# Re: current control algorithm

*From*: Arlet Ottens <usenet+5@xxxxxxxxxx>*Date*: Tue, 04 Oct 2011 14:16:09 +0200

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?

Every time you measure your current with the ADC, do something like this:

PWM += gain * (setpoint - current);

Calculations in floating point, or fixed point with sufficient bits, depending on your parameters, and clip PWM at min/max to avoid wrap around.

Experiment with different gain settings to see which one works best.

.

**Follow-Ups**:**Re: current control algorithm***From:*Tim Wescott

**References**:**current control algorithm***From:*cerr

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