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Discussions > Espresso > Espresso Mods > New Silvia...  
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philipmc
Senior Member


Joined: 4 Oct 2011
Posts: 32
Location: Singapore
Expertise: I love coffee

Espresso: Silvia
Grinder: Rocky
Posted Fri Dec 30, 2011, 5:35am
Subject: New Silvia Project - what would you add?
 

Hi,

I am planning to build a custom control setup for my silvia v3. I plan to go full electronic control, while still keeping the front buttons functioning the same. The setup will run from a remote control and have a screen to display menus and status.

I love my coffee, but have a lot to learn. So I'd like your input to know which of these features are essential, which are nice to have and which are a waste of time. Also, are there other features that you would want (the sky is the limit).

List of proposed features:
(1) PID control of boiler for brewing
(2) PID control for steam
(3) Configurable pre-infusion timer
(4) Temperature monitoring for
     (a) Boiler
     (b) Group head
     (c) Top of case (where you put the cups)
     (d) steam wand
     (e) reservoir water
(5) clock with timer function to warm up the machine
(6) buzzer to indicate when the machine is up to temperature
(7) quick presets for particular beans/brews
(8) calibration mode for sensors, for complete accuracy
(9) water level indicator (and alarm) - expensive
(10) water pressure sensor - expensive

So ideally, please reply along the lines of:
  Essential : 1,2,3,4,5
  Nice to have : 6,7,8
  Waste of time : 9,10
  Extra features : bluetooth pairing for control from iPhone
etc.

Many thanks,
Philip
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takeshi
Senior Member
takeshi
Joined: 12 Oct 2002
Posts: 1,015
Location: Houston
Expertise: I live coffee

Espresso: Alex Duetto 3.0
Grinder: Super Jolly
Roaster: Amaya Roasting
Posted Fri Dec 30, 2011, 7:14am
Subject: Re: New Silvia Project - what would you add?
 

Highly subjective.  At this stage, I'd consider it all a waste of time as I'm looking to upgrade from an SBDU and think that any money spent on attempting to improve the Silvia would be better spent on an upgrade to HX or DB.  Silvia currently starts out expensive as it is.
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philipmc
Senior Member


Joined: 4 Oct 2011
Posts: 32
Location: Singapore
Expertise: I love coffee

Espresso: Silvia
Grinder: Rocky
Posted Fri Dec 30, 2011, 7:51am
Subject: Re: New Silvia Project - what would you add?
 

takeshi Said:

Highly subjective.  At this stage, I'd consider it all a waste of time as I'm looking to upgrade from an SBDU and think that any money spent on attempting to improve the Silvia would be better spent on an upgrade to HX or DB.  Silvia currently starts out expensive as it is.

Posted December 30, 2011 link

Half the fun is taking the ideas, evolving them and then building it. Plus I like the design simplicity and elegance of the Silvia. I'm committed to this project.
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 8,034
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Fri Dec 30, 2011, 9:46am
Subject: Re: New Silvia Project - what would you add?
 

Do as you wish, I can think of much better platforms for your quest than Silvia but please do, by all means, modify to your hearts content.

Remember though, each bean, at each stage of aging, and depending on the grind will be entirely different than the next time you buy it. It sounds like you want to make an externally controlled  Super Automatic from a Silvia. Super Autos, excel at ease of use but fall far short of being able to cope with all the subtle changes that need to be taken into account every time you pull a shot.

You make no mention of the grinder you plan to use, the grinder is MORE important than the espresso machine so you need to take that into account too.

Computers are great but you will never get one that can match the hand of a barista who knows what they are doing.

Just saying.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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JGG
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JGG
Joined: 31 Mar 2006
Posts: 1,385
Location: Kentucky, US
Expertise: I like coffee

Espresso: PID Silvia; PID Alexia
Grinder: Mazzer SJ
Roaster: Hottop D w/HTC+TC4C
Posted Fri Dec 30, 2011, 10:01am
Subject: Re: New Silvia Project - what would you add?
 

I would do these for sure:
(1) PID control of boiler for brewing
(2) PID control for steam (but either use ON/OFF control or a very high proportional gain)
(4) Temperature monitoring for
     (a) Boiler
     (b) Group head

I would consider these nice to have, but at a lower priority:
(5) clock with timer function to warm up the machine
(9) water level indicator (and alarm) - expensive
(10) water pressure sensor - expensive
bluetooth pairing for control from iPhone

I would scrap these:
(3) Configurable pre-infusion timer
(4) Temperature monitoring for
     (c) Top of case (where you put the cups)
     (d) steam wand
     (e) reservoir water
(7) quick presets for particular beans/brews
(8) calibration mode for sensors, for complete accuracy (do this before installation)

I would pay extra to have this feature removed:
(6) buzzer to indicate when the machine is up to temperature

Jim
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rsinger
Senior Member
rsinger
Joined: 25 Jan 2008
Posts: 188
Location: Boca Raton, Florida
Expertise: I like coffee

Espresso: Bezzera Strega
Grinder: OE Pharos - #136!!  ;)
Posted Sat Dec 31, 2011, 3:56pm
Subject: Re: New Silvia Project - what would you add?
 

