Multi-Function Survival Solar Gadget on a Budget





Ever since I published my last instructable, I was surprised at its lack of popularity. I realized that I needed to think of a new thing if I want to have a chance to win the Survival Contest.

I came up with this. The idea came up just randomly. I had the solar panel laying around so i thought how i can use it. A solar panel is a device which converts light energy to electrical energy. I am using that electrical energy to charge a battery pack which is then used to charge other devices and power up lights. I have taken some considerations in mind while planning and building this gadget. I will go over them in detail. I also added "smart" capabilities to it by using arduino to control everything. That way I have freedom and i can improve the design later on. Although its working are not that hard to understand but still I am going to go over them in detail.

So hold on to your hats as I try to impress y'all but presenting you with a detailed, simplistic and fun to build instructable.

If you find my Instructable up to the mark, please take out the time to hit that trusted "Vote" icon.


Step 1: What Is It?

Well I think first i need to explain to you guys what it is that I have built here so you can decide weather or not you want to make one for yourself.

The Multi-Function Survival Solar Gadget is a homemade solar device which is designed to help you in sticky survival situations. May it be in a jungle, a campsite, outer space, mars, an urban setting or even a home or office, this gadget can be of real help.


1. Mobile Charger at 5V 1A capable of charging, on average, a mobile phone two times over
2. Bright LED Wide Angle Torch
3. SOS Signal

At present it has these three basic output functions but I am constantly brainstorming on what to add and how to make it better.


1. 5 Watt Solar Panel
2. Arduino controlled system
3. Over/Under Charge/Discharge Protection
4. 12V 2800 mAh Li Ion Battery Pack
5. 10 Watt LED
6. Indicator LEDs

These are the features of the device which I have built but these too are being brainstormed on as to improve the design.

Step 2: Considerations While Designing It

When I started to brain storm the design I had some considerations in mind.

1. Small Size + Weight : The device has to be as small as possible and as light weight as possible. No one likes a bulky gadget which is hard to handle. Being as small as possible means that the smallest possible size achievable with a 5 Watt Panel.

2. Low Price : The budget of a DIY ist is always tight and I am no exception so I also kept in mind the price of the gadget. It has to be low enough to be easily constructed and compare with on the market product prices.

3. Easy to Build
: The build should be easy. Nothing too complex for the rather beginners out there to understand. Keeping that in mind I kept the design simple and didn't implement ant charging control.

4. Reliable : So when you make a gadget, you expect it to perform. It wont be any good if it stops working in the heat or just bad connections. We cant have that so we have to make it reliable.

5. Practical : The gadget has to be practical. Its useless if you make it and not use it. It should be easy enough to use and helpful enough that you find good use for it in your daily life.

Step 3: How Does It Work

So you guys need to understand how this Solar Gadget works. Its good if you do because it will allow you to solve problems and improve the design using your own creative ideas.

First there are some terms I will define for the absolute beginners so that they don't have any issue in understanding the lingo.

1. Solar Panel : a panel consisting of an array of photo voltaic cells designed to absorb the sun's rays as a source of energy for generating electricity

2. Li Ion Battery : a battery which is a member of a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.

3. Arduino : it is a small micro controller board based on Atmel chips capable of processing and I/O

Once you have understood these terms, only then we can delve into the details of the workings of the gadget. So lets begin

1. It all starts with the solar panel which captures light and converts it into electrical energy. This electrical energy is then passed through a relay acting as a switch and fed into the battery pack.

2. The battery pack is 12 volts and the solar output is almost 16 volts but that is the open voltage. It comes down when connected to the battery. Now lets do some physics. The panel is 5 Watts and lets assume that it is giving a constant output of 12 volts. In that case Power = Voltage * Current so 5 = 12 * x therefore the current is 0.42 Amps. The battery is 2.8 Ah so it will take 2.8 / .42 = y which is 6.7 hours so according to our calculation, it will take 6.7 hours for full charge.

3. The output 5 volt charger circuit and the high brightness LED are both connected to the battery with a relay in between.

4. The arduino sits right in the center and controls everything. The three relays are connected to the arduino. There are three switch inputs to the arduino. There are 3 indicator LED outputs from the arduino for battery level. Two more LEDs for charging and output indicator. Each individual battery cell is connected to the arduino analog inputs.

