which is brighter or is there a diff?

Discussion in 'General Electronics Chat' started by scytzoh, Nov 14, 2015.

  1. scytzoh

    Thread Starter New Member

    Nov 8, 2015
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    i looked up the pland for a 14 led array and it gave me 2 possible ways of doing it . im asking just for curiosity sake but i notice the both drew different amounts of power one says draws current of 140 mA from the source the other says draws current of 100mA from the source. is one brighter ? im assumeing if one is it is the one drawing more? would it be noticable if so?? would the one drawing more burn out quicker because its same amount of lights but consuming more??
     
  2. MikeML

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    Oct 2, 2009
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    Without a circuit or data sheet, can't suggest anything...
     
  3. mcgyvr

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    The one with the higher "lumen" rating would be "brighter"
     
  4. WBahn

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    Mar 31, 2012
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    How can we possibly answer a question like this?

    You don't give the plans for the two methods, so there is no way for anyone to guess how much of those currents is actually going through the LEDs.

    I could make one circuit that had all of the LEDs in parallel with 10 mA going through each for a total of 140 mA and another circuit with the exact same LEDs in series with 100 mA going through each for a total of 140 mA. Which one will put out more light?

    Perhaps one circuit has power going to a regulating circuit that doesn't go through any LEDs.
     
  5. GopherT

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    Nov 23, 2012
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    Yes, that is what you should do. You have to consider that more isn't just more. Sometimes it is more but that more includes some of what doesn't help you whereas less is sometimes all of what helps you and nothing of what doesn't. So, I think you know what you need to do.
     
  6. KeepItSimpleStupid

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    Mar 4, 2014
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    Off Topic somewhat FWIW;
    A friend owned a consumer electronics store. Someone came in wanted to purchase a stereo amplifier. His only question: "How many watts is this?"
     
  7. WBahn

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    Did your friend tell him that, for a nominal fee, he could increase the power draw of the amp to whatever wattage he wanted? :D
     
  8. KeepItSimpleStupid

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    No. But it was just funny. Nothing about RMS, Peak or anything else, just Watts.
     
  9. GopherT

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    And if he asked for peak watts? How would the owner have answered him?
     
  10. dl324

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    Mar 30, 2015
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    The lack of relevant information in your post makes providing the answers you seek virtually impossible; hence your post has into something you (hopefully) didn't intend...
    Maybe, maybe not.
    LEDs operating at the same current could have different brightnesses.
    The human eye response to light is logarithmic and differences of less than 2X would probably not be noticeable.
    LEDs operated within specs have lifetimes measured in decades.
     
  11. wayneh

    Expert

    Sep 9, 2010
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    Not necessarily. Impossible to tell without a schematic. If the person drawing the different configurations was careful, they each deliver the same mA to each LED and will therefore be the same brightness.
    Not necessarily. Impossible to tell without a schematic.
    The brightness of an LED is nearly linearly proportional to the current supplied the LED, so yes, one configuration might be brighter if it puts more current through the LEDs. The life of an LED is inversely proportional to the current, but I don't think it's anywhere near linear. So if an LED will last 1 year at 20mA, at 15mA it will last "forever".

    Gaa!! dl324 beat me by seconds.
     
  12. dl324

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    Hopefully the OP will get the idea that EE types are detail oriented and a lack thereof leads one to fill in the blanks in not entirely predictable ways.:rolleyes:
     
  13. WBahn

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    Oh, well "obviously" he was talking about "peak music power"!

    I vaguely remember when that was the marketing buzz phrase for audio components.
     
    Sinus23 likes this.
  14. scytzoh

    Thread Starter New Member

    Nov 8, 2015
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    i think your over analyzeing this a tad it just a led power and resistor im posting something now Untitled.png
     
  15. #12

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    The whole point of that, "Wizard" is to design configurations in which every LED has the same amount of current, the same brightness, and the same life expectancy...so your basic answer is, "no".
     
  16. mcgyvr

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    Both solutions utilize the same 14 LEDs driven at the same current level..
    Brightness is identical..

    Once circuit is simply more "efficient" as its using the LEDs to drop the working voltage thus requiring the resistors to do less work (300mW vs 756mW)
     
  17. kubeek

    AAC Fanatic!

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    You have circled the completely irrelevant number. Look at the ńumbers for "togetgher, all resistors dissipate x W" and "togetgher, all diodes dissipate x W".
    Since in both cases diodes dissipate the same they will have the same brightness.
     
  18. scytzoh

    Thread Starter New Member

    Nov 8, 2015
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    Wow why does is seem like 80% of the responses are worded like I'm a fuckin idiot I'm new and trying to learn and news flash you learn by asking questions. And by getting responses back making the new person feel less than like duh you should know this its common knowlage.doesn't say much about your forum I'm 36 what if it were a 10 12 year old wanting to learn and you spoke to him like duh! The kid more than likely would leave and potentially not bother with this field that's I bit far fetched but stranded things have happens..at very least the kid would be reluctant to ask anything anymore for fear of looking stupid . what are those numbers then? That I circle d
     
  19. scytzoh

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    Nov 8, 2015
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    Thank you
     
  20. mcgyvr

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    In general most of us don't mean to come off harsh.. But many of us are Engineers or "technical" people and we rely on schematics and specifications which are better than a 1000 words..
    Brush it off.. Do your best to answer the questions and provide the information as requested..

    To give more information..
    In your images.. Each string set (by the resistors) to "drive" 20mA into those LEDs.. One simply has 5 strings (5 x 20 = 100mA) and the other has 7 strings (7 x 20 = 140mA)
    The one with higher resistor dissipation will put off more "heat".

    In general its always better to have more LEDs per string as each will "reduce" the total working voltage.. The closer you get to 0 volts left the less "work" the resistors have to do (less they will dissipate)..

    The first image is "better" IMO but depending on the Vf of the LEDs I would think you could put more LEDs in each string and reduce the total amount even more..

    Example.. If the Vf of the LED is 2.1V then you can have (12/2.1 = 5 LEDs per string) Note.. the sum of the Vf's must be lower than source voltage or there is no voltage left to do work..

    Calculators are great... But the knowledge to do the math yourself is so much better..
     
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