I am doing a project with my high school engineering class. We received a grant from Captain Planet to design and build a solar powered, Arduino controlled irrigation system to water raised bed gardens from a rain barrel - it is supposed to conserve water and be completely solar powered.
We set up the system for a soil moisture sensor to take a reading every morning and if the moisture level was low - the arduino would signal a solenoid valve to open and a pump (controlled through a power switch tail) to turn on for 20 minutes- water would be dispersed through a pvc pipe drip system, and then the pump would be stopped and the solenoid valve closed.
The arduino board is solar powered through a 9 volt batter and the pump is powered through a 12 volt battery (solar charged) through a dc converter.
I have the individual parts working but I am unsure about how to use a RTC to take the reading every 24 hours and I am unsure about the transistor or MOSFET I should use for the solenoid. Any ideas?
My code is attached - I know it needs work - I would appreciate any advice! Thanks
IrrigationProjectBorgeson.ino (1.69 KB)
Your description leaves me with two questions.
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Why do you need a solenoid valve if you have a pump that can be turned on/off?
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Do you have a spreadsheet showing the power requirements for each device and the power supplied by the solar panel? And is it worse-case for when there is complete cloud cover during the day?
Paul
Much of the power required could be reduced if the rain barrel were elevated allowing gravity to replace the pump. Is that possible? - Scotty
The power arrangement is odd: Arduino from 9V battery, the pump through DC converter? That should be the other way around. Get a regular 12V deep cycle lead-acid battery for your solar system to store the energy, and a 12V to 5V buck converter to power your Arduino. The same battery can also power the pump, no need to convert to AC for that. There exist really powerful pumps on 12V or 24V DC.
Also I see the word "breadboard" in the arrangement. Breadboards are fine for initial testing and experimenting, after that you should solder your circuit on a protoboard. Much more reliable and robust.
The pump can be switched using a MOSFET (it will use too much power for a transistor). The popular IRL540 comes to mind, switches well on 5V gate and can handle several amps of current without heat sink. Should be enough for your pump.
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