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Topic: Arduino Uno works fine without 5v connected, but shuts down when I connect it (Read 936 times) previous topic - next topic

Themisto-Adrastea

Hi, total noob here. I got an Arduino Uno starter for Christmas and I've just sat down to work through the basic examples. I know a bit about electronics, but I thought I would start from scratch anyway.

Problem is, I've followed the example here:
http://arduino.cc/en/Tutorial/Fade

and copied & pasted the code to avoid typos. Trouble is, my Arduino does nothing as long as the 5v lead is connected as shown in the linked diagram - it actually shuts down and removes itself from Device Manager on my PC. If I DISCONNECT the 5v lead, it works perfectly. I fI reconnect the 5v lead, it shuts down again.

What am I doing wrong? I don't want to brick my new toy.

SurferTim

How are you connecting the 5v to the Uno? It isn't enough voltage to connect to Vin or the barrel connector, and connecting 5 volts to the 5v bus is not recommended.

Themisto-Adrastea

Thanks for the reply Tim,
Its connected exactly as shown in the linked diagram: the 5v pin on the Uno has a red wire in it, and this goes to the +ve strip on the breadboard. There is nothing else connected to the +ve strip, yet as soon as I put the red wire into the breadboard, everything shuts down (including the two built in LEDs on the Uno itself).
Could the breadboard be faulty?

Themisto-Adrastea

OK - I took all the components off the breadboard, rotated the breadboard 180 degrees, then put all the components back on, and now it works just fine.
So:
1) should the breadboard be orientated a certain way? I assumed it was symmetrical.
2) or is my breadboard faulty?

SurferTim

I see now. You are not powering the Arduino on the 5v pin, just using it for the LED.

Insure the resistor is 220 ohms. In your circuit, remove the 5v (red wire) from the 5v pin on the Arduino. It isn't needed. If it is wired incorrectly, it could short the power supply on the Arduino.

Themisto-Adrastea

The resistor is 330 Ohms. I've just gone back to the book that came with the kit and re-looked at "Project 1 - LED Blink". I've wired it up as per the diagram there (including the 5v wire), and it now works perfectly. This is after I rotated the breadboard 180 degrees.
On closer inspection, it looks like the first 4-5 pins in the "top" -ve strip are crushed and I can't insert anything into them. I wonder if something inside is touching where it shouldn't be?
I guess I'm lucky my Uno is still working. I'll be contacting the supplier for a new breadboard I think.
Thanks for your help.

JohnLincoln

That red wire shown connecting the Arduino to the breadboard, and the other red wire are both un-neccessary for the LED circuit to work.

Maybe they were left over from another example, or a cut and paste error.


It is possible that there is a fault with your breadboard that was causing the 5V and GND to be connected directly together, that would certainly cause the Arduino to shut down as you described.

Glad you have managed to get it working.

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