This is a self sufficient Arduino board, which is powered by harnessing solar power and using a 9V rechargeable battery. It is perfect for anyone who is interested in doing Arduino projects that do not require a computer or any power supply. You can take this to the most remote places for any project.

What you will need:
9V Rechargeable battery
Solar cells (About 11V)
1N4001 diode
100uf 10V capacitor
Arduino board
9V battery connector
Power connector (to connect to the Arduino board)
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Step 1: Setting up the Arduino board

Picture of Setting up the Arduino board
This is probably the simplest step (please use the schematic as reference for wiring before doing anything else).

Change the jumper of the Arduino board to "EXT"

Step 2: Understanding the components

Picture of Understanding the components
This step would require you to have a basic understanding of the components and their polarities. This is probably the toughest bit of the setup. For easier understanding, I have used red wires for positive and black wires for negative.

Step 3: Getting the power connector ready

Picture of Getting the power connector ready
Solder the positive and negative wires to the power connector as shown in the picture. The power connectors come in different diameters, so do choose the correct size to fit the Arduino board.

Step 4: Wiring up the circuit

Picture of Wiring up the circuit
This shows the circuit I have soldered. I have made it bigger for easier understanding. It can actually be made much much smaller (half the size or even smaller).
You can download a more detailed document on this from my website at:

You're done! Now you can break away from power points and even have Arduino projects out in natural environments without a problem.
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Lucky7Gaming12 months ago

Is there any way where I could replace the battery with a 12v AC adapter and still use the solar power mostly during the day and AC adapter at night?

not sure if yr question is still actual,but the problem u havewith that is that the 12 v is higher than the 9 V from the solar power and thus in the current circuit, the solarcel would never be used. You would need to bring down the adapter voltage to about 8 Volt to do what you want

mohammadk11 months ago


My Question is :

Solar Cell : 11 Volt . OK . But How Much mA ?

krowney7 years ago
Very cool project. I've been wanting to use this myself for some time. What's the capacitor for? Is it to even out fluctuations in the voltage? I'm new to electronics and am just trying to understand stuff that doesn't make sense. I'm sure its correct, just trying to "get it".
p2man (author)  krowney7 years ago
The capacitor is to "smoothen" out the current. It is quite useful to have one in the circuit. :)
Lenny24 p2man5 years ago
Good Project. I Think you dont need the Cap. My Arduino (Duemilanove) Has Smoothing-Capacitors  "On Board".

I'm late but I think he means to smooth the flow of electricity if the batteries arn't charged and the sun keeps going behind clouds not smooth the flow of battery power. I think it just improves the overall performance a bit.
p2man (author)  wakojako3 years ago
@wakojako that's correct. Sorry for such a late reply! It does improve the overall performance a little bit. It was also to protect the batteries from too many fluctuations as well.
wakojako p2man3 years ago
qwerty156 p2man3 years ago
Actually, the battery anyway absorbs the current spikes and lows so the capacitor isnot needed at all.
p2man (author)  krowney5 years ago

Yes it does "smoothen" the flow of electricity to the batteries, as the electric output from a solar cell is not always constant. Here is a link that might help you understand more on capacitors :)

thesrikant3 years ago
scottinnh3 years ago
I am surprised no one added this, so I will: for a standalone Arduino, I would seriously consider a 3.3 volt board not the standard 5v edition.

Adafruit has a tutorial on converting an Arduino Uno from 5v to 3.3v. There are loads of 3.3v Arduino designs about (including the awesome JeeNode, which fits in a medicine bottle and can last months on a boosted AA battery).
LasVegas7 years ago
Your "Direction of flow of electricity" on your schematic is wrong. Electricity flows from negative to positive.
The author is using Conventional current convention
With the advent of the transistor, this theory was proven wrong and has since been replaced. BTW: I have an old electronics textbook that teaches using this theory. Including the now outdated Fleming's Right-Hand Rule.
Electrons flow from negative to positive, true.

The direction of the "flow of electricity," however, is an essentially arbitrary convention. Depending on the medium in question it may be most appropriate to understand what is going on in terms of electron flow (negative to positive) or "hole" flow (positive to negative) in, say, p-type semiconductors. In electrochemical circuits, the interesting portions of the circuit involve ion transport, not bare electron transport, in both directions at once, even for DC.

Conventional current, the flow of positive charge, is not an "incorrect" theory about which directions electrons flow. It is a very well established convention in electrical engineering. It is not wrong to use it.

See this page, for example, for more details.
I'm sure you're arguing just for the sake of arguing. You can call up as many pages as you wish and it still won't change the fact that electricity moves from negative to positive.

As quoted from the first page you provided: Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity. They were wrong!
Every electronics engineer is aware that current in wires is carried by electrons, and also that there are various situations in which it is carried by positively charged objects. The notion of "conventional current" is just that - a convention. This is surely elementary stuff taught, if not at school, certainly in the first year of a degree course.

