Remotely monitor freezer temperatures with Raspberry Pi

Elizabeth from Git Tech’d has shown us how to monitor freezers and fridges remotely with a temperature sensor and Raspberry Pi. A real-time temperature monitor dashboard lets you keep an eye on things, and text message alerts can be set up to let you know when the temperature is rising.

The idea came about after Rick Kuhlman‘s wife lost a load of breast milk she had stored in the freezer. To make sure that months of hard work was never wasted again, Rick came up with this $30 solution.

Kit list

The whole kit packed together in a transparent case
Everything packed together in the protective case

Setup

Easy does it: you just wire the temperature sensor directly to your Raspberry Pi. Rick has even made you a nice wiring diagram, so no excuses:

Wiring diagram for connecting Raspberry Pi Zero W to Adafruit BME280

There’s a little fiddling to make sure your Flat Flex cable attaches properly to the temperature sensor. The project walkthrough provides a really clear, illustrated step-by-step to help you.

The protoboard for the BME280 has 7 solder points, but the cable has 8 connectors
The temperature sensor has seven solder points but the cable has eight connectors, so you’ll need to get snippy

Software

Everything looks pretty simple according to the installation walkthrough. A couple of Python libraries accessed via Raspberry Pi OS and you’re there.

Screenshot of the temperature monitor
Initial State’s temperature monitor dashboard

You’ll need an access key from Initial State, but Rick explains you can get a free trial. The real-time temperature monitor dashboard is hosted on your Initial State account. If you want to have a poke around one that’s already up and running, have a look at Rick’s dashboard.

Alert!

You can configure your own alert parameters from within the dashboard. Set your desired temperature and how much leeway you can tolerate.

You’ll get a text alert if the temperature falls too far above or below your personal setting.

A phone screen showing a text alert that a freezer temperature has gone too high
Get alerts straight to your phone

We can see this affordable fix helping out science labs that need to keep their expensive reagents cold but don’t have the budget for freezers with built-in monitoring, as well as people who need to keep medication at a certain temperature at home. Or maybe food outlets that don’t want to risk losing loads of pricy perishables stacked up in a chest freezer. Nice work, Rick and Elizabeth!

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14 comments

Roger avatar

I did something similar. My oil fired heating furnace is in an unattached building . I have a Pi zero monitoring the water temperature. It sends by wifi the temps every 15 mins to my desktop running MYSQL. I have a web page showing the results. A Php script will send an email when the temperature falls below the operating range. It also sends my phone a text through verizon. I use Grafana to display the graph of the last 24hrs. I also am monitoring and recording outside temperatures in a similar fashion. I had a failure this past winter and knew about it before there was any change of temperature in the home.

Eduard avatar

Maybe you can make a tutorial with making this project. Will be useful. Thank you.

Stewart avatar

Roger, I’m interested in what hardware you use for sensing the temperature / wiring diagram.

CooliPi avatar

I’m interested too. Maybe onboard BME280 sensor? I need to measure much lower temperature, BME280 ends at 40˚C on the low side. I need about -200˚C for the next overclocking round. Raspberry Pi 4 ends at approximately -88˚C

Michael Stoops avatar

Nice work! I also did a similar project, I also built mine on the Pi Zero W but used Dallas one wire sensors (https://www.adafruit.com/product/381) connected through an Adafruit perma proto HAT. These sensors are super handy because they come with a long cord, waterproof package, and Raspberry Pi OS recognizes them immediately as thermal sensors. You just read the temperature in Celsius from a file. I pushed my data points up to AWS CloudWatch, which offers dashboarding, alarms, etc.

Thanks for sharing.

Bryan avatar

I also use the 1-wire protocol. Really simple, although I do have to reboot the pi every so often. I have sensors using cat 5 cable for the freezer and fridge. I also have 1-wire sensors with magnetic switches for the garage doors and for a water (leak) sensor.
I have also used emoncms for logging and graphing values.

Gabriele avatar

You don’t really need Initial state or any subscription based services, just make a Telegram bot in Python to send you the notification when needed.

Camden avatar

I wrote a little app a while back to pull data off of this sensor and the SHT31-D. It just publishes to MQTT and you can do whatever you want. I dumped it into a time series database and used grafana to see it.

https://github.com/fishnix/airmeter

Steve avatar

This is a terrific post…an interesting backstory, a great explanation of the project, and plenty of specific technical information for anyone who would like to replicate or adapt the project. I’d love to see more posts like this and fewer reprints of fluff articles from the RPF magazines.

Greg Hains avatar

Good morning.
Whilst Initial State have some great services, an alternative is Grafana which you can also host on the same Pi – keeping it self contained. I have no info on it here but there are plenty of tutorials out there for it.
Thanks for this fridge monitoring project – I’ll definitely be making this one. Thanks!
Greg

Patricia Leconey avatar

Great idea. I once lost a load of mommy juice, too. So frustrating – a huge load. Pump and pump again. Don’t forget the pump and dump after a few cosmos. These Babies get sore. If this guy helps one more mommy, he deserves a giant box of cheese sticks and Coors.

Bev avatar

Patricia, sorry to hear of your loss as well. Like you, I listened to the video. Sounds like Rick really does deserve some mozzarella sticks as he lost those, ribs and pork in a previous loss. Practical example of the use of Pi and integrative technology.

DAVID WHITELEY avatar

I’ve built a small PCB which interfaces to the TMP107 temperature probes from Texas Instruments. Telephone cable runs between them in daisy chain fashion. The cottage installation includes a bat house out back, the beach hut and lake with a total cable run around 200 FT and signal run nearer 300 FT.

Typical log entry from a midnight e-mail:
2020-12-15 20:01, 8.3, -11.7, -10.5, -5.2, -27.8, -27.5, -20.9, -24.2, 0.6,
First temperature is the Pi Zero CPU, last is the lake.

Barry Rutkin avatar

Just a thought. Instead of using an external web site as an intermediary for your data, it’s pretty easy to send an email instead. If you address the email to your cell carrier’s email to text gateway, you can even send a text. If you’re sending plain text this is a simple way to deliver it to your phone. My verizon email gateway is @vzwtext.com. You can find them easily with a google search.

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