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Thread: Digital Silvia. Er... Sort of

  1. #1
    Senior Member robusto's Avatar
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    Digital Silvia. Er... Sort of

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Miss Silvia has a digital thermometer. But not for long. An hour long in fact.

    The small digital multimeter stuck with blue tack to the wall behind her was hardly aesthetic. There was the yellow k-type thermocouple wire, and the two probes from the DMM connected to the T/c spades. *

    And since the DMM has no thermometer function, voltage readings (from around 1.0 to 4.7) had to be converted to degreesC.

    Its the thermometer you have when you havent got a digital thermometer. The mental gymnastics of converting volts to degrees was turning coffee making a chore.

    So, after much unsuccessful internet searching, yesterday I dropped in to Jaycar and bought a neat digital thermometer, about the size of a matchbox, *with its own probe, and high/low alarms.

    Mmmm, set the alarm for 95C and when it beeps, brew.

    Nope. The thermometer is too slow to respond to quickly changing conditions in that 300ml brass boiler. *It could be as much as 30secs to 60 secs behind reality. *

    It goes back to the shop today, and the $40 will instead be spent on a DMM with thermometer function (complete with k-type thermocouple). Thatll be the 4th multimeter here, not including 3 analogue ones.

    The blue-tack set up, however, has been great to evidence what is going on in the machine...temperature rise and falls, when it happens, and so on. *It proved at a glance that what is suspected of happening actually does. *

    -Robusto

  2. #2
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    Re: Digital Silvia. Er... Sort of

    Yep, Ive got the same one. I agree that it responds far too slowly. Apparently the SS tip can be removed so that the bead probe sits directly on top of the boiler in a puddle of heat transfer goop. Ill either PID my silvia or give that a shot after exams.

    For the moment, going by rate of change and actual temperature isnt too bad. I think that someone drew an analogy with getting on a train:

    Stock silvia = standing on the tracks, blindfolded, waiting for the train to hit you
    Temperature surfing = jumping blindfolded from a bridge
    Thermometer = jumping from a bridge without a blindfold
    PID = getting into the first-class carriage at the platform, where your private butler greets you with champagne and caviar

    Id love to hear which multimeter you end up getting. Does jaycar also have k-type probes?

    Cheers,

    Luca

  3. #3
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Yes, very good analogy, Luca. Each coffee shot reminds me of my secondary school years where we did science experiments and noted the data. A particular nightmare was the continuous-flow calorimeter experiment. I could see no use for such knowledge then...but it stood me in good stead for coffee thermodynamics now (much later).

    With each shot theres some sort of physics experiment going on, but not having testing equipment is really trying to be scientific while working blindfolded and having blind faith too.

    Just got back from Jaycar, with a new DMM: The cheapest they had ($40) with a thermometer function. It is a Digitech QM 1320 and seems to be working OK. It does the usual stuff and more, like transistor testing.

    Still using the $10 Dick Smith t/c with new DMM. Its stuck to the side of the boiler with some very humble masking tape as used for house painting.

    A PID would be ideal, but this morningI got a a quote from Onetemp (Australia) as follows:
    PID $294; thermocouple $33; SS relay $34. With GST, thats $397. Not willing to spend that much.

    -Robusto


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    Re: Digital Silvia. Er... Sort of

    400 bucks, thats a bit steep. But for the red carpet treatment it may be worth it. Bit of a chunk just to spend on making your machine maintain a certain temperature. Whatever floats your boat.

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    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Its not the affordability, but the principle of whether I want to spend another $400. And I dont think I want to part with that much. Much less than half that amount would begin to tempt me.

    They say theyll do cheaper than $295 + GST for PIDs if bought in lots of 5.

    The $33 thermocouple has PVC rated to 100C ....but my $10 Dick smith one seems to be doing the job at 1/3 the price.

