I am quite new to the science behind electronics (long time software guy), but here is my issue.
I have an Arduino UNO and an Ethernet shield attached to it, all powered by a 7.5VDC wall wart, rated at 1000mA. A multimeter shows that the wall wart is actually outputting around 10.6VDC, why is this?
When the unit is powered on, it immediately begins to heat up (near the power plug, is this called the voltage regulator?), eventually getting to the point of almost burning me.
Is this related to current being pumped into the Arduino? How can I fix it?
Best Answer
This sounds like a case where you are using an unregulated power supply, and it is expected to provide 7.5V only at its rated 1000 mA. The Arduino Uno and Ethernet shield use less than 1000mA, so the power supply, being unregulated, is supplying too high a voltage.
An Arduino Uno has a 5V regulator near the DC power plug, and it should be capable of handling 6 to 20 V input.
The voltage regulator will get warm when it's converting excess power to heat, and indeed it may seem excessively hot. Given that the voltage you measured is 10.6, there must be a lot of current flowing in order for it to get so warm. (Otherwise it would remain cool.)
The excessive heat seems to indicate a problem such as a short or failed component. Does this problem happen with a different power supply? Have you measured the current use with the power supply you are using now?
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