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Topic: Mistake in Arduino Projects Book: 220 Ohm leads to 12.7 mA at LED (Read 175 times) previous topic - next topic

grafzahl

Hi Forum!

I recently bought the Arduino Starter Pack and, next to the wrong data sheet for the red LEDs, I think I found a rather disturbing mistake in the manual.

On page 30 it says that 5V/22Ohm=0.0227...A, leads to the current (23mA) used by the LED.
But the LED leads to a voltage drop of ca. 2.2V, so the current should be around (5V-2.2V)/220Ohm=0.0127...A. I verified this, of course.

I am really a beginner with electronics and this was the first time I used a resistor!
Am I missing something important, or did the author of that book know even less about electronics than I do?

- Michael

grafzahl

I just found out, while looking for a pdf version of the manual, that it is common knowledge that the manual is full of errors.

Just one other question to those who are experienced with Arduino.
Is the whole Arduino stuff of this quality?

Flomach

Your are right. There is a voltage drop when a LED is lighten up. It is more around 1.6V for a red LED.

Your are also right, you have to count this drop doing the Ohm's law calculation.

But anyway, this book and these projects aims the complete beginner, who doesn't even know why using a resistor is needed. The first project is really simple but it is also a lot of information for the complete newcomer.

Seriously, Arduino has developed so many stuff, do you really think they forgot to mention that drop ? Don't you think they decided not to mention it to make things easier to understand ?

Concerning your second post, you can change what you dislike, everything is licence under "Creative Commons", why not write and sell your own book, with your own card and you own projects ? Second option, why don't you make a complete list of errors you notice and send it to Arduino so they can correct the ones who need to be ?

Easy bashing like yours is so casual nowadays.
Criticism is very easy but it never comes with proposals so what's the point ?

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