Hello All,
I am new to the wonderful world of Arduino and am enjoying my discoveries.
I was playing with a tutorial for beginner sketch / schematic and something about it looked wrong to me - it was a simple RGB LED schematic. It had power from Arduino going to the breadboard and ground going from the Arduino to the breadboard, then the common / ground pin of the RGB LED was connected to ground, and the R, G, B pins from the RGB LED were connected to digital pins 9, 10, 11 on the Arduino.
What I could not figure out was why the power was connected from the Arduino to the breadboard and then never used. I unplugged it and the RGB LED continued to loop through its colors.
I felt really satisfied that I had confirmed my suspicion that the power jumper was in fact serving no purpose. Then I had to ask, why was it included in the schematic in the first place ? It must have been designed by somebody far smarter that I am when it comes to electronics ???
Is there some universal electronics rule that requires power to alway be pulled from the source ?
If you experts need more info or a picture of the schematic I can provide that. When I look at the true schematic in the tutorial booklet that I'm working from I do in fact not see any reference to power at all so at least that part seems correct. Do the digital pins 9, 10 and 11 provide some source of power ??
Many thanks for any insights and for not laughing out loud at this noob
It must have been designed by somebody far smarter that I am when it comes to electronics
Not a good assumption. You will be amazed at how much very bad advice you can find about wiring Arduinos on the web -- advice that can end up destroying your Arduino.
If you have questions, forum members are here to help and bad advice gets shot down quickly.
At a guess what probably happened is that the layout ( it is not a schematic ) was taken from a standard starting point and wires removed or added to make that specific diagram and they forgot to remove it.
While the truth might be out there, there is a lot of rubbish as well.
Notice the red jumper from power on the Arduino to the + on the breadboard. There is nothing then connecting from the + on the breadboard to the rest of the layout so why is it needed.
As mentioned when I unplugged the jumper from the + on the breadboard it continued to function.
It is presumed that you do not remove the red and black wires for the busses from one project to the next, whether or not they are required. Less wear and tear that way.
lambsoft:
Do the digital pins 9, 10 and 11 provide some source of power ??
Nobody answered this part yet..... yes, they can give you 40mA max, reckon 20mA as a safe amount. As hukikz said, there need to be resistors to prevent the LEDs drawing more than is safe, and indeed I do see resistors in the circuit you linked. I can't read the colour code though...
I've had resistors oooops I mean LEDs still blindingly bright at under 10mA so you can almost certainly use larger* resistors than suggested, save a wee bit of power and still have brightness. (*Larger in Ohms that is, not physical size )
The ASSUMPTION is that NOBODY uses just ONE RGB led , and the power is for additional circuitry you might add . A single RGB led is not much of a circuit. It is assumed you would have other circuitry that would need the power that you did not need for your single RGB led. Possibly a RED power indicator LED powered by the arduino 5V so when the power is on, it is clearly visible because the led is on.
If your resistors are bright, you are likely overloading the circuit.
I will admit... I got a good laugh on this one...
I also agree that it is a good practice to always have your breadboard bus wires connected to power sources... it makes experimenting easier. If you are just blindly copying designs... you are only getting it half right. Take the next step... add stuff and experiment.
