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How To Make Sure This Led Is Working

Discussion in 'Troubleshooting and Repair' started by pharaon, Jan 25, 2017.

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  1. pharaon


    Oct 28, 2014
    how can i test if this led is working and what is it's right voltage



    [Mod Note: Resized oversized images]
    Last edited by a moderator: Jan 25, 2017
  2. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir Pharoan . . . . . . .

    If mine olde eyes are correctly seeing the color bands of the resistor as being Blue Gray Gold Gold, then that 6.8 ohm dropping resistor and your parallel arranged 3 LEDS . . . . . along with their phospor doped overlays, suggesting of these probably being WHITE or BLUE LEDS.
    With strongest suspicion of this being the light emitting cluster of a cheeeep dollar store flashlight . . . . therefore, with a WHITE LIGHT output.
    ( Correct me, if erring on the two first color bands of the dropping / current limiting resistor.)

    If you dont have a variable voltage adjustable power supply to slowly ramp up, surely you can round up enough random D-C-AA or AAA cells to then sequentially series string them . . .one by one . . . to feed the unit .

    SIMULTANEOUSLY you are monitoring the voltage across the dropping resistor and using ~ 0.408 volts as the benchmark of passed series current flow.
    At that voltage level across the dropping resistor, you would have ~ 20 ma across each diode, and have approached the potential maximum voltage wanted to be applied to the units, for a resultant decent lifespan.

    Lastly, there is the marked board identifier of dash 3, and just about all of these units that I have seen are using either 3 series AAA or button cells.

    73's de Edd
    Last edited: Jan 29, 2017
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