A while ago at work we used paper circuits at Lentil Festival in Pullman to teach young kids about electricity. I thought that this would make an excellent activity if applied to Valentine's Day. Homemade Valentines with leds is a great activity for kids or homemade gift for a friend, relative or significant other.

In this instructable I will go through:

- Collecting materials

- Circuit basics

- Paper circuits basics

- Examples of circuits used in cards

- How to make a slider switch for a more complex card

Step 1: Collect Your Materials

This is a great activity because you can use materials that you have around your house or you can use extremely inexpensive materials that make the circuits flat and easier to work with.

What you'll need for the circuit:

- A conductor

The easiest thing to use for the conductor is copper tape. It is flexible, flat, and has a sticky side, which makes it optimal for a card. You can purchase copper tape online easily for a couple of dollars. If you don't want to buy something new and have thin copper wire lying around you could easily use that, it would just require more tape

- Leds

In the making of my card with the dog I used the classic big old leds because we had some lying around. You can get those in bulk online easily for a couple dollars as well. If you want to make your card more streamlined, and able to be put in an envelope you can use special small leds as you can see on the heart shaped card in the intro. The second image in this step shows a strip of those tiny leds. The tiny leds are a bit harder to work with.

- A battery

The battery that I used is the CR2016 3V because it has the required power and is thin. However you could use any batteries lying around as long as they provide enough voltage for the led and you don't mind some bulk. You can purchase a 5 pack of these online for a couple of dollars.

What you'll need for the card:

- Paper

Both to make the card and to cover the circuit. I used colored and white paper.

- Glue stick

- Scissors

- Markers

- Tape

I used electrical tape.

- Other crafty things

glitter, stickers, buttons, etc.

Step 2: Circuit Basics

When making paper circuits its important to know some very important basics about circuits that might help you come up with ideas and save you a lot of headaches.

The most basic circuit you can use consists of a battery, a led, a some sort of conductor arranged like the circuit on the left side of my picture.

The battery provides current the flows from the positive side of the battery to the positive side of the led, through the led, then from the negative side of the led to the negative side of the battery and around and around like that. As long as the circuit is complete current will flow and the led with light. So for the led to be on, there can't be any breaks in the circuit.

One important thing to note is that both the battery and the led have polarity, or they have a positive and negative side, and the polarity must match up. The positive side of the battery must connect to the positive side of the led and the negative side of the battery must connect to the negative side of the led.

You can tell the negative and positive side of the battery because one or both sides will be marked with a + or a -. The led is a bit harder to tell. The positive side of the led will be the longer leg and the negative will be the shorter. If you are using the tiny leds there is really no way to tell other than testing it out. So put the led in your circuit and if it doesn't work, just flip it around.

Step 3: Paper Circuit Basics

As always, when dealing with something in practical use there are a few more things to think about than in theory. So here are some basics about paper circuits.

The first two image shows out the basic circuit I talked about in the previous step as it will be implemented in paper circuits. I highly suggest drawing the circuit before you actually lay down the copper tape so you can make sure the placement is right. In these images the copper tape is represented by the blue marker. Notice that the positive (red) sides are connected by copper tape and the negative (black) sides are connected by copper tape.

Although there are two battery circles you will only use one battery, I just wanted to denote where the negative and positive sides would go. The dotted line represents where the paper would be folded to complete the circuit, and is used as a switch.

The second two images show the circuit actually implemented. Notice that the shiny not sticky side of the copper is up. The copper tape is only conductive on one side so anywhere you want current to flow you must have shiny sides touching. So the shiny side must touch the battery, and the led. In this image I have the legs of the led taped with electrical tape to the shiny side of the copper so I know the connection is secure.

Now that you know the basics of paper circuits, lets apply that to a couple of valentines day cards.

Step 4: Example Card 1

In this example the circuit is cleverly hidden behind a heart, which is used as a "button." This uses the same basic circuit as implemented in the previous step.

The led was punched through the front so that it stayed secure and the wires were hidden. On the inside of the card, a short section of copper tape runs from the negative side of the led, punches through the crease in the heart "button," and runs up the top part of heart, as seen in the third image. Another short section of copper tape runs from the positive side of the led and to the positive part of the battery. The battery is on top of this section of copper tape. All of this is fastened together by cleverly disguised electrical tape cut into hearts.

