multiple LED's in SERIES one output

AWOL:

I was able to get it to work but it doesn't work on multiple LED's that are in series.

Describe "doesn't work".

Did you remember the voltage drop across series-connected LEDs adds up?

took my first C++ class this past winter quarter and could see many similarities of coding in arduino

Not surprising, because "arduino" is C++

When I mean it doesn't work. The LED's does not light up at all. Yes I do remember that components such as LED's and resistors drop voltage when in series but When I connect at least 2 LED's in series it does not light up at all or very faintly (could be barely detected by naked eye).
Interesting that arduino is C++, was it literally based off C++? Sorry I am a total newb and still in my learning process (which I know will never end) but I just started messing around with electrical circuits not too long ago. Thanks for responding and helping.

Uhh, what value is the resistor?

Resistor value is (supply voltage - sum of Vf for all LEDs) / current.

So, if you've got two LEDs in series, each with a 2V drop and a 5V supply, to get 20mA through them, you need a 50 ohm resistor

ok thanks for the electrical 101 refresher. It makes sense cause i had a 250ish ohm resistor but I also tried it without the resistor and it still is REALLY faint (barely noticeable). Why would this be?

I also tried it without the resistor and it still is REALLY faint (barely noticeable). Why would this be?

Because you've burnt the pin out?

Never, never, never, connect a LED to an output pin without a resistor
Did I mention never?

hahahahahahah damn. LESSON #1.

AWOL:

I also tried it without the resistor and it still is REALLY faint (barely noticeable). Why would this be?

Because you've burnt the pin out?

Never, never, never, connect a LED to an output pin without a resistor
Did I mention never?

so output #9 would be burnt out and would not be usable anymore?
I understand that a large amount of current is flowing because the resistor isn't there but
why is that when I connect a resistor back to #9, it is still able to be functional (the LED's in parallel are still fading in and out)?

I really don't know.
I don't have your hardware and I can't see what you can see.

There is really no reason that you couldn't put, say, two small red LEDs, each with a Vf of 1.8volts in series with an 82 ohm resistor and hang them both off one of the PWM pins, and see it fade up and down, assuming the AVR is powered from 5V.

(BTW, there's no need to set the pinMode of a PWM pin)

so output #9 would be burnt out and would not be usable anymore?

No, it may not be immediately obviously damaged, but could fail later.

Use transistor to drive the Multiple LED from a steady source of power (see the Attached Schematic).transistor can be BC558, 2n2222, BC 547, just care for the Base current needed to activate the Transistor, however the transistors listed above can easily be activated with the mA and voltage supplied from ATmega pins itself.

NI$HANT:
Use transistor to drive the Multiple LED from a steady source of power (see the Attached Schematic).transistor can be BC558, 2n2222, BC 547, just care for the Base current needed to activate the Transistor, however the transistors listed above can easily be activated with the mA and voltage supplied from ATmega pins itself.

Wow..thanks for the schematics, it really helps with the visual aid. So I'm able to have free access to PN2222 at my ECE department at school. I read in wikipedia that the PN2222 is a replacement of the 2n2222. (Replacements are commonly available now in the cheaper TO-92 packaging, where it is known as the PN2222 or P2N2222.) . So I'll definitely give your schematic a go next week. ALSO, will this schematic work with the code that was giving in the first post? Thanks!

The circuit will work with the code posted, but for safety, in case you change the value of fadeAmount, I'd change the comparisons for "<=" and ">="

Here's a quick working pic for you ATTACHED, The single LED is there other other ones are to be similarly connected.

Alright so I have a weird situation going on with the schematic. When I make all the connections according to the schematic and I plug in the arduino (already uploaded the code) nothing happens. When I take out one of the resistors and plug the LED in ( which I know that I'm not suppose to do according the post above) the LED lights up (fading in and out). The weird part of this is when I put a jumper wire in front of the LED with no resistor and it doesn't light up. For some reason the jumper wire is disabling the LED from lighting up? I have pictures. The first picture is of the schematic that was given in the previous post. The second picture is when I take the one of the resistors in front of the LED out and the LED lights up. And the third picture is when I put a jumper wire in front of the LED and it DOES NOT light up. I thought that this was extremely odd. Any insights?

STOP!

You are killing your Arduino , all the rails on the BreadBoard are electrically connected when you put your LED;s both leads and +ve and -ve leads both on the same rail AS YOU ARE DOING you are shorting the circuit by running the +ve and -ve current on the same rail.

NI$HANT:
STOP!

You are killing your Arduino , all the rails on the BreadBoard are electrically connected when you put your LED;s both leads and +ve and -ve leads both on the same rail AS YOU ARE DOING you are shorting the circuit by running the +ve and -ve current on the same rail.

SMH...lesson # 2...thanks. it's the lines that are horizontal that are connected together and the vertical lines are NOT connected. right?

.lesson # 2...thanks.

This would have Destroyed your Arduino chip pin's if you would have left it for a prolonged period enough.

attached see the diag. to understand the electrical connectivity, after that Please! visit google.com and search for BreadBoard tutorials.

bread.png

ok i recently had a lab class with digital logic chips. REALLY COOL! I made an XOR equivalence with NAND gates (picture 1). I totally forgot about the connections on the breadboard since I haven't played with it in a while (since fall quarter). I don't have many 330 resistors so I want wondering if I could do this connection (picture 2). I wanted to ask before I screw up my arduino any more.

eadizon:
I don't have many 330 resistors so I want wondering if I could do this connection (picture 2). I wanted to ask before I screw up my arduino any more.

No**!**

OK!!..Thanks! Why so? it would help to get an explanation on why this wouldn't work. Thanks!

You have LEDs in parallel and in series, and some other issues, it looks.

Here's what - Is it possible that you could sketch out what you have in mind to do, take a picture of that composition, and then post that here? Schematics are where it's at.

You don't need an Arduino to test out your creation there.
Just use 5V to the/its input, thereby simulating an Arduino output, and no innocent Arduinos get hurt.
But, don't do that anyway.

Horizontal and vertical are subjective depending on how you are viewing your breadboard.

On your breadboard, excluding the rows of power rails (the red and blue lines), the rows that are identified by letters are NOT connected together, the columns that are identified by numbers ARE connected together. Each column of 5 holes are connected together, the long rows are NOT connected together.