DIY Solar Bottle Lamp ( TH Version )

A few weeks ago I have published an Instructables on Solar bottle Lamp, it was highly appreciated by the people. If you don't know what is solar bottle lamp? let me introduce you, Solar Bottle Lamp is a solar-powered light that is constructed from waste plastic bottles. The design idea is to reuse waste plastic bottles by attaching a 3D printed solar lamp in place of their old plastic cap.

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Update On 09.08.2022

Now you can order the Solar Bottle Lamp kit from Tindie

The PCB board used in the earlier version was made of all SMD components as result users who don't have SMD soldering experience can't take advantage. So I thought to redesign the PCB by using all through-hole components so that anyone can make it.

Another advantage of this board is that it can easily assemble by school children. I mean this kit can be can also be used for STEM education in the school. By making this project they will aware of the sustainability and use of renewable energy. 

Recycling obviously helps make plastics more sustainable but sometimes, recycling can be less carbon-friendly than we would like for it to be so instead of recycling, why don’t we try upcycling. Upcycling is the process of reusing items in a way they were not necessarily intended for that gives them a new life rather than going into the trash or being sent off to be recycled.

Benefits:

1.   Reusing plastic bottles can significantly reduce pollution, greenhouse gas emissions, and energy usage.

2.   The use of the solar lamp will decrease the amount of local air pollution and saves energy.

3.   It can provide access to solar lamps at an affordable price to a wide range of people living in remote villages that are deprived of clean energy access.

4.  It also came out as an alternative business model with the potential to strengthen the overall rural economy by generating technology-based livelihood opportunities.

1. TP4056 Charger Module ( Amazon / Aliexpress )

2. Transistor 2N222A ( Amazon / Aliexpress )

3. StrawHat LED ( Amazon / Aliexpress )

4. Resistors - 1K, 10K ( Amazon / Aliexpress )

5. Resistors - 5R,22R ( Amazon / Aliexpress )

6. Flashlight Button Switch ( Aliexpress )

7. Schottky Diode -1N5819 ( Amazon / Aliexpress )

8. Solar panel 60 x 60 mm - 5.5V ( Tindie )

9. 14500 Li-Ion Battery ( Aliexpress )

10. Battery Spring plates ( Amazon / Aliexpress )

11. JST Connectors ( Amazon / Aliexpress )

12. Heatshrink Tube ( Amazon / Aliexpress )

13. Softdrinks Bottle

14. PCB ( PCBWay)

Tools Used:

1. 3D Printer ( Amazon / Aliexpress )

2. Soldering Iron ( Amazon / Aliexpress )

3. Nipper ( Amazon / Aliexpress )

4. Hot glue Gun ( Amazon / Aliexpress )

The entire circuit is broadly dived into 2 parts: 

1. Charger Circuit ( TP4056 Module ) 

2. LED Driver Circuit 

The power generated by the Solar Panel is extracted by the charger circuit and charges the battery and provides necessary protections to the Li-Ion Battery. The LED driver circuit is responsible for driving the LED. 

Charger Circuit: 

The charger circuit charges the battery by taking power generated from the solar panel. It is based on a single-cell Li-Ion charger module TP4056.  

LED driver Circuit: 

The LED driver drives the LED as well as controls the brightness. It also provides automatic turning ON of LED during the night. The circuit works as follows:

During the day, the solar cell generates voltage and turns ON the transistor Q2. So it does not have the current bias to the base of transistor Q1. It is OFF so the LED will go out.

When there is no sunlight, no solar current to base Q2, so it will not conduct but at the same time, transistor Q1 will conduct. Now the battery’s current will flow to LED through the resistors (R3 or R4).

The button switch is used to connect either R3 or R4 in the LED circuit. When the pole is connected to R3, the brightness is Low (High Resistance, Low LED Current) and when connected to R4, the brightness is High ( Low Resistance, High LED Current )

To make the Solar Bottle Lamp, first, you will need the controller PCB. There are two options to get the PCB. 

Option-1: 

You can make the PCB at your home by using the Gerber files. The link to download the Gerber files is given below 

https://bit.ly/3DTUZBz 

Option-2:

You can also order the PCB from the same link.

For assembling the PCB, you will need a decent Soldering Iron, Solder, and a Nipper. It is good practice to solder the components according to their height. Solder the lesser height components first. First, solder the resistors, then diode, then transistor, then the button switch, and finally the TP4056 Module.

The button switch shall be soldered on the bottom side of the PCB. 

