In these instructions we will show you how to create a light-up holiday card using Circuit Scribe, 2 LEDs and a sheet of standard printer paper.
Here is what you'll need:
Circuit Scribe conductive ink pen
A pencil and eraser
8.5x11" sheet of printer paper
2x Surface mount LED (1206 package, available at Sparkfun)
1x 3V coin cell battery
superglue (Loctite gel)
tweezers (for handling the LED's)
colored pens, pencils, or markers
Step 1: Fold and cut the card
Start by creasing the paper into four sections and folding over twice. When you place the card on the table and open it up, the long crease should be on the top edge of the card.
Next cut trim the card along the inner crease from the bottom up about an inch. Only cut through one layer of the paper. Fold over the triangular flap with a hard crease. Repeat this step in the top left corner. These flaps will become buttons for your electronic greeting card.
Finally, fold in the bottom right corner over using a soft crease. This will become the battery holder. Since we'll be drawing over the fold with the Circuit Scribe ink, try to make a soft bend rather than a hard crease.
Step 2: Illustrate the Cover
We sketched a poinsettia plant using red and green colored pencils. Plan on having two areas of your design light up from behind - we'll illuminate the centers of the flowers using red LEDs.
Step 3: Mark the LED location
Figure out where the surface mount LEDs need to be placed to align with your cover drawing. Mark this spot lightly using a graphite pencil
Step 4: Create the switches and battery holder
The bottom left and top right flaps will be switches that act like momentary buttons. The pattern we used are two sets of "fingers" that do not overlap with each other. When you fold over the flap and apply pressure, the large circular pad on the flap connect all of the fingers, completing the circuit.
This type of pattern is also called an "interdigitated" electrode.
The battery holder is a little simpler. It is composed of a large silver ink pad on the main area of the card and a second pad on the triangular flap.
Step 5: Design the circuit
Use a pencil to route wires and determine direction of the LEDs. You can always erase the pencil and start over if you need to! We've given you an example of two different wiring patterns -- your circuit might look a lot different from ours, depending on where you place the LEDs.
Start by wiring the LED that is closer to the battery. Route the flap portion of the battery holder to the lower left switch. Continue drawing a line from the other side of the "inter-digitated" pattern that continues up to the LED. Leave a 2 mm gap for the LED. Continue drawing a line to the inside battery pad. At this point, you can decide which way to orient the battery and LED. We put the negative side down, and the positive side touching the flap. Be sure to orient the LED accordingly - itís helpful to sketch in + and - signs as a guide.
Now repeat the process for the other LED. Draw a line from the outside flap of the battery holder to one side of the switch. Continue drawing from the other side of the switch pattern. Leave a 2 mm gap for the LED. Continue drawing to connect to the other side of the LED to the inner battery pad. Instead of drawing all the way to this pad, it might make sense to connect up to the same line that you drew for the other LED. You can decide based on where you place your own LEDs!
At this point, we usually erase the pencil lines so just a faint outline is still showing. Trace around the pencil guide with Circuit Scribe. Remember to leave 2 mm gaps for the LEDs! You can also add small circular pads where the LED electrodes will touch the circuit pattern. A little extra ink in this area will provide better contact to the LEDs.
Step 6: Add LEDs
Dab a spot of superglue between the LED electrodes - but be careful to not cover up the Circuit Scribe ink! Glue the LEDs in the right orientation and apply pressure. The glue should dry very quickly. Then you can go back and erase any remaining pencil marks, like the + and - signs.
You can go ahead and test your circuit now by folding the battery holder over the coin cell and pressing each of the button flaps down. If it doesn't work initially, try reversing the direction of the battery or reinforcing your circuit pattern with more ink.
Step 7: Embellish!
Draw some extra patterns using the silver ink or your colored pencils or pens. We decorated our circuit using a vine pattern, since we used a plant theme for the outer cover.
Step 8: Light up the card!
Use a binder clip to hold the coin cell battery in place. You can remove one or both of the binder clip arms to reduce the thickness of the clip. Then press the paper switches!
Now you can create your own designs! Some themes that work well for light-up cards are a string of Christmas lights, candles, or a city skyline. Leave us a comment below, or send us a picture of what you create!