I wanted to make a few light-up greeting cards this holiday season and couldn't believe that I couldn't find instructions/examples for paper circuit-based cards that light up when opened. There are instructions for cards with a push button that complete the card's circuit, but I didn't see anything that uses a slide mechanism to light up the card when it is opened without needing to press any buttons.

Hopefully this tutorial will fill that gap and help anyone who, like me, was looking for a fun way to amp up my holiday cards.

Supplies

2 sheets of cardstock (8 1/2" x 11")
2 LEDs (for a flat card, I recommend the LEDs HERE.
1/4" (conductive) copper tape
1 CR2032 3V coin cell battery
utility knife
clear tape
decorative embellishments (optional)

Step 1: Fold the Basic Card Shape

Begin by taking one sheet of the cardstock and folding it in half as shown in the images above. Then, fold it in half one more time (as shown) to create the basic card shape.

Note: Make sure to use a study piece of cardstock (not regular printer paper) for this project. Once we begin creating the slide mechanism the paper strength will be important.

Step 2: Plan the Design of Your Card

Before you can work out the details of the circuit and slider, you need to decide what your card will look like and what you want to light up. For this demo, I decided to use the snuggly Instructables robot as my decoration and will light up the ends of each of his antennae.

Step 3: Determine the Location for the LEDs

Carefully mark the spots you plan to have lit lightly with a pencil. Using a pin or pencil tip, poke a small hole through the top layer of the card. This has two purposes: (1) It will let you put a small dot on the paper below so you know where to attach the LEDs; and (2) it will let more light through the paper for a better glow once your circuit is complete.

Step 4: Diagram Your Circuit

Now that you know where the LEDs need to be placed, it's time to think about the circuit. I have included a rough diagram for the circuit I planned above, but you can get more ideas from other paper circuits on Instructables HERE.

You will want one portion of your circuit to go from the negative side of the battery to the negative side(s) of your LEDs and another separate strand to connect the positive sides of the LEDs to the positive side of the battery. (Note: I do not recommend more than 3-4 LEDs per circuit.)

Make sure the battery location is somewhere in the middle of the page horizontally and no closer than a 1/2" from the bottom of the card.

Step 5: Make the Slider

The slider is what will be used to connect your circuit once the card is opened.

Begin by cutting a 1" strip of cardstock from an extra sheet of cardstock. Halfway down the strip, cut two 1/4" slits as shown. Using a straight edge like a ruler, fold the paper inward as far as the slit on both sides of the paper until your paper looks like the above pictures. Next, cut a 1" x 1" tab at the end of the slider. Fold the tab in half in the same direction as the other folds. On the other end of the slider, fold the end back by at least 1/2". This will be used to attach the slider to the front portion of the card. Finally, tape down these folded pieces to strengthen the slider unit.

Step 6: Attach the Slider

The ultimate goal is for this step is to make sure the tab on the slider aligns with the battery location of your circuit when the card is opened. Be careful, though, because it is easy to put a slider in a location that seems like it works when opened, but then wants to extend past the card when closed. I recommend loosely taping your slider in place and testing it before moving forward.

Once you have found the right location, make a small slit through one sheet of the cardstock on the front half of the card for the slider end to slip into. Unfold the card and secure the slider in place with tape.

Step 7: Cut a Hole for the Slider

Now that you know the exact location of the slider tab when opened and closed, you can connect those locations to create the rectangle of paper you will need to remove from the top layer of the card to allow the slider to move freely.

Cut the rectangle carefully with a utility knife, making sure the height of the rectangle is just slightly larger than the height of the slider arm to ensure a smooth motion.

Step 8: Create the Battery Arm

There is one last piece to prepare before we can begin taping down the circuit.

Cut a 3/8" strip of cardstock and attach it to the inside of the card (on one side only) with a piece of tape as shown. The battery will be attached to the end of this strip.

Step 9: Create the Circuit

Now that you have everything in place, it's time to use the conductive tape as the wiring of your circuit to connect the battery and LEDs.

Begin where the battery will be and work to the planned negative side(s) of the LEDs in one strip of tape. Do not cut the conductive tape when you go around the corners, but instead fold them neatly as shown and continue. Use a separate piece of tape to create the portion of the circuit that will connect the positive side of the LEDs to the battery, which includes going all the way down the newly created battery arm.

Your circuit should look like the image shown above when you have completed this step.

Step 10: Attach the LEDs

Now it's time to attach the LEDs to your copper tape. Carefully align them, making sure to correctly orient them so that negative terminals will connect to the same copper tape and the same for the positive terminals. Make sure the exposed metal on the LED is directly touching the copper tape on both sides and tape each LED into place.

Note: If your battery arm will cross over (touch) any other portion of your copper tape wiring when the card is folded up, make sure to put a piece of tape over that portion of the circuit to act as an insulator and ensure you won't short out your circuit inadvertently.

Step 11: Attach the Battery

Fold the battery arm down into place and attach the battery to it with tape as shown, positive side up. It is important the battery be located on the top arm piece to ensure the slider is heavy enough to hold the circuit on when complete.

At this point, you should be able to touch the negative side of the battery to the tape to light your LEDs.

Step 12: Attach the Slider and Battery Arm

Next, fold the card and tuck the slider into the hole you previously created. Carefully, tape the battery arm and battery to the tab, ensuring that you leave the face of the battery free from tape so it can connect to the copper circuit.

Step 13: Decorate the Card

Before you get out your decorations, I recommend gluing the edges of the card together for two reasons. First, this gives the card a much cleaner, neater finished look. Second, it put a bit of pressure on the card that helps make sure the battery firmly touches the copper tape when the card is opened.

All the technical portions of your card are now be complete. The last thing to do is to decorate the card and give it to someone you so they can gush over how amazing you are.

Good luck!