5. The arduino basically switches off the charging relay when battery is charged. When the output switch is turned on, the arduino switches on the relay and output is turned on for the mobile charger. If battery is empty, relay is switched off to prevent over discharge. The LED torch is also controlled by the arduino. It is driven by the relay which can change modes from all on to SOS using a switch.

6. The battery voltage is being measured and can be displayed using a switch and an RGB led for battery level indication.

7. There is a switch to control power going into the arduino. This is in case you have to store the device, you can turn it off to prevent discharge. In the off position the battery will charge but there is a short fall that over charge protection is not present. It will only be in place when the arduino is turned on.

So this is the working of the gadget. It has possibility for expansion and improvement. But to keep it simple, I just kept it at this.

Step 4: Materials

Major Parts

  1. 5 Watt Solar Panel Amazon Link
  2. 3x 18650 Li Ion Rechargeable Cell Amazon Link
  3. 4 Relay Module Amazon Link
  4. 5 Volt Regulator Board Amazon Link
  5. Arduino Uno Amazon Link
  6. 5/10 Watt 12 Volt High Brightness LED Amazon Link
  7. Plexiglass Sheet

Small Parts

  1. RGB Led
  2. 2x Led Indicator
  3. 5x toggle switch
  4. 2x 1k resistor
  5. 3x 220 Ohm Resistor
  6. 3x 10k resistor
  7. 1 diode
  8. Perf Board
  9. Wire
  10. Mounting Nuts and Bolts
  11. USB Female Connector
  12. 10 K Variable Resistor
  13. Heat Sink
  14. 2x Block Connector
  15. LED Driver Circuit
  16. Male/Female connectors


  1. Soldering Iron and Soldering Wire
  2. Drill machine with appropriate bits
  3. Plexiglass cutter
  4. Wire cutter
  5. Tape
  6. Ruler
  7. Sharpie
  8. Hot Glue Gun

Step 5: Electrical Diagram

The first diagram above will give you an idea about the basic layout. The second one is the exact circuit we will have to build. Its not complex but it is a little elaborate so it will take time to construct. I found it easiest to hand draw it so if you have any questions, do ask.

Step 6: Constructing the Battery Pack

I will show you how to build a 3 cell Li Ion battery pack, complete with diagram and everything but if you prefer the easy road, what you can do is buy a 3s Lipo of whatever size you want. It has the desired outputs for individual cell voltage measurement. But I like to make things myself so I went with a DIY approach instead.

First have a look at the circuit diagram above. The three cells are connected in series and then the main output is taken from the open ground and open positive terminal. There is one more output line for voltage measurement.

What you will do is place the three cells side by side such that middle cell is flipped. Tape them together.

Next you will solder the wires as shown. Now i know some of you may say that its dangerous so solder batteries but if you do it quickly without holding the iron on it for too long, then it wont be any issue.

Once all the wires are soldered, secure them using tape and finish off the pack.

Step 7: Constructing the Circuit

Well the construction begins by cutting a decent piece of perfboard. Solder the block connectors and diode. Make the necessary connections. Wire the switches along with the 10k resistor grounds. Basically just follow the diagram and take help from the pictures. Take note that the +ve of the toggle switches will be +5v so wire that to the arduino. The voltage divider is also fairly simple. Once you have done all the connections, measure the voltage on the arduino connections before connecting it to the arduino. None should exceed +5v. Also take note that the voltage divider can output greater that +5v so don't turn the 10k Variable without measuring the output.

The circuit is a bit haphazard bit its stable. Wire in the relays where you have to. For the solar relay, i extended wires from the perfboard circuit and for the other two relays, I wired them directly to the modules.

Solder the USB connector with the output charging module and wires in the input. Before getting all excited and connecting your cellphone, make sure its set to +5.30 Volts. Power it up and measure the output. Turn the pot to get the desired voltage. Solder the indicator Led with a resistor inline. As for the LED Driver, just solder it correctly and make the connections.

The RGB Led is simple. Connect 220 Ohm resistors on its three leads and then wire them to the arduino. Ground the longest pin.

