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Practicing soldering: Making tiaras/copper crowns!

10
Aug/15

We are happy that lots of people expressed their excitement about using soldering irons for the first time on the Coursera forum! We'd like to share a project that's good for practicing your soldering skills even more, by making light-up tiaras or copper crowns.
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We like making Copper Crowns because they're a whimsical approach to creating a functional circuit that allows you to express your aesthetic ideas, while practicing using a real tool. Practicing soldering doesn't have to happen on a PCB board (printed circuit board), instead, just grab a couple of copper wires and LEDs and turn them into a wearable LED crown! Here's how you can make one:

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Supplies:
- copper wire (18 gauge)
- LEDs
- coin cell battery
- coin cell battery holder
- wire cutter
- pliers (round nose, square nose)
- soldering iron and solder
- safety goggles

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To get the correct size, wrap the wire around your head and cut it (allowing some extra length for any adjustments later will be helpful). Once you get the wire, cut it in half. One wire will be the negative side, the other will be the positive side.

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1) Before you solder the LED, it is helpful to identify which lead is positive and which is negative. The longer lead of the LED is positive, and the shorter one is negative. 2) We like to use a third-hand device for soldering.

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When soldering the LED to the wire, you can wrap the lead of the LED around the end of the copper wire. This creates stronger connection and makes easier to solder.

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Here is how it looks after soldering. Grab the other wire and do the same thing on the other lead.

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It's already starting to look like a crown!
Let's place a battery holder so you can light up the LED. At this point you might want to test to make sure that the LED and the battery pack are aligned in the correct direction since current flows only one way.

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The battery pack has a tiny hole on each side, but it is too small for 18 gauge wire. To make the hole a bit bigger, we usually use a drill, but a push pin also works. With the push pin, try to push it gently through the hole. If it is too hard, use a hammer and softly tap on it.

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To test your circuit, put each end of the wire through the hole on the battery pack with the battery in. If your LED lights up, the direction of the LED and the battery pack are aligned correctly. If it doesn't light up, flip the battery holder. To tell which side is positive or negative on the battery pack, I usually look for an "E" shape. Do you see there is a shape that looks like an "E" between my fingers on the left? That is the positive side.

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After making sure your circuit is working, solder the battery pack to the wire. BE CAREFUL! Remove the battery while you are soldering, it is dangerous to solder with the battery in because the battery gets hot and could explode.

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Once you make a crown with the LED working, you can add a couple more LEDs on your crown, making a pararell circuit. Here, I am adding one more smaller LED above the first one. As long as it is wired in parallel to the first LED, you can make the wire in any shape: coil, twirl, swirl, twist, ...etc!

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Here is a simple illustration to show how this circuit works. As you can see, as long as the LEDs are placed as a bridge between the positive and negative copper leads (and they are aligned correctly), you can use multiple LEDs on your crown!

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It doesn't look like a parallel circuit that you might see on a text book, but yes it is!

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Here is another way to think about how parallel circuits can be done!

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This is also a great example because it uses an insulated wire (the yellow wire) so wires can touch each other without messing up the circuit. Also, it doesn't have to be a crown, you can make a pair of reading glasses with LEDs!

Let us know if you made your own crown and please share them in the forums and on our social media wall!

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