Al Gore and company have helped us to see that our planet is in peril. Lend a hand, make a toast, and help illuminate ways for saving Earth — all at the same time! It’s easy to do your part: recycle, refill, and recharge.
Just take your fave beverage bottle (keep the cap), drop in a flexible solar panel, a step-up switching regulator circuit, a rechargeable battery pack, and a powerful LED, cap it, and you’ll have a self-sufficient garden lantern that is ideal for shedding some light on solving environmental issues. You will have to choose your bottle carefully, though. Clear glass rules. Also, wide-mouth bottles are easier to convert than narrow opening long-neckers. Like your grandfather who built ships in discarded bottles, put a modern spin on bottle building while being conscientious of your world. Cheers!
TIME: 4 hours
DIFFICULTY: moderately hard
- Recycled clear glass bottle, with cap (free)
- PowerFilm solar module MP3-25, 3V (Jameco Electronics #227993; $2.89)
- 1N5817 diode (Digi-Key #1N5817FSCT-ND; $0.37)
- Wide-Range power-supply controller TL499A (Digi-Key #TL499ACP-ND; $1.25)
- Inductor power toroid 50µH (Digi-Key #513-1108-ND; $1.60)
- 100µF electrolytic capacitor (Digi-Key #P803-ND; $0.16)
- 1µF electrolytic capacitor (Digi-Key #P824-ND; $0.14)
- .1µF ceramic capacitor (Digi-Key #478-4275-1-ND; $0.30)
- 4.7K-ohm 1/6W resistor (Digi-Key #4.7KEBK-ND; $0.05)
- 150-ohm 1/6W resistor (Digi-Key #150EBK-ND; $0.05)
- 10-ohm 1/6W resistor (Digi-Key #10EBK-ND; $0.05)
- 1W white LED (Digi-Key #516-1712-5-ND; $4.05)
- 2.4V 700mAH Ni-Cd battery pack (Digi-Key #SY114-L021-ND; $4.77)
- SPDT switch (SparkFun Electronics #COM-00102; $1.50)
- Hookup wire (RadioShack #278-1224; $5.99)
1. Refer to the [schematic](https://www.popsci.com/files/Light Beer Schematic.jpg). Assemble the step-up switching regulator circuit with the TL499A controller, toroid inductor, and support components. Keep the profile of your regulator circuit small enough so that it can fit through the bottle’s neck. Attach one pole of the switch to the circuit.
2. Solder two wires to the anode and cathode leads of the LED and connect the wires to the regulator circuit.
3. Carefully solder a “pad” on the positive and negative terminals of the solar module. Connect the diode to the solar module’s positive terminal pad and attach one moderate length of wire to the diode’s other lead. Attach another length of wire to the solar module’s negative terminal solder pad. Wire the module into another pole of the switch.
4. Connect the battery pack to the final pole of the switch and tidy up any remaining connections.
5. Slip the solar module, circuit, LED, and battery pack inside the bottle. Route the switch wiring harness up and out of the bottle. Fit the bottle’s cap over the wiring harness so that it holds the switch firmly in place on the outside of the bottle.
6. Place the bottle in the sun for charging. Slide the SPDT switch to the solar module connection for charging the battery pack. A partially drained battery pack will take 2-3 hours to fully recharge. Once the pack is fully charged, slide the switch to the circuit connection and the LED will illuminate. This high-powered LED will drain the battery quickly; so expect about 30 minutes worth of light from a fully charged battery pack.
7. Toast the sun and help save the planet. It sure beats pulling the label off the bottle and heaving it in the trash.