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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 | Jim Nagel <jimnewsm13c@abbeypress.co.uk> |
|---|---|
| Date | 2015-09-06 15:20 +0100 |
| Subject | controlling a mains-powered oven |
| Message-ID | <b201e7fe54.jim@abbeypress.net> |
Has anybody used a Pi to control a mains-powered device? I'm looking for some tips. The electronic controller of our electric double oven is no longer reliable -- temperature varies far too much, according to the independent external thermometer I bought. Rather than spend £200 to replace the controller, I fancy using a Pi instead. It could live inside a nearby cupboard door, with a nice big screen at eye level instead of the present little thing for which I have to don specs. 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.) Would this be feasible? Anybody done it already? -- Jim Nagel www.archivemag.co.uk >> "from" address is genuine but will change. website has current one.
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| From | "gareth" <no.spam@thank.you.invalid> |
|---|---|
| Date | 2015-09-06 17:40 +0100 |
| Message-ID | <mshq7c$jql$1@dont-email.me> |
| In reply to | #9539 |
"Jim Nagel" <jimnewsm13c@abbeypress.co.uk> wrote in message news:b201e7fe54.jim@abbeypress.net... > Has anybody used a Pi to control a mains-powered device? I'm looking > for some tips. > The electronic controller of our electric double oven is no longer > reliable -- temperature varies far too much, according to the > independent external thermometer I bought. Rather than spend Ł200 to > replace the controller, I fancy using a Pi instead. It could live > inside a nearby cupboard door, with a nice big screen at eye level > instead of the present little thing for which I have to don specs. > 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.) > Would this be feasible? Anybody done it already? Yes, very feasible, but there is a lot you may need to know about closed-loop control systems, otherwise you may end up with temperature oscillations that outshine those that you describe.
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| From | Andy Burns <usenet.feb2014@adslpipe.co.uk> |
|---|---|
| Date | 2015-09-06 17:56 +0100 |
| Message-ID | <bJudnRkGGueg7XHInZ2dnUU78VOdnZ2d@brightview.co.uk> |
| In reply to | #9541 |
gareth wrote: > Jim Nagel wrote: > >> Has anybody used a Pi to control a mains-powered device? I'm >> looking for some tips. The electronic controller of our electric >> double oven is no longer reliable -- temperature varies far too >> much > > Yes, very feasible, but there is a lot you may need to know about > closed-loop control systems, otherwise you may end up with > temperature oscillations that outshine those that you describe. This may be a helpful starting point <https://en.wikipedia.org/wiki/PID_controller> does a Pi have any PWM controlled I/O?
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2015-09-06 18:40 +0100 |
| Message-ID | <mshtpu$50e$1@news.albasani.net> |
| In reply to | #9543 |
On 06/09/15 17:56, Andy Burns wrote: > gareth wrote: > >> Jim Nagel wrote: >> >>> Has anybody used a Pi to control a mains-powered device? I'm >>> looking for some tips. The electronic controller of our electric >>> double oven is no longer reliable -- temperature varies far too >>> much >> >> Yes, very feasible, but there is a lot you may need to know about >> closed-loop control systems, otherwise you may end up with >> temperature oscillations that outshine those that you describe. > > This may be a helpful starting point > > <https://en.wikipedia.org/wiki/PID_controller> > > does a Pi have any PWM controlled I/O? > > since the response time is minutes, it doesn't need a high frequency PWM controlled output. Essentially anything that says '10 degrees below desired, two elements, less than 10 degrees below : one element, above: no elements' is going to be a good starting point. If you get massive overshoot, then start looking at rate of change feed forward stuff. But I doubt it would be needed -- 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 | Bernard Peek <{bap}@gamma.shrdlu.com> |
|---|---|
| Date | 2015-09-07 20:16 +0000 |
| Message-ID | <WgmHx.439123$0B6.27888@fx27.am4> |
| In reply to | #9550 |
On 2015-09-06, The Natural Philosopher <tnp@invalid.invalid> wrote: > > If you get massive overshoot, then start looking at rate of change feed > forward stuff. > > But I doubt it would be needed > Ovens don't normally have PID controllers. -- Bernard Peek bap@shrdlu.com
