Power Up Arduino Uno Using Battery
The video shows how to make up a cable to connect a 9V battery to an
Arduino Uno.
A 2.1mm barrel connector is soldered to a battery clip with
the positive (red) wire connected to the centre of the barrel
connector.
The pre-loaded blink program starts working, when connected or powered up!
The voltage of the battery will be about 9V if six 1.5V cells are
used in the battery holder. If rechargeable cells are used, the battery
will produce about 7.2V.