Re: current control algorithm

On Mon, 03 Oct 2011 13:58:06 -0700, cerr wrote:

Hi There,

I have two strings of 5 LEDs and a I need to control them with a pwm to
reach a certain intensity (I can measure the current). Now due to lack
of time , I didn't go with a PI controller (which I think would be the
right way) instead, I just calculate a hysteresis of x counts (10bit
adc) and the measured current has to be within this hysteresis. Now I
unfortunately got a high jitter on my LED current (that's controlled by
the duty cycle) - I assume this is because of a time delay from the time
i set the duty cycle until i measure the current rise/fall. How do I
best go about this? Is there a quick method to resolve this or do i
actually need to take the time to study and implement a PI controller?

You just need integral control, which is dead easy.

If I tried to count the number of times I've wasted far more time on a
"time saving simplification" than I ended up spending finally doing a
control loop right, I'd run out of fingers and toes before I even
finished accounting for the first few years of my career.