Garduino-Automated Gardening System

This instructable is a guide for setting up an automated gardening system using an arduino and other cheap electronic parts.  It allows sustainable gardening by using sensors to determine soil moisture, as well as a webscraper to determine future weather.  It uses this information to save water by only using the requisite amount.   Requirements for this project include experience soldering, some basic programming experience, and much patience for debugging.

See video for example of why we need this.

 

Step 1: Build-Moisture Sensors

The moisture sensors rely on the resistivity of water to determine the moisture level of the soil.  The sensors measure the resistance between two separate nails by sending a current through one of them and reading a corresponding voltage drop due to a known resistor value.  The more water the lower the resistance, and using this we can determine threshold values for moisture content.
We will use three such sensors and use a multiplexor to alternate reading between them without using more than one arduino analog port.
While we will include a circuit board diagram, we recommend building the circuits on a breadboard first which will allow for both understanding and debugging. 
Each sensor uses two nails, a 100 ohm resistor, and a 100 K-ohm resistor.  We built a casing for each sensor with acrylic tubes, however this is not necessary.

Comments

[shemul3091]

waw! so cool ! :D

[diy_bloke]

Upon rereading my earlier comments, I realized that maybe my tone as a far as one can detect one in writing, maybe came across with a harshness that I did not intend at all.

I am not critical of yr project, not at all, I think it is great, but I just had a couple of questions that hopefully cld help me understand and or learn from

[diy_bloke]

Why would you want the delay of 24 hours? In the video you say it is because it has been watered already so it does not need watering for another day. But then what is the sense of the probes??

If yr probes would indicate that the soil is dry after half a day, yr system just ignores that (as I understand) wouldn't it be easier then to just open yr tap once a day and say 'done' and use the arduino for something completely different?

Wouldn't it be more logical to let yr program always react to the readings of the probes.
1 if dry give water, if dry within 24 hrs again, water again

[diy_bloke]

just a question. It is indeed smart not to leave yr pump run dry, but if you have a continous waterflow to the tank, then why use a pum at all. Wouldn't it be simpler then to just use an electric valve to open and close the mains water supply?

Also, I use galvanized material for my spikes and that works great.

Your sensors look fantastic, but it seems a bit overkill to use length of acrylic tube, just to attach 2 nails to. Might as well just put them on the bottom of a bamboo stick with tie wrap, or am i missing a point here? Is there any added value in using the acrylic tubes

[DisplacedMic]

Truly remarkable!
thank you for posting! i will try something similar this summer

[JSWheeler]

This is awesome! I actually had a project in one of my engineering classes that asked for something just like this. Good job!