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Groups > comp.sys.raspberry-pi > #9539 > unrolled thread
| Started by | Jim Nagel <jimnewsm13c@abbeypress.co.uk> |
|---|---|
| First post | 2015-09-06 15:20 +0100 |
| Last post | 2016-02-21 21:50 +0000 |
| Articles | 20 on this page of 90 — 22 participants |
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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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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-09-08 05:32 -0400 |
| Message-ID | <msn2hr$lae$1@dont-email.me> |
| In reply to | #9566 |
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. -- Rick
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| From | Folderol <general@musically.me.uk> |
|---|---|
| Date | 2015-09-08 18:21 +0100 |
| Message-ID | <20150908182109.45fde42d@debian> |
| In reply to | #9575 |
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
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| From | Jim Nagel <jimnewsm13c@abbeypress.co.uk> |
|---|---|
| Date | 2015-09-08 19:03 +0100 |
| Message-ID | <4711030055.jim@abbeypress.net> |
| In reply to | #9577 |
Folderol wrote on 8 Sep: > 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 :) I was imagining software that would cause the heating element to switch on or off only when the sensor gets to, say, 10% above or below the desired temperature. Am I being electrically simplistic? -- Jim Nagel www.archivemag.co.uk >> "from" address is genuine but will change. website has current one.
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| From | Folderol <general@musically.me.uk> |
|---|---|
| Date | 2015-09-08 19:11 +0100 |
| Message-ID | <20150908191145.551bce78@debian> |
| In reply to | #9580 |
On Tue, 08 Sep 2015 19:03:31 +0100 Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: > Folderol wrote on 8 Sep: > > > 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 :) > > I was imagining software that would cause the heating element to > switch on or off only when the sensor gets to, say, 10% above or below > the desired temperature. Am I being electrically simplistic? > No, not at all. For a domestic oven that's quite good enough. It only (potentially) becomes a problem with big industrial heaters where you want precise temperature control and the heating system itself has a minutes long thermal inertial, because when you reach your setpoint and switch off, the element will still be pumping out heat for some time, and vice-versa for cooling. -- W J G
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-09-08 14:15 -0400 |
| Message-ID | <msn8he$g9l$1@dont-email.me> |
| In reply to | #9580 |
On 9/8/2015 2:03 PM, Jim Nagel wrote: > Folderol wrote on 8 Sep: > >> A low temp coefficient, near perfect resistor (heating element) is the >> simplest load of all to drive. Use a zero-crossing SSR and you then >> need only minimal - if any - EMI suppression. Also, pick up the mains >> itself and use it as your gate trigger source, and you will always use >> complete cycles, so no nasty DC offset being created. > >> In theory, with full PID control that gives you a 20mS response time. >> Considering the thermal inertia of the oven is in tens of seconds, >> this is way over-engineering :) > > I was imagining software that would cause the heating element to > switch on or off only when the sensor gets to, say, 10% above or below > the desired temperature. Am I being electrically simplistic? 10% is a bit large, but no. This is how electric oven controllers have worked for a hundred years, give or take. Some folks would call this a bang-bang controller, all on or all off. Hysteresis prevents rapid oscillations. The idea of PID control would be to supply power in an amount that equals the loss of the oven maintaining a more accurate temperature without the wavering of the bang-bang controller. In reality there is little need for it in an oven and they are not so easy to make without oscillations. -- Rick
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2015-09-08 22:27 +0100 |
| Message-ID | <msnjsr$ssu$1@news.albasani.net> |
| In reply to | #9580 |
On 08/09/15 19:03, Jim Nagel wrote: > Folderol wrote on 8 Sep: > >> A low temp coefficient, near perfect resistor (heating element) is the >> simplest load of all to drive. Use a zero-crossing SSR and you then >> need only minimal - if any - EMI suppression. Also, pick up the mains >> itself and use it as your gate trigger source, and you will always use >> complete cycles, so no nasty DC offset being created. > >> In theory, with full PID control that gives you a 20mS response time. >> Considering the thermal inertia of the oven is in tens of seconds, >> this is way over-engineering :) > > I was imagining software that would cause the heating element to > switch on or off only when the sensor gets to, say, 10% above or below > the desired temperature. Am I being electrically simplistic? > yes. but its more than good enough. -- New Socialism consists essentially in being seen to have your heart in the right place whilst your head is in the clouds and your hand is in someone else's pocket.
