Test LEDs with a Coin Cell Battery

The battery (CR2450) in my garage door sensor was getting low, so I replaced it. I’ll keep the old one in my electronics kit for LED testing, as shown in this video. Touch the longer leg (anode) of the LED to + and the shorter leg (cathode) to . Usually + is the top of the battery where the words are. Don’t worry, you won’t hurt the LED if you connect it the wrong way.