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-09-06 18:09 +0000 |
| Message-ID | <mshvgg$6jk$1@dont-email.me> |
| In reply to | #9539 |
In article <b201e7fe54.jim@abbeypress.net>, Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >Has anybody used a Pi to control a mains-powered device? I'm looking >for some tips. > >The electronic controller of our electric double oven is no longer >reliable -- temperature varies far too much, according to the >independent external thermometer I bought. Rather than spend Ł200 to >replace the controller, I fancy using a Pi instead. It could live >inside a nearby cupboard door, with a nice big screen at eye level >instead of the present little thing for which I have to don specs. > >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.) > >Would this be feasible? Anybody done it already? In the process of putting stuff together to do this myself. thermocouples: http://skpang.co.uk/catalog/thermocouple-typek-glass-braid-insulated-k-p-1152.html thermocouple amps: http://skpang.co.uk/catalog/thermocouple-amplifier-max31855-breakout-board-with-spi-output-p-1135.html then there's the hard bit: controlling the power. Solid state relays are what I'm looking at. Something like ebay item No. 121748369571 if I can find a UK source for them. I'm looking to add a microswitch to detect when the door opens so I can kill both the heater and fan. Then there's the software... Gordon
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| From | mick <invalid@invalid.invalid> |
|---|---|
| Date | 2015-09-07 08:03 +0000 |
| Message-ID | <55ed44da$0$16739$c3e8da3$76a7c58f@news.astraweb.com> |
| In reply to | #9551 |
On Sun, 06 Sep 2015 18:09:20 +0000, Gordon Henderson wrote: > In article <b201e7fe54.jim@abbeypress.net>, > Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >>Has anybody used a Pi to control a mains-powered device? I'm looking >>for some tips. >> >>The electronic controller of our electric double oven is no longer >>reliable -- temperature varies far too much, according to the >>independent external thermometer I bought. Rather than spend £200 to >>replace the controller, I fancy using a Pi instead. It could live >>inside a nearby cupboard door, with a nice big screen at eye level >>instead of the present little thing for which I have to don specs. >> >>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.) >> >>Would this be feasible? Anybody done it already? > > In the process of putting stuff together to do this myself. > > thermocouples: > > http://skpang.co.uk/catalog/thermocouple-typek-glass-braid-insulated-k- p-1152.html > > thermocouple amps: > > http://skpang.co.uk/catalog/thermocouple-amplifier-max31855-breakout- board-with-spi-output-p-1135.html > > then there's the hard bit: controlling the power. > > Solid state relays are what I'm looking at. Something like ebay item No. > 121748369571 if I can find a UK source for them. > > I'm looking to add a microswitch to detect when the door opens so I can > kill both the heater and fan. > > Then there's the software... > > Gordon SSRs are great. An alternative is to use an optically-isolated triac to trigger a big triac (via a resistor) to control the element. At least that way you can make the control voltage and output current anything you like - but watch the isolation!
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| From | Alan Adams <alan@adamshome.org.uk> |
|---|---|
| Date | 2015-09-07 09:48 +0100 |
| Message-ID | <4a744cff54.Alan.Adams@iyonix.adamshome.org.uk> |
| In reply to | #9551 |
In message <mshvgg$6jk$1@dont-email.me>
Gordon Henderson <gordon+usenet@drogon.net> wrote:
> In article <b201e7fe54.jim@abbeypress.net>,
> Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote:
>>Has anybody used a Pi to control a mains-powered device? I'm looking
>>for some tips.
>>
>>The electronic controller of our electric double oven is no longer
>>reliable -- temperature varies far too much, according to the
>>independent external thermometer I bought. Rather than spend £200 to
>>replace the controller, I fancy using a Pi instead. It could live
>>inside a nearby cupboard door, with a nice big screen at eye level
>>instead of the present little thing for which I have to don specs.
>>
>>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.)
>>
>>Would this be feasible? Anybody done it already?
