# My LED Driver?

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

Steve
unaffiliatedperson (author)  steveastrouk6 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?
6 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.
unaffiliatedperson (author)  steveastrouk6 years ago
so the 3rd resistor could be a potentiometer?
6 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
unaffiliatedperson (author)  steveastrouk6 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?
6 years ago
Yep, it would adjust the brightness.
unaffiliatedperson (author)  steveastrouk6 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?
6 years ago
Should work. Try it.

Steve
unaffiliatedperson (author)  steveastrouk6 years ago
forgot to add for the pot thats a 1 watt pot at 2K ohms
6 years ago
The pot power rating, used like this, is irrelevant, so don't worry. Have fun with it.
unaffiliatedperson (author)  steveastrouk6 years ago
ok ill get some and let u know how it works thanks!!