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| From | Theo Markettos <theom+news@chiark.greenend.org.uk> |
|---|---|
| Date | 2015-09-09 14:05 +0100 |
| Message-ID | <tzd*IUaFv@news.chiark.greenend.org.uk> |
| In reply to | #9580 |
Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: > I was imagining software that would cause the heating element to > switch on or off only when the sensor gets to, say, 10% above or below > the desired temperature. Am I being electrically simplistic? One thing I would do is implement a hard thermal cutout: so a bug in your software doesn't cause your oven to emulate a blast furnace and set your kitchen on fire. Theo
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-09 13:10 +0000 |
| Message-ID | <mspb4b$f2v$1@dont-email.me> |
| In reply to | #9588 |
In article <tzd*IUaFv@news.chiark.greenend.org.uk>, Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: >Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >> I was imagining software that would cause the heating element to >> switch on or off only when the sensor gets to, say, 10% above or below >> the desired temperature. Am I being electrically simplistic? > >One thing I would do is implement a hard thermal cutout: so a bug in your >software doesn't cause your oven to emulate a blast furnace and set your >kitchen on fire. The cheap (domestic) oven I have already has this, so I imagine most domestics also have one. However I couldn't see one on the commercial ovens I have... Gordon
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| From | Theo Markettos <theom+news@chiark.greenend.org.uk> |
|---|---|
| Date | 2015-09-09 15:46 +0100 |
| Message-ID | <rzd*ygbFv@news.chiark.greenend.org.uk> |
| In reply to | #9589 |
Gordon Henderson <gordon+usenet@drogon.net> wrote: > In article <tzd*IUaFv@news.chiark.greenend.org.uk>, > Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: > >Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: > >> I was imagining software that would cause the heating element to > >> switch on or off only when the sensor gets to, say, 10% above or below > >> the desired temperature. Am I being electrically simplistic? > > > >One thing I would do is implement a hard thermal cutout: so a bug in your > >software doesn't cause your oven to emulate a blast furnace and set your > >kitchen on fire. > > The cheap (domestic) oven I have already has this, so I imagine most > domestics also have one. However I couldn't see one on the commercial > ovens I have... I should rephrase that... a /resettable/ cutout. Thermal fuses and such are all very well, but you don't want to have to buy a new element - I suspect some cutouts are use-once. Theo
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| From | Rob <nomail@example.com> |
|---|---|
| Date | 2015-09-09 16:08 +0000 |
| Message-ID | <slrnmv0mce.d7e.nomail@xs9.xs4all.nl> |
| In reply to | #9590 |
Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: > Gordon Henderson <gordon+usenet@drogon.net> wrote: >> In article <tzd*IUaFv@news.chiark.greenend.org.uk>, >> Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: >> >Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >> >> I was imagining software that would cause the heating element to >> >> switch on or off only when the sensor gets to, say, 10% above or below >> >> the desired temperature. Am I being electrically simplistic? >> > >> >One thing I would do is implement a hard thermal cutout: so a bug in your >> >software doesn't cause your oven to emulate a blast furnace and set your >> >kitchen on fire. >> >> The cheap (domestic) oven I have already has this, so I imagine most >> domestics also have one. However I couldn't see one on the commercial >> ovens I have... > > I should rephrase that... a /resettable/ cutout. Thermal fuses and such are > all very well, but you don't want to have to buy a new element - I suspect > some cutouts are use-once. Just use an oven with a built-in thermostat. It should not be a modern electronic thing but the old style big knob on the front with crude indications of the temperature. Set the thermostat to the max temp you want to get, and switch the power to the entire oven using a solid-state relay. No real problem when the control sticks, the thermostat will limit the temperature. Maybe the oven even has a timer (mechanical tick-tock thing that you wind up to some time and that ticks back). That will limit the amount of time that it can heat itself. I don't know what your application is, but e.g. for solder reflow on printed circuit boards with SMD components, the use of a cheap "kitchen oven" with an external controller is a wellknown trick.
