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How long will LM317T drive 3V 350mA Power LED?

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AinaLaw

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Dear all,

I want to drive 3v 350mA Power Led with LM317T.
The Battery rated 6V 4A.
I use a 286 ohm resistor for the led. ( LM317T is set to 3,1V).

My question is:
How many hour can this 6V 4A battery drive the Led ?

Thank you

Aina L
 

Re: LM317T for PowerLed

I guess 4A you mean 4 ampere / hour
Batteries manufacturer declaration on A/h are very fuzzy and depend on the current consumption and maximum battery voltage drop allowed
The best way is to test
 

LM317T for PowerLed

Hi Jepeto
A.h and not A/h
 

Re: LM317T for PowerLed

If this is 3V LED, the voltage regulator is set to 3.1V and 286Ω resistor is connected in series with the LED then something is wrong, as this combination will allow only 0.35mA through the LED ..

Better configure the LM317 as 350mA constant current source and don't use any resistor in series with the LED ..

If your battery is rated for 4Ah then, in theory, you can draw 350mA for (6Ah/0.35A) 17h ..

Regards,
IanP
 

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