setting current level for high power LED

Discussion in 'General Electronics Chat' started by sumit123, Dec 7, 2013.

  1. sumit123

    Thread Starter New Member

    Oct 28, 2013
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    I want to set the desired current level for high power LED as per datasheet the following comments are mention can anybody help us to understand.

    "To set the desired current level a short may be connected between LED+ and LED-,then use a current probe and turn the POT clockwise until the desired current is reached"

    1) I know the position of POT in the Ckt.
    2) I know the current level requirement.
    3) How to short the LED+ & LED- ?
    4) How to use current probe ?
     
    Last edited by a moderator: Dec 7, 2013
  2. MrChips

    Moderator

    Oct 2, 2009
    12,432
    3,360
    Get a DMM and set the range switch to measure 20A DC.
    Connect the two meter probes to the meter, one (RED) to the 20A socket and the other (BLACK) to COM.

    Connect the RED probe to LED+.
    Connect the BLACK probe to LED-.

    (It is ok if you reverse the connections.)
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,779
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    Are you doing this for real, or is it a simulation?
     
  4. sumit123

    Thread Starter New Member

    Oct 28, 2013
    11
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    Thanks Mr.Chips,

    Requested to confirm if we connect the load(LED) in parallel with DMM is it safe?

    or instead we can use ampere meter with shunt for measurement.

    Actually we need to understand the meaning of short may be connected between LED+ and LED- ?
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,432
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    An ammeter is a "short".

    The ammeter alone will create a short circuit across the supply and will indicate the short circuit current.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    The low ohmic resistance of the Digital Multi Meter (DMM) will act as the short. The DMM contains the shunt you mention in post #4. As a precaution, I would disconnect the LED until the current level has been set. If the LED were still in the circuit and the DMM leads would come loose before the current level is reduced to the proper level, damage to the LED may result.
     
  7. sumit123

    Thread Starter New Member

    Oct 28, 2013
    11
    0
    Thanks for advice it's really helpful.
     
  8. sumit123

    Thread Starter New Member

    Oct 28, 2013
    11
    0
    Thanks BillB3857
     
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