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-09 19:14 +0000 |
| Message-ID | <msq0eq$d0a$1@dont-email.me> |
| In reply to | #9592 |
In article <slrnmv0mce.d7e.nomail@xs9.xs4all.nl>, Rob <nomail@example.com> wrote: >Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: >> Gordon Henderson <gordon+usenet@drogon.net> wrote: >>> In article <tzd*IUaFv@news.chiark.greenend.org.uk>, >>> Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: >>> >Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >>> >> I was imagining software that would cause the heating element to >>> >> switch on or off only when the sensor gets to, say, 10% above or below >>> >> the desired temperature. Am I being electrically simplistic? >>> > >>> >One thing I would do is implement a hard thermal cutout: so a bug in your >>> >software doesn't cause your oven to emulate a blast furnace and set your >>> >kitchen on fire. >>> >>> The cheap (domestic) oven I have already has this, so I imagine most >>> domestics also have one. However I couldn't see one on the commercial >>> ovens I have... >> >> I should rephrase that... a /resettable/ cutout. Thermal fuses and such are >> all very well, but you don't want to have to buy a new element - I suspect >> some cutouts are use-once. > >Just use an oven with a built-in thermostat. It should not be a modern >electronic thing but the old style big knob on the front with crude >indications of the temperature. > >Set the thermostat to the max temp you want to get, and switch the power >to the entire oven using a solid-state relay. No real problem when >the control sticks, the thermostat will limit the temperature. >Maybe the oven even has a timer (mechanical tick-tock thing that you >wind up to some time and that ticks back). That will limit the amount >of time that it can heat itself. > >I don't know what your application is, but e.g. for solder reflow on >printed circuit boards with SMD components, the use of a cheap "kitchen >oven" with an external controller is a wellknown trick. My application (and that of the OP IIRC) is replacing the capilliary tube mechanical thermostat in a domestic oven with a Pi... As well as the geekery I do I also run a small catering company/bakery and I'm looking to eventually have a nice overall control system for all my ovens - 2 commercial ones and a domestic one as well as the prover/retarder and possibly timers for my mixers too. I do know of several people who've done the "toaster oven" into SMD reflow mods though - helped several with interfacing to a Pi and the software, etc. (I write & maintain the wiringPi library FWIW which interfaces nicely with a BASIC intepreter which I also wrote...) so for me it's now "eating my own dogfood", or rather bread in this case :-) Using the existing thermostat in my domestic oven isn't good - as the replacement doesn't go as high as I want it to - the original would get the oven up to 250C - the replacement barely reaches 230C so that's one reason I want a new controller for it - might as well be geeky about it even though the controller will end up costing more than the oven :-) Gordon
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| From | Folderol <general@musically.me.uk> |
|---|---|
| Date | 2015-09-09 21:00 +0100 |
| Message-ID | <20150909210051.53048055@debian> |
| In reply to | #9594 |
On Wed, 9 Sep 2015 19:14:34 +0000 (UTC) Gordon Henderson <gordon+usenet@drogon.net> wrote: > In article <slrnmv0mce.d7e.nomail@xs9.xs4all.nl>, > Rob <nomail@example.com> wrote: > >Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: > >> Gordon Henderson <gordon+usenet@drogon.net> wrote: > >>> In article <tzd*IUaFv@news.chiark.greenend.org.uk>, > >>> Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: > >>> >Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: > >>> >> I was imagining software that would cause the heating element to > >>> >> switch on or off only when the sensor gets to, say, 10% above or below > >>> >> the desired temperature. Am I being electrically simplistic? > >>> > > >>> >One thing I would do is implement a hard thermal cutout: so a bug in your > >>> >software doesn't cause your oven to emulate a blast furnace and set your > >>> >kitchen on fire. > >>> > >>> The cheap (domestic) oven I have already has this, so I imagine most > >>> domestics also have one. However I couldn't see one