> In the process of putting stuff together to do this myself.
> thermocouples:
> http://skpang.co.uk/catalog/thermocouple-typek-glass-braid-insulated-k
> -p-1152.html
> thermocouple amps:
> http://skpang.co.uk/catalog/thermocouple-amplifier-max31855-breakout-b
> oard-with-spi-output-p-1135.html
> then there's the hard bit: controlling the power.
> Solid state relays are what I'm looking at. Something like ebay item
> No. 121748369571 if I can
> find a UK source for them.
> I'm looking to add a microswitch to detect when the door opens so I can
> kill both the heater and fan.
> Then there's the software...
> Gordon
Don't forget to make sure your relay or equivalewnt provides a
complete break between the pi and the mains. Mechanical relays do this
of course, and opto-isolators controlling triacs will do so too. Solid
state relays may include this, but you need to check.
--
Alan Adams, from Northamptonshire
alan@adamshome.org.uk
http://www.nckc.org.uk/
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| From | mm0fmf <none@mailinator.com> |
|---|---|
| Date | 2015-09-07 19:19 +0100 |
| Message-ID | <GykHx.413223$Dx3.70705@fx39.am4> |
| In reply to | #9556 |
On 07/09/2015 09:48, Alan Adams wrote: > Solid > state relays may include this, but you need to check. There may be SSRs that don't opto-isolate the input but when I was using SSRs in my day job (15years back) I never came across any. In fact the reason you chose an SSR over Triacs and Thyristors was because they were opto-isolated and could be had with TTL level inputs. We used them extensively to drive heating elements in medical tissue processors which need to keep a couple of litres of paraffin wax at 60C +/- 0.5C. You get a zero crossing switch for free. Paraffin wax is a terrible conductor of heat which is why your candle doesn't melt as soon as you light it and so was the stainless steel used in the tanks. So without careful control of the heating, the wax next to the surfaces of the tanks would melt and then get burnt. Which resulted in poor tissue processing and the doctor then telling you the biopsy results were not clear and to come back when your lump had regrown so they could chop it again. Understandably, patients didn't like this! ISTR we ran the heater loop at 10Hz to start with but it wasn't sync'd to the mains and you could see the effect of the control when the loop was beating with the mains or when they remained almost sync'd up. In the end we chose some odd frequency that was always going to beat with 50 or 60HZ mains and they gave more consistency. As for the OP's oven controller problem, I would suggest that he stop faffing with a solution best described as intellectual masturbation and buy a new controller. ;-)
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| From | Kallu Wiegand <spam.only@roev.de> |
|---|---|
| Date | 2015-09-08 21:12 +0200 |
| Message-ID | <d58qk6Fk2n1U1@mid.individual.net> |
| In reply to | #9560 |
Am 07.09.2015 um 20:19 schrieb mm0fmf: > As for the OP's oven controller problem, I would suggest that he stop > faffing with a solution best described as intellectual masturbation and > buy a new controller. ;-) I think it's also better to show a bill for an original spare part to the insurance agency after your kubicle has smoked up. :-D Greetings, Kallu -- Have a nice day <
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| From | Jim Nagel <jimnewsm13c@abbeypress.co.uk> |
|---|---|
| Date | 2015-11-20 14:08 +0000 |
| Message-ID | <7c93852555.jim@abbeypress.net> |
| In reply to | #9551 |
Gordon Henderson wrote on 6 Sep: > In article <b201e7fe54.jim@abbeypress.net>, Jim Nagel wrote: >> Has anybody used a Pi to control a mains-powered device? I'm looking >> for some tips. >> >> The electronic controller of our electric double oven is no longer >> reliable -- temperature varies far too much, according to the >> independent external thermometer I bought. Rather than spend ?200 to >> replace the controller, I fancy using a Pi instead. It could live >> inside a nearby cupboard door, with a nice big screen at eye level >> instead of the present little thing for which I have to don specs. >> >> 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.) >> >> Would this be feasible? Anybody done it already? > In the process of putting stuff together to do this myself. > thermocouples: http://skpang.co.uk/catalog/thermocouple-typek-glass-b > raid-insulated-k-p-1152.html > thermocouple amps: > http://skpang.co.uk/catalog/thermocouple-amplifier-max31855-breakout-b > oard-with-spi-output-p-1135.html > then there's the hard bit: controlling the power. Solid-state relays > are what I'm looking at. Something like ebay item No. 121748369571 if > I can find a UK source for them. > I'm looking to add a microswitch to detect when the door opens so I can > kill both the heater and fan. Then there's the software... Sorry to quote so much, but revisiting a thread from September. 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. -- Jim Nagel Somerset
