Autonomous Plant Monitoring – Update 1

Progress Update as of 27/1/2018

Preface

One of the exciting things about working on mini projects is the rapid progress that can be noticed within the first couple of days. This blog is a nice space for me to share such progress with you all. I hope you enjoy going through it!

The idea of this mini project is to install a subsystem on top of the Unmanned All-Terrain Vehicle ‘UATV’ (you can read more about it in this page). The motive behind this is that I will be representing Bahrain Polytechnic in Bahrain International Garden Show 2018 (BIGS) which is to be held later in February. In order to accommodate the theme of the show, and out of pure interest in showcasing the unlimited possibilities of autonomous vehicles, I started to work on this since the 22nd of Jan 2018. I will be sharing weekly updates with you.

Functionality of the system

The system functionality is straightforward: It is required to measure the temperature and moisture of the soil, and display those readings on an on-board screen. I do not want to fiddle around with the existing connections inside the vehicle, and focus on maintaining the system as an add-on feature. Therefore, my approach is aided towards ensuring that everything can be added and removed easily. Simply, I am happy with the current functionality of the vehicle, and do not want any permanent modifications to it!

I purchased two sensors for that; DS18B20 digital temperature sensor (due to its corrosion resistance ability), and DFRobot capacitive analog soil moisture sensor (again, due to its corrosion resistance!).

Soil Moisture sensor (left), and Temperature sensor (right).

Mechanism Conceptualization

Such sensors have to be submerged into the ground in order to obtain measurements. Therefore, it is necessary to design a mechanism that can lower the sensors into the ground when it is required to obtain the measurements, and then lift it up when the vehicle is about to move again. The following figure shows the designed mechanism to do that.

Designed mechanism to lower the sensors into the soil, as shown in the model in pink.

As you can see from the figure, I’ve chosen to use a rack and pinion mechanism to deploy the sensors. The reason behind that is the relative simplicity of this mechanism, and the force that it can provide to push the sensors through the soil. A standard 20kg.cm servo will be used to rotate the pinion. All the mechanism components will be 3D printed. As for the readings, they will be interfaced on a TFT 2.4″ lcd display. I already experimented with interfacing the ili9341 screen driver with the Arduino using some libraries, and got some good progress quickly!

Interfacing the LCD display with an Arduino.

I added some arbitrary float numbers to simulate reading the moisture and temperature, and got them displayed in the screen as you can see below.

Displaying the interface that will be used to show the readings to the user.

Remaining things to be completed

Hopefully by next week, I will have the software code ready, and all mechanism components printed. The electronics will be placed on a veroboard, and a case will be designed for them to be placed on top of the vehicle. The project should be in the testing phase within 2 weeks.

Anyhow, thanks to Jannat Alasfoor for giving a hand in modelling the sensors and screen, and thanks to Ahmed Sadriwala for helping in the veroboard design.

See you next week for the second update!