on the commercial > >>> ovens I have... > >> > >> I should rephrase that... a /resettable/ cutout. Thermal fuses and such are > >> all very well, but you don't want to have to buy a new element - I suspect > >> some cutouts are use-once. > > > >Just use an oven with a built-in thermostat. It should not be a modern > >electronic thing but the old style big knob on the front with crude > >indications of the temperature. > > > >Set the thermostat to the max temp you want to get, and switch the power > >to the entire oven using a solid-state relay. No real problem when > >the control sticks, the thermostat will limit the temperature. > >Maybe the oven even has a timer (mechanical tick-tock thing that you > >wind up to some time and that ticks back). That will limit the amount > >of time that it can heat itself. > > > >I don't know what your application is, but e.g. for solder reflow on > >printed circuit boards with SMD components, the use of a cheap "kitchen > >oven" with an external controller is a wellknown trick. > > My application (and that of the OP IIRC) is replacing the capilliary tube > mechanical thermostat in a domestic oven with a Pi... > > As well as the geekery I do I also run a small catering company/bakery > and I'm looking to eventually have a nice overall control system for > all my ovens - 2 commercial ones and a domestic one as well as the > prover/retarder and possibly timers for my mixers too. > > I do know of several people who've done the "toaster oven" into SMD > reflow mods though - helped several with interfacing to a Pi and the > software, etc. (I write & maintain the wiringPi library FWIW which > interfaces nicely with a BASIC intepreter which I also wrote...) so for > me it's now "eating my own dogfood", or rather bread in this case :-) > > Using the existing thermostat in my domestic oven isn't good - as the > replacement doesn't go as high as I want it to - the original would get > the oven up to 250C - the replacement barely reaches 230C so that's one > reason I want a new controller for it - might as well be geeky about it > even though the controller will end up costing more than the oven :-) > > Gordon It's always more fun doing your own thing isn't it? :) As an aside, I think you want a J type thermocouple. It should be adequate for the range (600C?), is fairly linear and you can get standard 'cold junction' offset amplifier modules. -- W J G
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-09 21:59 +0000 |
| Message-ID | <msqa41$jj6$1@dont-email.me> |
| In reply to | #9595 |
In article <20150909210051.53048055@debian>, Folderol <general@musically.me.uk> wrote: >It's always more fun doing your own thing isn't it? :) Indeed.. >As an aside, I think you want a J type thermocouple. It should be adequate for >the range (600C?), is fairly linear and you can get standard 'cold junction' >offset amplifier modules. Maybe, but it's too easy to just plug some easy to use stuff together and I know that a K type and a MAX31855 chip does everything with an SPI interface and I know these work as I've helped others get them going: http://skpang.co.uk/catalog/thermocouple-typek-glass-braid-insulated-k-p-1152.html http://skpang.co.uk/catalog/thermocouple-amplifier-max31855-breakout-board-with-spi-output-p-1135.html I'm also under the impression that J types aren't good in some high humidity conditions and another thing I am considering is plumbing the oven into the water supply to make steam... (One of my commercial ovens already has this facility although it's fairly crude - washing machine type solenoid spraying a jet of water onto the plate in-front of the fans!) Cheers, Gordon
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| From | Theo Markettos <theom+news@chiark.greenend.org.uk> |
|---|---|
| Date | 2015-09-09 23:58 +0100 |
| Message-ID | <szd*O5cFv@news.chiark.greenend.org.uk> |
| In reply to | #9594 |
