As part of the maker club my husband and I run at a local school we came up with these simple light up cards for the kids to get experience with creating a circuit. Although there are many fun products for kids to learn about circuits we found many of them to be cost prohibitive for a club with 60 kids. This project uses inexpensive supplies so that everyone can join in the fun.
Card stock (2 sheets per card)
Mini glue dots
1/4" copper tape (available at Amazon.com)
LEDs (2 or 3 per card)
Metal Brads (used for the on off switch)
Coin Cell Battery
Markers and items to decorate your card
Step 1: Sketch your design
Use a pencil to sketch your design for the front of the card, then determine where you want the LEDs to be placed. Sketch the location of the battery. It should be near one edge of the card, you will need to push on this spot to make the card light up - keep that in mind when placing (i.e. a teddy bear with eyes that light up could have the battery located at it's belly button). We will be creating a parallel circuit, so sketch in two lines for the copper tape starting at the LED locations - one should end under the battery and the other should be about 3/4" to one side of the battery.
Step 2: Add copper tape and battery
Cut 2 lengths of copper tape to match your sketch and peel off the backing and apply to your card. Use two mini glue dots to to attach the battery over the copper tape per your sketch. Make sure the bottom of the battery makes contact with the copper tape.
Step 3: Add your LED
Select a couple of LEDs for your card. Bend the legs flat and place on the copper tape. Use a small scrap of copper tape set on the battery to complete the circuit. Check if your LED lights up. LEDs have a polarity, so if it does not light up spin the LED 180 degrees so the legs are now touching the opposite pieces of copper tape.
Step 4: Secure your LED
Once your LED lights up you can secure it to the card. To make the best connection cut a small piece of copper tape and stick the backing side to a piece of scotch tape. Then lay the copper square over the LED leg on the copper tape strip and press everything together. Secure all the LED legs in this way.
Step 5: Make a Switch
Now you need a switch to complete the circuit. The simplest version is a pressure switch, simply secure the scrap of copper tape you used in step 3 to test your LED. I usually tape the end touching the copper tape strip and leave the end over the battery loose. This works for cards you will be giving to someone in person, but since this is easily triggered you can quickly run out the battery if the card is placed in an envelope.
A metal brad can be used to create an on/off switch. Cut a small strip of card stock and poke both brad legs through it. Bend the brad legs flat. Now place the head of the brad on the end of the copper tape strip without the battery. The brad needs to be close enough to the edge of the paper so that you can move one of the legs back and forth outside the card. The other leg should be able to touch the back of the battery. It is better if it overlaps the battery a bit. Once you have the switch positioned tape down the piece of card stock the brad is through. Make sure the brad still moves freely.
Step 6: Make the front of the card
Take a second piece of card stock and lay over your circuit, this will be the front of your card. Mark where the LEDs hit the outer card and poke holes. Check that the LEDs fits through the holes. Now remove the outer card (cover) and decorate. Once the card is decorated place the outer card over the inner card and secure around all the edges except where the switch is located. Make sure to add a small label indicating on and off as well as where to press to trigger the LED.