setting current level for high power LED

Thread Starter

sumit123

Joined Oct 28, 2013
11
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 ?
 
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MrChips

Joined Oct 2, 2009
30,794
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.)
 

Thread Starter

sumit123

Joined Oct 28, 2013
11
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- ?
 

MrChips

Joined Oct 2, 2009
30,794
An ammeter is a "short".

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

BillB3857

Joined Feb 28, 2009
2,570
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.
 
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