computer controlled rgb leds

Discussion in 'The Projects Forum' started by slisgrinder, Dec 14, 2008.

  1. slisgrinder

    slisgrinder Thread Starter Active Member

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    hey guys,


    i am modding my basement and making this computer controlled rgb leds to go with the basement, and i just want to know if anybody can help me out...

    http://www.ledcontroller.de.vu/

    there is a schematic and from help from other forums i am told that the 1rf9350 has a ratng of 12a so that means that a total of 48a of current int he entire circuit, is that fine with a 12v powersupply like a pc powersupply and will anything burn out in the schematic?

    and what is that seperate schematic above the mega8-p ic?

    i am a complete noob in electronics and would appreciate any explanations on how this circuit works... i am however good at soldering and following instructions... i would also like to know if this circuit is good too...they put up their schematics online and they also sell this but is this a complete schematic?

    product: http://www.brilldea.com/product_LEDPainter.html
    schematic:

    http://www.brilldea.com/assets_files/LEDPainter/SCH-LED_Painter-Rev000.pdf

    datasheet:

    http://www.brilldea.com/assets_files/LEDPainter/LED_Painter-Datasheet-Rev010.pdf

    the controller to go with the led painter circuit:

    product:

    http://www.brilldea.com/product_PropBlade.html

    schematic:

    http://www.brilldea.com/assets_files/PropBlade/SCH-Prop_Blade-Rev000.pdf

    datasheet:

    http://www.brilldea.com/assets_files/PropBlade/Prop_Blade-Datasheet-Rev011.pdf

    i know this is a lot of question but again, i am a complete noob, thankx for any input...:D
  2. bertus

    bertus Administrator Staff Member

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    Hello,

    For your first question, the little schematic on top.
    This is the schematic of the stabilizer , this circuit makes 5 Volts needed for the controller from the 12 Volt input voltage.
    As far as I can see the first schematic can control one set of RGB leds.
    This board has its own software controlled via RS232.

    The boards from Brilldea are more difficult to make as they contain SMD parts that are very smal and some more difficult to solder.
    The Billdea boards can control 16 sets of RGB leds via DMX control.
    This looks more flexible.
    It needs a DMX signal to work.

    Greetings,
    Bertus
  3. slisgrinder

    slisgrinder Thread Starter Active Member

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    thnkx for the quick reply...i just got the eagle schematics from the author himself and what i don't get is that is this a common ground for the led's? this is for the rgb controller, not the brilldea one, i am scratching that addition in my basement mod...
  4. bertus

    bertus Administrator Staff Member

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    Hello,

    On the website is stated:

    I just realized, that some people are confused where to put the LEDs. The anodes of the LEDs should be connected to X2-1, X2-2. and X3-1.
    The cathodes are connected to X4-1/2. The 4th output (X3-2) is for UV (blacklight) LEDs. I decided to make an extra output in case I wanted to connect some UV LEDs.
    This output is not used in this version though. So you can just leave it if you dont want UV LEDs.

    This means all leds have the cathode on ground connected to X4 1 or 2.

    Keep in mind that there are no current limitting resistors in the schematic.
    You have to calculate the resistors for the leds you are going to use.

    Greetings,
    Bertus
  5. slisgrinder

    slisgrinder Thread Starter Active Member

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    ok,


    so what is the forward voltage the circuit supplies to the leds on each channel? i am assuming 12V? and also how many amps per channel?

    thankx for the explanation...
  6. bertus

    bertus Administrator Staff Member

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    Hello,

    The current PER led is dependend on the type of led.
    There are leds that can only handle 20 mA , there are POWER leds that can handle 700 mA.
    For each type of led you will need another resistor.
    The value of the resistor can be calculated as ( Vpowersupply - Vled ) / Iled.
    Your power supply is 12 Volts.
    For RED leds the Vled is about 1.7 Volts (dependend on the brand and type, Look in the datasheet of the LED ).
    If the current should be 20 mA, the resistor must be (12 - 1.7) / 0.02 = 515 Ohm, this is not a regular value so I take the first next E12 value, that is 560 Ohm.
    For BLUE leds the Vled is about 3.8 Volts ( also dependend on the brand and type, Look in the datasheet of the LED ).
    The resistor must be (12 - 3.8) / 0.02 = 410 Ohm, again next value , 470 Ohm