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-11-21 14:23 +0000 |
| Message-ID | <n2pupq$e3a$1@dont-email.me> |
| In reply to | #9976 |
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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| From | Folderol <general@musically.me.uk> |
|---|---|
| Date | 2015-11-21 14:55 +0000 |
| Message-ID | <20151121145514.27148a0e@debian> |
| In reply to | #9989 |
On Sat, 21 Nov 2015 14:23:54 -0000 (UTC) Gordon Henderson <gordon+usenet@drogon.net> wrote: > 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 Thanks for the update. It looks like a very successful project, and you can be proud of having done it yourself :) -- W J G
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-11-21 10:50 -0500 |
| Message-ID | <n2q3oc$174$1@dont-email.me> |
| In reply to | #9989 |
On 11/21/2015 9:23 AM, Gordon Henderson wrote: > 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 Yeah, that's a pretty huge difference. Seems like you have it working pretty well. What are the units on the X axis, seconds? The algorithm seems to work rather well. I'm curious though why it doesn't cycle on a more regular basis. It looks like it may actually be the characteristics of the oven. I can find a number of spots where the power is on for a longer period and the temperature actually drops for the first half of it, then finally rises, but to more than the set temperature. I suppose the heat circulation is chaotic. Or is there a level of noise in the temperature measurement? I see in the periods when the heater is on for an extended time there is a lot of noise. Given that your control is only on/off, why do you feel the need for a PID controller? I would think just a simple measurement of the temperature compared to the set point would do a good job. The only thing I can think of that might improve the temperature profile would be to anticipate how much heat is in the heating element to limit overshoot. With your current PID controller, I expect the overshoot is due to the I term in the controller. If you eliminate that the only remaining overshoot will be from the thermal mass of the heating element. So an I term could be used to anticipate the heat in the element and added to the measured temperature (or subtracted from the set point) to allow for the ultimate rise in temperature. But all this would likely be icing on the cake (pun intended). Clearly you have reached a point that optimizes the temperature control as much as will have an impact on the baking. I'm just curious about what is limiting the accuracy of control. -- Rick
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-11-21 19:06 +0000 |
| Message-ID | <n2qfau$h3o$1@dont-email.me> |
| In reply to | #9991 |
In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >On 11/21/2015 9:23 AM, Gordon Henderson wrote: >> 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 > >Yeah, that's a pretty huge difference. Seems like you have it working >pretty well. What are the units on the X axis, seconds? Mostly. I'm only sampling the data every second - the PID control loop is running 10 times/sec. >The algorithm seems to work rather well. I'm curious though why it >doesn't cycle on a more regular basis. It looks like it may actually be >the characteristics of the oven. It may also be that the stats. output is missing a lot of oven on/off cycles - they can be for as short a duration as 1/10 second while the stats. sampling is per second. I've measured a few other things in there too - the lag from turning the heater on to seeing it on the thermocouples is 5 seconds - when the oven is empty. Stick a few kilos of water in it (in the form of bread, cakes, etc.) and things really slow down. You can also see in the graphs when I open & close the door - when closing, there is a spike then it falls again - I'm assuming the spike is take up by the fabric of the oven giving a boost to the heater before it runs out of capacity. My other ovens have a much greater storage heater effect, so when I get round to putting thermocouples in them, it'll be interesting to see how they actually cope when I throw 12Kg of dough into them... > I can find a number