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Electronics => Electronics => Topic started by: jorj on July 21, 2009, 04:16:44 PM

Title: high voltage
Post by: jorj on July 21, 2009, 04:16:44 PM

I build an electricl circuit, the circuit is source of current of 320 mili ampere
The maximum permitted current and voltage in the luxeon led is
350 mili ampere and 3.4 volt
Indeed the current was constant after I connect the supplier
But the voltage vary and arrive to 12 volt
Why the led not burn ?
How this circuit work ?

Title: Re: high voltage and the led don't burn, why ?
Post by: madchimp on July 21, 2009, 05:20:33 PM

Have you looked through the data sheet you posted? It has several different illustrations on how to hook up that regulator and the circuit you posted isn't one of them.

Title: Re: high voltage and the led don't burn, why ?
Post by: jorj on July 22, 2009, 03:52:59 PM

I want to understand how this circuit work
The data sheet is only for help because it  have summarize of LM317

jorj

Title: Re: high voltage and the led don't burn, why ?
Post by: JSM_Xorudd on July 23, 2009, 10:25:19 AM

I believe I'm right in saying the LM317 is an op amp of some sort.

It looks like it's lowering the voltage going to the LED, so that would be why it's not burning out.

Title: Re: high voltage and the led don't burn, why ?
Post by: SmAsH on July 23, 2009, 04:35:51 PM

Quote

I believe I'm right in saying the LM317 is an op amp of some sort.

the LM317 is an adjustable voltage regulator. it does lower the voltage from the source, yes.

Title: Re: high voltage and the led don't burn, why ?
Post by: jorj on July 24, 2009, 12:34:15 PM

I don't understand what is this loop
That exit from ADJ and close with resistor that connected to Vout
Did the led don't burn because there is a resistor ?
thanks
jorj

Title: Re: high voltage and the led don't burn, why ?
Post by: awally88 on July 28, 2009, 08:02:56 AM

I have hooked up small LED's to 9V and 12V batteries before, they work fine for a few minutes but then they blow when they start to get too hot. I'm assuming you aren't running this circuit for very long, run it for a few minutes and your LED's will blow!