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.

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:

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.

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

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.
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.

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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Welcome to October, the month in which spiderwebs become decor and anything vaguely gruesome is considered ‘seasonal’. Such as bats. Bats are in fact cute, furry creatures, but as they are part of the ‘Halloweeny animal’ canon, I have a perfect excuse to sing their praises.

Tegwyn Twmffat was tasked with doing a bat survey on a derelict building, and they took to DesignSpark to share their Raspberry Pi–powered solution.
UK law protects nesting birds and roosting bats, so before you go knocking buildings down, you need a professional to check that no critters will be harmed in the process.

The problem with bats, compared to birds, is they are much harder to spot and have a tendency to hang out in tiny wall cavities. Enter this big ultrasonic microphone.

After the building was declared safely empty of bats, Tegwyn decided to keep hold of the expensive microphone (the metal tube in the image above) and have a crack at developing their own auto-classification system to detect which type of bats are about.
The ultrasonic mic picks up the audio data using an STM M0 processor and streams it to Raspberry Pi via USB. Raspberry Pi runs Alsa driver software and uses the bash language to receive the data.

It turns out there are no publicly available audio records of bats, so Tegwyn took to their own back garden and found 6 species to record. And with the help of a few other bat enthusiasts, they cobbled together an audio dataset of 9 of the 17 bat species found in the UK!


Tegwyn’s original post about their project features a 12-step walkthrough, as well as all the code and commands you’ll need to build your own system. And here’s the GitHub repository, where you can check for updates.
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We know crawl spaces are creepy, sweaty, and confining but, hear us out…

You need to keep an eye on the humidity level in your crawl space, as it can seriously affect the whole house’s overall health. It’s ideal to be able to do this remotely (given the creepy, sweaty atmosphere of the space), and a Raspberry Pi allows this.

Jamie Bailey took to Medium to share his Raspberry Pi setup that allows him to monitor the humidity of the crawl space in his home from a mobile device and/or laptop. His setup lets you check on the current humidity level and also see the historical data over time. You can also set alarms to be sent to you via text or email whenever the humidity level exceeds a certain threshold.
Jamie’s walk-through is extensive and includes all the command line code you’ll need too, so make sure to check it out if you attempt this build.

The BME280 sensor has four pins you need to connect to your Raspberry Pi. This will send the humidity data to your Raspberry Pi, which you’ll have already set up to let you know what’s happening remotely.


Once you have all your software sorted and your hardware connected, turn your Raspberry Pi off and take it down to your crawl space (monitor, keyboard, and mouse are no longer necessary). Jamie advises hanging your Raspberry Pi from the floor joists instead of letting it touch the ground, to avoid contact with any water. He put a nail in one of the floor joists and draped the power cord over the nail (see above). Turn your tiny computer on, make sure data starts flowing into your dashboard, and you’ve got yourself remote humidity sensor!
PS We’re English so… is a crawl space the same as an attic or what? Asking for a friend!

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Keeping an eye on bee life cycles is a brilliant example of how Raspberry Pi sensors help us understand the world around us.
The setup featuring an Arduino, RF receiver, USB cable and Raspberry Pi
Getting to design and build things for a living sounds like a dream job, especially if it also involves Raspberry Pi and wildlife. Glyn Hudson has always enjoyed making things and set up a company manufacturing open-source energy monitoring tools shortly after graduating from university. With access to several hives at his keen apiarist parents’ garden in Snowdonia, Glyn set up BeeMonitor using some of the tools he used at work to track the beehives’ inhabitants.
Glyn checking the original BeeMonitor setup
“The aim of the project was to put together a system to monitor the health of a bee colony by monitoring the temperature and humidity inside and outside the hive over multiple years,” explains Glyn. “Bees need all the help and love they can get at the moment and without them pollinating our plants, weíd struggle to grow crops. They maintain a 34∞C core brood temperature (± 0.5∞C) even when the ambient temperature drops below freezing. Maintaining this temperature when a brood is present is a key indicator of colony health.”
BeeMonitor has been tracking the hives’ population since 2012 and is one of the earliest examples of a Raspberry Pi project. Glyn built most of the parts for BeeMonitor himself. Open-source software developed for the OpenEnergyMonitor project provides a data-logging and graphing platform that can be viewed online.
BeeMonitor complete with solar panel to power it. The Snowdonia bees produce 12 to 15 kg of honey per year
The hives were too far from the house for WiFi to reach, so Glyn used a low-power RF sensor connected to an Arduino which was placed inside the hive to take readings. These were received by a Raspberry Pi connected to the internet.
Diagram showing what information BeeMonitor is trying to establish
At first, there was both a DS18B20 temperature sensor and a DHT22 humidity sensor inside the beehive, along with the Arduino (setup info can be found here). Data from these was saved to an SD card, the obvious drawback being that this didn’t display real-time data readings. In his initial setup, Glyn also had to extract and analyse the CSV data himself. “This was very time-consuming but did result in some interesting data,” he says.
Almost as soon as BeeMonitor was running successfully, Glyn realised he wanted to make the data live on the internet. This would enable him to view live beehive data from anywhere and also allow other people to engage in the data.
“This is when Raspberry Pi came into its own,” he says. He also decided to drop the DHT22 humidity sensor. “It used a lot of power and the bees didn’t like it – they kept covering the sensor in wax! Oddly, the bees don’t seem to mind the DS218B20 temperature sensor, presumably since it’s a round metal object compared to the plastic grille of the DHT22,” notes Glyn.
Unlike the humidity sensor, the bees don’t seem to mind the temperature probe
The system has been running for eight years with minimal intervention and is powered by an old car battery and a small solar PV panel. Running costs are negligible: “Raspberry Pi is perfect for getting projects like this up and running quickly and reliably using very little power,” says Glyn. He chose it because of the community behind the hardware. “That was one of Raspberry Pi’s greatest assets and what attracted me to the platform, as well as the competitive price point!” The whole setup cost him about £50.
Glyn tells us we could set up a basic monitor using Raspberry Pi, a DS28B20 temperature sensor, a battery pack, and a solar panel.
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