of spots where the >power is on for a longer period and the temperature actually drops for >the first half of it, then finally rises, but to more than the set >temperature. I suppose the heat circulation is chaotic. Or is there a >level of noise in the temperature measurement? I see in the periods >when the heater is on for an extended time there is a lot of noise. When the oven is in a steady state - ie. with the power on, fan on, but heater off, the readings from the thermocouples are more or less constant. There is the possibility of electrical noise when the heater is on - but its just a resistive element, so hard to see how that could generate any - however it might be worth while sticking a scope on a thermocouple to see. Running my monitor program now - gordon @ beaky-pi$ sudo ./monitor 249, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 247, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 248, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 249, 252, 258, 0, 253, 0 249, 252, 258, 0, 253, 0 249, 252, 258, 0, 253, 0 249, 252, 258, 0, 253, 0 249, 252, 258, 0, 253, 0 250, 252, 258, 0, 253, 0 250, 252, 258, 0, 253, 0 250, 252, 257, 0, 253, 0 250, 252, 257, 0, 253, 0 250, 252, 257, 0, 253, 0 250, 252, 257, 0, 253, 0 249, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 249, 252, 257, 0, 252, 0 That's running at 10/sec. the first 3 columns are the thermocouples - the column of mostly 252's is the average of the 3 thermocouples. (All temp * 10°C) >Given that your control is only on/off, why do you feel the need for a >PID controller? Because I can. I could treat the heater as a very slow PWM though - currently the minimum on period is 10th second, but I do wonder if the electrickery people would whinge about that.. It's also a test-bed for some other stuff I want to do. Next on the bakehouse front is a retarder/proofer... This is an insulated box that can be cooled down to about 4°C kept at a relatively high level of humidity and then at a set time heated up to about 28°C. This is to control bread dough development. I have the bits, just need to make the box.... And stick another Pi on it. I have this vision of a Pi on every device in the bakehouse - including the mixers, but there's a limit to just how lazy you really want to be :-) > I would think just a simple measurement of the >temperature compared to the set point would do a good job. Which is what the mechanical one does. (although with more hysteresis than I think is good for it) > The only >thing I can think of that might improve the temperature profile would be >to anticipate how much heat is in the heating element to limit >overshoot. With your current PID controller, I expect the overshoot is >due to the I term in the controller. If you eliminate that the only >remaining overshoot will be from the thermal mass of the heating >element. So an I term could be used to anticipate the heat in the >element and added to the measured temperature (or subtracted from the >set point) to allow for the ultimate rise in temperature. But all this >would likely be icing on the cake (pun intended). Indeed - I've run through some "quick & dirty" tuning, but proper tuning takes time. I'll do it one day, but its good enough for now. >Clearly you have reached a point that optimizes the temperature control >as much as will have an impact on the baking. I'm just curious about >what is limiting the accuracy of control. I think its simply that its a cheap oven. The fan sucks air in from the cavity and sends it back into the cavity via a slit at the top and 4 vents that point downwards. (The bottom shelf is actually hotter than the top!) My suspicion is that this was just made up at the time without any air flow analysis - which would cost more money. This oven was £195. The ones they use in Bake-Off cost £1200 more and do have digital controllers... Gordon
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-11-21 20:52 -0500 |
| Message-ID | <n2r708$6j1$1@dont-email.me> |
| In reply to | #9994 |
