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My LED Driver? Answered


Right so i asked about how i could dim this circuit but i forgot to put a link of the circuit in question . i wanted to know how i can control dimming of an LED. i have 3 LEDs into one LED RGB they use 350 MAh 3.7 V each and i used 1W 3.9 ohms resistor on each Vreg. they have + as the Common.   is it possible to just put a potentiometer between the driver and the battery?  or do i need to a high tech micro controller? 

https://www.instructables.com/id/Super-simple-high-power-LED-driver/

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steveastrouk

Best Answer 7 years ago

You don't need a microcontroller, but you can't use pots. TRy a circuit like this (X3)

Steve

trimmable current source.JPG
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unaffiliatedpersonsteveastrouk

Answer 7 years ago

so with this circuit i could easily adust brightness as i need it?? so its a 1K oh on adj and out then another 500 ohm in line and a 3rd reistor?

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steveastroukunaffiliatedperson

Answer 7 years ago

That's right, the values of the 3rd resistor needs to be worked out for the 350mA. I should write up how !

The LM317 will adjust the output VOLTAGE to maintain the voltage between out and Adj at 1.2V (Lets be algebraic, and call it Vref)

I've worked up the maths into an image I can post. See if this helps.

Copy of maths.jpg
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steveastroukunaffiliatedperson

Answer 7 years ago

Rsense ? No. It'll be a relatively high power resistor, pots aren't suited to it.

You COULD replace the pot and Radj with a 2K pot, and that should give you control from 0 to 1.22/Rsense

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unaffiliatedpersonsteveastrouk

Answer 7 years ago

so then i could adjust brightness as i need it while its turned on? and the 2K pot on the adjust would be on the original diagram or the one u supplied?

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unaffiliatedpersonsteveastrouk

Answer 7 years ago

so just to sum this one up put a 2K pot inline with the 3.9 ohm resistor in the original diagram to adjust the brightness?