12 x 5mm LED light fails ?

Discussion in 'The Projects Forum' started by RodneyB, Feb 21, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Well I am at my wits end.
    I have been trying to Sort out a system so that I have some quality of life whilst we have these 15 hour daily power cuts.
    I made up some LED lights with LED's I imported. (Attached Datasheet)
    I used the following on line LED calculator to design the layout and work out the resistors (Only cause I don't know how to make the correct driver)
    I made the resistors bigger as I want the LED's to last.
    Measuring the current at 12 Volts using my mason power meter it reads 0.06 Amps, 0.7 Watts. I assumed this would be ok.
    Well 90% of them have failed within a month. Before I make a fool of myself and blame the LED's I want to understand if this is the problem OR the calculator OR me.
     
  2. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Sorry Left out the attachment
     
  3. #12

    Expert

    Nov 30, 2010
    16,343
    6,827
    It looks right.
    15 ma per series string, the right amount of voltage across the resistor...
    I'm coming around to blaming the LEDs.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    Do you have the datasheet of the leds?

    Bertus
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    To many failed I just wanted to be sure! Here
     
  6. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Sorry to many failed so I thought it best to get advice, Here is the datasheet
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    The datasheets tells me that the absolute constant current is 20 mA.
    With the 150 Ohms resistor and the lowest voltage given in the datasheet ( 3.0 Volts), you will be at this 20 mA.
    Raise the value of the resistor to 180 or even 220 Ohms to be safe.

    Bertus
     
  8. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Hi

    Thanks very much, I will change it and give it a test. Thank you for your help

    Rod
     
  9. #12

    Expert

    Nov 30, 2010
    16,343
    6,827
    But RodneyB measured 60 ma for 4 strings in parallel. :confused:
     
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