(Solved) How to properly power the Arduino R3 from the mains?

Question

Arduino

Made my first experiment on Arduino Uno R3. Initially powered from the USB port, made the traditional blinking with a built-in LED with a pause. Everything is fine, the program was sewn up successfully. Decided to take a look at the Arduino work offline. I found a 9V 800mA power supply lying idle at home, connected the Arduino to it and found an interesting state of the board - the LED started blinking about every 100ms, although I indicated 2000ms (2 seconds). I connected it back to the computer via the USB port - again the LED blinks after 2 seconds. What does it mean? I specifically found the specification for the Arduino UNO R3 ( lib.chipdip.ru/984/DOC000984650.pdf ), the voltage is 7-12V, which means I fit in with my 9V. True, I don’t know what current is required to power the Arduino, maybe 800mA is too much in my case?
Video explanationhere .
It turned out that the problem was inadvertently using the AC power supply instead of DC. I hope others will learn from my mistake to pay attention to the type of power supply as well. The question is closed.

Answer 1

Does the power supply deliver what it promises? Maybe he is not in vain "lying idle"?
Try some other power source, even a Kron battery

Answer 2

Read here: here

Answer 3

800mA is the maximum current. Arduino will take as much as it needs. Of course, within the capabilities of the PSU, but what you have is quite enough. If 5V 500mA from USB is enough.

Answer 4

Soot on 12V 1A is enough for everything - relays, motors, a bunch of sensors :)