Firefly is a night lamp made from recycled mason jars and e-waste. It is a beautiful and useful craft. The main intention is to reuse old rechargeable batteries and give them a second life away from the dumpster.

By use of a Tilt Switch, these lamps turn on and off by just flipping them upside down. Since the circuit is so simple, it is a good project for a first approach to electronics or to build with kids.

These lamps are meant to be used as night lamps, so you can find your way without dazzling yourself.

This written guide is meant to complement the build process shown in video format, it is recommended to fully watch the video and read the guide before starting the build.

Supplies

The following materials are employed in this build :

Medium sized Mason Jar (clean)
Recovered LiPo battery (from an old cell phone, speaker, power bank, etc.)
Kapton Tape (Not indispensable)
Blue Painter's Tape (Masking Tape)
TP4056 Battery charging and protection module
Beige Spray Paint
2-Part Epoxy Glue (preferably transparent)
Mercury Tilt Switch
LP2950 3.3v LDO Voltage Regulator
SPDT slider switch
Red & Black Wire
10 Ohm resistor

The tools needed for the build are:

Soldering Iron + Lead Free Solder
Drill + Step Bit
100 Grit Sandpaper
Adjustable helping hands
Wooden mixing tool (for Epoxy Glue)
Post-It Note pack (to mix the glue on)

Step 1: Recover a Battery

Now a days e-waste is one of the biggest pollution issues worldwide. Thus, it is best to repurpose and extend the life of what has already been manufactured to prevent it from going into landfills. Especially rechargeable batteries. most kinds of recent e-waste contain some sort of rechargeable batteries, and in many cases these are still perfectly usable, just with a little less capacity.

For this project we want to find a LiPo battery, commonly present in old mobile devices, power banks, rechargeable speakers and alike. These mainly come in either a rectangular or a cylindrical shape. We can reuse both kinds, although some rectangular batteries may not fit into thin-necked mason jars so keep that in mind.

Almost any kind of LiPo battery will work, but the choice of battery will significantly influence the light's duration. Small batteries from older MP3 players have a capacity of around 500 to 1,500 mAh whilst the standard 18650 Cylindrical cells usually range from 1,000 up to 3,000 mAh. For the Firefly lamp the power consumption is 40 mA, thus even the smallest kind of batteries should give you a good 10+ hours of runtime between charges, but the bigger cells can yield upwards of 60 hours of runtime between charges.

Step 2: Prepare the Mason Jars

To have the soft light effect, we want to paint the Mason Jars from the INSIDE so first we must clean the insides using some regular alcohol and a pen to reach the bottom. Next, we will wrap the outside with some cleaning towels and start doing some VERY LIGHT coats on the inside, rotating and letting them dry in between coats. We want to achieve a thin but even coat, and most importantly avoid prominent drips on the inside.

Step 3: The TP4056 Charger Module

LiPo batteries are great because they are very efficient, easy to use, and provide a high enough voltage for standard white LEDs BUT they can also be DANGEROUS, so it is important to use them in combination with a dedicated charging and protection circuit. Luckily, these are so commonly used that they come in small, cheap modules called TP4056 boards, these include the USB port that will be used for charging and they come in both USB Micro and USB C variants. Depending on the source, you can get them as cheap as $1 USD each so I recommend buying them in panel.

To prepare our battery we must first remove any loose plastic wrapping and either leave the cell bare or wrap it in Kapton tape to secure the wires. Next we will glue the TP4056 module onto the battery with Epoxy Glue using a small wooden spacer, and solder the connections for the input and output leads. Now we have a complete battery management module to power our project.

Step 4: Mount and Reinforce the Battery

Now it's time to mount the battery onto the metal cap. For this, first center the battery over the cap and trace around it, next mark the center of the USB connector and drill a sufficiently big hole. Also sand the inside of the cap and clean it with alcohol. Finally apply thin layers of Epoxy glue to set the battery in position and reinforce the assembly.

Step 5: Schematic and Circuit Explanation

After the Battery Charging and Protection Module (TP4056), the core of the circuit consists of two switches in series feeding a voltage regulator which feeds a stable voltage to the LED array through a current limiting resistor. The first switch is the master switch so the lamp can be turned off permanently for storage or transport and the second switch is the Mercury Tilt Switch which server as the orientation sensor. But why use a voltage regulator if we have the resistor to limit the current?

A characteristic of LiPo batteries is that their output voltage varies widely while they discharge, thus we must use a voltage regulator to have a consistent power output as otherwise the lamp would be much brighter when just charged and dim significantly as it discharges. We don't want that.

The 10 Ohm resistor determines how much current will pass through the LEDs. To calculate this we must measure the voltage drop of our LEDs, subtract it from the 3.3 volts provided by the regulator and divide this by the ammount of current (in Amps) we want flowing through the LEDs.

For my LEDs the dropout voltage is 2.65 volts, so subtracting that from the regulated voltage means the resistor must drop 0.65 volts. If the resistor is 10 Ohms (a standard value) the current through it will be 0.065 Amps or 65 miliAmps distributed over the 4 LEDs. This is 16.25 mA per LED which is just under their maximum reliable rating of 20 mA. This will yield a power output of 2.65 volts x 0.065 amps = 0.17 Watts and give a runtime of 11.5 hours with the rectangular 750 mAh battery and 34 hours with the cylindrical 2,200 mAh battery (18650 cell).

Step 6: Mount and Connect Components

The main 3 components aside from the LEDs can all be mounted on the side of the battery, just be sure to orient the tilt switch the right way around. Make use of thin connection wire to bridge all the components together. Pay close attention to which are the input and output sides of the voltage regulator.

Step 7: Build the LED Array

For the LED array we want to assemble 4 LEDs so that they all face outwards perpendicular to each other. This can be done with just about any kind of LED, even SMD LEDs. I recommend Piranha LEDs because they are themselves a rigid structural element which are easy to assemble and connect together, but you can use what ever kind of white LED you have available.

Step 8: Mount the LEDs and Test

Once we have the LED assembly ready, we will mount it over the 10 Ohm resistor, connect the ground, and test that everything works properly. Next set the assembly in place over the center of the battery with some more Epoxy Glue.

Finally, once everything works correctly, add one more epoxy layer over all the soldered connections for increased durability.

Step 9: Adjust the Color Temperature

Most likely your LEDs will be kind of blueish which can yield a weird greenish tint on the light, but don't worry, we can tune the color temperature by applying a thin layer of pigment onto the LEDs. For this you can use orange sharpies or acrylic paint, just be sure to apply it very thin. Ideally you want to use neon pigment as this will actually convert part of the blue light into orange otherwise regular orange pigment will work fine, just a little dimmer.

Step 10: Add Rubber Feet

The Firefly night lamp is almost ready! To finish up the build, we can add some tiny rubber feet around the rim of the cap. For this we will cut the strips in between rows of some generic rubber feet and cut tiny rectangles from these strips.

Apply these rectangles in a hexagonal pattern around the rim of the cap.

Step 11: Charge and Use!

Congratulations! You have successfully completed the Firefly lamp! Now just charge it up fully and put it to good use!

Step 12: Afterthoughts

I developed this project as a simple electronics exploration but gradually it grew into something much more significant and refined. As I completed the first one I realized this is not only a good project for a first approach to electronics but it is actually a very beautiful and useful object while also being a pertinent craft to spread awareness and make an impact on the current worldwide e-waste issues and overall approaches.

If you made it all the way, make more of these! Give a second life to e-waste by giving away some of these to friends and family.