On 11/21/2015 2:06 PM, Gordon Henderson wrote: > In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >> On 11/21/2015 9:23 AM, Gordon Henderson wrote: >>> 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 >> >> Yeah, that's a pretty huge difference. Seems like you have it working >> pretty well. What are the units on the X axis, seconds? > > Mostly. > > I'm only sampling the data every second - the PID control loop is running > 10 times/sec. I'm not sure why you would run the two at different rates. Do you know why? >> The algorithm seems to work rather well. I'm curious though why it >> doesn't cycle on a more regular basis. It looks like it may actually be >> the characteristics of the oven. > > It may also be that the stats. output is missing a lot of oven on/off > cycles - they can be for as short a duration as 1/10 second while the > stats. sampling is per second. I seriously doubt your controller will have many cycles much faster than your temperature sample rate. > I've measured a few other things in there too - the lag from turning the > heater on to seeing it on the thermocouples is 5 seconds - when the oven > is empty. Stick a few kilos of water in it (in the form of bread, cakes, > etc.) and things really slow down. You can also see in the graphs when > I open & close the door - when closing, there is a spike then it falls > again - I'm assuming the spike is take up by the fabric of the oven > giving a boost to the heater before it runs out of capacity. My other > ovens have a much greater storage heater effect, so when I get round > to putting thermocouples in them, it'll be interesting to see how they > actually cope when I throw 12Kg of dough into them... I think you are confusing lag time with rate of temperature change. The amount of thermal mass (the bread) will affect the rate of change of the oven temperature, but not much the lag time. I expect the lag time is mostly the few seconds it takes for the heating element to warm up once power is turned on. Even though electrical power is applied to the burner, it won't make significant heat in the oven until the element temperature has risen significantly above the oven temperature. The temperature spikes you see on opening the oven door is because of the inrush of cool air cooling the thermocouple. Once the door is closed the air is heated quickly to the oven temperature. I've never been convinced the oven temperature in the first few minutes matters so much. If the dough is cool, the delta temperature won't be so much different if the oven cools some trying to heat the bread. There is still a couple of hundred degrees difference. If the oven recovers in 5 or 10 minutes I expect it to have little impact on the bread while it is coming up to temperature itself. If your oven can't return to temperature after a few minutes, that's a different matter. >> I can find a number of spots where the >> power is on for a longer period and the temperature actually drops for >> the first half of it, then finally rises, but to more than the set >> temperature. I suppose the heat circulation is chaotic. Or is there a >> level of noise in the temperature measurement? I see in the periods >> when the heater is on for an extended time there is a lot of noise. > > When the oven is in a steady state - ie. with the power on, fan on, but > heater off, the readings from the thermocouples are more or less constant. > There is the possibility of electrical noise when the heater is on - but > its just a resistive element, so hard to see how that could generate any - > however it might be worth while sticking a scope on a thermocouple to see. > > Running my monitor program now - > > gordon @ beaky-pi$ sudo ./monitor > 249, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 247, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 248, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 249, 252, 258, 0, 253, 0 > 249, 252, 258, 0, 253, 0 > 249, 252, 258, 0, 253, 0 > 249, 252, 258, 0, 253, 0 > 249, 252, 258, 0, 253, 0 > 250, 252, 258, 0, 253, 0 > 250, 252, 258, 0, 253, 0 > 250, 252, 257, 0, 253, 0 > 250, 252, 257, 0, 253, 0 > 250, 252, 257, 0, 253, 0 > 250, 252, 257, 0, 253, 0 > 249, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > 249, 252, 257, 0, 252, 0 > > That's running at 10/sec. the first 3 columns are the thermocouples - > the column of mostly 252's is the average of the 3 thermocouples. (All > temp * 10°C) They seem pretty noise free. >> Given that your control is only on/off, why do you feel the need for a >> PID controller? > > Because I can. Yes, this shows a keen insight to the nature of the PID algorithm... or maybe not. ;) > I could treat the heater as a very slow PWM though - currently the > minimum on period is 10th second, but I do wonder if the electrickery > people would whinge about that.. If you want to treat it as a PWM, then you need to PWM your output, not turning it on an off at relatively random periods. I am sure you can get better control of the temperature without the PID controller. The integral term of the PID controller creates overshoot and results in a ripple in the temperature. As I said before, a simple on/off