    Greetings,
    Bertus
  7. slisgrinder

    slisgrinder Thread Starter Active Member

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    the leds that i am getting for all red green and blue, they are rated at 3.4V - 3.6V forward voltage and current of 20mA each, that means that if i have a 200 leds in parallel in each of the three channels that would mean a combined current required of 4A per channel...right? so i have to reduce the voltage from 12V to 3.4 V and supply 12 - 16A of current altogether? and if so, would i have to use a resistor at the anode of each of the leds or right where i connect the chain of leds to the circuit?
  8. bertus

    bertus Administrator Staff Member

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  9. slisgrinder

    slisgrinder Thread Starter Active Member

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    sorry,


    you are right, i just hada look at the specs now...so for my other question, do the resistors have to be at each anode of the led or at the very beginning of the chain, since the chain is in parallel?
  10. bertus

    bertus Administrator Staff Member

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    Hello,

    Each led must have its own resistor.
    Are you using RGB leds with common cathode or separate leds?
    When you use seperate leds, you can put some leds in series with a smaller resistor.
    EXAMPLE:
    RED leds with 1.7 Volts.
    The value of the resistor is (Vpowersupply - number of leds * Vled) / Iled.
    For safety I would like to have 3 Volts minimun on the resistor.
    So I can put (12 - 3) / 1.7 = 5.3 leds => 5 leds in series.
    The resistor will be (12 - 5 * 1.7) / 0.02 = 175 Ohm , nearest value E12 will be 180 Ohms.

    Greetings,
    Bertus
  11. slisgrinder

    slisgrinder Thread Starter Active Member

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    i am using seperate leds for each color, and i am using the following led calculator:
    http://led.linear1.org/led.wiz
    if you put the source voltage as 12, diode forward voltage at 1.9, diode forward current at 20 and the number of leds at 100, you should get 2 solutions at the bottom, if you scrool down all the way there should be solution number two, thats where i am confused...i the +12V is on the left and the "-" is on theright, y have the resistor on the right?
  12. bertus

    bertus Administrator Staff Member

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    Hello,

    I would go for the 5 leds in a string solution. (this gives 2.5 Volt on the resistor).
    If the powersupply fluctuates in the 6 led version the current can get out of proportion if the voltage is rising.
    That is why I say try to keep 3 volts or more on the resistor, it gives a more stable current.

    Greetings,
    Bertus
  13. slisgrinder

    slisgrinder Thread Starter Active Member

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    ok, i scraped this schematic after going to the local electronics shop and coming back only to find out that they don't have the mega8-p controller and the mosfets...so i scraped this schematic and am going to order an arduino "2009". now i want to control a new set of leds which are going to be the 1 watt 350 mA leds. I don't know what the leds are rated at but i am assuming 3.4V? so if i have 15 leds in each R-G-B channel and the leds are in the following order:

    +12V-------------grnd
    |----------------|
    |-5 leds in series-|
    |-5 leds in series-|
    |-5 leds in series-|

    5 leds in series and having three of these strands in parallel, how much voltage and current is that? and if so, how and what type of transistor (i figured out that i need a NPN transistor) but to what specs i need them to be is what i don't know...

    this setup should hopefully save me from being more that screwed by new years if all this works out...

    thankx for your patience and all the help given...
    Last edited: Dec 16, 2008
  14. SgtWookie

    SgtWookie Expert

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    Never assume. Get the part number(s), find the datasheet for it/them, and attach it/them.
    350mA LEDs will require much better power regulation, and the LEDs themselves may require heat sinks.
    You have not provided adequate specifications for the LEDs yet.
    All that we know is that you have a 12v supply, and some 350mA LEDs either on order, or in hand.
    For LEDs that require so much current, you should be looking at N-channel power MOSFETs instead of transistors. Something like an IRL640 or IRLZ44, an N-channel logic-level MOSFET could be controlled directly by your uC (microcontroller).

    You have a deadline? This is not the time of year to try to hurry up projects, particularly if you're a "newbie". You've just completely changed a number of aspects of your project, and are somehow hoping that we'll "bail you out", even though you have provided woefully inadequate information about your changes at this late date.

    We're pretty patient around here, but patience does have it's limits.

    You've taken on a somewhat ambitious project (particularly for a beginner) and have made a number of changes along the way. This does not bode well for the successful completion of the project, particularly if there are time constraints involved.

    It's fair to no one.
  15. slisgrinder

    slisgrinder Thread Starter Active Member

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    i have a new years deadline, meaning everything needs to work for newyears and for its party...this is again for my basement.


    i have a handful of 2n3055 and 2n3772 npn transistors and i have seen them work on 10 20ma leds, i know that this is less than the 15 350ma leds but it was a thought...right now i am sort of panicking to get the parts before the end of this week since its christmas so ya...


    i am not asking anybody to bail me out of anything...and you are right, its fair to no one...
  16. SgtWookie

    SgtWookie Expert

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    This is unfortunate. Your time and options are extremely limited. You also have a steep learning curve ahead of you to get the Arduino programmed.
    2N3055 transistors require considerable current through their bases in order to provide current via their collectors. Yes, they are capable of sinking a good deal of power, but they are not capable of doing so without sufficient drive current, which is considerable. At saturation, the base current is roughly 1/30th of the collector current.
    It's a cool idea, but it really is too ambitious for a "newbie" project. I don't see how you could get it built and working, even if you ordered a kit with instructions - and at this point, you're basically starting from scratch. Everything's out the window; new uC, new LED's, new transistors, etc.

