Also Microchip's AN531 app note on their website has some PID code in it.
Good luck
Justin Grimm    reaper@southwest.com.au


----------
> From: Mark Lezama <mfidel@TELCEL.NET.VE>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: PID question.
> Date: Saturday, 7 March 1998 22:39
>
> Yes, you are right. but I have and interface with a host computer, and
the
> parameters need to be change from a long distance. Is there any way to do
this
> with OP-amps? at lest in digital comuniation.
>
> Mark Lezama
>
> Calvin escribis:
>
> > 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
> > >