Single SMD Led powered by 5v ?

Discussion in 'General Electronics Chat' started by pete1986, Oct 12, 2013.

  1. pete1986

    Thread Starter New Member

    Oct 12, 2013
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    0
    ok so i used an online led calculator to workout what resister i would need to run a single blue smd led off a pc power supply using the 5v. iv read that these online led calculators can be wrong so thought i would ask.

    will this resister work (100 ohms)
    http://www.ebay.co.uk/itm/300778913069?var=600057335107&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

    on one of these leds
    http://www.ebay.co.uk/itm/261119055582?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

    connected like this
    [​IMG]

    any help will be much appreciated thanks :)
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,028
    3,237
    100Ω should give a nominal 18mA at 5V which should be fine for that LED.
     
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  3. pete1986

    Thread Starter New Member

    Oct 12, 2013
    15
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    thank you very much for your reply and help :) does it matter which side of the resister is on the led ?
     
  4. #12

    Expert

    Nov 30, 2010
    16,321
    6,818
    No. Resistors don't have a polarity preference.
     
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  5. pete1986

    Thread Starter New Member

    Oct 12, 2013
    15
    0
    thanks. sorry im kinda new but learning :) am i right in thinking. if the led is too bright for me can i simply add another resister so thats 2 100ohms resisters connected in series ?
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,871
    1,393
    Yes, you can add additional resistors in series, but don't short out the 100Ω resistor, or your LED will go "poof." For fun, you might want to add a potentiometer (say 5k) in series with the 100Ω. Then, by adjusting the pot, you can dim the LED.
     
  7. pete1986

    Thread Starter New Member

    Oct 12, 2013
    15
    0
    cool! thankyou very much :) im having some pcb's made so just wanted to be 100% sure i have everything correct as its costing me £14 ($22) for 3 boards made that are 9cm long 2cm wide. i personally think that expensive.
     
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