Hi Philip:


You're in for a lot of fun!  The Silvia platform is great to modify and you've got several great ideas to play with.  I'm sure you've seen what others have done before you, but just in case you may have missed it, I'll point you in the direction of the thread here outlining a couple of approaches using the Arduino microprocessor as a basis for achieving electronic control.  Coffeegeek Thread: New Silvia Mods - Wii Nunchuck, Clock, PID, Water Level Alarm, and my blog: Silvia and Arduino outlining the mods that I made.  When you get there, let me know if you'd like any of my code.  At the time that I did the mods to my machine, the available memory in Arduino was extremely limited, now however, there is much more available, opening the door for including programing for all of the functions you are interested in.

I'd recommend, as long as you will have real-time clock functionality (and presumably some sort of LCD to read your menus and settings), to include a re-settable shot timer that starts and stops with activation and shut off of the brew button.  I particularly enjoyed that option.

Good luck...  keep us posted.

Best,

Rick

 
New Bezzera Strega
OE Pharos: #136!!
Silvia's a virgin.....  again! (and sold)
Brasilia Cappuccino Del-1 Hx (sold too)
http://www.flickr.com/photos/66189160@N04/sets/72157628015297112/show/
http://espressoproject.blogspot.com/2008_10_01_archive.html
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philipmc
Senior Member


Joined: 4 Oct 2011
Posts: 32
Location: Singapore
Expertise: I love coffee

Espresso: Silvia
Grinder: Rocky
Posted Sun Jan 1, 2012, 6:36am
Subject: Re: New Silvia Project - what would you add?
 

Hi Rick,

Your project and the twisted affair are indeed part of my inspiration for my own project. Thank you immensely for your kind offer of help. I am indeed planning to prototype using an Arduino also. I've got some of the components, so the IR remote, and 16x2 LCD and thermistor setup are working well. Just waiting for the other components to arrive (especially the thermocouple and digital interface breakout!).

One item I'm struggling a little with is the SSR. I noticed your parts list contains three? I was thinking of using just one, supplying the element with all the logic built into the arduino. Have I overlooked something and oversimplified?

I have a few more questions about SSR selection too. Here's a typical spec sheet:
Click Here (docs-asia.electrocomponents.com)
  • the input impedance is listed as <20mA. It's therefore ok to drive direct from an Arduino digital pin, right?
  • the rated output current is quite low without a heatsink, and drops with temperature. Given it's going to be inside the case, other than thermal material and heatsinking it to a machine panel, is there anything to help prevent meltdown? How much heat do these items generate?
  • what happens if they overheat?
  • how frequently do you switch on/off? I see these are rated at 10Hz max.

Many thanks in advance. =)
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rsinger
Senior Member
rsinger
Joined: 25 Jan 2008
Posts: 188
Location: Boca Raton, Florida
Expertise: I like coffee

Espresso: Bezzera Strega
Grinder: OE Pharos - #136!!  ;)
Posted Sun Jan 1, 2012, 10:51am
Subject: Re: New Silvia Project - what would you add?
 

Hi Philip:


So, to begin with, my parts list shows 3 SSR's because I just wanted people to have an accurate idea of the costs involved, what i mean is, I was able to order all three on eBay for the price shown, but only one was used in the project, and as you suggest, all of the logic was built into Arduino.  Yes, you can run the control side of most typical 25A load SSR's directly from the Arduino digital (or analog) pin without any problems whatsoever.  Lastly, I did not find any need for a heat sink, if you notice that I mounted the SSR directly on the wall that supports the 3-way valve (behind the front panel that is behind the group head), I think I may have even put a bit of heat conducting paste between the back of the SSR and the SS panel, in effect acting like a heat sink.  I really don't know what happens if the SSR over heats, because it never happened.  

Regarding how fast the SSR switches on and off, this is a direct function of the PID algorithm that you write, and how close to the set temp you are on the heating curve. At one time I had saved digital time/temperature plots of the PID response curves that I used for tuning the PID parameters, but I have since switched computers, and can no longer find one with good resolution, I've attached the low res one that I could find easily, but suffice it to say, that the temperature recovery after a shot, begins with 100% heater power, then as the temperature rise accelerates, and as the temperature approaches the set temp, the ideal response is where the curve is asymptotic relative to the set temp (i.e., it is most efficient, if your time/temp curve approaches the set temp without any oscillation above and below the set temp, but just approaches it directly and becomes tangent to it).  In order for this to occur, the rate of adjustment of the PID algorithm (and hence the frequency of firing of the SSR) will increase with some diminishing fraction of full power as the temp gets closer and closer to the set temp.  To make a long story short, the firing frequency of the SSR is not the limiting factor in the process, rather it is hysteresis and the lag in the heating element; that said, however, with careful attention to the PID parameters you set, you will easily get a response that rivals or exceeds that of most commercial PID's.

