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Groups > comp.sys.raspberry-pi > #9989

Re: controlling a mains-powered oven

From Gordon Henderson <gordon+usenet@drogon.net>
Newsgroups comp.sys.raspberry-pi
Subject Re: controlling a mains-powered oven
Date 2015-11-21 14:23 +0000
Organization Drogon Towers
Message-ID <n2pupq$e3a$1@dont-email.me> (permalink)
References <b201e7fe54.jim@abbeypress.net> <mshvgg$6jk$1@dont-email.me> <7c93852555.jim@abbeypress.net>

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In article <7c93852555.jim@abbeypress.net>,
Jim Nagel  <jimnewsm13c@abbeypress.co.uk> wrote:

>Here, the project went onto the proverbial back burner for a while, 
>but it's heating up again.  I wonder if Gordon or others have gone 
>further with it in the meantime and might have further wisdom to 
>impart.

Ah, I'd almost forgotten about this too - however the oven is Pi
controlled and working really well. The PID still needs some fine
tuning, but for now it's good.

Here is a graph of the oven under the existing capillary tube thermostat:

http://unicorn.drogon.net/beaky2.png

The three lines are 3 thermocouples - 2 are at the left back and right
back, the 3rd (blue trace) is at the front. (All at the top, clipped to
the grill element which is not functional) That was with the oven set
to 180°C. The first dip is when I opened the door to stick a cake in,
the others are when I checked it.

This:

http://unicorn.drogon.net/beaky-rye3.png

is with the Pi controller - initial setpoint was 250°C - the dip is
when the loaves were loaded in and note that the feeble little 2Kw heater
couldn't get it back up to 250 before I turned it down to 210°C.

This: http://unicorn.drogon.net/beaky-rye3gp2.png

is the same data once I'd learned how to drive gnuplot, zoomed in. Red
line is the setpoint and the blue & purple lines are +/- 1°C (as are
the cyan and yellow lines at the 2nd temp.)

This: http://unicorn.drogon.net/wholemeals.png

is a run this morning with 4 large wholemeal loaves - so the oven was
effectively loaded with just under 4Kg of very wet dough and asked to
get on with it... The blue line is the power to the heater (appears on
the graph as either 200 < setpoint or 100 < setpoint when on), green is
the actual temperature. Talk about being woefully inadequate to bring
the oven temp back up to 250°C.... However it gets up to 210°C OK.
The extra dip at the end of the 250 section is when I opened the door
to move the tins about, and the next big dip is when I de-tinned the
loaves and put them back in for a bit more time. The oven was then used
at the same 210°C to cook a batch of buns...

I've done a few more tweaks to the PID and it's marginally better, but
seeing that it maintains inside 1°C (with minimal over/under shoot)
for the most part is good enough for me. (For now - I will tune it better
when I get more time)

This is the controller: http://unicorn.drogon.net/IMG_20151108_165714.jpg

The thicker grey wire goes to the SSR which is on a heatsink mounted
inside the oven cabinet. It's wired in parallel to the existing thermostat
so for now I can still use that if I need to. The 3 other wires go to
the thermocouples.

I guess the real question is: Does it cook any better (or worse!) and
I'm fairly sure that it does. Certainly my cakes appear better and more
evenly baked - I still have to turn them, but it's a really cheap oven
and without a lot of mechanical shenanigans to fix the airflow that's
not going to change but I think having much short bursts of heat (once
its at temperature) rather than longer periods of heating/cooling is
much better - I see less scorching in the places that would normally
get a bit too hot.

Cheers,

Gordon

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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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