Simple LED Pendant

In this instructable I will show you, how you can make the easiest 2-LED pendant. You might think this is not an everyday pendant and you are right. This is for special occasions, wild parties and festivals. Here are the things you will need:

• Solid core wire (fairly thick)
• 2 SMD LEDs
• 3V coin cell battery (any kind, I used CR2032)
• Utility knife
• Pliers
• Tweezers
• Soldering iron
• Side cutter
• Ruler

First of all you have to get the wire to work with. Most likely you will have a roll or a long piece of wire, but we only need a few centimetres of it. You have to strip it first. Use a wire stripper or a utility knife. Be careful not to leave marks on the copper. You can use aluminium, that way the soldering will not be that visible.

Cut a piece of wire, at least 12cm long. If it is not straight do not worry. You can put it on a wooden board and use another wood to straighten it with rolling.

This way you will get a nice and straight piece of wire.

This design is maybe the simplest, but we have to do it in one hour, that is why I went with this one. First you have to make a 90 degree angle. I have the ruler on the pictures, but you might have to try other sizes or lengths for other batteries. I used a CR2032 battery. This small end piece will hold the bottom of the battery. Then you have to make a more or less 45 degree angle. Playing with the lengths will give you different designs, so be creative.

You have to determine the length of the pendant and make a little loop at the top. You can use a screwdriver to help you form the loop. After bending the loop make the base symmetric. Cut the excess copper.

You can make a little ring from another piece of wire. After inserting the ring around our loop, close the ring with a little bit of solder. This ring makes it easier to insert a fine chain or lace for a necklace.

Now you will need the two SMD LEDs.

You have to determine the anode and the cathode of the LEDs. The anode goes to battery plus and the cathode to the battery minus. Most likely there will be a little triangle on the back of your LED. Mine had no printed triangles, but one of the front corners is different. This corner shows the side of the cathode. If you have a triangle, the base shows the anode and the tip the triangle is the cathode side.

(If there are no marks on your LED, you can connect it to battery and find out the polarity yourself. With small LEDs you can just touch it to the side of the battery so the LED touches the positive and negative sides.)

Our base will connect to battery plus terminal, and the back piece will be our negative terminal. Now you have to tin the two ends of our base piece. Grab your LEDs with tweezers and solder them to the ends of the base piece. If your solder joints are not pretty enough, don't worry, later we will reheat it.

To make the back piece, you will need a little piece of wire. Mine is about 14mms long. You have to bend it a little. This piece will be our negative terminal, so it goes to the LED cathodes.

Tin the two ends of this little back piece and solder it to the LED cathodes. Make sure that it bends downwards. It should be tight enough to hold the battery, but not too tight. It should not break the little legs of the LEDs.

Once you are done you can reheat all the solder joints one by one, so they look pretty. Make sure to wait before reheating another joint. Avoid using too much solder, but be sure to have a solid connection.

You are done!
You can use pliers to give the base a little twist. Use some clothes or leather to cover it before, so the pliers will not make marks on the copper (sadly I did not think of it beforehand, so mines look a little bad).

I also made a smaller white pendant, with an additional bend in the bottom, without a twist. With some practice you will definitely make prettier pendants than me. You can get really creative with this.

I made it so the battery can be changed later. I did not test the battery time, but I am sure it can last for at least a couple of hours, so a night of partying should be no problem for it to handle.

But how can it work? Why don't the LEDs burn out?

First of all, the voltage is not high enough. The voltage rating for white, blue and green LEDs is around 3.3V. Our battery can not produce high enough voltage to burn them.
Second, the internal resistance of the battery does not let the LEDs get too high currents. The internal resistance of CR2032 batteries is around 10Ohms. Also the resistance will typically increase during discharge.
So don't worry, it will not burn your LEDs.

I hope you liked this instructable, please give it a try and share your fancy and pretty designs.