My 5 year old son's school has a theme this week called 'gruwelijk eng'. (super scary)
The kids are encouraged to come dressed up scary on the closing day.
He got the idea to dress up like a ghost, so his mother made him a costume. I made a couple of bright LED's to add to the scary ghost-effect.
These lights are incredibly easy to assemble and require only a few parts.
Step 1: The Electronics.
You only need a 3V lithium coin cell and one or more LED's for this to work.
The forward voltage of white LED's is about 3 Volts. This incredible coincedence means you don't need a current limiting resistor for this to work like with another power scource.
I chose to use four LED's per cell to maximize the light output. More or less? That's up to you.
Step 2: Preparing the Bottle Cap.
The other thing you need is a standard soda bottle. The CR2032 coincell fits perfectly in the cup of the cap as shown.
Use a needle to punch through the cap where the LED terminals will go. Make sure you go as low as possible, so the terminals sit low. That way, there is enough room for the coin cell to fit in.
From the outside inwards, press it through the cup. The low terminals will connect to the negative side of the coin cell.
Keeping in mind the thickness of the coin cell, make another hole for the positive terminal of the LED. Make sure it goes a bit diagonal above the negative one, or else they will short circuit at the next step.
Step 3: Place Your LED's
Pressing carefully through the holes, install the LED's and bend them upwards.
Repeat this until you are satisfied the amount of LED's is enough for your costume/project.
Bend the positive terminals upwards slightly to allow the coin cell to be placed later on.
Step 4: Add a Drop of Solder
To improve reliability, I've soldered the negative terminals together. Otherwise you stand the chance of one out of four not connecting properly to the coin cell and the LED won't light up.
To protect the plastic cap I used a piece of tin foil (aluminium foil) to prevent the heat melting the plastic.
The two positive terminals I soldered together improve the ease of which the coin cell can be placed. This will make it more rigid.
Step 5: Get Some Thread
To press the coin cell and the positive terminals firmly in place, the thread of the bottle van be used.
I sawed the neck just under the thread. Now you can use this to secure the contact of the terminals to the coin cell.
Do not overtighten this. It will go on just a single turn of thread or so and needs minimal fastening.
Step 6: Done
Now you have a multi purpose LED light which will last for at least 9 hours. We used it to spook up our son's ghost costume, but the possibilities are endless. Light up your pumpkin, your magic wand or whatever. Just make sure to leave me a picture of the result. :)