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Jeff's GeekBearCave on LJ

[no user serviceable parts inside.]


September 28th, 2011

milk going bad before its date - an opportunity to install sensors @ 12:28 am

Location: apartment 9B
Mood: contemplative contemplative

Yes, the last two half-gallons of skim milk have started to turn sour a day and days before the date on the container. I suspect the refrigerator may be the culprit. As some of you may know I have a penchant for remote monitoring, there are sensors in and around the camper in season, there are sensors in and around the apartment and the house. All dutifully monitored and watched over by rescued laptops or re-purposed network devices (NSLU2).

I've decided to reuse a set of temperature sensors that I had on the camper's propane tanks to monitor the temperatures in the apartment fridge and freezer to see if what I was seeing earlier today is actually what's happening. Yesterday I put the temp probe from my DVM into the fridge and saw that the temp in the refrigerator section went from about 36 degF to 43 degF. Earlier today I was watching the real-time readings and I saw them drop just after the compressor & fans started and then I saw them rise slightly and then drop and rise about a degree or 2 a couple of times and then the temp started back down. The odd readings prompted me to setup the newly re-purposed propane tank sensors to monitor the fridge and freezer. I'll keep you posted on the findings. ;)

Be Well,
Jeff
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For example, this is the last set of readings from the camper before I shut down the NSLU2 for the season: http://www.camp-geek-bear.com/1wire/current_conditions.txt
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From:oscarlikesbugsy
Date:October 2nd, 2011 09:10 pm (UTC)
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Cool.

Where is a good place to buy sensors that are 'computer-ready'? Or, does one typically have to set-up an interface for them, maybe?
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From:geekbearjeff
Date:October 3rd, 2011 05:21 am (UTC)
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I guess it depends on your OS of choice and what you're interested in doing with the sensors. All of the environmental sensors that I'm using came from: http://www.hobby-boards.com .

I use Linux for the devices that are recording the readings from the sensors. I've coded some custom scripts that request/record the readings, another set of scripts that upload the readings to that web page and still another set that creates graphs.

The electrical protocol that the sensors use is 1wire or one-wire. On Linux there's a FUSE based interface to the one-wire protocol called OWFS - One Wire File System - which takes much of the fuss out of getting readings from one-wire devices. OWSF performs device discovery and presents the (in almost all cases) complete set of available readings and settings as convenient files in directory trees.

To get it up and running simply plug in a USB-to-1wire adapter, plug-in the rj11 to rj45 adapter cable and plug a module onto the end of the rj45 cable and you're ready to start the OWFSd and start measuring your environment.

I hope this helps!

Jeff's GeekBearCave on LJ

[no user serviceable parts inside.]