What did I do wrong in wiring up my LEDs? Pics included

Discussion in 'General Electronics Chat' started by JaredSD, May 27, 2017.

  1. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    This is my first LED project and I am new to the circuitry world in general. I wired up 28 LEDs into in a painting. Spec sheet is in images; I am using yellow, red, and orange. I am using a 5V 1.2A power source. I wired them all up in line and used a 150 Ohm resistor in between each one. I just tested the end points and it doesn't light up, which sucks because now I have to figure out how to fix this. I would love any ideas to troubleshoot.

    I am pretty sure they are all connected from a neg to pos each time to make the current flow. I suppose it is possible I did not? However, how the heck would I know now that I have cut some of and can't tell which is which? I knew due to one being longer than the other? Any ideas on how to test it? I used solder to make everything stay together, and from what I understand that would carry the current as well.

    The work doesn't look pretty haha, but I don't care as it is on the back.
     
  2. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    Update:

    I did a little testing and can get the first two to light up. However, the 3rd and beyond does not light up. The connection seems to be tight? Is this a wiring issue perhaps? Did I do it wrong?
     
  3. bertus

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  4. dl324

    AAC Fanatic!

    Mar 30, 2015
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    It appears that you have the LEDs, each with a resistor, wired in series.

    What voltage is the power source?

    To test for backwards LEDs, you can use your coin type battery to check each one individually. All should light when connected to the battery in the same polarity.

    The next time you're wiring LEDs, test them after forming the leads and before soldering. Improperly formed leads can break the bond wire. Too much heat will soldering can do the same. So you need to test after lead forming and after soldering.
     
  5. bertus

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    Hello,

    An other trick to "see" the orientation of the led is looking agains te light and see the cup and arm in the led:

    ledintrofigure1.jpg

    Bertus
     
  6. #12

    Expert

    Nov 30, 2010
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    Dude! Start over!
    LEDs have a break-over voltage which you must supply or they won't start up. (The voltage is different for each color.) When you have (3) 2.2 volt LEDs in series, they need more than 5 volts just to start up.
    They also don't work backwards.

    Your best hope is what bertus said, make a bunch of twos with a resistor and place a bunch of them in parallel with each other.
     
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  7. ian field

    AAC Fanatic!

    Oct 27, 2012
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    About the 90s ish, there were ultra bright LEDs with a back to front header - its a useful trick, but not 100% reliable.
     
  8. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    Thanks man. I knew something was up with what I did haha. What would this 2 LED system look like? Anyway you could do a quick diagram of it so I could physically understand it? I work better with seeing things. Maybe backtracking won't be so bad as all it is is removing solder and reconfiguring?
     
  9. bertus

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    Apr 5, 2008
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    Hello,

    In the link I gave you there is an example for 3 leds, see figure 1.2 in post #2

    You must use two leds in stead of 3 leds due to the lower supply voltage.

    Bertus
     
  10. EM Fields

    Active Member

    Jun 8, 2016
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    From the data sheet, it appears that the LEDs will each drop about 2.1 volts when there's 30 milliamperes through them, and if by "in line" you meant that you connected the LEDs in series then, even with no resistors, the voltages across the LEDs will add up to 2.1V X 24LEDs = 50.4 volts and, since you're using a 5 volt supply, there's no way you'll get enough current through the string of LEDs to light them up.
    So, for a 5 volt supply, you're left with two choices:

    1. Connect a resistor in series with each LED and connect all 24 strings in parallel, or,
    2. Connect two LEDs and a resistor in series and connect those 12 strings in parallel.

    For the former, the value of the resistor will be: RSERIES = (VSUPPLY - VLED ) / ILED = 2.9V / 0.03A ~ 100 ohms.
    For the latter, the value of the resistor will be: R
    SERIES = (VSUPPLY - 2VLED ) / ILED = 0.8V / 0.03A ~ 27 ohms.


    Arguably the easiest way to fix things would be to unsolder the entire array and test the polarity of each LED by connecting a 100 ohm resistor in series with supply + and then connecting the open end of the resistor and supply - to each LED in turn. If the LED lights, its anode will be connected to the resistor and, if it doesn't, it'll be connected backwards, with its anode connected to supply -.

    Once you've determined which end of the LED is which, you can proceed with the wiring, which will look like one or the other, or a combination of, these:
    LED array 1.png
     
    Last edited: May 29, 2017
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  11. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    Gotcha, so something like this perhaps? All sets of two connecting to the same power point? I am just trying to imagine it as if it were on the back of the painting is all.
     
  12. bertus

    Administrator

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    Hello,

    Have a look at the drawings EM Fields made in post # 10.
    You basicaly have the two powerlines running parallel with each time the leds in between.

    Bertus
     
  13. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    The resistors I have are 150 ohms. Will those still work for option 1?
     
  14. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    One other thing....I am trying to imagine how the wiring would look. I see the option 1 diagram. I am guessing this option creates many "loops" of current? Is that correct? Would that mean along the way, on both sides of the cord, that I would need to strip away some of the wire coating to allow the resistor to connect and do the same thing on the other wire to allow the LED to flow back to the power source?
     
  15. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Yes, it will work.
    The ledcurrent will be about 20 mA, wich is a safe value.
    The leds will be less bright as with 100 Ohm resistors as EM Fields suggested.

    Bertus
     
  16. EM Fields

    Active Member

    Jun 8, 2016
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    From Ohm's law: I = E/R, we can write: I LED= (VSUPPLY - VLED) / Rs = (5V - 2.1V) / 150R = 0.019 ampere, so yes, it'll work, but the LEDs won't be as bright.
    They'll probably be plenty bright, though. Try it.
     
    Last edited: May 29, 2017
  17. EM Fields

    Active Member

    Jun 8, 2016
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    In a word, "yes".
     
  18. JaredSD

    Thread Starter New Member

    Apr 3, 2017
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    Haha, perfect, thanks. I envision it being something like this. I am guessing the ends just die off somewhere? Cap them off and call it a day?
     
  19. KeepItSimpleStupid

    Distinguished Member

    Mar 4, 2014
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    Picture a ladder and the rails are power. The Plus side and the Minus side.

    The take a resistor and a LED and place it across the rails with the LED facing the same direction (polarity).

    or two LEDS: +LED1- & +LED2- & resistor; the resistor value will be different; the order does't matter. The polarity does.
     
  20. EM Fields

    Active Member

    Jun 8, 2016
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    Yup, you got it! :)
     
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