Re: controlling a mains-powered oven

From	Folderol <general@musically.me.uk>
Newsgroups	comp.sys.raspberry-pi
Subject	Re: controlling a mains-powered oven
Date	2015-09-08 18:21 +0100
Organization	A noiseless patient Spider
Message-ID	<20150908182109.45fde42d@debian> (permalink)
References	<b201e7fe54.jim@abbeypress.net> <gbmQNMZ+8e7VFwSL@invalid.uk.co.demon.merlyn.invalid> <msl493$35c$2@news.albasani.net> <9d3accff54.Alan.Adams@iyonix.adamshome.org.uk> <msn2hr$lae$1@dont-email.me>

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On Tue, 8 Sep 2015 05:32:13 -0400
rickman <gnuarm@gmail.com> wrote:

> On 9/8/2015 4:04 AM, Alan Adams wrote:
> > In message <msl493$35c$2@news.albasani.net>
> >            The Natural Philosopher <tnp@invalid.invalid> wrote:
> >
> >> On 07/09/15 21:10, Dr J R Stockton wrote:
> >>> In comp.sys.raspberry-pi message <b201e7fe54.jim@abbeypress.net>, Sun,
> >>> 6 Sep 2015 15:20:49, Jim Nagel <jimnewsm13c@abbeypress.co.uk> posted:
> >>>
> >>>> Seems to me the Pi's job would basically be to read a temperature
> >>>> sensor in each oven (smaller upper one and larger lower one) and
> >>>> trigger relays (or nowadays maybe thyristors?) to switch various
> >>>> heating elements on and off accordingly. (That's top and bottom
> >>>> element in each oven plus a fan element in bottom oven.)
> >>>
> >>> If, rather than switching things on and off every few seconds or
> >>> minutes, you alter the point in each mains half-cycle at which the mains
> >>> is applied to the elements, you _may_ increase the life of the elements.
> >>>
> >> I haven't ever even met someone who has had an oven element go in the
> >> last 30 years....
> >
> > I've had two go in the last 2 years. Awaiting the repair mine as we
> > write.
> 
> A friend had one of those under-glass range tops and a burner went out 
> in the first year.  I took a look and it clearly was a manufacturing 
> defect although I don't recall the detail at the moment.  I doubt there 
> was anything that could have been done with a controller to prevent it 
> burning out.  I can't imagine how switching at 50/60 Hz zero crossings 
> would make any difference to a heating element that takes on the order 
> of seconds to reach operating temperature.
> 
> As pointed out, these things normally go for many, many years unless 
> they were made badly.
 
A low temp coefficient, near perfect resistor (heating element) is the simplest
load of all to drive. Use a zero-crossing SSR and you then need only minimal
- if any - EMI suppression. Also, pick up the mains itself and use it as your
gate trigger source, and you will always use complete cycles, so no nasty DC
offset being created.

In theory, with full PID control that gives you a 20mS response time.
Considering the thermal inertia of the oven is in tens of seconds, this is way
over-engineering :)

