PID question

bronxbomber92 · #1 10-01-2008, 15:27

I've seen several PID sources posted on the forum, and all of them divide the proportional output by 100, the integral output by 1000 and the derivative output by 10. Then the return value of the PID goes something like this:

Code:

return Limit_Mix(2000 + 127 + P + I - D);

Why do this? Why not just set the gains for P, I, and D to something that'll work within the range of 0 to 255 and the integral max to 255 and min to 0? I don't quite understand where the 100, 1000, and 10 came from either? Could someone please explain this?

Thanks,
Jedd

Edit - Another question? How do most people find reasonable constants for the gains of P, I and D?

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