Basically, hydroponics is growing plants without the use of a traditional dirt medium by using a nutrient rich water solution. Those mediums used to "plant" in range from fiberglass to sand and from fired clay balls to nothing at all. Several branches of hydroponics include aeroponics, aquaponics, etc. But WHY would I want to take all this extra time and effort to grow my plants in this "special water"? Well, hydroponically grown foods not only taste better and are more nutritional, you can change the properties of your food, monitor what goes into your food and pollute less. You can also grow more in less space. This is especially great for those people that that have limited areas in their backyard to grow in. With the right plant selection, you can also keep pests away; a citronella plant has oils that keep away mosquitoes and other pests. Now if this wasn't enough for you to jump right in to hydroponics, listen to this: hydroponics uses 70 to 90 percent LESS water than conventional growing does.
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Step 1: Gather Your Supplies
To build the Hydruino, you're going to need to first gather some supplies.
Hydroponics Pots (I'm using 10 - 3" pots for this)
1" PVC Pipe and Fittings + Drain Pipe and Fittings
These aren't necessarily the cheapest places to get these items, so if you're not in a rush, consider searching on a place like dx.com or on other eBay listings (may or may not be shippnig from China) to find the best possible deal.
Step 2: Building
What I ended up doing was constructing basically a "table" for the system to sit on. The weight of the water in the drain pipe makes it heavy enough for it to easily stay on without a problem. The nice thing about this is that it can be easily scaled to almost any size and all the instructions stay the same (except for the actual construction of the system of course) - there would be no need to change the code...maybe just things like adding more lights, fans, etc.
I don't have a digital copy of all the dimensions of the pipe if you're looking to make a replica of what I've done, but I'll try to get everything entered in within the next couple of days.
For the reservoir, you'll need to drill two holes for the float sensors - one at the very lowest your water can be and one at the top - and also a hole for the solenoid to fit in (which you will glue in). To connect a garden hose to the solenoid, I used 3/4" hose to pipe adapter made by Orbit (found at Home Depot) and a 3/4" to 1/2" reducer to get it down to the right size.
Once you've constructed the frame, you'll want to wrap the entire thing in a transparent plastic, of which you'll have to cut out a couple holes for your fans. With the drain pipe, you'll want to drill out about 3 1/2" or so holes with a hole saw so your pots will fit in. Cut a hole in each end of the drain pipe - one is where water is pumped in from the reservoir, the other is where water drains out back in to the reservoir to be recirculated.
I never got finished with the container for everything to fit into, however, I'm sure that shouldn't be a problem for most of you to figure out. I took the cardboard that my relay shield came in and am working on getting everything to fit in there, since that's a really easy way to put it all together, but you can use whatever you'd like.
Step 3: Wiring
Here is a list of the pins:
A1 - Photoresistor
A2 - pH Sensor
7 - Lower Float Sensor
8 - Upper Float Sensor
20/21 - RTC
43 - pH Min Peristaltic Pump (Relay)
45 - pH Plus Peristaltic Pump (Relay)
47 - Solenoid Valve (Relay)
48 - Grow Lights (Relay)
49 - Fans (Relay)
50 - Temperature/Humidity Sensor
53 - SD Card
For the float sensors, you're going to have to add in a resistor on each, as shown here, for it to work effectively with your Arduino.
Step 4: Code
Attached is the most current Arduino code for the project. It will be updated based on feedback given by others; I don't expect my way to always be the best way! I haven't had weeks to test it "out in the real world" so there may still be a few kinks in it. Be sure to adjust the lux value for measuring the time for the supplemental lights...the optimal value may vary depending upon your sensor. Also, if you're using a different pH sensor, the calculations may need to be changed to fit that particular one. Big thanks to BillieBricks for working out a lot of the code.
Congratulations! You've successfully (hopefully!) built your first (or second, or third...) hydroponics system! You're now able to grow your plants in a smaller area while also using less water. Remember that you'll have to keep track of how often to add nutrient mixture. This system could be easily modified or scaled to fit your needs/desires. Please feel free to leave feedback, especially on the code, as there is always room for improvement and it will only help everyone!
Also, please vote for me in the Microcontroller Contest! It would be amazing to have any of those prizes that they're giving out! Thank you!