Gordon Henderson <gordon+usenet@drogon.net> wrote: > My application (and that of the OP IIRC) is replacing the capilliary tube > mechanical thermostat in a domestic oven with a Pi... > > As well as the geekery I do I also run a small catering company/bakery > and I'm looking to eventually have a nice overall control system for > all my ovens - 2 commercial ones and a domestic one as well as the > prover/retarder and possibly timers for my mixers too. > > I do know of several people who've done the "toaster oven" into SMD > reflow mods though - helped several with interfacing to a Pi and the > software, etc. (I write & maintain the wiringPi library FWIW which > interfaces nicely with a BASIC intepreter which I also wrote...) so for > me it's now "eating my own dogfood", or rather bread in this case :-) For Jim (OP's) benefit, this is the kind of controller intended for the 'toaster oven' type modification: http://www.ospid.com/ (though this particular project is a bit neglected - there are others based on the software) I see no reason why this isn't applicable to a 'proper' oven. While the form factor might not be what you initially thought of, one option is to have a pre-existing device like this to do the control, and use a Pi as the user interface. That way you don't have to worry about 'disc full' burning your dinner (or your house). Going along the lines of Pi-as-UI train of thought, OSPID is based commercial PID controllers like this one (and those substantially more expensive): http://www.dx.com/p/digital-temperature-controller-66334 http://www.dx.com/p/xmt7100-1-3-screen-pid-intelligent-temperature-controller-black-192851 I don't know the field well, but I imagine if one of those has a serial port it would enable you to set the temperature profile without having to use the buttons and display on the unit as-is. Don't forget to check that you can switch the current though - a cooker is on a 30A circuit, so you may need to beef up the switching. Theo (for whom the 'toaster SMD reflow oven' is one of those projects on the eternal backburner)
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-10 06:17 +0000 |
| Message-ID | <msr7a0$2mf$1@dont-email.me> |
| In reply to | #9597 |
In article <szd*O5cFv@news.chiark.greenend.org.uk>, >Don't forget to check that you can switch the current though - a cooker is >on a 30A circuit, so you may need to beef up the switching. Cookers yes, but most domestic ovens are 13A or less. (there are a few exceptions though - the ones used on Bake-Off are 4.5Kw ovens, but they cost over a grand )-: My domestic oven has a 13A plug and takes 10 of those 13A. The 2 commercial ovens I have are both 13A (3.1Kw) devices too. One that I may Pi control after the first oven has 2 x 1.5Kw elements and I'd switch them separately (2 SSRs) - more to negate needing heatsinks on the SSRs than anything else. This is an issue for the home based microbakery - most commercial ovens are three phase... And if you think this is OTT... :-) Some commercial ovens now have USB sockets to let you connect up a PC to allow uploading of bake/temperature/steam profiles... Gordon
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-09-09 23:48 -0400 |
| Message-ID | <msqufn$c8q$2@dont-email.me> |
| In reply to | #9590 |
On 9/9/2015 10:46 AM, Theo Markettos wrote: > Gordon Henderson <gordon+usenet@drogon.net> wrote: >> In article <tzd*IUaFv@news.chiark.greenend.org.uk>, >> Theo Markettos <theom+news@chiark.greenend.org.uk> wrote: >>> Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >>>> I was imagining software that would cause the heating element to >>>> switch on or off only when the sensor gets to, say, 10% above or below >>>> the desired temperature. Am I being electrically simplistic? >>> >>> One thing I would do is implement a hard thermal cutout: so a bug in your >>> software doesn't cause your oven to emulate a blast furnace and set your >>> kitchen on fire. >> >> The cheap (domestic) oven I have already has this, so I imagine most >> domestics also have one. However I couldn't see one on the commercial >> ovens I have... > > I should rephrase that... a /resettable/ cutout. Thermal fuses and such are > all very well, but you don't want to have to buy a new element - I suspect > some cutouts are use-once. They are also ten cents. -- Rick
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| From | Alan Adams <alan@adamshome.org.uk> |
|---|---|
| Date | 2015-09-08 19:02 +0100 |
| Message-ID | <caed020055.Alan.Adams@iyonix.adamshome.org.uk> |
| In reply to | #9577 |
In message <20150908182109.45fde42d@debian>
Folderol <general@musically.me.uk> wrote:
> 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 :)
Just make sure that you supply complete cycles, not an odd number of
half-cycles, which will introduce a significant DC component.
