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RGB LED Driver/Controller Help? Answered

I officially feel inept.  As I am more of a wordsmith than electrician, this should come as no surprise to me.  Anyway, I have 6 RGB LEDs that I am embedding into a DIY background for my aquarium.  I bought RGB, LED strip lights which came with a controller/driver which I have installed in my canopy.  I thought it would be cool to place 5mm RGB lights encased in siliconed capsules in the caves and recesses of my background.  I have already wired and tested the LEDs underwater and all works as planned...individually. 

To my question:  I have enough know how to complete the simple circuit with a cell battery, but I want to control the LED's, inexpensively, with some type of knob control (potentiometer??? I have many from an old classroom) so that I can "color-mix."  My research seemed to indicate arduino as my only option.  I'm not really interested in that.  So?  Any thoughts?  A schematic even a dummy like me can follow with six RGB LEDs??

Thanks for the help.  I will be posting the background build once I am through.

Sincerely,
Eric

Discussions

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frollard

7 years ago

6 rgb leds is 18 leds...Do you want individual colour control on each, or simply 3 sliders for overall colour control (making only 3 channels)...

There are LOTS of led driver circuits here on ibles. Some use microcontrollers/arduino, some just use less efficient pot/mosfet drivers that limit the power that way.

What EXACTLY do you want control over, and we'll be happy to help? :)

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mretuckfrollard

Answer 7 years ago

Hmmm....found a lot of those ibles but there were too many variables for my mathematically challenged mind to really grasp. I'm trying though =)

Not sure if I am using the correct vernacular, but I want to be able to control each color and its intensity in each LED. So like....R @ 70%, G @ 50%, and B @ 100%..... or R@100%, G@0%, B@100%.... and so on. Does that make since...err, sense?

Thanks for the help,
Eric

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frollardmretuck

Answer 7 years ago

Right, so rgbx6 = 18 control circuits; that's pretty really hard without a microcontroller.

If you want all 6 rgb leds to show the same colour, (just 1 rgb channel) is 3 controls. Steveastrouk has a great circuit; not extremely efficient at less than 100% brightness, but definitely easy and inexpensive.

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mretuckfrollard

Answer 7 years ago

Frollard, would the attached diagram work? The chart at the top shows the RGB-LED qualities, the diagram shows what I think might work, but I don't know what power supply to use or if I need resistors between the LED and switches. Thanks for any help.

Sincerely,
Eric

RGB LED Pic2.png
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frollardmretuck

Answer 7 years ago

That should work, and yes you need INDIVIDUAL resistors for each diode (3 per rgb led).

I could do the math for you, but will again point you to an led wizard -- in this case you're running 6 parallel leds on one circuit, so you want your forward voltage to closely match your led forward voltage.

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mretuckfrollard

Answer 7 years ago

Thanks for the input Frollard. In the wizard I used the info from the diagram above which came from the vendor's website. However, I can't find anything about forward current.

So, I used:
24v Power Source (old laptop)
3.5 as my forward voltage
20mA as my forward current (wizard suggested)
18 total LEDs (6 p/color)

It suggested 1/4w resistor @ R = 150 ohms p/6 LEDs.

If I run it this way will I be able to run different configurations of lights? Green On, Blue On, Red Off..... for example .... or...
Green Off, Blue Off, Red On... as another.

The LEDs are set into my project and replacing a burned out LED will be near impossible. Should have tested the circuits before moving forward. Oh well. Thanks for any help. Sincerely, Eric

led array.png
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frollardmretuck

Answer 7 years ago

That is exactly right! Great job on doing the homework! 20mA is suitable for most leds. 25 is ok but they will burn out 10x faster, 15 is great because they will last seemingly forever.
**Important!!!**
red, green and blue leds take DIFFERENT voltages because they have different chemicals inside!
Run the simulator again saying 24v input, 20ma but only 6 leds.
Change the Vf for each colour to find the value.
Red typical: 1.8-2.0V
Green typical: 2.0-2.5V
Blue typical: 3.4-3.8v
http://www.oksolar.com/led/led_color_chart.htm (use the real numbers from your real led's datasheet!)


If you want to control rgb individually, you'll need to add a switch in series with each resistor (or on the + side of each string if you prefer). Good design would have all the components close to one another -- so switch+resistor is a good thing.
**see picture**

Advanced:
Now, in place of a switch, you could use a transistor or relay, which allows 'something else' to control whether the string is turned on. The advantage to the transistor route, is you can use a micro-controller (arduino etc) to dim the leds with PWM, making thousands of colours instead of 7.

ledswitch.PNG
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mretuckfrollard

Answer 7 years ago

Thanks, Frollard. I didn't get any documentation with my LEDs except what was on the vendor's Ebay site. It can be seen here http://bit.ly/tEzd90

Vf stands for forward voltage correct? Should I use the Min or Typ forward voltage number in the wizard?


I am all about the KISS rule on this one. I would love the idea of more color control, but without detailed, do-this-then-do-that directions, it is a little over my head.  Not to mention that would significantly raise the cost...I think?

Thanks again!

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mretuckfrollard

Answer 7 years ago

Oh yeah... knew I would leave out something. All six LEDs would be the same color. So three separate controls. 1 per color. Thanks for the input.

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steveastrouk

7 years ago

Hi Eric,

Use three circuits like these, one for red, one for green, one for blue. Put each colour in series, and run them from a 24V supply

trimmable current source.JPGCopy of maths.jpg
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mretucksteveastrouk

Answer 7 years ago

Oh yeah....and on the potentiometer ( I think I just figured out you are calling that a pot) there are 3 terminals. They are not marked. Which does what?

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steveastroukmretuck

Answer 7 years ago

Middle pin is usually the one marked with the arrow.

If I knew what current your LEDs needed, I'd tell you what all the parts you need are.

Steve

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mretucksteveastrouk

Answer 7 years ago

The following image is a screen capture from the Ebay page from which I bought them. Does that help?

RGB LED Pic.png
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mretucksteveastrouk

Answer 7 years ago

I really should have paid much more attention in math. As much as I appreciate the input, I have no clue what any of that means. Can you break it down for me? I know how to connect a series and add juice. My knowledge ends about there. Would I add potentiometers between the power supply and each color? Do I need resistors? Perhaps I will draw a schematic tomorrow and throw it up for scrutiny =0)

Thanks again for your time.

Eric