Raspberry Pi IoT Project: Temperature Part 1 – Initial Planning (Raspberry Pi)

Time for a new project for my Raspberry Pi 3B, this one has the current aim of regularly taking a rooms temperature and recording the results. However, for this project I will also be looking at the possibility of later expanding it so I am going to look at multiple options.

Which Pi ?

I currently own a Pi2, Pi3B and a Pi ZeroW, but what if I was starting from scratch? I’m going throw in the requirement that whichever Pi I use it needs to be able to be wi-fi compatible. This rules out the Pi, Pi 2 and Pi Zero unless a wi-fi dongle is used.

The MagPi did a great article benchmarking Pi specifications at https://www.raspberrypi.org/magpi/raspberry-pi-specs-benchmarks/ , I’ve summarised the basics of each model I would think about using:

For costings I am going to use my favourite supplier of Raspberry Pi equipment, Pimoroni. At this stage I am not including a case and I’m making the assumption that a power supply, keyboard/mouse, HDMI cable, etc… are already available but will factor them in later on.

If I had the money I would purchase the Pi 3A+, although it has half the RAM of the Pi 3B that I currently have it has better power consumption, a better processor and supports both 2GHz and 5GHz wi-fi compared to the 3B only supporting 2GHz wi-fi. However, I am currently on a budget so will be reusing my trusty Pi 3B.

Which Operating System?

Depending on which Pi model is being used can also open up the opportunities of operating systems available for my project.

As well as Raspbian (a Debian based OS) there are the likes:

• Windows 10 IoT Core
• Ubuntu Core
• Ubuntu Mate
• RISC OS

However, I am going to stick with Raspbian Stretch (current version of Raspbian) for the reasons:

a) I know it works with the hardware, i.e. no driver issues 

b) I have experience with it

Sensors

I’ve selected a Pi model and an OS, but without a sensor I will not be getting any sensory data, and that is what this project is all about. So it’s time to look at sensors, of which there are many for the Pi.

Official Sense Hat

Made for the AstroPi missions, the official sense hat can read temperatures, output to an LED display and has an accelerometer. However, it has the draw back of being above £30 in cost and reports that its temp readings can be thrown off due to interference from the Pi CPU. 

BMP280 Breakout: Temperature, Pressure, Altitude Sensor

Coming in at just under £8, the BMP280 breakout has all sensors I need for my current project idea including the relevant Python libraries. The board contains the pins for soldering but I would probably just buy the Breakout Garden for an additional £12.50 incase of the need for future expansion (hint, this project may get bigger…).

DS18B20 Temp Sensor (or similar thermistor)

Starting out at under 20p and with full guides available (see PiHut: https://thepihut.com/blogs/raspberry-pi-tutorials/18095732-sensors-temperature-with-the-1-wire-interface-and-the-ds18b20) there is the option of building a circuit with the relevant sensors in. This is great option for those that like hands on electronics.

Choice

I’m going to go with the BMP280 breakout, as I am also future planning for use with other sensors.

Notes

If you are doing this project from scratch please note you may also need:

• A USB power supply – to power the Raspberry Pi. 
• USB / HDMI adaptors if using a Pi Zero W  – depending on setup of Pi / how Pi is being used
• USB Keyboard / Mouse – depending on setup of Pi / how Pi is being used
• A HDMI cable – depending on setup of Pi / how Pi is being used
• A microSD card – for installing the OS. A higher class is better. 8GB or more.
• A case – to project the Raspberry Pi.