I sitting here in my basement and plays with my Arduino. Really fun! I want to order some RGB leds for random use and i just can't find answer of witch RGB led type i shoud choose between Cathode and Anode RGB leds.
I know the difference regards pluss and minus etc. but why should i choose the one over the other and what is most common?
Or should i buy booth types?
raschemmel:
White or wheat ?
?
Common anode RGB LEDs are easy to work with.
The cathode of the LEDs need to be brought to GND to turn on the particular colour. Need 3 control transistors for one RGB LED.
Common Cathode need to have +5V switched for each anode, a bit harder to do. Need 3 control transistors for one RGB LED.
NeoPixels are RGB too, they do not need series resistors as the above LEDs does. NeoPixels can be daisy chained many times over, are very bright, multiple pixels are controlled with just one Arduino output pin.
Nice to have all three in stock 
I like 'Common Anode' and NeoPixels.
larryd:
Common anode RGB LEDs are easy to work with.
The cathode of the LEDs need to be brought to GND to turn on the particular colour. Need 3 control transistors for one RGB LED.Common Cathode need to have +5V switched for each anode, a bit harder to do. Need 3 control transistors for one RGB LED.
NeoPixels are RGB too, they do not need series resistors as the above LEDs does. NeoPixels can be daisy chained many times over, are very bright, multiple pixels are controlled with just one Arduino output pin.
Why is it harder?
You need four wires and three resistors on booth types?
If you are just using a single RGB LED with an Arduino (5 volt LED supply) it does not make much difference which LED you buy as can be seen in the 2nd last schematic in the previous post.
With more involved applications where the LED power supply is say 12VDC:
NPN transistors and N channel MOSFETs are easy to come by (especially Logic MOSFETs) for controlling 'Common Anode' LEDs.
PNP transistors and P-channel MOSFETs are more difficult to find, they are used with 'Common Cathode' LEDs.
Level shifting from the 5 volt Arduino to these LED drivers needs to be added too.
larryd:
If you are just using a single RGB LED with an Arduino (5 volt LED supply) it does not make much difference which LED you buy as can be seen in the 2nd last schematic in the previous post.
For the most i just use one or two leds in my Arduino projects. The only difference I can see is that if you have to switch on and off an anode you must set "LOW" if ju must turn it on in the sketch.
If that employee is a geek, he wood say:
There are two big differences: how they’'re processed and how healthful they are. The flour for both is made from wheat berries, which have three nutrient-rich parts: the bran (the outer layers), the germ (the innermost area) and the endosperm (the starchy part in between). Whole wheat is processed to include all three nutritious parts, but white flour uses only the endosperm. When put head-to-head with whole wheat bread, white is a nutritional lightweight. Whole wheat is much higher in fiber, vitamins B6 and E, magnesium, zinc, folic acid and chromium.
I do not espect to get any answer to this inn a store. But i espect to get an better answer regards to Arduino questions in an arduino forum.
A good answer could have been:
If you want to build that or that, choose that one. If you just want to build this, choose the other one. Just make an scenario and post the answer for each.
I do not have an exact answer regards to what i'm going to build, but i know that some RGB leds is godd to have in the drawer.
larryd:
- PNP transistors and P-channel MOSFETs are more difficult to find, they are used with 'Common Cathode' LEDs.
Not so much harder that I for one find it an issue. Both types are easy enough to get on, I never had the feeling it's hard to find a p-MOS or PNP.
What is of more concern, for pMOS at least, is that they are more expensive and always have higher on resistance (typically 2-3 times the equivalent nMOS). Add to that the difficulty in switching them off for higher voltage supplies makes an nMOS the preferred device.
For a single LED that's not a concern at all, of course. Most RGB LED strips are common cathode for this very reason. LED display drivers also usually require common cathode displays
Bjerknez:
Or should i buy booth types?
No - stick to one type, much easier. CA or CC doesn't matter much unless you expect to use many; in that case CA. Do mind that if connected directly to the pins a CA LED is on when the pin is set LOW. Takes a little to get used to in the beginning 
Also do check out the WS2812B LEDs. On a strip barely more expensive than RGB LEDs, but you can have a lot more fun with them. The FastLED library is awesome.
raschemmel:
A better questioneould have been:
"Which leds should I use if I wanted
to build this ?
Choose a scenario and the ask about that one.
It's your project. That's your job.
Ok. Witch led should i use if i want to buld an temperature controlled relay with DS18B20, when i want a led to light up red when the relay is active and green when it's not?
Anode og Cathode?
Doesn't matter. Both will do just fine.
wvmarle:
Not so much harder that I for one find it an issue. Both types are easy enough to get on, I never had the feeling it's hard to find a p-MOS or PNP.What is of more concern, for pMOS at least, is that they are more expensive and always have higher on resistance (typically 2-3 times the equivalent nMOS). Add to that the difficulty in switching them off for higher voltage supplies makes an nMOS the preferred device.
For a single LED that's not a concern at all, of course. Most RGB LED strips are common cathode for this very reason. LED display drivers also usually require common cathode displays
No - stick to one type, much easier. CA or CC doesn't matter much unless you expect to use many; in that case CA. Do mind that if connected directly to the pins a CA LED is on when the pin is set LOW. Takes a little to get used to in the beginning
Also do check out the WS2812B LEDs. On a strip barely more expensive than RGB LEDs, but you can have a lot more fun with them. The FastLED library is awesome.
Thanks!
The best answer until now
Since i allready have used an Cathode RGB when lights up when i set it to "HIGH" i think i will go for cathode.
Maybe you may want to try it
both ways and see which makes
more sense to you?
Not to state the obvious but you should spend your time studying electronics online instead of asking absurd questions on the forum.
I'm really sorry that i don't live up to your standard regards to my questions. I promise, i will never bother you and anybody else in this forum ever again.
With google, youtube and other channels, i'm sure i can figure out problems and things i want answer to on my self.
Thanks for some users in this tread for good answers btw.
Wow. This thread got bad real quick.
Way to help people out! It's attitude like this that gives the Arduino forum a bad name. Shame on you.