I hope that this information has been helpful.

p.s. - In the plot below, the upper horizontal line is the steam set temp, the lower horizontal line is the brew set temp, the curve is real-time time/temp response (the width of each box on the x-axis, i.e. horizontal scale, is  60 sec, so from beginning of shot to recovery to brew temp is 75-80 sec, btw, the vertical scale is such that each vertical box is 50 F).  Also, I just want to mention, that I really am happy to help or answer any questions that I can, but starting Tuesday, real life begins again, and my schedule is incredibly crazy, so although I'll try my best, my answers may not come as quickly as they did this week :)  Keep up the good work, it's a fun project!

Best,

Rick

rsinger: Time : Temp .jpg
(Click for larger image)

 
New Bezzera Strega
OE Pharos: #136!!
Silvia's a virgin.....  again! (and sold)
Brasilia Cappuccino Del-1 Hx (sold too)
http://www.flickr.com/photos/66189160@N04/sets/72157628015297112/show/
http://espressoproject.blogspot.com/2008_10_01_archive.html
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philipmc
Senior Member


Joined: 4 Oct 2011
Posts: 32
Location: Singapore
Expertise: I love coffee

Espresso: Silvia
Grinder: Rocky
Posted Sun Jan 1, 2012, 8:31pm
Subject: Re: New Silvia Project - what would you add?
 

Thanks again. I am considering trialling a different approach to getting up to temperature. Why not just have a continuous burst of heating based on the current temperature, ambient temperature and desired temperature?

Its been a while since I tackled any real mathematics and Ive never looked at thermal equations, but my reasoning goes along the lines of:

Constants:
Specific heat capacity of the boiler including water
Rate of heating when the element is on

Variables:
Rate of heat loss (depends on the ambient temperature) - guessing this is exponential based on the difference between the two temps

Ignoring heat loss (and phase change for steam) for a second, then I believe the energy needed to raise the temperature is linear. Say 1 second of heating for 5 degree C. So if we were at 70C and targeting 100C then we would need 30/5 = 6s of heat. Putting heat loss back in and well need to add a little extra heat to compensate. I was thinking of just using a lookup table based on measured values to top it up a little (though I could venture into the equations later). Once temperature is reached, then we could revert to a PID algorithm to keep it stable. If a shot/water is pulled then it would switch back into continuous burst mode to compensate.

How does that sound?

Any idea what the lag is between turning the element on and sensing the temperature change?

Im back to work tomorrow too, so this will once again become an evening project. =)
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rsinger
Senior Member
rsinger
Joined: 25 Jan 2008
Posts: 188
Location: Boca Raton, Florida
Expertise: I like coffee

Espresso: Bezzera Strega
Grinder: OE Pharos - #136!!  ;)
Posted Sun Jan 1, 2012, 9:11pm
Subject: Re: New Silvia Project - what would you add?
 

Phillip:

The problem with taking a linear approach to reaching a set "brew" temp is "thermal inertia" ( I=SQRT(krhoc) where k=thermal conductivity, rho = density, c = specific heat capacity, and (rhoc) = volumetric heat capacity) ... you'll always way overshoot the set temp, and once having done so, the only way to get back down is zero power to the heating element, having done so you are then dependent on conduction and radiation for cooling which is really slow and inefficient, and so not only is the response / recovery terrible, but so is the start up, there would tend to be large amplitude overshooting of the set temp, and long cooling times back down, over and over again, with smaller and smaller amplitudes until steady state was approached (or not).

Many industrial processes require temperature control, most are interested in energy / time/ production efficiency out of these concepts and the characteristics of thermal responses of heat sources (of all types) was born the concept of approaching as rapidly as possible, but cutting back in time so as not to overshoot the desired set temp, and if possible not oscillate around it, in other words to "titrate" the energy input to arrive precisely at the set temp....  this led to PID type algorithms and devices.  (a lot of people before us have "been there done that!"  But you are thinking creatively!  :)

Besides, sort of what you are describing is a crude PID without feedback control built in, or modulation of power to the heating element.  

Take a look at PID Without a PhD.

Best,

Rick

 
New Bezzera Strega
OE Pharos: #136!!
Silvia's a virgin.....  again! (and sold)
Brasilia Cappuccino Del-1 Hx (sold too)
http://www.flickr.com/photos/66189160@N04/sets/72157628015297112/show/
http://espressoproject.blogspot.com/2008_10_01_archive.html
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