Intro: How to Make a Safe Power Supply for Arduino With 9 Volt Battery
You'll need a 9V battery clip (snap connector), a 2.1mm power plug, a soldering iron and some solder. Any hobby shop should have these items.
a stable (regulated) 5V DC, which you can either supply via the USB power lines, or via the shield connectors, oran unregulated 6-20 V DC (7-12V recommended), which you can supply via the 2.1 mm centre-positive barrel plug connector.
Before connecting with arduino check with a multimeter .Watch that video to learn more.
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