Hi, I need to control a soil moisture sensor (like this one, cheap soil moisture sensor for Arduino) and a solenoid (this one, 12v solenoid valve) with an Arduino Uno and I need them to be powered on for the whole summer. Since having them be connected to wall power is very impractical, a solar panel would be the obvious choice, obviously connected to a battery to charge it during the day and have it power everything at night. Unfortunately I don't know what solar panel specs I should go for, nor how to connect the solar panel to a battery, nor which battery to buy. I found this solar panel that should output 30W, which seems way above what the arduino and the components would consume. Should I try to find a solar panel that outputs less? How do I connect it to a battery? What batteries should I buy? (Probably Li-ion, but is there a specific kind that's best? I assume I need a circuit to charge it or power things too.)
Thank you.
How much current does the solenoid take and how often/how long will it be turned on ?
solar cell to reverse current protection diode to a solar charge controller to a battery.
I use LiFePo4's. They work well in extreme conditions and have a generous deep cycle life.
Measure the current of the entire project to determine supply needs.
The page doesn't say. It's a bistable linear solenoid in case it helps. It'll be turned on whenever the soil's not dry enough, so probably like twice a day for some minutes.
I use this diode.
This charge controller does not have a power wasting display,
I use a 12V (loaded) 50W solar panel.
Perfect, thank you!
I use this
one over the components just below the 6R1. I use one heat sink that fit over both the MOSFETS.
The diode prevents reverse current from flowing through the solar cell which can damage a solar cell.
Replying to this because I don't want to make another thread. Can I plug the output from this battery straight into the arduino? Seeing as it's 12v, so within the input rating of the arduino, it should be fine right? The input from solar panel circuit (SOL6N) goes on the battery too, is that going to cause any issues?
Yes, you can connect that battery directly to an Arduino, but do not try to use the Arduino as a power supply for other devices. The moisture sensors will be ok.
DO NOT CHARGE A lead-acid battery directly from a solar panel without a charge controller of some type. You want to STOP charging when the battery is fully charged, not continue to pump current into it.
The solar panel has a charge controller integrated into it, it's supposed to be connected directly to the battery. Is it gonna cause any problems if both the leads from the solar panel and the wires that go into the arduino are connected to the battery at the same time?
If you mean the wires from the solar panel controller, say so. They should be connected directly to the battery and the battery connected to your project. So, you are wiring correct. While the solar panel is generating enough power, it will be powering the project, not the battery. The battery will be "floating" along in the circuit and acting like a very large capacitor.
Be sure not to allow the battery to get too hot as it will vent acid onto the project.
Good luck!
Thank you!
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