12W LED light controller?!!

[Navid T]

Hi friends
I have a 12W LED ( 12X1W ), I need a circuit to control it's light, i use this circuit but after few hours pot heat goes up and makes problem. what do you suggest to control light of 12W led with potentiometer?
View attachment led.bmp
Regards

 

[kam1787]

use a 20k or 50k pot
and
try;
- using a 2n3055 with higher gain; hfe
or
- use a darlington for Q1
or
- use a different Q1 with higher gain

 

[Navid T]

thanks for answer
I have uased 20K pot before 1K and i had same problem, my resistors are 5W resistor, 2n3055 max collector current is 75A and in this circuit max current is 1A, main problem is POT!! anyway i try 50K too
Thanks

 

[kam1787]

does it happen at full power? Sorry - I jumped too soon - - I think the value of R1 is too low. Increase the pot [ 20K s/b ok ] and R1. The "upper side" of the pot and R1 are setting the current - you have too much current flowing when at or near full power. Q1 needs too much base current for the pot.
But after increasing the pot and R1, Q1 may not be able to drive the LED to full power.
then you have to;
- use a 2n3055 with higher gain; hfe
or
- use a darlington for Q1
or
- use a different Q1 with higher gain

R1 does not have to be 5W.



It would be better [less power wasted] to control it using PWM. A simple 555 based circuit can have a duty cycle from 50% to 99%.
A little more complex 555 circuit has a broader duty cycle.

Or you could control the current rather than the voltage.

 

[Navid T]

Thanks Kam, i'll do everything you say and i'm sure i'll get what i want

 

[kam1787]

any success?

 

[Navid T]

as my customer said i changed this circuit from base, i used a selector key tu have 4 different light with 4 different 5W resistor, i'll try this circuit when i'll be free too
best regards for you attention kam