Imagine, running wall clocks for 6-12 months with water, you'll never need to leave your house just to buy batteries and there's no need to recharge them. What could be more convenient than replenishing your batteries with tap water? :D
The flashlight runs 30mins continuously with tap water and 2 hours with saltwater. Not bad for a single celled prototype :D This thing also works well with calculators, clocks & radios Remember, adding a second cell triples the glow and lighting time!
How Does It Work?
This is a type of battery called the "Galvanic Cell", having 2 different types of metals and is connected by a salt bridge. It works like your typical battery but uses water as its electrolyte. If you want to read more about how batteries work "click here" The output voltage is pretty faint and isn't enough to run a single LED. By the help our trusty "Joule Thief Circuit", the LEDs would glow even at low voltages.
Is It Really Powered By Water?
Well not really, the water serves as an electrolyte, a replacement for toxic chemicals used in regular batteries, which usually ends up in dumpsites. So why call it water powered? Of course no one would be interested in the title "Galvanic Flashlight" plus that's what easily pops up in people's minds. The Redox reaction takes place in this project.
1st.) If you got lost and stranded out in the woods, you can't rely on batteries, eventually they run out. A mini version would save stranded people in the woods. Just go to the nearest river and fill her up! Whala, you have light!
2nd.) School science experiment
3rd.) A fun and educational project for all ages!
WATER POWERED FLASHLIGHT VIDEO!
Step 1: Gathering Tools & Materials
- PVC Pipe 4" Long (3/4"Ø) [Local Hardware]
- PVC Coupling 3/4" to 1" [Local Hardware]
- Recycled 3xLED Torch [Inventory = Free]
- Toroidal Core/ Bead [Recycled From CFL Bulb]
- 2N3904 Gen. Purpose NPN Transistor [Radioshack]
- 1K Ohm Resistor (1/4w) [Radioshack]
- Cooper & Zinc Strip [Local Hobby Shop]
- Magnet Wire/ Copper Wire [Inventory/ Local Hardware]
- 4 Sheets Of Tissue Paper [Toilet/ Bathroom]
- 2x2" Sheet of Acetate [Bookstore/ Office Supplies]
Tools & Equipment:
- Leatherman MultiTool
- Soldering Iron
- Hot GlueGun
- Teflon Tape
- Super Glue
Step 2: Preparing the Power Cells
Procedures: Assembling The Power Cell:
1st.) Roll tissue paper around your "Copper Strip" until you reach the 3rd sheet.
2nd.) After reaching the third sheet, roll the "Zinc Strip" until you reach your final sheet, which is the 5th sheet.
3rd.) Now tie some copper wire around the PowerCell, this prevents your tissue from tearing once it gets wet.
4th.) I recycled a pulley since it fits snugly on the PVC Coupling, puncture 2 slits for the metal strips to fit in.
5th.) Insert both metal strips through the pully's hole and seal/ waterproof it using epoxy/ superglue/ hotglue.
Step 3: Assembling the Joule Thief
A "joule thief" is a circuit that helps drive an LED light even though your power supply is running low. What can we do with it? We can use it to squeeze the life out of our drained batteries. Bottom-line, this circuit makes LEDs glow even at low voltages.
Let's get started! Hummm, you probably encountered a joule thief before. Lucky for you I have a more detailed guide about making a simple joule thief found here: Making A Simple Joule Thief (made easy)
If you already know how to build one, you can just follow the simple diagram from above. I needed to make my circuit more compact so I soldered my transistor below the LED's board while the toroidal core was glued above the LED's board.
Step 4: Combining the PowerCell & Joule Thief
For this step, solder the wires of the "PowerCell" to the "Joule Thief" then apply superglue around the coupling. Finally superglue the LED's reflector to your coupling.
Step 5: Preparing the Water Storage Cylinder
Step 6: Fill Her Up!
Attention: Tap water won't last for more than 30 mins. They lack electrolytes. Saltwater will boost to the flashlight's glowing time but still it would only last for 2 hours. Vinegar & Gatorade works best, since they both contain electrolytes (lots of them).
Adding a second cell triples the glow and lighting time!
Tested Liquids As Fuel:
- Tap Water = 0.5v - 0.6v (@400 mAh)
- Saltwater = 0.6v - 1v (@600 mAh)
- Vinegar = 0.8v - 1.2v (@850 mAh)
- Gatorade = 0.9v - 1.1v (@700 mAh)