--
Alan Adams, from Northamptonshire
alan@adamshome.org.uk
http://www.nckc.org.uk/
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-08 11:23 +0000 |
| Message-ID | <msmgf1$8ia$1@dont-email.me> |
| In reply to | #9564 |
In article <msl493$35c$2@news.albasani.net>, The Natural Philosopher <tnp@invalid.invalid> wrote: >On 07/09/15 21:10, Dr J R Stockton wrote: >> In comp.sys.raspberry-pi message <b201e7fe54.jim@abbeypress.net>, Sun, >> 6 Sep 2015 15:20:49, Jim Nagel <jimnewsm13c@abbeypress.co.uk> posted: >> >>> Seems to me the Pi's job would basically be to read a temperature >>> sensor in each oven (smaller upper one and larger lower one) and >>> trigger relays (or nowadays maybe thyristors?) to switch various >>> heating elements on and off accordingly. (That's top and bottom >>> element in each oven plus a fan element in bottom oven.) >> >> If, rather than switching things on and off every few seconds or >> minutes, you alter the point in each mains half-cycle at which the mains >> is applied to the elements, you _may_ increase the life of the elements. >> >I haven't ever even met someone who has had an oven element go in the >last 30 years.... I've had 2 elements go in the past year. Admittedly the oven in question was a very cheap one - Beko - both the main element round the fan and the top grill element have gone "phut". This was after a years use, 6 days a week heated up to 250C then having a lot of water/steam sprayed into it. (I'd only used the top grill element a few times to make pizza though and I've not replaced this element yet) Easy and cheap enough to replace though - this is the oven I'm about to convert to Pi control... I'm not sure about mid-cycle switching of the incoming mains though - basically the same as a light dimmer in operation - prone to noise (suppressible though) and is it that efficient with a resistive/heating load? Gordon
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| From | mm0fmf <none@mailinator.com> |
|---|---|
| Date | 2015-09-08 12:41 +0100 |
| Message-ID | <jPzHx.299569$qz2.131266@fx04.am4> |
| In reply to | #9567 |
On 08/09/2015 12:23, Gordon Henderson wrote: > I'm not sure about mid-cycle switching of the incoming mains though > - basically the same as a light dimmer in operation - prone to noise > (suppressible though) and is it that efficient with a resistive/heating > load? > > Gordon > If you use an SSR you get zero-crossing switching.
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| From | Ahem A Rivet's Shot <steveo@eircom.net> |
|---|---|
| Date | 2015-09-08 12:58 +0100 |
| Message-ID | <20150908125802.536194730e3e5362d976e343@eircom.net> |
| In reply to | #9567 |
On Tue, 8 Sep 2015 11:23:13 +0000 (UTC) Gordon Henderson <gordon+usenet@drogon.net> wrote: > I'm not sure about mid-cycle switching of the incoming mains though > - basically the same as a light dimmer in operation - prone to noise > (suppressible though) and is it that efficient with a resistive/heating > load? That's the best kind of load for this kind of dimmer (inductive loads hate this treatment). Still it will be hard to suppress - a cut off near the peak will have a fearsome dI/dt - read big spike if there's any appreciable inductance around and plenty of energy for radiating interference. It is possible though - theatrical lighting boards switch similar loads regularly without crackling up the sound system. Still given the inherently slow response of an oven I'd be inclined to go for essentially pulse width modulation with the width measured in half cycles of the mains and switch at zero crossing - perhaps using patterns in say 16 cycles to provide various power levels or just KISS and use slow bang/bang with hysteresis (but then why bother with a computer), either way zero crossing means no interference problems. -- Steve O'Hara-Smith | Directable Mirror Arrays C:>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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