control based on temperature will give you great control. Overshoot from the thermal mass of the heating element can be reduced by using an anticipater term. Controlling the on/off burner state directly from the temperature will in effect give you PWM control of the burner much like the ADC in a sigma-delta converter. > It's also a test-bed for some other stuff I want to do. Next on the > bakehouse front is a retarder/proofer... This is an insulated box that can > be cooled down to about 4°C kept at a relatively high level of humidity > and then at a set time heated up to about 28°C. This is to control bread > dough development. I have the bits, just need to make the box.... And > stick another Pi on it. > > I have this vision of a Pi on every device in the bakehouse - including > the mixers, but there's a limit to just how lazy you really want to be :-) > >> I would think just a simple measurement of the >> temperature compared to the set point would do a good job. > > Which is what the mechanical one does. (although with more hysteresis > than I think is good for it) Clearly the mechanical thermostat has more hysteresis than you want. Otherwise it is all you need to get optimal temperature control. PID is for controlling devices that have a range of settings, not so much for on/off devices like heaters. If you want to learn more about this aspect, try discussing this in sci.electronics.design. There are a lot of folks there with lots of controller experience including heaters. >> The only >> thing I can think of that might improve the temperature profile would be >> to anticipate how much heat is in the heating element to limit >> overshoot. With your current PID controller, I expect the overshoot is >> due to the I term in the controller. If you eliminate that the only >> remaining overshoot will be from the thermal mass of the heating >> element. So an I term could be used to anticipate the heat in the >> element and added to the measured temperature (or subtracted from the >> set point) to allow for the ultimate rise in temperature. But all this >> would likely be icing on the cake (pun intended). > > Indeed - I've run through some "quick & dirty" tuning, but proper tuning > takes time. I'll do it one day, but its good enough for now. Tuning the PID won't help much. It is just the wrong algorithm, or I should say, not the optimal algorithm. At least that is my experience. >> Clearly you have reached a point that optimizes the temperature control >> as much as will have an impact on the baking. I'm just curious about >> what is limiting the accuracy of control. > > I think its simply that its a cheap oven. The fan sucks air in from the > cavity and sends it back into the cavity via a slit at the top and 4 vents > that point downwards. (The bottom shelf is actually hotter than the top!) > My suspicion is that this was just made up at the time without any air > flow analysis - which would cost more money. This oven was £195. The ones > they use in Bake-Off cost £1200 more and do have digital controllers... > > Gordon > -- Rick
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-11-22 10:11 +0000 |
| Message-ID | <n2s4da$etd$1@dont-email.me> |
| In reply to | #9997 |
In article <n2r708$6j1$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >On 11/21/2015 2:06 PM, Gordon Henderson wrote: >> In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>> On 11/21/2015 9:23 AM, Gordon Henderson wrote: >>>> In article <7c93852555.jim@abbeypress.net>, >>>> Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >>>> >>>>> Here, the project went onto the proverbial back burner for a while, >>>>> but it's heating up again. I wonder if Gordon or others have gone >>>>> further with it in the meantime and might have further wisdom to >>>>> impart. >>>> >>>> Ah, I'd almost forgotten about this too - however the oven is Pi >>>> controlled and working really well. The PID still needs some fine >>>> tuning, but for now it's good. >>>> >>>> Here is a graph of the oven under the existing capillary tube thermostat: >>>> >>>> http://unicorn.drogon.net/beaky2.png >>>> >>>> The three lines are 3 thermocouples - 2 are at the left back and right >>>> back, the 3rd (blue trace) is at the front. (All at the top, clipped to >>>> the grill element which is not functional) That was with the oven set >>>> to 180°C. The first dip is when I opened the door to stick a cake in, >>>> the others are when I checked it. >>>> >>>> This: >>>> >>>> http://unicorn.drogon.net/beaky-rye3.png >>> >>> Yeah, that's a pretty huge difference. Seems like you have it working >>> pretty well. What are the units on the X axis, seconds? >> >> Mostly. >> >> I'm only sampling the data every second - the PID control loop is running >> 10 times/sec. > >I'm not sure why you would run the two at different rates. Do you know >why? Yes. I wrote the program, so I know exactly why. Gordon
