April 2014
I'm using an external 6V supply to power an Arduino circuit which is giving me problems. I heard somewhere that the Arduino requires at least 7 or 8 VDC input. Doesn't the Arduino run on 5V? Can someone clarify?
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According to the Anduino specifications at http://arduino.cc/en/Main/ArduinoBoardUno, "The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts." So you must either provide 5 volts through the USB port from a PC or a USB hub, or a minimum of 7 volts through the power jack from the external power input. I recommend a 9 volt, 500 milliamp wall-wart.
Welcome to the world of analog voltage regulators. Typical analog regulators require input voltages about 2 volts above the output, i.e., 7 volts minimum for 5 volts out). There are Low Drop Out (LDO) regulators that need their inputs less than a volt higher than the output. Also, digital switching regulators are available that can operate with input voltages lower than their output (boost switching regulators). You do need additional current as Pin = (Pout / Efficiency).
