About: The Green Energy Harvester, loves to make things related to Arduino, Solar Energy, and Crafts from used stuff.



In India, one of the world’s largest, most populated countries, over 74 million rural households live without power. Children study in harmful smoke, average people spend 5% of their income on lighting fuel, people burn wood for lighting.

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A single kerosene wick burns an estimated 80 liters of fuel, producing more than 250 kilograms of carbon dioxide per year. Multiply that across the developing world and kerosene lamps emit 270,000 tons of black carbon annually – equivalent to 240 million metric tons of CO2.

To help people living in villages, I made this solar light bulb for providing a low-cost solution by replacing their harmful kerosene lamps. This will empower the world’s poor to replace kerosene with clean solar-powered light. I got inspiration from NOKERO.

I always prefer to make something from used things to recycle it. I made this solar light bulb by using used stuff and a few electronics components.

Features :

1. One-day charging can give light up to 20-22 lumens (about three times the brightness of a kerosene lamp) for the entire night.

2. A 2000mah AA battery can be charged fully in two days of bright sunlight. You can use the hanger as well as the multi-purpose stand for charging. Just hang it on a wire outside or place it at your window.

3. Uses a high-quality AA NiMH battery that can work at least for 5 years.

4. Uses a high-quality solar panel to charge the battery.

5. Automatically switches off in bright light to save charge and switch on in dark.

6. Battery over-discharge protection circuit.

Advantages :

1. Improves literacy: Solar light bulb improves literacy because people can read after dark more easily than they can by a candle or kerosene lamp.

2.Saves Energy: As the light is the bulb is charged through solar energy (free energy) it saves energy.

3. Reduces air pollution: The use of solar light bulb decreases the amount of local air pollution. With a decrease in the amount of kerosene used for lighting, there is a corresponding reduction in the amount of pollution produced.

4. Reduces greenhouse gases: Solar light bulb gives light with no carbon dioxide (CO2) emissions.

Uses :
1. Night Lamp

2.Reading Lamp

3.Portable Emergency Light

4.Camping and Hiking Lamp

5.Garden/Lawn Light

Video Tutorial:



1.Solar Panel ( 2V,40mA or 2V 150mA or 2V,300mA )

2. 0.5W Straw Hat White LED ( eBay )

3. Rechargeable AA / AAA battery ( amazon )

4. IC QX5252F (eBay )

5. 33uH Inductor ( eBay )

6. Switch ( eBay)

8. AA / AAA Battery Holder ( eBay )


10.Prototype Board

11. Plastic Container

12.Aluminium Hanger

13. PCB V2.0 ( PCBWay )

Note : Choose any one from the three solar panel mentioned.


1.Soldering Iron

2.Hot Glue Gun


4.Wire Stripper and cutter

Step 2: Schematic and Working:

The heart of this light bulb is a very small 4 legged IC QX5252F. It works very similar to "Joule Thief " circuit.

But the advantage of using this chip is that ,it does not require a bulky and heavy toroid.It do the same job using only a simple inductor, single AA / AAA battery and a LED.

Most of the solar garden light uses this small intelligent chip.I came across these ICs when one of my Instructable friend talk me about this and send the data sheet and information.

Connection :

Pin-1 -> Solar panel positive terminal

Pin-2 -> Battery positive terminal and one leg of Inductor

Pin-3 -> All ground ( Solar panel,Battery and LED negative terminal)

Pin-4 -> Other leg of Inductor

Step 3: Bread Board Testing

Before soldering the Circuit,It is always a good idea to prototype any circuit on a breadboard. This lets you check to make sure that all of your components are working perfectly.

Make the circuit on your bread bard as per the schematic.The LED should not glow if the circuit is correct.

To simulate the dark condition,cover the solar panel with your palm.Now the LED should glow.

Step 4: Out Put Waveform and Observation :

To check the performance of the circuit, I remove the LED and hook up my Oscilloscope probe.

The output is not a steady DC voltage but a voltage that fluctuates rapidly.In my case the frequency is around

184.5 KHz. The peak to peak voltage is nearly 7.28 V and the average value is around 1.0 to 1.20V.

Note : If you try to measure the voltage by a normal meter,it will show near to your battery voltage.Because your meters only measure the average value of a fluctuating voltage.