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-11-22 10:47 -0500 |
| Message-ID | <n2snud$l0l$1@dont-email.me> |
| In reply to | #9998 |
On 11/22/2015 5:11 AM, Gordon Henderson wrote: > In article <n2r708$6j1$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >> On 11/21/2015 2:06 PM, Gordon Henderson wrote: >>> In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>>> On 11/21/2015 9:23 AM, Gordon Henderson wrote: >>>>> In article <7c93852555.jim@abbeypress.net>, >>>>> Jim Nagel <jimnewsm13c@abbeypress.co.uk> wrote: >>>>> >>>>>> Here, the project went onto the proverbial back burner for a while, >>>>>> but it's heating up again. I wonder if Gordon or others have gone >>>>>> further with it in the meantime and might have further wisdom to >>>>>> impart. >>>>> >>>>> Ah, I'd almost forgotten about this too - however the oven is Pi >>>>> controlled and working really well. The PID still needs some fine >>>>> tuning, but for now it's good. >>>>> >>>>> Here is a graph of the oven under the existing capillary tube thermostat: >>>>> >>>>> http://unicorn.drogon.net/beaky2.png >>>>> >>>>> The three lines are 3 thermocouples - 2 are at the left back and right >>>>> back, the 3rd (blue trace) is at the front. (All at the top, clipped to >>>>> the grill element which is not functional) That was with the oven set >>>>> to 180°C. The first dip is when I opened the door to stick a cake in, >>>>> the others are when I checked it. >>>>> >>>>> This: >>>>> >>>>> http://unicorn.drogon.net/beaky-rye3.png >>>> >>>> Yeah, that's a pretty huge difference. Seems like you have it working >>>> pretty well. What are the units on the X axis, seconds? >>> >>> Mostly. >>> >>> I'm only sampling the data every second - the PID control loop is running >>> 10 times/sec. >> >> I'm not sure why you would run the two at different rates. Do you know >> why? > > Yes. I wrote the program, so I know exactly why. Can you explain? -- Rick
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| From | Gordon Henderson <gordon+usenet@drogon.net> |
|---|---|
| Date | 2015-11-22 18:17 +0000 |
| Message-ID | <n2t0qs$qim$1@dont-email.me> |
| In reply to | #9999 |
In article <n2snud$l0l$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >On 11/22/2015 5:11 AM, Gordon Henderson wrote: >> In article <n2r708$6j1$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>> On 11/21/2015 2:06 PM, Gordon Henderson wrote: >>>> In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>>>> On 11/21/2015 9:23 AM, Gordon Henderson wrote: >>>>>> 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 >>>>> >>>>> Yeah, that's a pretty huge difference. Seems like you have it working >>>>> pretty well. What are the units on the X axis, seconds? >>>> >>>> Mostly. >>>> >>>> I'm only sampling the data every second - the PID control loop is running >>>> 10 times/sec. >>> >>> I'm not sure why you would run the two at different rates. Do you know >>> why? >> >> Yes. I wrote the program, so I know exactly why. > >Can you explain? Yes. Gordon
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2015-11-22 13:51 -0500 |
| Message-ID | <n2t2ms$2ff$2@dont-email.me> |
| In reply to | #10000 |
On 11/22/2015 1:17 PM, Gordon Henderson wrote: > In article <n2snud$l0l$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >> On 11/22/2015 5:11 AM, Gordon Henderson wrote: >>> In article <n2r708$6j1$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>>> On 11/21/2015 2:06 PM, Gordon Henderson wrote: >>>>> In article <n2q3oc$174$1@dont-email.me>, rickman <gnuarm@gmail.com> wrote: >>>>>> On 11/21/2015 9:23 AM, Gordon Henderson wrote: >>>>>>> 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 >>>>>> >>>>>> Yeah, that's a pretty huge difference. Seems like you have it working >>>>>> pretty well. What are the units on the X axis, seconds? >>>>> >>>>> Mostly. >>>>> >>>>> I'm only sampling the data every second - the PID control loop is running >>>>> 10 times/sec. >>>> >>>> I'm not sure why you would run the two at different rates. Do you know >>>> why? >>> >>> Yes. I wrote the program, so I know exactly why. >> >> Can you explain? > > Yes. Ok, if you decide you'd like to learn rather than obfuscate, I gave you the group where you can learn things. -- Rick
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