    The $34 SSR is rated 240V and 40 Amp. Thats very reasonable compared to many USA ones specified with the Ebay PIDS, where the volts can be 24 only and the amps either 3 or even milliamps. A 1100 watt Silvia boiler will draw about 4.8 amps.

    Buying one on Ebay is fraught with dangers. Most--if not all-- will NOT handle coffee machine electrical currents.


    When Silvia stabilises in temperature, Ill take some readings suitable for temperature surfing and post them later on.

    Robusto

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    Re: Digital Silvia. Er... Sort of

    Try and speak to Ron Fowler at Onetemp. He quoted me $120 for a PID controller (plus GST). He also gave me some thermocouple wire (I prefer the $10 K-type bead thermocouple from Dick Smith). The $30 for a SSR is about right. Should come to under or about $200.

    For the PID controller, you have to go for the basic model. Forget fuzzy logic, you dont need it. All you need is a PID controller with an autotune function, so that it can guess the PID parameters. Mal on this forum got his PID setup from onetemp, and Im sure it cost him less than $200 for the whole kit.

    If you contract Ron, just tell him its for a project to temperature stabilize your coffee machine. Hes heard that all before from me and Mal and probably others, so that should put him in the correct frame of mind.



    The other source is ebay. I got all my gear from ebay, but you have to be careful what you bid on. The PID controller I got had relay outputs. I modded it to drive a SSR, but the relay clicking is driving me nuts. So Im going to remove the relay from the controller and bridge the relay driving signal to the output. That will give me a silent 5V signal to drive the SSR. So a bit of stuffing around and for only a modest saving compared to the Onetemp device (plus the Onetemp device is much smaller than the one I got).

    Its a fun project. Goodluck.

    Mark.




  7. #7
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Yes, Sparky, that clicking--- every couple of seconds, is it?---would be annoying, especially if you leave your machine on for several hours.

    Thanks for the advice, I only emailed Onetemp asking their recommendation for the gear, but speaking would probably be more productive if I go down that path.

    As you say, dont need fuzzy logic, but an auto-tune would be desirable, especially with such a small, 300 ml mass to heat where overshooting cant be helped otherwise.

    So far, Ive taken readings showing wild fluctuations ranging from 87 - 95C (heat on) to
    96-102 (light off), with overshooting then continuing to 107.

    Robusto

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    Re: Digital Silvia. Er... Sort of

    The clicking didnt sound too bad. I got used to it. I even used to just listen to the sound and know when my boiler had hit steady-state. But my wife hated it and would make me turn the machine off as soon as Id made my coffee...

    Ron at Onetemp said hed sell at OEM prices to us coffee hobbyists, so you really have to get on the phone to get those prices.

    As for the wild fluctuations in the Silvia. Yep Ive seen them as well. One of the biggest sources of fluctuation with these single boiler machines is the element switching on and off. When run with a thermostat, the temperature swings are huge, but also there are convective currents set up during the heating phase. These currents take a while to damp out after the element has turned off. While theyre on and churning, the boiler temperature can be very erratic. I found that 1-2 minutes after the element switched off, the temperatures settled down and the Silvia started producing flatter temperature profiles. When you install a PID, you effectively stabilize the entire boiler system and you no longer have these wild convective currents. Therefore you can brew at any time and get good results. So its not just temperature settability, it also gives you enhanced stability. Its really worth it.

    cheers,

    Mark.

  9. #9
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Had a chat with Ron Fowler at Onetemp in Brisbane, but while he was very helpful, a PID remains too high.

    He quoted $180 plus GST, for the PID, $31 for the SSR. Plus $15 for posting if it cant be picked up.

    Keep a-looking, Maria.

    -Robusto

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    Re: Digital Silvia. Er... Sort of

    All this talk about PIDing a Silvia is making me drool...is the only option for a PID a brand new one? Should I be searching the wreckers for cruise control computers and other industrial equipment?

    I might wait until the warranty expires first before I tinker. ;)


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    Re: Digital Silvia. Er... Sort of

    For reference, it would seem the temp variation at idle is similar on other machines as well.

