Wednesday, 20 March 2013

Raspberry Pi - Fridge Monitor

My fridge-freezer has this control unit on the front of it:

As a geek I'm not prepared to believe this display so I thought I'd have a closer look at the environment in the fridge using the AirPi environment monitor I previously built.

Breaking out the battery pack I previously use for our Pi powered Lego car I was able to get the whole unit to run in my fridge.  As you can see from the image below, the Pi looks at home with it's distant cousins!

The WiFi worked OK through my fridge door so I was able to upload the measurements to COSM.  Here's how the temperature changed over the 4 hours period I monitored:
The chart isn't great, each vertical column represents 30 minutes and and the Y-axis scale is a tad screwy.  You can see that I put the monitor in the fridge at just before 1800 and took at out at 2200.  It actually took about 50 minutes to get down to the temperature of the fridge; I assume that this is because of the residual heat in the temperature monitor and it's surroundings.  You can then see the temperature go through about 3 cycles with the minimum point being ~3.8C and the maximum point being ~5.6C.  So I would say it spends more time above 4C than below it...

This chart shows the light level:

The light level needs calibration but you can see relative light levels quite easily.  I only take samples every minute so I may have missed instances when I opened the fridge that evening.  However there is a definite peak at about 1830 so caught an instance then.

This chart shows humidity:

The fridge boasts some form of humidity control, (some form of fan kicks in when you close the door).  To me there's not too much of a pattern, perhaps some form of cycle going on in the mid part of the evening.

This chart shows barometric pressure:

The pressure just grows throughout the evening.  I didn't have a pressure sensor outside so I don't know if this is what was happening in the general environment.

All in all,very interesting; might have to do it again some time.  I was considering doing the freezer as well but was worried what would happen if the kit got frosty..  

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