Solving the refrigerator problem

We have a refrigerator downstairs that once in a while gets left open, and since it’s downstairs, we sometimes don’t catch it in time to save to food. Will and I decided to make something to help solve this.

Our plan is to use our Particle Proton (a tiny Wi-Fi development kit) and connect a temperature sensor. We’ll report that temp to “the cloud” and if the temp rises above some threshold, we’ll use IFTTT to text or call us to let us know to check the fridge.

I got us a free DS18B20 temperature sensor as a sample from Maxim Integrated (how cool is that?) and found some nice sample code here.

The prototype is now sitting in the fridge (photo above), dutifully sending out the temp every 10 seconds. The code is crazy simple.

Things we talked about while doing this:

  • Resistors in parallel and in series
  • Reading resistors
  • Analog-to-digital conversion
  • What numbers look like in binary
  • Trusting a component’s data sheet first
  • How to debug when Papa tells you to put the resistor in the wrong place

Refrigerator Problem_bb

UPDATE: The 2200mAh 3.7V battery didn’t last until morning, so Next up will be to see whether there’s a way to reduce power consumption. Fewer temp reports to the cloud will obviously help. I wonder if there’s a “low power mode”.

4 thoughts on “Solving the refrigerator problem”

    1. It took a little over an hour. I bought the Photon kit a while ago… that was about $30. The rest was free or stuff I had laying around. If we keep it Wi-Fi, we’re pretty much done (except for deciding how we want to power it). If we ditched Wi-Fi and just made it sounds a loud buzzer, the whole project would be closer to $5.

    1. Just running off a USB back up power thing for prototyping. Not sure how we’ll want to power it yet. Thinking about modding the light. :)

      Also considering a mod to improve temp distribution… it’s pretty uneven.

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