Home     Contact     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science     RSS     Terms of services     Privacy policy  
   
 Home     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science   

Author Topic: Two 555s and a FET to make robust dimming circuit  (Read 8425 times)

0 Members and 1 Guest are viewing this topic.

emueyes

  • Guest
Two 555s and a FET to make robust dimming circuit
« on: May 26, 2012, 10:42:28 AM »

Hi all

It looks like this topic has been addressed here before, but I couldn't find a solution for my requirement. I'd like to drive an LED bulb with a PWM circuit that allows full 100% on for the LEDs. The bulb in this vase is a car foglamp replacement with 120 surface mount LEDs.  It requires 12V and draws 200mA (and is very bright - I want to use it as an indoor table lamp, but it really needs dimming, and I'd like to control that).

I've seen such a circuit, I believe it uses two 555s to give a fixed frequency and variable duty cycle, so avoiding the frequency drift problem a single 555 astable has.

I guess getting the oscillator circuit wouldn't be too hard, but I don't know how to drive the FET properly with my somewhat patchy knowledge. If anyone has such a circuit it'd be a great help.

Rob


kam

  • Administrator
  • Hero Member
  • *****
  • Posts: 1849