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 To: 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 >> 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 >