For my creative switch I wanted to use something you typically wouldn’t want near electricity, water. Using water as a switch might seem strange at first, because you might think mixing water and electricity is a bad idea, but water can work just like any other conductor. I decided to make a bottle light up differently depending on how much water is put in it. At a low water level, one LED lights up, half full, a second LED lights up and when full a third LED lights up. As more water is put in the bottle, a pressure sensor gives less resistance allowing the LEDs to shine brighter for more liquid in the bottle.

 

Materials:

• Empty bottle
• 3 LEDs
• Wire (Red and Black for power and ground)
• 3V Coin Cell Battery
• Conductive thread
• 3 Metal Beads
• Velostat
• Tape or glue
• (Not pictured) Soldering Iron / Solder
• (Not pictured) A third metallic object, such as another bead, or a coin as I used
• (Aluminum foil pictured but not used)

Step 1: Wiring LEDs

The first step in wiring everything up is connecting all of the negative leads on the LEDs to one wire. Solder a piece of wire to each negative lead, and solder all three wires into another wire so the three LEDs all lead to a singular negative wire.

Next, solder the negative lead to the negative terminal on the battery, also solder a wire to the positive terminal on the battery. Once this is done, you can test your LEDs and they should all light up.

Now the first step is done, and you can attach your battery and LEDs to the bottle with tape or glue. Each LED should be placed at a different height for each water level it will light up for.

 

Step 2: Wiring inside

To get a positive current to the LEDs, attach a metal bead to the end of conductive thread, and attach the other end to the positive lead. Each LED should have it’s bead suspended around the same height in the bottle. Once attached to the LED, solder the connection.

 

Step 3: Pressure sensor

The last step is to wire the positive battery lead to the water. You could just wire right into the water and it would work, but here I made a pressure sensor that will act as a resistor. Attach the positive lead from the battery to a piece of velostat, using copper tape. Next, measure and cut a wire that will reach from the bottom of the inside bottle to the bottom of the outside of the bottle. Using a metal bead or coin, solder to the end of the wire to give it weight, attach the other end of the wire to the other side of the velostat with copper tape the same way as the positive lead. The velostat can now be attached to the bottom of the bottle and it is complete!

 

Final Step: Activate Switch

Now that the circuit is complete, just add water to complete the circuit. Using salt water is a good idea as it will conduct much better than tap water. As the bottle fills up, each LED should light up and as the pressure increases, the lights should get brighter.