Received: by 10.50.181.233 with SMTP id dz9mr3516568igc.1.1352590909313; Sat, 10 Nov 2012 15:41:49 -0800 (PST) X-BeenThere: hackerspace_brisbane@googlegroups.com Received: by 10.42.84.2 with SMTP id j2ls6500422icl.0.gmail; Sat, 10 Nov 2012 15:41:48 -0800 (PST) Received: by 10.42.216.84 with SMTP id hh20mr9652139icb.20.1352590908759; Sat, 10 Nov 2012 15:41:48 -0800 (PST) Received: by 10.42.216.84 with SMTP id hh20mr9652138icb.20.1352590908742; Sat, 10 Nov 2012 15:41:48 -0800 (PST) Return-Path: Received: from mail-ob0-f172.google.com (mail-ob0-f172.google.com [209.85.214.172]) by gmr-mx.google.com with ESMTPS id dx8si708422igc.1.2012.11.10.15.41.48 (version=TLSv1/SSLv3 cipher=OTHER); Sat, 10 Nov 2012 15:41:48 -0800 (PST) Received-SPF: pass (google.com: domain of denomina...@gmail.com designates 209.85.214.172 as permitted sender) client-ip=209.85.214.172; Authentication-Results: gmr-mx.google.com; spf=pass (google.com: domain of denomina...@gmail.com designates 209.85.214.172 as permitted sender) smtp.mail=denomina...@gmail.com; dkim=pass header...@gmail.com Received: by mail-ob0-f172.google.com with SMTP id wo10so2206117obc.17 for ; Sat, 10 Nov 2012 15:41:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=54gHocgtfsPGvQOBDaPXW0SY0OEp6Mdq8qk6JFFsAdU=; b=EkCo+HDp4+YDOx2NWw0UeNkcIjaARCwrS5yNlWPKf/lYUrnRfs320d8nwkKxTUYcru NKDN2crjZOWXJ+zTgTK6OpRKfzryaRbTeJm7jOvLCiLJphiInUDEiM5nPpBdmACjWa7S sQwU6GqaQxOQX1lh/beTkrSfrrmFLt4k+204ltNgoRa5S1Nd+pZw7a1Zv+TaSu/rjY4S cRaCIoVNxYrDJ99w2ZgXoz7ASqNqXahEJtAmSCJAr7bwaFGy8FNmMjFOE9Pe1IsaypMX D2qgSA5JgrqBfRldmazG9pTO7J6rc+h4aVOypclZ7EW/kxY3JjT5h5u+IWfSmWyWg/kw d+bg== MIME-Version: 1.0 Received: by 10.182.38.101 with SMTP id f5mr12120462obk.80.1352590908289; Sat, 10 Nov 2012 15:41:48 -0800 (PST) Received: by 10.76.74.165 with HTTP; Sat, 10 Nov 2012 15:41:48 -0800 (PST) In-Reply-To: <770dba05-b928-4347-ab8a-8b3bbfa5697d@googlegroups.com> References: <509C921B.3030...@shikadi.net> <509C9F37.7040...@shikadi.net> <3870537192979100259@unknownmsgid> <770dba05-b928-4347-ab8a-8b3bbfa5697d@googlegroups.com> Date: Sun, 11 Nov 2012 09:41:48 +1000 Message-ID: Subject: Re: Upgrading an old electric furnace From: Jimmy Bowler To: hackerspace_brisbane@googlegroups.com Content-Type: multipart/alternative; boundary=f46d044630089d72c904ce2c9c9d --f46d044630089d72c904ce2c9c9d Content-Type: text/plain; charset=ISO-8859-1 Then it wouldn't be a digital input or output then would it. They would be analog in the physical world. They might not be as accurate as the ones you describe buy they are still a closed loop system just like a normal house hold oven is PID controlled in a closed loop. On Sat, Nov 10, 2012 at 8:03 PM, Luke Weston wrote: > > > On Saturday, 10 November 2012 18:29:31 UTC+11, tjhowse wrote: >> >> So a PID controller can't be implemented in digital logic, by your >> reasoning? >> >> > Sure, you can and routinely do have PIDs implemented in digital machines, > of course... with some sort of ADC and DAC between the PID algorithm in the > digital machine and the analog (physical) system. > So all such systems are subject to some (negligible in practice) > discretisation error. > > More generally, calculus isn't usually implemented exactly in a digital > machine... only numerical approximation methods. > > -- > You received this message because you are subscribed to the Google Groups > "hackerspace_brisbane" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/hackerspace_brisbane/-/IqbziBWwdfAJ. > > To post to this group, send email to hackerspace_brisbane@googlegroups.com > . > To unsubscribe from this group, send email to > hackerspace_brisbane+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/hackerspace_brisbane?hl=en. > --f46d044630089d72c904ce2c9c9d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Then it wouldn't be a digital input or output then would it. They would= be analog in the physical world. They might not be as accurate as the ones= you describe buy they are still a closed loop system just like a normal ho= use hold oven is PID controlled in a closed loop.

On Sat, Nov 10, 2012 at 8:03 PM, Luke Weston= <reindeerfloti...@gmail.com> wrote:


On Saturday, 10 November 2012 18:29:31 UTC+11, tj= howse wrote:
So a PID controller ca= n't be implemented in digital logic, by your reasoning?


Sure, you can and routinely do have PIDs im= plemented in digital machines, of course... with some sort of ADC and DAC b= etween the PID algorithm in the digital machine and the analog (physical) s= ystem.
So all such systems are subject to some (negligible in practice) discr= etisation error.

More generally, calculus isn't usually implemen= ted exactly in a digital machine... only numerical approximation methods.

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=20 To post to this group, send email to hackerspace_brisbane@googlegroups.com<= /a>.
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