Need help with understanding PID control

[Megahertz]

Ok, I am actually starting to understand it better now, thanks to all.

I would like to ask, if I use pot to set this gain, the maximum decimal value I will get is 1024 i.e. $0400 (1024/256) which is 4 in terms of Kp. How do I increase Kp if I want to? (If I multiply Kp by 2 or 3 or 4 etc then I start to skip few 2nd decimal digits (pic attached). Any way around it?

[HenrikOlsson]

Hi,
Well, you could introduce some oversampling and increase the effective resolution from 10 to say 12 bits. Ie take 40 samples, add them up and divide the result by 10, you now have a 12bit value instead of a 10bit one. Or, you could use two pots, one for coarse and one for fine adjustment.

However, I wouldn't worry too much about dropping a digit after the decimal point. Just do what you we're going to and multiply your ADC value with whatever you need to get into the range that you want, it'll work fine.

/Henrik.

[Megahertz]

Thanks a lot. I now will start with the prop control and add integral and then post the code to discuss any issues.

[Aussie Barry]

If you need to increase the gain greater than 1024 (1024/256 = 4) without losing resolution then simply add 1024 to the ADC pot value (range 1024-2048).
If you still need more gain then add 2048 to the ADC pot value (range 2048 -3072).

I do agree with Henrik though, don't worry too much about dropping a digit after the decimal point.
Perhaps use the multiplication method to quickly get you into the ball park and then use the addition method to fine tune the control if required.
This is the method I used to tune my motor speed controller PID loop.

Cheers
Barry
VK2XBP