While the analog solution may be elegant, there is nothing inherently
analog about generating a correction signal that is the sum of three terms;
one proportional to the error, one proportional to the time integral of the
error, and one proportional to the time derivative of the error.

Thanks for listening
Dave

----------
> From: Calvin <tgo@CHIH1.TELMEX.NET.MX>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: PID question.
> Date: Friday, March 06, 1998 3:23 PM
>
> Comment:
>
> PID controls are inherently analog. This does not mean they cannot be
> implemented digitally, but it is generally a lot easier to do it with one
or
> two op-amps.
>
> Just a thoght
>
> Calvin
>
>
> -----Original Message-----
> From: Justin Grimm <reaper@SOUTHWEST.COM.AU>
> To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
> Date: Viernes 6 de Marzo de 1998 11:45 AM
> Subject: Re: PID question.
>
>
> >Funny you should ask, Im working on the same project at the moment.
> >The only problem Im having is the maths routines, they seem to be
getting
> >up to
> >64 bit.
> >The actual calculation is-
> >dMV=G[dE + E*T1*I + D* (dE/T2)]
> >where-
> >dMV  = change in Manipulated Variable
> >G      = Gain (100/Proportional Band)
> >E      = Error (SetPoint - ProcessVariable) for reverse action,
> >           Error (ProcessVariable - Setpoint) for direct action
> >dE    = ErrorThisScan - ErrorLastScan
> >T2     = Time between scans (in minutes)
> >T1     = Time since error occured (in minutes)
> >I       = Integral time (R/M)
> >D     = Derivative time (minutes)
> >
> >There are other things to consider as well, integral windup, bumpless
> >transfer
> >from manual to auto, etc
> >
> >Anyone knowing any alterations to this equation or anything else
> >that might make writing this code easier are most welcome to reply
> >
> >
> >
> >Justin Grimm    reaper@southwest.com.au
> >
> >
> >----------
> >> From: Mark Lezama <mfidel@TELCEL.NET.VE>
> >> To: PICLIST@MITVMA.MIT.EDU
> >> Subject: PID question.
> >> Date: Friday, 6 March 1998 21:09
> >>
> >> I have working with RTU designe base in PIC16c74. I have to control a
> >> valve with a 4-20 ma signal, but I want to implement a digital PID
> >> controller, anyone here have a PID code or can explain me how I have
to
> >> implement.
> >>
> >> Thanks in advance!
> >>
> >> Mark Lezama
> >