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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 Sun Feb 12, 2012, 6:11am
Subject: Re: New Silvia Project - what would you add?
 

A touchscreen is certainly one way to go. Though the only implementations that I have seen use a lot of pins (possibly meaning I'd need to move from an Arduino Uno to a Mega) and are quite expensive in comparison to a straight TFT. Also a touchscreen behind the steam wand? Watch out!
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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 Feb 17, 2012, 4:26am
Subject: Re: New Silvia Project - what would you add?
 

The software is taking a little longer than expected and I've decided to prototype it out of the machine and then install it when complete.

Further progress:
- hooked it up to an apple remote with the following functions
 - left = change to graphing mode
 - right = change to display PID and Duty varliables
 - up = increase target temperature by 1C
 - down = decrease target temperature by 1C
- created a test rig using an SSR and extension lead. I plan to use a kettle and prove I can get the PID to control the temp to 80C
- tweaked the timer code to use a hardware timer to create even cycle pulses for heater control (ready for zero crossing SSR use).
- debugged and fixed issues with interrupts and pin conflicts with the TC4 board

It's up to 24k of the 32k limit for the board, but some of the

Other items to do
- simple display mode (no variables) for the non geek user (the missus!)
- write the variables to non volatile storage (keep the settings even if the power runs out)
- implement the PID control libraries
- write a menu screen and remote handler for setting PID variables and other settings
- case and install

Anything else worth adding?

I'm also curious about the settings for the SSR control and PID sampling frequency. Any experts out there? Should the PID sampling frequency match that of the PWM frequency? If I use a 0-100 duty cycle with 50Hz mains, then the PWM frequency is 0.5Hz or 2 seconds. I was planning to run PID sampling at 1Hz/every 1s. Any pros/cons?

Image of the graph display mode below...

philipmc: DSC03195.JPG
(Click for larger image)
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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 Feb 17, 2012, 4:27am
Subject: Re: New Silvia Project - what would you add?
 

Variables display mode (still some space, anything else useful to go here?)

philipmc: DSC03194.JPG
(Click for larger image)
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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 Feb 17, 2012, 4:33am
Subject: Re: New Silvia Project - what would you add?
 

Picture of the logic components and display:
L to R : Arduino Uno R3 (main processor and software), RC4 Shield (thermocouple handing and SSR control), Arduino Protoshield (TFT display header, IR remote receiver, interface for uSD card), 1.8 TFT display with uSD card slot on the reverse. Apple remote pictured below. The attached white wire is a type K thermocouple.
The boards stack one on top of another with the left on the bottom.

philipmc: DSC03197.JPG
(Click for larger image)
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patrickff
Senior Member


Joined: 15 Aug 2011
Posts: 36
Location: DC
Expertise: Just starting

Espresso: Silvia v2
Grinder: Baratza Vario
Drip: Aeropress
Posted Fri Feb 17, 2012, 2:14pm
Subject: Re: New Silvia Project - what would you add?
 

The graphs give the whole gig a high geek factor - which is not a bad thing.

Do you plan to interface the Arduino with the original switches (as input)?
Some examples:
  • Power switch - turns the PID on/off
  • Brew/Steam switch - sets different P,I,D values
  • Brew switch - shot timer, or a least starts a visual counter
    etc.
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JGG
Senior Member
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 Feb 17, 2012, 7:55pm
Subject: Re: New Silvia Project - what would you add?
 

philipmc Said:

I'm also curious about the settings for the SSR control and PID sampling frequency. Any experts out there? Should the PID sampling frequency match that of the PWM frequency? If I use a 0-100 duty cycle with 50Hz mains, then the PWM frequency is 0.5Hz or 2 seconds. I was planning to run PID sampling at 1Hz/every 1s. Any pros/cons?

Posted February 17, 2012 link

I think you'd have pretty good luck with either 1Hz or 0.5Hz.  At 50Hz, you have 100 opportunities per second to turn the SSR on or off.  So a 1Hz PWM frequency fits nicely.

In the high resolution mode of the ADC on the TC4 shield, it will take around 600ms, total, to sample both TC channels (boiler and group).   So you should not have any problems updating the duty cycle once per second.  And this is plenty fast for good control of the machine.

Jim
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philipmc
Senior Member


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

Espresso: Silvia
Grinder: Rocky
Posted Sat Feb 18, 2012, 7:24am
Subject: Re: New Silvia Project - what would you add?
 

JGG Said:

I think you'd have pretty good luck with either 1Hz or 0.5Hz.  At 50Hz, you have 100 opportunities per second to turn the SSR on or off.  So a 1Hz PWM frequency fits nicely.

In the high resolution mode of the ADC on the TC4 shield, it will take around 600ms, total, to sample both TC channels (boiler and group).   So you should not have any problems updating the duty cycle once per second.  And this is plenty fast for good control of the machine.

Posted February 17, 2012 link

Great point Jim! I had forgotten that a 50Hz signal crosses zero twice per cycle! I've now rigged up the kettle test bed. It's all working as it should with both the sampling and PWM (hence SSR) running at 1Hz. I found the temperature readings to be a little erratic which makes PID tuning trickier than it should be. I put this down to the thermocouple being attached with tape to the kettle. I'm pretty sure a more solid mount will give better results, which is what I will try next.

patrickff Said:

Do you plan to interface the Arduino with the original switches (as input)?
Some examples:
Power switch - turns the PID on/off
Brew/Steam switch - sets different P,I,D values
Brew switch - shot timer, or a least starts a visual counter
etc.

Posted February 17, 2012 link

I quite like the idea of minimising the amount of internal mains rewiring needed. I was thinking of adding a real time clock, so the Arduino could wake the Silvia (rather than the other way around!). I have a hall effect sensor in my prototype kit, so I may try that on the brew switch wiring to see if I can setup a simple shot timer.

I have to say I am quite surprised at the amount of time all this is taking. I am a bit of a perfectionist with my code, so there have been several rewrites (and I've resisted the temptation to tweak existing libraries ... so far). Great fun though. =)
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JGG
Senior Member
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 Sat Feb 18, 2012, 7:56am
Subject: Re: New Silvia Project - what would you add?
 

philipmc Said:

I found the temperature readings to be a little erratic which makes PID tuning trickier than it should be. I put this down to the thermocouple being attached with tape to the kettle. I'm pretty sure a more solid mount will give better results, which is what I will try next.

Posted February 18, 2012 link

I don't know how much use you are making of the code in the TC4 software repository.  If you are  using the cADC library, it includes a digital filtering class.

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 Sun Feb 19, 2012, 11:18am
Subject: Re: New Silvia Project - what would you add?
 

Hi Philip:

Looks like you are making great progress... I've been off the forum for a while, I just sent you an email with all of my code.  Feel free to use anything you like of it, if it fits in with your approach.  Continued good luck... let me know if you have any questions.

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 Mon Feb 20, 2012, 5:26am
Subject: Re: New Silvia Project - what would you add?
 

Rick,
I didn't get the email, but noticed a slight typo in my email. Would you mind trying again? Thanks.

Jim,
I had avoided it as the algorithm made my head spin. With the help of excel, I now get it. Quite simple and effective in reality. Thanks.
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