Hi there, I'm an absolute beginner in programming and arduino.
Is there a chance to have two +12V power units and smoothly regulate them to get one output +12V using ADUINO module?
Let’s say there is a solar panel with output +12V as one unit.
And +12V battery as the second.
If I’ll cover/uncover the solar panel (or night may come :o)) I need constant +12V on the output.
Is the arduino module able to control it without interruption and “ANY” voltage change?
Thank you so much.
If you connect diodes from the two power sources, with the "arrows" on the diode symbols pointing and connected to the Arduino Vin input, then the one with the highest voltage will "capture" the Vin input. You would need to be careful that the solar panel would not go much over 12v as it could exceed the Vin max on the processor - for this you might use a quite hefty zener diode with a slightly higher voltage to shunt current from the solar panel if its voltage goes much above 12v. The Arduino wouldn't have to do anything, it's all done by the diodes. To make it more efficient you could use "Schottky" diodes that have a smaller forward voltage drop (~0.2v) than standard rectifier diodes.
A better approach though would be to have a solar charge controller that tops up the battery from the panel when the sun is shining but makes sure it doesn't overcharge - these are available on Amazon and eBay, seemingly at ridiculously low prices. You could do this using some external circuitry using the Arduino for control, but then you might have a "bootstrap" problem; and you'd have to run that code alongside the code you want to run anyway.
Why don't you directly connect +12 to +12 directly (with a diode in between to prevent backflow of current to solar panel)
You will be much better off using a solar charge module designed for the purpose. They are cheap and reliable.
I use and recommend this Sunforce charger for small (up to 300 watt) solar/lead acid battery systems.
Maybe it needs a bit more description.
I’m after a VERY cost effective solution.
I’ve got a VAN which I wouldn’t call a campervan but more like a multi purpose VAN I can sleep in :o) and I want to connect some electronic devices (laptop, Tablet … and so on ) where I need not +5V but +12V power output I can connect to.
I’ve got a solar panel with a solar charge controller which I’d like to be the main power unit and I want to “drain” any other battery only if I’ll drive to the shade (tunnel …) or at night or better to say I don’t want to lose the power.
It looks like nonsense but that was the idea as many times I’m not able to recharge my additional battery enough when I’m not using the VAN regularly.
I was hoping to get as much energy from the solar panel as possible and take only a bit or nothing from the battery…
Or in winter time or very cloudy dark days take at least something from the panel to help the battery.
Look for diode battery isolator. Also, consider using a single pole, double throw knife switch.
A few I've found are too expensive on first place but it looks like it has one input and two outputs and I have two inputs which I need to get to one output.
I think you are looking for something like this
It looks promising as it has two inputs and one output but considering there is a USB port I guess it’s only 5V output as it doesn’t have much of description.
As everyone is advising me of a solar charge controller I guess I’m missing some knowledge here how it actually works.
So if there is enough sunshine and I’ll connect my laptop (see the image) it means the laptop (or other device) is not going to use any power from the battery? So If I disconnect the battery will it still run on solar energy? Or am I completely wrong? Because that's what I’m after. It’s hard to test it now without the sun :o).
)I know, not the best drawing.)
@iamardu
First thing is it safe to directly connect your laptop with 12 supply
Secondly (as far as I know) laptops communicates to its charger and decide a certain amount of power to be delivered
And do you really disconnect the battery (can I ask you reason)
Thanks for the reply anyway.
I think Automatic power switching like this will work for you
And Arduino also can do this
But you will also need a voltage regulator if you don't want above 12v as these things mentioned above can only switch between battery but can't control voltage
That’s exactly what I was talking about except the fact, that unit is based on a relay so
switching would be a bit intermittent every time it will switch to other input and in case I’ll drive in to the tunnel it will switch to the battery but if the tunnel will end I guess it will stay on battery input and don’t switch back to solar panel that’s why I was hoping it need some intelligent like ARDUINO.
Arduino will constantly control voltage coming from the solar panel and if any change it will switch or ADD more voltage from the backup battery and as soon as solar can produce enough power switch it back. Not just simple relays or diodes.
Connect your laptop to the battery, or to the battery through a suitable inverter.
If solar power can't keep the battery mostly charged, for the intended load, then the system design is wrong.
But Arduino can't handle that much power
You will have to use relay with Arduino also
Yeah you are right
It should be connected like this
I think it is the best method to connect
I thought the Arduino could handle 12V. On the other side, transistors can easily handle it.. Arduino will only control them. They also can smoothly regulate voltage but I’m so long out of school that I remember a SH.. what I was learning. 
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