    To be blunt, there is no way in heck that a uC will be able to get those 2N3055's even close to saturation. Which means that you will have to have driver transistors for them, and associated resistors, etc. It just keeps getting more complex, and the likelyhood of failure increases exponentially with each increase of complexity.

    You're out of time and options. Not a nice place to be.

    Why not take the pressure off, and forget about the deadline? Your project exceeded your skill level to begin with. That's not meant to belittle you in any way, as I don't like it when people fail to accomplish their goals.

    Try some smaller projects first; some things that you can finish within a few hours. Sometimes, just getting a single LED to flash how you want it to can be a big challenge.

    Don't give up. At the same time, don't try to take on projects that are too complex.

    It's hard to know what's what in the beginning. But the more parts that are involved, the more likely that the project will fail.

    Failures may lead to disillusionment, which is not good. However, even if a project fails, knowledge can be learned. Keep an optimistic outlook, but try to take smaller steps.
  17. slisgrinder

    slisgrinder Thread Starter Active Member

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    thankx for the reality check and i know where i stand...its just that i was planning this from the beginning but it was simpler as i did not involve any computer controlled led concept... but then i dug a hole so deep that i could not get out of it...right now i am not too worried about the program as i am a first year student in comp-sci and we have been doing c++ but i am a noob at electronics...i know how deep i am and now its starting to rain so to speak so i am going to try (and i fully know that failure is imminent) but i don't want to lose out know, even if it means missing the deadline - i still want to deliver all i have. so on that note the transistors that i also have on hand are 2n188a. now could you please explain how a transistor works with the examples of the transistors that i have?
  18. SgtWookie

    SgtWookie Expert

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    Are you serious? :eek:

    Look, we're pretty patient, but you're not going to be able to learn all this stuff within a couple of weeks and get this project finished successfully, no matter how nicely you ask.

    Try doing Google searches for "2n188a datasheet" and go from there.

    Or if you want the "fast road", start here:
    http://www.allaboutcircuits.com/vol_3/index.html

    If you can get through that, you will at least have a basic understanding on how transistors work.
    [eta]
    I think you may have missed this sentence, a couple of replies above:
    you should be looking at N-channel power MOSFETs instead of transistors. Something like an IRL640 or IRLZ44, an N-channel logic-level MOSFET could be controlled directly by your uC (microcontroller).
  19. slisgrinder

    slisgrinder Thread Starter Active Member

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    i just found something on this forum that is actually doing almost the samething as me:
    http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1224420893
    but do mosfets work with pwm control?

    EDIT: nvm, i figured it out, mosfets are good for pwm.
    How do i calculate the curret limiting resistor if for example the red led uses 1.8V to 2.6V max but the same curent of 350mA then if i have 5 leds in series and supply a voltage of 12V then each led is going to get 2.4V and if i have 3 of these links of 5 leds in parallel that would be (350mA * 3) 1050A per color. I am going to be powering the leds through a mosfet by a PC powersupply, will the powersupply "overpower" the led chains in current, and thus the current limiting resistor question. I am aware of how much power the leds would have to dissapate, unless i am wrong...this is the only simple solution i could cook up with a panicking hamster running in its wheel...

    red/yellow leds use up to 1.8V to 2.6V
    white/blue/green leds use up 3.0V to 3.3V

    i am going to power the red, green and blue at the same voltage of 12V

    secondly, the arduino can only output 40mA per i/o pin so how could i calculate the values of what the mosfet would have to have? and where do the common ground go in the arduino? is it the "grnd" connector?
    Last edited: Dec 17, 2008
  20. SgtWookie

    SgtWookie Expert

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    Yes, they are.
    Use the average Vf @current specification in that LED wizard you linked to earlier.

    Pay attention to the resistor's power ratings.
    Don't panic. That leads to confusion and mistakes.

    It depends upon what the manufacturer specifies in the datasheets. Your actual milage may vary somewhat. Order 10% more LEDs than you need, because some of them will have a significantly higher or lower Vf at the rated current.
    Then you will likely different values of resistors for each color. Read the specifications, perform the calculations.

    An IRLZ24 or IRLZ34 would be able to handle the current required. You'll need at least 3 of them. You will also need to connect the gates of the MOSFETs to the Arduino using a resistor to prevent high-frequency oscillations. A 220 Ohm resistor should be adequate.
    Yes.
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