For a while I’ve been wanting to show a project that makes use of a ‘soft circuit’ – a flexible circuit designed for paper or fabric. And ta da, here is my first one! It is a Christmas Tree with real lit LED holiday lights, and I’ll show you here how to make your very own.
There are lots of materials you can use to make a soft circuit – sewing with conductive thread, using conductive paint, etc. I tried all of those and am still experimenting with them, but the method I’m showing here seems the most reliable and less tricky. To start I’ve taken a thin sheet of craft copper which I’ll be cutting to the shape of my desired circuit.
First I’ll stamp the image I want to work with. I’m using Pine Tree by Nature’s Blessings Fine Art Stamps, and I’ve stamped it on the copper in Onyx Black StazOn ink which works well with metal and other non-porous surfaces.
Now I’ll sketch out my circuit. I need one set of copper ‘wires’ for the positive side of the circuit, and another set for the negative. They need to run alongside each other, but must not touch or you’ll end up with a short circuit and it won’t work! I used a ruler, and ‘drew’ a set of parallel lines by pressing the surface of the copper with a blunt point – the metal tip of a ball point pen should work well. If you mess up a bit, like I did at the bottom, don’t worry you can redraw your lines and fix things in the next step.
Now, take a permanent marker like a Sharpie, and draw your actual circuit ‘wires’ following the lines you drew in the previous step as your guide. You will be now cut along these lines (be careful, as the cut edges of the copper will be sharp and pointy).
Here I’ve cut out my circuit, and cleaned things up a bit by removing the ink and Sharpie lines with a bit of rubbing alcohol. I’ve also stamped Pine Tree again on a piece of card stock, and I’ll use this card to build my circuit. To get the copper to stick, spray it with a light coat of spray adhesive on the bottom.
Now you will want to assemble your LEDs. I had a few red and green ones around and so decided to go with those. You will also want to have a couple of alligator leads. These are rubber coated wires with clips on the end protected by flexible plastic. You’ll be using these to test your LEDs and your circuit. I like to use a red one for the positive side of the circuit, and a black one for negative / ground. You will also want to have a 3v coin cell battery and holder.
Start by testing your LEDs. One reason to do this is to make sure they work! Also, you will want to find out which of the leads /wires coming out of the LED is positive and which is negative. You may be able to tell by looking, if one lead is longer than the other it is the positive one. But test to be sure. Spread the leads of the LED out 180 degrees from each other so the LED basically lies flat. Clip one end of your red alligator lead to the positive side of the battery, and one end of the black alligator lead to the negative side. Then clip (or simply touch) the other ends of the leads to the LED. If it doesn’t light, swap which lead of the LED is connected to black and which one is connected to red. Once it lights and you know for sure, mark the positive lead in some way. You could use a sharpie pen, or stick a piece of tape on it. Do this with ALL of your LEDs.
Now choose which side of your circuit will be positive, and which side negative. I’ve made the right side here positive, and marked it with a red plus sign “+” to indicate this. The other side is negative / ground, and I’ve marked it with a black minus “-” sign. Trust me, this makes everything lots easier!
Now comes a fun step…decide where you want your lights to go! It will help at this stage to stick them down with tape. If you’ve marked your LEDs with tape in the last step, that makes things more straightforward. Since you’ve spread out the leads of your LEDs 180 degrees, you can stand up the LED light while each lead rests on one side of the circuit. Make sure you have the right LED lead on the right side! Match positive lead to the positive side of the circuit, and the negative lead to the negative side of the circuit. Use the tape to keep your LEDs in place. You should end up with something like this:
The next step involves a bit of soldering. This may sound scary if you have never done it, but TRUST ME IT ISN’T! If you can use a glue gun or a heat gun or hammer a nail you can solder. And you should really know how to do it – it is a basic life skill in my opinion. You just need a few inexpensive tools and supplies. I won’t go into the details of how to do it here, as there are plenty of beginner guides online.
Solder all of your leads, and trim the leads with wire nippers to keep everything tidy. Now, slightly bend up one small corner of your negative and positive copper ‘wires’, and attach them to your coin cell battery with the alligator leads. Your LEDs should glow beautifully! If not, go back and check to make sure each LED works, if not, you may have attached the leads the wrong way, or your solder point may not be a good connection. Also make sure you have a fresh battery. Mine are all working as you can see in the image below.
Now, you’ll want to attach your battery holder and battery. I’ve stuck the battery holder to the paper with a bit of double-sided tape, up in a corner where it is out of the way but still close to the circuit. Next I’ve cut three short segments of wire. One of these I’ve used to solder and connect the positive side of the battery holder to the positive side of the circuit.
The other two short wire segments I’ve connected to a small ‘on/off’ switch hidden on the back side of the card. One wire is soldered from the negative side of the battery holder to one lead on the switch. The third wire is soldered and connects the other lead on the switch to the negative side of the circuit. This is an optional step, but a useful one because it allows you to turn your Christmas Tree on and off, saving your battery power for when you want to display it.
Here is the backside of the card, showing the detail of the small switch. This switch actually had six leads, but I only needed two of them. So I trimmed off the other four. I punched a small hole in the card, poked the remaining two leads through the hole, and bent them 180 degrees from each other which does a great job of holding the switch firmly in place. The leads are exposed on the circuit side of the card. One is soldered to the wire that goes to the negative side of the battery holder. The other is soldered to the wire that is connected to the negative side of the circuit.
When the switch is off, no current is flowing through the circuit.
When you switch it on, it completes the circuit and the current flows, and voila your Christmas Tree glows!
At this point, if you really want to show off your handiwork with the circuit visible you could leave it as is. I’ve chosen to hide my circuit a bit behind a piece of vellum. I’ve stamped another image of the tree on top of the vellum, and trimmed it to size. I also used another piece of card stock cut to the same dimensions as the first one, and trimmed out the center to make a frame. To get everything lined up correctly, put small pieces of masking tape on the edges of the vellum, sticky side up. Place the vellum over your lit circuit and move it into place so the lights are where you want them to be. Then carefully lay the frame over the top until it sticks. You can now lift off the framed image and make sure the vellum is taped all the way around.
For the last step, stick a few double-sided adhesive foam dots on the card that has the circuit on it, in three of the corners, but not the one with the battery on it. this will keep the second card elevated off of the circuit, but the LED lights will still show through. You can easily access the battery in the corner if you need to change it, and the on/off switch is neatly hidden in back. Attach the top frame with the stamped vellum image.
If you want to send or give your card, be sure to switch it off to save battery power. Another idea is to buy an inexpensive mini wooden easel, and use it to display your card like this!