Go about it slow and steady. Take your time and try not to do it one sitting. I did it myself so i know its not easy. Just required a rested mind.

Step 8: Case Building

To build the case we will be using 3mm Plexiglass. Follow the steps below.

1. First of all measure the size of the panel and cut a piece exactly of that size. Use the score and snap method throughout the constructions.

2. For the side walls, measure 1.5 inch width lengths for the sides and cut them.

3. Use a sand paper to fit everything together and fit it using tape to ensure they dont move while gluing.

4. Use hot glue to join all the seams from the inside. Make sure the glue is hot.

5. Let it cool and then remove the tape.

Tip : Rough the areas to be glued for a stronger bond.

Step 9: Putting It Together

We have to mount the large components on the plexiglass. So place the arduino, relay module, charging module and perfboard. Set them as you like keeping in view the control panel and LED side. Mark the holes and drill them. Secure the components using nuts. For the LED, drill and secure the heat sink on which ever side you wish. Drill holes and secure the LED on the heat sink. Run wires through another two holes.

Drill holes for the switches, leds and USB. Mark out the location of the holes. I just marked out 1 cm apart dots and drilled them. For the USB, you will have to drill out multiple holes and refine it using a file.

All of this is just a guideline of how I did it. Your design can vary and could be an improvement over my design.

Once all the holes are done and components secures, you will have to wire everything. Plug in the DC Jack in the arduino. Wire the grounds of the LED and Output. Wire the arduino inputs and outputs. Secure the battery using double sided tape. Remove the arduino connections and plug in the battery. Test everything. Make sure that the switches are working fine and giving the output desired. The voltage divider output should be checked. Once all it well, connect the arduino connections. Turning on the power switch should turn on the Arduino and Relay board. If not, then check every connection and check the circuit.

Interesting fact is that i made a mistake in the circuit and had to pay for it with an arduino. The arduino got damaged so I had to replace it. So try to learn from my mistake.

Fix the toggle switches and the indicator leds in the desired holes. Make any final connection and you are good to go.

Tip: Test every module and switch and led before installing it. Or else tracing an issue will be next to impossible.

Step 10: Programming

So once the circuit is built all according to the diagram and tested. We shall program it. First we have to calibrate the voltage divider circuit. For that, upload the calibration code given. Open the serial monitor. Measure the actual battery voltage using a multi-meter. Make sure the power switch is On and then turn the pot so that the voltage on the serial monitor matches the one on the multi-meter.

Next upload the main code. If you did everything right, there shouldn't be any problems at this point. If you turn On the power switch, the Battery indicator should indicate the correct color. Turning on the Output switch should which the relay, turn on the indicator led and give +5 V output. It you turn on the LED switch, the led should turn on. The mode switch will be used to toggle between SOS and constant on. If you turn both, the output and LED switch at once, they will shut down. The code is written to only allow one at a time.

Step 11: Post Production Performance Testing

Testing this device was a good feeling as I got a better outcome than expected.

First of all, the charging time is longer than the calculated time. But that is to be expected as the panel is not 100% efficient. It takes about 8 to 10 hours for full charge, which is not that bad.

The charging output can charge a cell phone almost one and a half times. That is also pretty good.

The LED can run on full mode for about 3 to 4 hours and on SOS mode for about 8 to 10 hours. That is also pretty good for survival as it can run almost all night which is what we need in a survival situation.

Plus I found that I can keep the device Off when not needed and turn it on only when I am using it or when it is charging. Better yet, don't even turn it on for charging because the chances of overcharging are slim to none if you are using the device on a regular basis.

Step 12: Usage and Utility

The usage and utility of this Solar Gadget is very vast. The most obvious use it to charge your mobile. What I do is keep it in my car on the dash board. It receives plenty of sunlight and charges up. Then I can use it whenever I want. It will be especially helpful in situations where you are out camping and you need to charge up your devices. It is bigger than the commercial chargers and has a battery hence you can charge your phone quickly and then leave the device in the sun to charge up.

The LED flashlight is also very practical. It will help you find your way in the night weather it is a camping area or your car. You can use it to see around while you change your tire.

The SOS function of the LED will be helpful in emergency situations. People and rescue personnel will be able to spot the flashing light in the night from far away and come to your rescue. It will also charge so you can have it for a long period.

