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Topic: Control 8 seperate RGB superflux LEDs (Read 2136 times) previous topic - next topic



iam new to the arduino community and do have some questions about a project I want to realize and public as a howto.

I want to control 8 RGB LEDS separately (light intensity and color). I thought doing all this in 3 development steps:

1# At the first step i want to control light density of 8 LEDs separately.(1 Byte)

2# I want to add the opportunity to control the full RGB spectrum of RGB LEDs - that means 24 seperate channels (3 Byte and maybe even more if visible). And if possible i want to use 1W RGB.

3# I want to control 8 3W RGB LEDs

Which Arduinoboard is going to be sufficient for my project (until #2)? Which hardware additional hardware like resistors... do i need (until #2)?
I know there are a lot of questions like this here, but no thread I read could answer my questions.




Which Arduinoboard is going to be sufficient for my project

Anything will do.

However you will need external hardware if you are going to control LEDs that take more than 20mA.

Power LEDs are difficult to drive correctly if you are a beginner with no experience in electronic design. It is best to get one of the pre built power LED modules like this one:-
Although there are lots of others available if you google.


Mar 14, 2012, 10:15 pm Last Edit: Mar 14, 2012, 10:20 pm by saland Reason: 1
@Grumpy_Mike thx four your reply. The shield looks like a good investment for my project, but my budget is to small for that.

Why can i only control LEDs with 20mA? I thought the Arduino is giving me 40mA for each port.

Could I drive 8 RGB LEDs with 40mA with there full power on an arduino Mega 2560 (like this one: http://bit.ly/yCGOQR - ebay link)? Would i be possible to control light density and color as well?

I appreciate you help.



I thought the Arduino is giving me 40mA for each port.

No 40mA is the point at which damage starts to occur. It is not advisable to run it at this current.
You could push it to 30mA but doing so for a lot of outputs makes you run into other limits on the chip like 200mA total through the +5V line and the group restrictions on the ports. See the data sheet, section 28, for full details.

Would i be possible to control light density and color as well?

Yes if you can control colour you automatically can control light density and vice verca.

However you do talk about 1W and 3W LEDs they are a totally different matter.


Puh. For 8 RGB LEDs with 20mA i would need a board with at least DC current 480 mA, right?

Is the chipKIT a good alternative or does anyone have a idea how to power such a project cheaper as with pre-build power LED modules?

Iam lucky that i didn't bought any arduino and thanks for your help!


According to this blog post: http://bit.ly/wTCTTx or this post: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270486354
to control 8 RGBs with 1W seperatly i would need:

24x TIP122
8x 1W RGB LEDs
1x constant current supply
hand full of resistors
1x arduino compatible board with at least 24 I/O Ports
and sufficient cooling for the TIP122

Could that work as a head start?
Is it true that i could also use ports without PWM to control the transistors? is this as good (same effect) as the hardware pwm?



I don't know why you say that, it is not a conclusion I get from looking at those threads.

1x constant current supply

In general you need one constant current supply per LED or string of LEDs in series.



until now I see 3 Options to realize 24 constant current supplys with one DC. It would be nice, if you could judge my ideas and give me some input.

1# Use of a LM 317 https://en.wikipedia.org/wiki/LM317 with a adequat resistor (U=R*I) controlled by the arduino
Is around 3€ for each RGB LED
2# Use of a ST Microelectronics 7805 http://octopart.com/l7805cp-stmicroelectronics-526753#technical_specs and a TIP 122 TNP-transistor
Is around 3€ for each RGB LED
3# Use a AMC 7135 http://www.micro-bridge.com/data/add/amc7135.pdf LED Driver with a TIP 122 TNP-transistor
Is around 3€ for each RGB LED

What do you think of those ideas? I would be happy about your feedback.



1) - Yes this would work.
2) - No this is a fixed voltage regulator, it will not work.
3) - While this is a constant current supply it is fixed at 350mA which is about half of what you need isn't it?

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