Step 5: Parts Selection :

1. Battery :

You can use any AA or AAA rechargeable battery.As per my experience I can sayeneloopbatteries are the best one.They are sold in pre-charged condition, so that you can use it directly after purchasing just like an standard alkaline battery.It can be reused up to 2100 times. When they weren't in use,could hold their charge for a lot longer than traditional NiMh battery.It can hold 70% charge after 5years of use.

For more details on eneloop batteries click here

Though a standard alkaline AA battery also works,but you can not charge the battery from solar power.

2. Solar panel :

Rating : A 2V solar panel is perfect for charging a AA NiMh battery (1.2v).Along with solar panel voltage,the current rating is also very important.Higher the current rating quicker the battery will charge.

I used a 2V,150mA solar panel.Choose according to your choice.

Size : Be sure during buying that the size of the panel is perfect to sit over the lid.In my case it is 55.1x55.1x3.59mm

3. Inductor :

The LED brightness can be controlled by using different values of inductor.

As per data sheet LED Power =( 2* Vbat / L )* 10^-6

As per my observation 33uH and 47uH works good for these 0.5W straw hat LED.

You can also try with other value and let me know which value works good for you.

3.LED :

I used a 0.5W stray hat white LED.It produce very bright light.I can say a single LED with fully charged battery is enough for basic lighting need.For specification of the LED I used is shown in the above picture.

You can also use a standard white LED but it will not produce sufficient light.

Step 6: Drill Holes for Hanger

Drill two holes diametrically opposite, near the top portion of the container.

It will used for mounting the hanger.

Step 7: Make the Hanger

First cut the hanger with the pliers back blades at the both ends.Now use the hanging part and keep the straight part for future use.

Trim at the both end according to the height of hanger you prefer.In my case it was nearly 12mm.

Bend at the both ends by using a nose plier.

Then insert the end in to the container holes made earlier.

Step 8: Make the Multi Purpose Stand

Now it is time to use the straight part of the hanger.

First bend it at the centre.

Then make two folds 9cm away from the centre.

Make two folds at the end with length 1.5cm each.

Insert the plastic container at both ends and finally cover the lid.

This stand is very useful for

1. Charging : During charging you can change the orientation of the solar panel to get maximum sun light.

2. Lighting : To focus the light you can change its facing.

Step 9: Solder the Components

In order to make the finished circuit, I soldered the components onto a perforated board.

I have attached a PDF copy of schematic.You can use it during the soldering.

Step 10: Solder the Solar Panel Terminals

All the solar panel have pre marked terminals polarity.One is positive (+ ) and other is negative ( - ).

Solder a red and a black wire to the positive and negative terminals of the solar panel respectively

Step 11: Mount the Solar Panel

Drill a 3mm hole at the center of the lid.

Pass the wires from solar panel through the underside of the lid.

Apply glue on the lid and press the solar panel to sit firmly.(You can cover the hole also,it ensures more air tight)

Step 12: Mount the AA Battery Holder

Apply hot glue on the back side of the Battery holder.

Place it on the underside of the lid and press it until the glue dry out.

Step 13: Connect a Switch

Trim the battery holder's red wire in two parts. Solder the trimmed pieces to the centre terminal of the switch and the red wire still connected to the battery holder to the switch's outer terminal.Cover the joints with insulating tap to avoid short circuit.

Step 14: Connect the Solar Panel and Battery to the Circuit

Solder the wires from the solar panel and battery to the circuit board .

Red wire is for positive and black wire is used for GND connection.

Step 15: Mount the Circuit Board and Switch

Apply hot glue at the centre of the lid's underside.Press the circuit board to fix it perfectly.

Then place the switch to the side of the circuit board and apply glue to the surrounding.

Use a generous amount of glue, but be mindful of not getting any on the lid's inner edge, or it will no longer fit on the container.

Then finish the extra wire by using duct tape.

Step 16: Insert the Battery

Insert the battery into the battery holder.

Step 17: Finishing

To test the lamp slide the switch to ON position and switch off your room light.

Close the lid of the container and you're done.

To charge the light keep the light on bright sun light.Tilt the light lid towards the sun for fast charging.

Hope my solar light bulb will give light to many rural people around the globe.

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