What is the red wire for (connected to nothing on the board) in the 1st example?

Hello everyone !

I am a total newbie in electronic, my background is in computer science (AI research). I completed the first Arduino example, the famous one with the LED :), on the Inventor's Kit from SparkFun. I want to understand it fully, and I have an issue that is bugging me:

the documentation of the kit asks for a red wire from the Arduino power to the breadboard, but it seems to me that there is nothing else connected to this power rail on the breadboard !

The current goes from the ground to the LED & resistor and to a digital pin, so why do I need to put this red wire ? Is it in the instruction manual only because it is a "good practice" to always put it, even if useless? Or is there another, maybe sinister :-D, reason?

Thanks for any light you may have on the situation :-) (and sorry for my english, which is not my mother tongue).


Could you provide a link to that tutorial or instruction, where you saw a red wire?

Sounds like for that one example there is not a need for access to +5vdc. However it is very common for one to start playing around with their breadboard power rails already wired to ground and a regulated +5vdc voltage source, as most circuits one is playing with will require a voltage source. So your grip is a little silly really.

If an arduino is going to power a led, through a series resistor, you have two choices. If you wire the external led to +5vdc, then the led will light up when the arduino digital output pin is set to LOW. If you wire the external led to ground, then the led will light up when the arduino digital output pin is set to HIGH. It's your choice how you want to wire it up and code it in software.


In my experience (and Im certainly not any sort of expert), but I think Sparkfun create all their breadboard examples from a starting template.

This template always seems to include wires from the Arduino to the breadboard power rails by default, regardless of whether they are needed or not. I would ignore it personally, unless theres no other source of power

Here is the page with the schema:


(only difference with the one in the printed booklet is the resistance value)

Thanks for all your answers. I guess you are right, there are no reasons except that the schema was probably made from a template.

Too bad I spent three hours researching every information on "breadboard internal connexion" to see if my model may have some mysterious internal wiring :-D


If its any consolation, I suffered from the same confusion with Sparkfuns breadboard templates :-D

Even their 'breadboard tutorial' has the same ambiguity, which is a shame because overall Im really impressed with Sparkfun as a company.