-- 
W J G

Thread

controlling a mains-powered oven Jim Nagel <jimnewsm13c@abbeypress.co.uk> - 2015-09-06 15:20 +0100
  Re: controlling a mains-powered oven "gareth" <no.spam@thank.you.invalid> - 2015-09-06 17:40 +0100
    Re: controlling a mains-powered oven Andy Burns <usenet.feb2014@adslpipe.co.uk> - 2015-09-06 17:56 +0100
      Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-09-06 18:40 +0100
        Re: controlling a mains-powered oven Bernard Peek <{bap}@gamma.shrdlu.com> - 2015-09-07 20:16 +0000
  Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-06 18:09 +0000
    Re: controlling a mains-powered oven mick <invalid@invalid.invalid> - 2015-09-07 08:03 +0000
    Re: controlling a mains-powered oven Alan Adams <alan@adamshome.org.uk> - 2015-09-07 09:48 +0100
      Re: controlling a mains-powered oven mm0fmf <none@mailinator.com> - 2015-09-07 19:19 +0100
        Re: controlling a mains-powered oven Kallu Wiegand <spam.only@roev.de> - 2015-09-08 21:12 +0200
    Re: controlling a mains-powered oven Jim Nagel <jimnewsm13c@abbeypress.co.uk> - 2015-11-20 14:08 +0000
      Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-21 14:23 +0000
        Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-11-21 14:55 +0000
        Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-21 10:50 -0500
          Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-21 19:06 +0000
            Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-21 20:52 -0500
              Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-22 10:11 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 10:47 -0500
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-22 18:17 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 13:51 -0500
                Re: controlling a mains-powered oven Andy Burns <usenet.feb2014@adslpipe.co.uk> - 2015-11-22 18:59 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 14:26 -0500
                Re: controlling a mains-powered oven Andy Burns <usenet.feb2014@adslpipe.co.uk> - 2015-11-22 19:50 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 15:05 -0500
                Re: controlling a mains-powered oven Andy Burns <usenet.feb2014@adslpipe.co.uk> - 2015-11-22 20:17 +0000
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-22 20:52 +0000
                Re: controlling a mains-powered oven Jim Nagel <jimnewsm13c@abbeypress.co.uk> - 2015-11-27 01:06 +0000
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-27 18:15 +0000
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-22 20:21 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 15:40 -0500
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-11-22 20:54 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-11-22 16:08 -0500
                Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-11-23 05:02 +0000
                Re: controlling a mains-powered oven Charlie <cdknospam@msn.com> - 2015-12-11 21:27 -0500
                Re: controlling a mains-powered oven Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-12-12 13:53 +0000
                Re: controlling a mains-powered oven Charlie <cdknospam@msn.com> - 2015-12-15 22:17 -0500
                Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-12-16 10:01 +0000
                Re: controlling a mains-powered oven Charlie <cdknospam@msn.com> - 2015-12-19 19:47 -0500
                Re: controlling a mains-powered oven Stuart <Spambin@argonet.co.uk> - 2015-12-20 12:28 +0000
                Re: controlling a mains-powered oven Kallu Wiegand <spam.only@roev.de> - 2015-12-20 15:59 +0100
                Re: controlling a mains-powered oven Stuart <Spambin@argonet.co.uk> - 2015-12-20 16:26 +0000
                Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-12-20 17:54 +0000
                Re: controlling a mains-powered oven Kallu Wiegand <spam.only@roev.de> - 2015-12-20 23:21 +0100
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-12-21 09:52 +0000
                Re: controlling a mains-powered oven Andy Burns <usenet.feb2014@adslpipe.co.uk> - 2015-12-21 12:30 +0000
                Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-12-21 12:39 +0000
                Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-12-21 18:28 +0000
                Re: controlling a mains-powered oven mm0fmf <none@mailinator.com> - 2015-12-22 08:52 +0000
                Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-12-22 08:56 +0000
                Re: controlling a mains-powered oven Charlie <cdknospam@msn.com> - 2015-12-22 10:53 -0500
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-12-20 13:18 -0500
                Re: controlling a mains-powered oven Paul <paul@pcserviceselectronics.co.uk> - 2015-12-22 13:44 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-12-22 10:47 -0500
                Re: controlling a mains-powered oven Paul <paul@pcserviceselectronics.co.uk> - 2015-12-22 18:33 +0000
                Re: controlling a mains-powered oven Charlie <cdknospam@msn.com> - 2015-12-22 11:08 -0500
                Re: controlling a mains-powered oven mm0fmf <none@mailinator.com> - 2015-11-22 19:42 +0000
  Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-09-07 14:25 -0400
  Re: controlling a mains-powered oven Dr J R Stockton <reply1500@merlyn.demon.co.uk.invalid> - 2015-09-07 21:10 +0100
    Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-09-07 23:49 +0100
      Re: controlling a mains-powered oven Alan Adams <alan@adamshome.org.uk> - 2015-09-08 09:04 +0100
        Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-09-08 05:32 -0400
          Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-09-08 18:21 +0100
            Re: controlling a mains-powered oven Jim Nagel <jimnewsm13c@abbeypress.co.uk> - 2015-09-08 19:03 +0100
              Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-09-08 19:11 +0100
              Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-09-08 14:15 -0400
              Re: controlling a mains-powered oven The Natural Philosopher <tnp@invalid.invalid> - 2015-09-08 22:27 +0100
              Re: controlling a mains-powered oven Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-09-09 14:05 +0100
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-09 13:10 +0000
                Re: controlling a mains-powered oven Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-09-09 15:46 +0100
                Re: controlling a mains-powered oven Rob <nomail@example.com> - 2015-09-09 16:08 +0000
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-09 19:14 +0000
                Re: controlling a mains-powered oven Folderol <general@musically.me.uk> - 2015-09-09 21:00 +0100
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-09 21:59 +0000
                Re: controlling a mains-powered oven Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-09-09 23:58 +0100
                Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-10 06:17 +0000
                Re: controlling a mains-powered oven rickman <gnuarm@gmail.com> - 2015-09-09 23:48 -0400
            Re: controlling a mains-powered oven Alan Adams <alan@adamshome.org.uk> - 2015-09-08 19:02 +0100
      Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-08 11:23 +0000
        Re: controlling a mains-powered oven mm0fmf <none@mailinator.com> - 2015-09-08 12:41 +0100
        Re: controlling a mains-powered oven Ahem A Rivet's Shot <steveo@eircom.net> - 2015-09-08 12:58 +0100
          Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-08 13:26 +0000
            Re: controlling a mains-powered oven Ahem A Rivet's Shot <steveo@eircom.net> - 2015-09-08 14:50 +0100
              Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-09-08 14:24 +0000
                Re: controlling a mains-powered oven "A. Dumas" <alexandre@dumas.fr.invalid> - 2015-09-08 17:17 +0200
      Re: controlling a mains-powered oven Dr J R Stockton <reply1500@merlyn.demon.co.uk.invalid> - 2015-09-08 22:05 +0100
  Re: controlling a mains-powered oven Gordon Henderson <gordon+usenet@drogon.net> - 2015-12-20 10:15 +0000
  Re: controlling a mains-powered oven David <wibble@btintenet.com> - 2016-02-20 14:37 +0000
    Re: controlling a mains-powered oven Rob Morley <nospam@ntlworld.com> - 2016-02-20 14:53 +0000
    Re: controlling a mains-powered oven David <wibble@btintenet.com> - 2016-02-20 16:33 +0000
      Re: controlling a mains-powered oven Paul <paul@pcserviceselectronics.co.uk> - 2016-02-21 21:50 +0000

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