    I have a multimeter with an rs232 datalogging capability and the results on machines I tested were -

    Rancillio Silvia 21 degrees *
    Vibiemme Domobar 16 degrees
    Sunbeam Ristretto 18 degrees

    Ive succesfully modded all three with my project electronic controller and reduced them all to 1-2 degrees variation.

    My next attempt will be trying a PID algorithm in the microcontroller and use a SS relay to see if I can produce a PMPID (Poor Mans PID!). *

    Robusto - do you have the probe on top of the boiler of halfway up the side?

  12. #12
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Matt, any modifications during or after warranty should be such that components are readily removed without trace. No drilling holes, and original parts left in situ.

    Ive read about domestic computers being utilised to controll coffee machines and roasters. Im no expert, but I cant see why youd need much more than a readily downloadable algorithm program, an interface, the usual SSR, and perhaps a dedicated spare computer (and bench space for it in the kitchen).

    Robusto

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    Re: Digital Silvia. Er... Sort of

    Unfortunately bench space in the kitchen is prime real estate. If I take up any more it could end in divorce :-/

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    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    LW, the readings were taken with the thermocouple halfway down the boiler to the left of the water inlet.

    -Robusto


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    Re: Digital Silvia. Er... Sort of

    Quote Originally Posted by LW link=1130885499/0#10 date=1130976691
    Ive succesfully modded all three with my project electronic controller and reduced them all to 1-2 degrees variation.

    My next attempt will be trying a PID algorithm in the microcontroller and use a SS relay to see if I can produce a PMPID (Poor Mans PID!). *
    Youve aroused my interest. What is the project electronic controller youve employed? Is it cost effective compared to the $300-odd PIDs? Details appreciated.

    -Robusto

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    Re: Digital Silvia. Er... Sort of

    Quote Originally Posted by robusto link=1130885499/0#14 date=1131004257
    Quote Originally Posted by LW link=1130885499/0#10 date=1130976691
    Ive succesfully modded all three with my project electronic controller and reduced them all to 1-2 degrees variation.

    My next attempt will be trying a PID algorithm in the microcontroller and use a SS relay to see if I can produce a PMPID (Poor Mans PID!). *
    Youve aroused my interest. What is the project electronic controller youve employed? *Is it cost effective compared to the $300-odd PIDs? *Details appreciated.

    -Robusto
    See this thread for more info -

    http://coffeesnobs.com.au/YaBB.pl?num=1129537928

  17. #17
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Thanks, LW.....I thought it all looked familiar. We seem to be going round in circles!

    The confusion arose because the original thread about the controller was posted by Croweater.

    I asked Croweater for details....and didnt notice they were supplied by your good self, LW.

    Which begs the question: Is Croweater and LW one and the same?

    Robusto

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    Re: Digital Silvia. Er... Sort of

    Hi Robusto
    LW & croweater are not one in the same - the initial thread that I started was answered by LW because Lindsay & LW are one in the same.
    Sorry for the confusion but LW made the controller for me. That made him more qualified than I to answer the questions for you.
    I live in SA hence Croweater, LW in VIC and we are family.
    I have been using the Silvia with the controller and yes I am bias towards family but I believe LW has done a great job with his economical device.
    The Silvia is on a timer set for 6am so as to when I get out of bed in the morning I have confidence that I can go to Miss Silvia and not worry about the wild Temp variations but grind lock and load and extract at the Temp set.
    As I am sure you would appreciate not having to wonder with you are going to get a sour cup or bitter from the original thermostat is a major improvement.
    I hope this clears the confusion for you.

    Croweater

  19. #19
    Senior Member robusto's Avatar
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    Re: Digital Silvia. Er... Sort of

    Behmor Brazen - $249 - Free Freight
    Situation clarified, thanks, Croweater. Yes, LW did a great job with the controllers.

    Robusto



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