PomodoPi: The ultimate tomato-growing assistant

Charly Kuehnast works in a datacentre in Germany and is a keen hacker in his spare time. He uses his Raspberry Pi to help him with growing tomato plants at home.

What is your invention?

PomodoPi uses a Raspberry Pi to constantly measure moisture of the soils in which some tomatoes are growing, and displays it on a 7-segment display. If the soil moisture drops below a certain level, the Pi sends a signal to a relay board which in turn opens a valve. The tomatoes are then watered until the soil moisture has been raised to a more agreeable level. Just for fun I’ve added two webcams and a status website that shows all parameters, including air and soil temperature, amount of rain and duration of sunshine.

Why did you decide to make this?

Two reasons: I planned to travel to Tuscany in early summer 2015 and needed something to water my plants. Also, at that time I was co-writing a book about the Raspberry Pi and needed material for the book’s 'fun projects' part.

How does it help you?

My plants don’t die when I’m away for a few days!

How easy was it to make - did you come across any challenges

This is definitely a beginner’s project. You don’t need to handle any voltage over 12 volts, and you don’t even need to solder anything (although I did to make it more durable). The hardest part is to get the soil moisture sensor’s readout into the Raspberry Pi. However, all of this is well documented online.

How did you learn how to use your Raspberry Pi?

I’ve been using Linux since its very beginnings and was excited to see it come to a small and affordable piece of hardware. I was lucky to get one of the first ones. Together with a camera I put it into a birdhouse in my garden to get live footage of breeding birds. It’s still there. It never ceases to amaze me that after several years and temperatures between -18 and +42 degrees centigrade, it still works.

How much did all the parts cost?

The parts you can’t do without amount to 120 Euros because I used an exceptionally expensive soil moisture sensor (50 Euros). You can get soil moisture sensors for a tenth of that, but their bare metal electrodes corrode within weeks. The 120 Euros do not include the webcams since they are optional extras.

What tips would you give to someone who is interested in making something with a Raspberry Pi?

If you are new to programming, don’t hesitate to start with the 'Scratch' programming environment. Yes, it’s designed for children and looks the part, but it will teach you the basics in no time, give you results quickly and it’s fun. Go to hackerspaces, Fablabs, repair cafes. People there usually are a very agreeable bunch, and there’s bound to be someone there who knows about the Raspberry Pi and can teach you to code and to solder.