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{ 2010 10 24 }

Arduino Inventor’s Guide CIRC-01 (Blinking LED)

The first circuit in the Inventor’s Guide is a simple one that turns on and off a single LED repeatedly. I used:

  • 1 x Arduino Duemilanove
  • 1 x breadboard
  • 1 x 5mm Yellow LED
  • 1 x 330 ohm resistor
  • 3 x wires (1 each for gnd, 5v and pin 13)

You can download a copy of the breadboard layout sheet here, or watch an assembly video here.

This was a good introductory circuit to cut my teeth with correctly wiring the parts together, as well as uploading the C program to the Arduino from the IDE.

ArduinoCIRC-01

Arduino CIRC-01

Posted by Aaron on Sunday, October 24, 2010, at 2:40 pm. Filed under Arduino. Tagged . Follow any responses to this post with its comments RSS feed. You can post a comment or trackback from your blog.

{ 2 } Comments

  1. Selim Achour | May 13, 2011 at 11:07 am | Permalink

    I don’t understand why we need the red wire connected to the 5V output. I disconnected it and the sample still works fine, pin 13 is outputting the 5V on digitalWrite(13, HIGH) … Am I missing something ?

  2. Aaron | May 16, 2011 at 5:57 pm | Permalink

    Hi Selim, it looks like a good breakdown of the reason for this is here.

    Pins configured as OUTPUT with pinMode() are said to be in a low-impedance state. This means that they can provide a substantial amount of current to other circuits. Atmega pins can source (provide positive current) or sink (provide negative current) up to 40 mA (milliamps) of current to other devices/circuits. This is enough current to brightly light up an LED (don’t forget the series resistor), or run many sensors, for example, but not enough current to run most relays, solenoids, or motors.

    Depending on what model of Arduino you have, it can potentially output enough current from a digital pin to power an LED. I’m able to duplicate this same behaviour you are experiencing with my own Duemilanove. I suspect that the 5V input is part of the circuit diagram to demonstrate best-practices, as well as for the case where pin 13 acts as a sink instead of a source. Thanks for the comment, that was really interesting to investigate :-)

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