Fun with LEDs part II - Secret Message

In my previous post, I talked about how cool integrating LEDs on your table pieces can be.

In this post I'll walk in a more detailed fashion on making a secret message crystal, using an UV LED.

Parts List

• Plastic fancy champagne glass (plastic)
• Cutoff Acrylic crystal (from the craft shop)
• 2x Neodymium magnet (6x1mm from Dealextreme, ignore the one in the pic)
• 1x 33 Ohm resistor
• 1x UV LED from LighthouseLeds
• A socket mount (optional, but I wanted the circuit to be reusable for other LEDs)
• Some wiring
• A CR2032 battery

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The Mounting

Solder the resistor at the base of the socket mount, then solder the wiring.

Tip: Use needle pliers to make a loop on both ends, and then solder them

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Insulate your connections, I used thermoretractable tube but regular electrical tape works just as well.

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Measure roughly the length of each wire by dry mounting the battery, then cut accordingly and solder them to the magnets.

The tricky part here is knowing where to solder the connections, I opted for soldering at the side of the magnets, so I can mount the battery with the magnets off-center with the connections going up at the center.

Tip: Tin the magnets before trying to solder the wiring

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I glued the crystal with just some drops of regular white glue (not a very strong bond on plastic-plastic, but it's enough).

Using a drill, I also hollowed out the midsection of the plastic cup, with enough room for the whole mount to pass through, while hiding the battery at the bottom.

Having a low profile and easy to remove circuit is amazing for reusability.

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Et Voila!

The pic is a bit unimpressive... my lighting is too bright.

But now comes the fun part =)

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A Secret Message

Remember I said at the beginning that there would be a secret message?

Thirdhand finds a sacred scroll.
Legend has it that only the power of the Crystal can shed light into its mysteries...

Well the cool thing about UV lights is fluorescence, some materials emit visible light when hit by UV, so you can encode a secret message for your players!

To write the message, either use one of those secret message pens or go the DIY route and dissolve some highlighter ink into water and use a toothpick as a "brush".

I hope you guys enjoyed it as much as I did building it.
See you in part III of Fun with LEDs =)

The message is revealed!