Step 13: Variation and Improvement Possibilities

There are a number of things you can change or improve on.

1. You can build a bigger battery pack using six cells instead of three. Make three, two parallel cells packs and then follow the instructions given. Assume the two cell pack as one.

2. You can use a Lipo pack pre built for better performance and ease of use.

3. You can use a bigger or better solar panel. New technologies with more efficient PV cells are becoming popular and can be used.

4. You can add a solar charge controller pre built to replace the arduino to make the build easier. Just make sure its output can be turned on during that day as well because most controllers only turn on output when solar input is cut off.

5. You can incorporate a MPPT (Maximum Power Point Tracking) in the Arduino using FETs. There are many guides on instructables so you can search it up. I found it too complex to incorporate that and expensive as well.

6. You can construct a PCB for the entire thing and combine all the circuits in one.

7. You can use a portable jump starter and replace it with the battery pack so that you can have jump starting capabilities as well.

8. You can add hand crank generator as well so that you can charge your device in the night. It will be a true survival gadget.

These are some of the improvements I can think of. If you can think of anymore, please do comment and try them out yourself.

Step 14: Concluding Remarks

Well folks it has been a long journey to build this device from start to finish and not without its problems but I can proudly say that I have succeed. The goal was to build a small, practical, low cost and smart solar charger and that is what I did. I am very happy with the gadget. It looks great, works even better. It comes with the satisfying feeling of successful DIY which is very fulfilling.

Now I did my level best to ensure a complete and in depth guide of the entire process. But even then if there is any confusion, please comment.

Lastly, a small request. This is my third and final instructable for the Survival Contest. I worked so hard despite my upcoming exams. So please vote for me. I shall be ever grateful to all of you who support me. I promise to continue to bring more ibles.

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    53 Discussions


    3 years ago

    If you have to use Arduino, add in more feature to fully utilize its capacity :)

    For example, you can use this to control your home device if u r not compaing anywhere


    3 years ago

    Its cool but I dislike having to sacrifice an arduino in a project like this. per haps a hardwired version in the future? I'd have voted for this.

    Avik wadhwa

    3 years ago

    nice idea but try working on improving the amount of time it takes to charge up and the amount of output it gives. A wonderful project indeed

    1 reply
    badarsworkshopAvik wadhwa

    Reply 3 years ago

    thanks. i am working on an improved version right now. please dont forget to vote


    Reply 3 years ago

    Well the solar power is just there so that you can charge with it. it does that pretty well.


    Reply 3 years ago

    well the cells are 4.1 volts when charged so that makes it 12.3 v on full charge. what you can do it use a lipo and a small balance charger. the panels input will be regulated by the balance charger and system will become more efficient.


    3 years ago on Introduction

    Great job! I liked your hand cranked generator idea at the end. Are you planning to build it anytime? Kudos to your efforts!

    1 reply

    3 years ago on Step 1

    Maybe you could add some sort of fire starter (soldering iron kind of thing).

    2 replies

    If you included a 12V power slot like they have in cars, not only could you expand it's range of capabilities, but if you kept one of those cigarette lighters designed for those ports you might, at least in theory, be able to use one of those for a fire starter. I don't really know how well that would work though, just an idea.


    3 years ago on Step 1

    Nobody knows Morse code these days... but it used to be a lifesaver and may still be in the future.

    I propose you use the solar cells to detect flashes of light (the code) and decode it by software. Also, the flashlight can be made to send a response.

    Another survival function built in!

    2 replies

    you might want to add a photoresistor if you do something like that, might be more sensitive to relatively low light. Another way is that you could possible use a button that users could press to match a morse code signal they see and have it translate that signal. Has the advantage that it would work during the daytime like if someone was using a signaling mirror.


    Reply 3 years ago

    8 x 5 x 2. a little bigger than expected but acceptable as the first version.


    3 years ago on Introduction

    Got my vote! Definitely more power, higher base voltage(12v inside, w/ 5 volt outlet for usb stuff, 12v outlet for 12v stuff, and thn the recommended 110v outlet for 110v stuff... UNIVERSAL gadget is Gr8 idea, thnx for posting and all of your and others ideas as well! Gr8 work...