%
> of normal temperature capacity at -10 degrees celcius. That's a good sign
> for you I think :-)
>
>
>
>
>
>
> >
> >     I don't mind experimenting, but if I get battery acid in
> > the freezer, I'll be in Trouble! (with a capital T). I
> > already have petri dishes of genetically engineered e. coli
> > in the refrigerator, and am about to put small frozen viles
> > in the freezer... oi! :)
> >
> > Glen
> >
> > On Apr 10, 2010, at 8:54 PM, "Lee Sonko" <leelist at lee.org> wrote:
> >
> > > A thermister is probably what you want.
> > >
> > > maybe Jameco product 207037
> > > http://tinyurl.com/ydgvzgo
> > >
> > > The resistance changes according to a curve so it needs to
> > be massaged
> > > a little. This should do it for you.
> > > http://www.arduino.cc/playground/ComponentLib/Thermistor2
> > >
> > > If I remember correctly, it's accurate to about +-0.2 degrees.
> > >
> > >
> > > For the batteries at subzero temperatures... ugh. Buy extra
> > batteries?
> > > This cheap charger works great:
> > >
> > http://lee.org/blog/2008/07/10/vanson-8-aa-nicad-nimh-battery-charger/
> > >
> > >
> > >
> > >
> > >
> > >
> > >> -----Original Message-----
> > >> From: noisebridge-discuss-bounces at lists.noisebridge.net
> > >> [mailto:noisebridge-discuss-bounces at lists.noisebridge.net]
> > On Behalf
> > >> Of Glen Jarvis
> > >> Sent: Saturday, April 10, 2010 7:40 PM
> > >> To: Noisebridge Discussion List
> > >> Subject: [Noisebridge-discuss] Termperature sensor datalogger
> > >>
> > >> I am doing a diy bio experiment on survival rate of e. Coli after
> > >> freezing (with different cryo agents). I'd like to make a quick
> > >> arduino data logger.
> > >>
> > >> I need to measure temperatures around -20 degrees C (about
> > -4 degrees
> > >> F.)
> > >>
> > >> I did something like this with my Lego mindstoms sometime
> > back - but
> > >> it was for a very short amount of time.
> > >>
> > >> I need to take regular measurements (like once every 15 min) for a
> > >> month.
> > >>
> > >> Does anyone know a good vendor for a temperature sensor in this
> > >> range?
> > >> What are the issues I may encounter operating a battery in
> > sub zero
> > >> freezing temperatures on an ongoing basis? I don't mind
> > changing out
> > >> batteries or retrieving device for data retrieval once per day.
> > >>
> > >>
> > >> Glen
> > >> _______________________________________________
> > >> Noisebridge-discuss mailing list
> > >> Noisebridge-discuss at lists.noisebridge.net
> > >> https://www.noisebridge.net/mailman/listinfo/noisebridge-discuss
> > >
>
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