[Noisebridge-discuss] Termperature sensor datalogger

[Lee Sonko]

>If you're just logging, and have $40 to spend on a solution, look at the
DalSemi^WMaxim thermochron iButton:
 
Where's the fun in that?  ;-)
 
 



  _____  

From: Mikolaj Habryn [mailto:dichro at rcpt.to] 
Sent: Sunday, April 11, 2010 12:30 AM
To: Lee Sonko
Cc: Glen Jarvis; Noisebridge Discussion List
Subject: Re: [Noisebridge-discuss] Termperature sensor datalogger


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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