You can follow the following steps to solder the components: 

1. Push the component legs through their holes, and turn the PCB on its back. 

2. Hold the tip of the soldering iron to the junction of the pad and the leg of the component. 

3. Feed solder into the joint so that it flows all around the lead and covers the pad. Once it has flowed all around, move the tip away. 

4. Trim the extra legs of the component by using a nipper.

The enclosure has 5 parts: 

1. Main Body 

2. Top Cover 

3. LED Holder 

4. Diffuser 

5. Button 

The Main Body is basically designed to fit all the components including the battery. The top cover is to cover up the main body and mount the solar panel on it. The LED holder is used to hold the LED and the diffuser is used to diffuse the LED light in all directions. The button is used to operate the switch on the PCB from outside. 

Download the .STL files from Thingiverse.

You need support structure for printing the main body and top cover. You can print the enclosure parts either in PLA, ABS, or PTEG filament.

Both the top and bottom parts are printed with support structure, so we have to remove them before final use.

Removing support from the main bodies is quite easy, just squeeze them with fingers, and they will be easily separated from the main body.

Removing the support from the cap threaded area may need a screwdriver or any sharp object. After removing the support, you have to smooth out the cap threaded area. You can easily do it by twisting and untwisting a few times with a soft drinks bottle.

You have to use a solar panel that can be fitted to the enclosure. The slot is made for mounting a 55x55mm solar panel. The solar panel that I have used here is rated for 6V and 50mA.

Insert the terminal wires from the solar panel into the slot in the top cover and solder them to the PCB ( SOL+ and SOL-). Mount the solar panel on the top cover by using epoxy glue.

Seal the panel from inside also, so that water will not enter the enclosure.

Solder JST connector terminal wires to the battery terminals. I always prefer to use red wire for the positive terminal and black wire for the negative terminal. The spring shape contact is the negative terminal. Solder the terminal wires to the PCB ( BAT+ and BAT- )

Then install the terminal plates into the battery slots as shown in the above picture.

I have used an 8mm 0.5W straw hat LED. Solder JST connector red wire to the positive terminal and black wire to the negative terminal of the LED.

Mount the LED into the holder and then install it into the main enclosure as shown in the above picture. The notch shall be aligned properly.

Now seal the LED from all sides by using epoxy glue. Then install the diffuser, you can apply epoxy glue to the joint.

Insert the Switch button cap into the slot given in the main body. You have to align the notches perfectly.

Align the PCB mounting holes with the mounting studs in the enclosure. Then secure it with two M3 screws.

Now solder the terminal wires from LED, Battery, and Solar panels. The polarity is marked on the PCB.

Connect the terminal wires from the Solar panel, Battery, and LED to the PCB terminals.

You can connect it with JST connectors or directly solder it to the soldering pads.

If you prefer to solder directly to the soldering pads, be sure the polarity is correct. The avoid mistakes; polarity is marked on the PCB.

After installing all the parts, close the top cover by aligning the mounting studs. For a better joint, a snap and fit arrangement is also provided in the top cover. Now use M3 screws to tighten both the parts together. You may apply epoxy glue at the joints to make it weatherproof.

Now the lamp is ready for use.

The solar lamp is compatible with any soft drinks bottle cap. Take an empty soft drinks bottle and clean it thoroughly.

Fill the bottle with water and add a few drops of chlorine to avoid algae formation.

Close the bottle with Solar Bottle Lamp and your lamp is ready.

The lamp can be charged in two different ways:

1.   Solar Charging

2.   USB Charging 

Before the first use, it is recommended to charge the battery. You can easily charge the lamp through a micro USB cable by connecting it to any USB power source like a mobile charger. The red LED indicates that the battery is charging and blue LED indicates charging is complete.

You can also charge the battery by placing the bottle lamp in bright sunlight for at least a day.

Testing the Lamp:

Press the button switch to set the desired brightness (Low / High) and test it by covering solar cell by your hand. The light should be turned ON.

Place the bottle lamp in the bright sunlight, the solar cell will charge the battery. When the sun goes down, the bottle lamp will be automatically switched ON.

Suggestion:

1.   Apply epoxy spray at the joint of the 3D printed enclosure to make it more weather resistant.

2.   Apply conformal coating to the PCB to protect the board and its components from the environment and corrosion. 

3.   You can use PVC wrapped battery with JST connector to avoid the use of terminal plates.

4.   You can add some soap solution to the water to diffuse the light more.

5.   You may add food color to the water, to make the light colorful.

6.   You can make a few similar bottle lamps and place them in your garden or lawn. Now enjoy your new solar bottle lamps.

7.   If you want to use this lamp for lighting the room, you can follow this Instructables to mount it on the roof.