It's a convention which is so universally employed that producing a circuit diagram with the arrows reversed would cause confusion rather than enlightenment.

Regards, Pete
I agree that there is not a right or wrong flow. If I make a circuit that is built around either flow, either will work as long as you are consistent.
I believe that the hyperphysics web site I linked to second is a quite reputable source. You are, of course, free to disagree. You sound like you already have your mind made up that I am wrong, which is fine, but I want other readers to have the chance to make up their own minds. Just be clear that the flow of electricity is not the same thing as the flow of electrons, as my examples pointed out.
The realisation that conventional current was "wrong" long predated the invention of the transistor - dating to the discovery of the electron. However engineers had been using conventional current for so long that they decided to continue to use the existing convention. Note the direction of the arrow on the transistor symbol, and also that of the diode: all these symbols are designed around the concept of conventional current.

In semiconductor devices current isn't always carried by electrons - it can be carried by holes which have positive charge so the notion of a "correct" direction independent of the type of carrier is rather weak.

Engineers always use conventional current. I write as a retired electronics design engineer with a lifetime's experience.

Regards, Pete
How the electrons move is generally not important at all.

More important is the movement of energy potential.  In an electrical circuit the High energy state to Low energy state moves from the positive terminal to the negative terminal.  The electrons flow directly opposite of that to balance the energy between the positive and negative terminals.

When talking about flow, it's far more useful to use conventional notation because that is actually how the energy moves, even if it's not how the electrons move.

The electrons move in the opposite direction of the electrical energy, which means tracking electron flow is usually pointless.

That's why the conventional method is still taught in electrical engineering, and why the vast majority of books on the subject prefer the conventional method.
oh here we go again with the "Electricity flows from negative to positive." speech <_<
p2man (author)  LasVegas7 years ago
What I was intending to show was that electricity flows from the solar cells to the battery. I have mentioned earlier that I will update and improve on the current schematic. Wouldn't want to confuse anyone who reads it. Thanks for the feedback though :)
konto895 years ago

would a 12v  200mA solar panel be enough?

Great project. This was part of project I'm working on and now it's done. Many thanks.
p2man (author)  Spritegeezer5 years ago
Thanks :) Glad it helped
zerOne5 years ago

Nice Project. 
But one question, how big should the Solar-Panel be to charge the battery ?
Can it also be to big and overcharge?


p2man (author)  zerOne5 years ago
Thanks for the comment :)

It really depends on the voltage of your battery. Different solar cells have different ampere rating and voltage, so you would not something that is too powerful or too weak in comparison to your battery.
booyaa7 years ago
I can't access the PDF on your website, I keep getting the following error: HTTP Error 401.2 - Unauthorized: Access is denied due to server configuration. Internet Information Services (IIS)
p2man (author)  booyaa5 years ago
Hi sorry for the late reply. My website was down but it's up and running again! :) You can now access the website as well as the file. p2man
p2man (author)  booyaa7 years ago
It seems alright to me. I think there might have been a problem with my hosting company, but I just checked and it's fine :)
Hello... i am also getting the same IIS error... it seems that permissions for that file, or folder, have been set to deny access to anonymous user. The whole site, for that matter, appears to have been set this way. Any chance you could repost this document again? Thanks again! Wonderful project!
fishhead4557 years ago
Just a quick question(s): Are you sure the flow of electricity is in the direction you indicated? Is the diode oriented correctly? Electrons flow from negative to positive while holes flow from positive to negative...looks like you are using both theories, which makes it a bit confusing to a person who does not study electron/hole flow. Great project though...not knocking a thing, just looking for a bit of clarification. Keep up the great work and thanks.
p2man (author)  fishhead4557 years ago
Thanks for bringing that up, I might revise the circuit diagram a little. The electricity flows from the solar cell to the 9V battery to charge it. The diode prevents flow in the opposite direction. Great feedback :)
iwansuryo p2man5 years ago
Can you recommend which solar panel that can be used for this appliction? Maybe one from Solarbotics? I need it to make sure. Thanks
Kiteman7 years ago
Oh, serendipity! This Instructable has arrived in perfect time to help with my latest project.

So, I have questions:

The only programmable chip I have any experience with is the picaxe system. Will this 'ible work for a picaxe board as well?

The one I own runs off 4.5V (3xAA batteries in a pack), so would I be correct to assume that I should replace the 9V cell in your circuit with 3 rechargeable AA cells?
p2man (author)  Kiteman7 years ago
Yes you can just replace it. You may not need 11V of solar power however, probably slightly less. I just had a look at picaxe it should most definitely work :) Good luck on your project, seems really interesting.
iwansuryo p2man5 years ago
Can you recommend to me, where can I buy the solar panel at online shop, which exactly match to your specification? Maybe you can choose one from SolarBotics store,

Thank you very much. It is very useful.
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