Could you purpose any IC for PWM generator?
- Thread starter theasus
- Start date
Those IC's are pretty much gone. We have a member who works with the common LM555 timer. See his article on using them for PWM - http://forum.allaboutcircuits.com/showthread.php?t=24028
The 555 is much like a swiss army knife, you can approach this problem several ways. Here is another oldie but goodie.
I pulled this schematic from chapter 5 of this article...
LEDs, 555s, Flashers, and Light Chasers
I pulled this schematic from chapter 5 of this article...
LEDs, 555s, Flashers, and Light Chasers
This what I designed for my boat as a 12v lamp (and fan) dimmer. It gives full control from 0 to 100% using a single LM324. Frequency of operation can be set as per the formula on the diagram.
The output of the integrator is a linear ramp that goes from about -3v to +3v (referenced to the mid-rail). When this output value is higher than the voltage set by VR1, the comparator output goes positive and the MOSFET turns ON switching on the lamps. When the integrator output is below the voltage set by VR1, the lamps are OFF. The output of the integrator also feeds the Schmitt trigger thus forming a regenerative loop (oscillator) which produces a square wave at the output of the Schmitt and the linear ramp at the output of the integrator.
VR1, R6 and R7 are calculated such that the voltage at VR1 wiper can be set just below -3v to just above +3v (referenced to the mid-rail) allowing full 0 to 100% control of the lamp brightness.
If anyone wants to know how the frequency formula is derived, I am happy to add it to the thread.
The output of the integrator is a linear ramp that goes from about -3v to +3v (referenced to the mid-rail). When this output value is higher than the voltage set by VR1, the comparator output goes positive and the MOSFET turns ON switching on the lamps. When the integrator output is below the voltage set by VR1, the lamps are OFF. The output of the integrator also feeds the Schmitt trigger thus forming a regenerative loop (oscillator) which produces a square wave at the output of the Schmitt and the linear ramp at the output of the integrator.
VR1, R6 and R7 are calculated such that the voltage at VR1 wiper can be set just below -3v to just above +3v (referenced to the mid-rail) allowing full 0 to 100% control of the lamp brightness.
If anyone wants to know how the frequency formula is derived, I am happy to add it to the thread.
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