The Circuit Playground already comes with everything we need except an on/off switch. If you're making this project with kids and don't want to do any soldering, you can skip this part and just plug the battery directly into the circuit playground. You'll turn the necklace on and off by unplugging the battery.
I've found that having a switch makes the necklace much more user-friendly, and makes your battery last longer since you can turn it off when nobody is looking.