Step 5: Example Card 2

This card doesn't actually work, hence the "You light up my life (almost)," but I thought it was important to include here because you can see the whole circuit and it is a good example of one of the issues with the copper tape.

It also shows use of a different type of led.

A very important note is that the copper tape is only conductive on one side, so if you are trying to connect multiple pieces of copper tape together you can't just put one on top of the other, you have to fold it over so shiny side touches shiny side. In the second image you can see the copper tape is touching sticky side to shiny side, so there is no connection and electricity doesn't flow.

However, this card is a great idea for a simple card with a simple circuit.

Step 6: Example Card 3

This card uses a slider switch to alternate which led is on based on a tab that you slide in and out. You can see a the result in the first image, and the circuit idea in the second image.

The idea of this circuit seemed pretty straight forward but I discovered that the materials were as cooperative as I wanted to be. I had a lot of struggles making this card but I think the result was so cool it was worth it.

Also the card features my dog jericho. :) He's adorable. I think I did a pretty good job of making him out of paper.

Step 7: Slider Switch

You can see the idea of the slider switch in the image in this step. The actual circuit is a bit more complex to implement as you will see in the next few steps.

Step 8: Slider Switch Step 1: Place Leds

Punch a hole in the front of the card for each led. I wanted the leds to be in the center of the hearts so thats where I punched my holes. The holes need to be just big enough to stick the leds through. Then flip the card open and bend the legs apart so that the leds stay in place. You may want to mark which leg is the negative and which is the positive on the card. It's hard to tell which is which once the legs are bent.

Step 9: Slider Switch Step 2: Place the Copper Connecting the Negative Legs

Stick the copper that connects to the negative side of the led on the front of the card. Make sure that the shiny side of the copper tape is touching the leds. Then use electrical or masking tape to ensure that the negative legs stay up against the copper. Try to keep the bottom of the strips of copper as straight and evenly spaced as possible.

Step 10: Slider Switch Step 3: Create Contact Surfaces for the Positive Legs

Cut off small sections of the copper tape and place them under the positive legs of the leds. Make sure that the shiny side of the copper tape is touching the legs of the leds. You may want to make these contacts a bit larger than I did in this image.

Next secure the legs down with some electrical tape.

Step 11: Slider Switch Step 4: Mark the Location of the Contacts

Fold the card closed and mark the location of the contacts you just made on the other side of the card. Also mark where the copper tape touches the bottom of the card.

I've marked both the contacts and the bottom tape in pink in the image. I actually marked it in pencil on the card but it wasn't super obvious in the picture.

Step 12: Slider Switch Step 5: Place the Copper Tape for the Positive Side

Lay the copper tape connecting the two marks for each led that you made in the previous step. Be very careful not to overlap the copper tape.

It isn't very conductive on the sticky side, but its enough to cause problems if you overlap the copper tape.

Step 13: Slider Switch Step 6: Cover All the Copper Tape But the Contacts With Paper

As the card is now, when you close it the two sides of the circuit will touch, causing a short, which will cause all sorts of problems.

So we need to put an insulator (paper), to block the current between the two sides of the circuit. I put the paper over the card and then marked the spots that I needed to cut out. Then cut it out and glued the paper on.

Step 14: Slider Switch Step 7: Create the Slider Tab

Cut a strip of stiffer paper slightly longer than the width of your card. Wrap a strip of copper tape around the tab, and secure the battery on top with electrical tape. I put my battery with the positive side down so that the copper tape on the other side will be positive.

Step 15: Slider Switch Step 7: Create a Track for the Slider

Make two loops for the slider to slide through as shown on the image. I made mine out of electrical tape. I took a piece of electrical tape and wrapped another piece around it, so that I have a section as wide as the slider that wasn't sticky.

Slide the slider in the loops and close the card and you've finished!

You may have some problems with the connections not being super reliable. If you do you can trouble shoot in the following ways:

1. Make the contacts wider

2. Secure your led legs tighter

3. Test each circuit with a loose led and battery to ensure the connections are secure

I hope you enjoyed this tutorial and please comment if you have any questions at all!

About This Instructable




More by Commanderfranz:Decoding VGA Signals With a Portable Logic Analyzer How to Use the Protocol Analyzer on the Discovery to Test Sensors How to Turn Your Computer Into an Oscilloscope 
Add instructable to: