Archive for ‘IoT’ category

* Automatic plant watering with Raspberry Pi

3. December 2018, Jakub Horák. Categorized as IoT.

Who hasn’t had hers/his plants die at home while traveling for a few days? Unfortunately my plants suffered from this fate too. Since I already have my plants connected to the internet via Raspberry Pi, notifying me whenever the soil gets dry, one solution is to have that same event trigger actual plant watering. That’s what I set out to accomplish. By researching online, I stumbled upon an interesting tutorial Raspberry Pi Automated Plant Watering with Website which describes the hardware build very well, but adds a web server on top, which I find useless. I decided to run my own software stack.

Hardware parts necessary (assuming Raspberry Pi plant sensor is built already):

After getting all the necessary parts, first step is to cut the USB charger phone part off and expose red and black wires. Next, solder the red wire sticking from the pump to the red wire exposed from the USB charger cable.

When the soldering is done, it’s time to connect everything together. See the complete wiring diagram with two moisture sensors in the figure below.

Complete wiring

I have two sensors for two plants, but only one water pump for now.

Ports (as per used for the pump are (first relay, then Raspberry Pi 3):

The next step is to fill the water container with water, tape the pump as close as possible to the container’s floor and use something (e.g. a wine bottle) to hold the outlet from the hose. I measured, that the motor can pump 23ml of water each second, thus it should be enough to pump for 1 or 2 seconds each time when the soil is dry.

Watering system

As for software, get my updated scripts from the associated GitHub repo. The configuration from can be seen below. First the moisture sensors are set-up:

# Define the GPIO pin that we have our digital output from our sensor
# connected to and URL which to call on sensor state change
sensors = {
        "peace_lily": (17, "** URL 1 **"),
        "parsley": (23, "** URL 2 **")

then the water pumps:

# Define the GPIO pin that we have our digital input to the
# respective relay connected to and number of seconds to pump
# each time
pumps = {
        "parsley": (27, 1)

When I get my second water pump, after wiring, I will just add a new entry under “pumps” with the corresponding pin.


In action

Watering system in action

That’s all folks, happy farming!

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* Feiertag Alexa skill update

3. October 2018, Jakub Horák. Categorized as AWS, IoT.

As it turns out, several people use my Feiertag Alexa skill, which I’ve described in a previous article. Recently I’ve upgraded it to use Amazon’s new device location API. Therefore now immediately after you install the skill through the Alexa app, you get asked, whether you want to share device country and postcode with the skill. That makes the user experience much easier, since you are no longer required to link an Amazon account to the skill. For backwards compatibility reasons, I’ve left the account linking in, but made it optional. So current users don’t have to change anything and will still get the correct Feiertag for their Bundesland.

Check out the updated skill in Alexa Skill Store. Just install it and ask: “Alexa, frage Feiertag, wann der nächste ist.”

Source code is in my GitHub repo.

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* Connecting plants to the internet

25. July 2017, Jakub Horák. Categorized as IoT.

I have a couple of pelargonium plants on my balcony and I’m always struggling to determine, when to water them. By chance I also have a Raspberry Pi 3 lying around, so I’ve decided to do a little IoT project, turn the plants into cyborgs and let them tell me, when they need watering.

The connected plant

The connected plant

The basic setup is inspired by the Moisture Sensor Tutorial. But instead of sending emails and needing an SMTP server, I just submit the data to ThingSpeak, a very useful IoT analytics platform. An event in ThingSpeak can be configured every time a differing value is received in the input data stream. I’ve configured such an event to trigger sending a tweet, check the plant’s Twitter account here. On my phone, I’ve then tweaked the notifications in the Twitter app using my personal account to notify me on every tweet on the plant’s account.

Raspberry Pi 3 with Witty Pi 2 mounted on top

To provide electric energy, I bought the Ravpower powerbank with capacity 26800mAh. However even the massive battery doesn’t last more than three days in this setup. That’s when I found a nice extension board for Raspberry Pi called Witty Pi 2, which will handle turning the Pi on and off based on a schedule, thus conserving huge amounts of energy. See the photo on the left. I set the schedule to turn the Pi on for 2 minutes once every 2 hours. The whole thing can keep running like this for about a month without recharging.

To summarize, here is a complete list of used components:

  • Raspberry Pi 3
  • Witty Pi 2
  • Ravpower powerbank with capacity 26800mAh
  • Moisture sensor
  • Breadboard
  • 5 jumper wires


Placement in a drawer on my balcony

Placement in a drawer on my balcony

Raspberry Pi 3 with Witty Pi 2 on top and a powerbank

Raspberry Pi 3 with Witty Pi 2 on top and a powerbank

ThingSpeak chart

The hardware running smoothly, finally, let’s discuss the code. I started off with the tutorial’s Python sample and extended on that. I ended up with Ansible scripts. Ansible takes care of the configuration deployment, so whenever I’d format the Pi, I just need to install Raspbian, replay the Ansible playbook and I will get the same software installed and configured on it. Check the repo on Github. Pretty sweet!

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