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Step 8: Done

Picture of Done

Now place a battery into the necklace and see how nicely it lit up! There are different types of coin batteries with different diameters and thickness. The only requirement is to use 3V battery. The battery depending on the size and number of LEDs used will last around 24h.

You might be wondering why there is no current limiting resistor. Won't the LED burn? My design uses an internal resistance of the battery. The battery itself won't allow such high current to burn the LEDs. Nasty trick.