When a drink is placed on this coaster, an internal circuit is closed. A closed circuit causes the three 3 LED lights to shine on the glass. Materials Cork, conductive fabric tape, masking tape, 3 LEDs, 3V cell battery, white foam core, glue.
Cork, conductive fabric tape, masking tape, 3 LEDs, 3V cell battery, white foam core, glue.
Cut a circle in a cork square. This will be your coaster's base.
In that circle, cut three small indents, each large enough to snugly fit a mini LED. Insert an LED into each indent, and connect them to a 3V cell battery using conductive fabric tape in a parallel circuit. (Solder LEDs to circuit tape along the way.) Leave about 4in of tape left at the end of the circuit; rather than closing the circuit with this end, leave the positive end of the battery unconnected for now.
Add a thin insulating material over the conductive tape that crosses through the center circle of the cork. This can be masking tape, paper, etc. Take the extra ~4 inches of tape at the end of the circuit, and zig-zag across this new insulated surface. (Note that the circuit is still not closed. This is intentional.)
Add a spacer in the middle of the circle using an insulating material. This spacer will keep the circuit open while no drink is on the coaster.
On a new piece of insulting material, create the rest of the circuit. This will be placed face-down on top of the spacer you placed in Step 3. Leave a tail to connect to the positive end of the battery.
Once the tail is touching the positive end of the battery, you should be able to test your circuit. It should be open (LEDs off) by default. It should be closed (LEDs on) when the center is pressed. You can even test it with a glass at this point.
Add white foam core (or some other material that will let light through) to the center of the coaster. This material should be flush with the rest of the square. This is now a surface that can hold a drink evenly, but will still act as a "button" to close the circuit.
If needed, use a final thin layer of cork on the top and bottom to hide any imperfections. Congratulations, your coaster is complete and ready for use!