Color-changing RGB Christmas Tree Lights

Step 3 Prepare the wire

Now you need to cut two wires to the lengths you want. One will be the positive side, the other will be the negative side. Strip one end of each wire and (optional, but recommended), tin the ends. Next, connect one wire to the positive lead of the battery holder and the other to the negative. Insert the batteries (3 rechargeable AAs worked best for me, 2 alkalines would probably work fine).

Now you have a live wire, so avoid shorting it out. Keeping it live while you assemble the strand solves two problems: you'll know immediately if you have the polarity reversed, and you'll also know immediately if you've damaged an LED.