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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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## 12 Replies

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

Steve

unaffiliatedperson (author)2011-01-07

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?

steveastrouk (author)2011-01-08

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.

unaffiliatedperson (author)2011-01-08

so the 3rd resistor could be a potentiometer?

steveastrouk (author)2011-01-09

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

unaffiliatedperson (author)2011-01-09

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?

steveastrouk (author)2011-01-09

Yep, it would adjust the brightness.

unaffiliatedperson (author)2011-01-11

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?

steveastrouk (author)2011-01-11

Should work. Try it.

Steve

unaffiliatedperson (author)2011-01-12

forgot to add for the pot thats a 1 watt pot at 2K ohms

steveastrouk (author)2011-01-12

The pot power rating, used like this, is irrelevant, so don't worry. Have fun with it.

unaffiliatedperson (author)2011-01-12

ok ill get some and let u know how it works thanks!!