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Yet another Silvia mod..
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Discussions > Espresso > Espresso Mods > Yet another...  
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mani
Senior Member


Joined: 7 Mar 2011
Posts: 8
Location: Stockholm
Expertise: I love coffee

Espresso: Rancilio Silvia
Grinder: Campak K3 Touch
Posted Mon Mar 7, 2011, 10:15am
Subject: Yet another Silvia mod..
 

Hi,

Peuw! I have finally finished my Silvia PID mod project!
I went for a completely "home made" solution and it turned out quite nice.
Have a look at mackro.se/coffee
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Nathan
Senior Member


Joined: 10 Nov 2010
Posts: 148
Location: Montreal
Expertise: I love coffee

Espresso: Rancilio Silvia v3
Grinder: Vario
Vac Pot: Hario
Posted Mon Mar 7, 2011, 11:52am
Subject: Re: Yet another Silvia mod..
 

Well done. I'm currently working in a similar project, only it uses a thermocouple. I like the graphs you have. It's interesting you mention the PID constants you needed. Currently I have these constants (not sure these are really inter compatible).

#define P_CONST 70 //Proportional Constant  
#define I_CONST 10 //Integral Constant
#define D_CONST 25 //Derivative Constant

These are from the TC4 project, which is a PID that is made for a roaster mostly, so it might not really be compatible in terms of its PID calcs.
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mani
Senior Member


Joined: 7 Mar 2011
Posts: 8
Location: Stockholm
Expertise: I love coffee

Espresso: Rancilio Silvia
Grinder: Campak K3 Touch
Posted Mon Mar 7, 2011, 12:20pm
Subject: Re: Yet another Silvia mod..
 

I guess the values depend on the implementation, different algorithms, sensors etc.

Since the response of the heater is slow I found it easy to get overshoots and oscillations. It is more stable for me when using a lot of D-gain and only a little I-gain.
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Nathan
Senior Member


Joined: 10 Nov 2010
Posts: 148
Location: Montreal
Expertise: I love coffee

Espresso: Rancilio Silvia v3
Grinder: Vario
Vac Pot: Hario
Posted Mon Mar 7, 2011, 12:26pm
Subject: Re: Yet another Silvia mod..
 

Correct me if I'm wrong, but it looks as if your system is slightly built on the TC4 as well?

I also can't find your PID values in your source.
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mani
Senior Member


Joined: 7 Mar 2011
Posts: 8
Location: Stockholm
Expertise: I love coffee

Espresso: Rancilio Silvia
Grinder: Campak K3 Touch
Posted Mon Mar 7, 2011, 12:39pm
Subject: Re: Yet another Silvia mod..
 

Never heard about TC4 but I found the skeleton for the PID code on the internet so it might be from that one.
The PID values are not in the source code because they are set from the menu.
Currently I am using:
P=9
I=0.7
D=135

But again, different implementations will have different values.
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Nathan
Senior Member


Joined: 10 Nov 2010
Posts: 148
Location: Montreal
Expertise: I love coffee

Espresso: Rancilio Silvia v3
Grinder: Vario
Vac Pot: Hario
Posted Mon Mar 7, 2011, 5:58pm
Subject: Re: Yet another Silvia mod..
 

I noticed on mine that it only pretty much starts slowing down when it's within 10 degrees, slows down pretty harshly, and then stops. I haven't connected this to the actual machine yet, so it could work well, who knows. Thanks for the info though.
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JGG
Senior Member
JGG
Joined: 31 Mar 2006
Posts: 1,357
Location: Kentucky, US
Expertise: I like coffee

Espresso: PID Silvia; PID Alexia
Grinder: Mazzer SJ
Roaster: Hottop D w/HTC+TC4C
Posted Mon Mar 7, 2011, 6:26pm
Subject: Re: Yet another Silvia mod..
 

Hi, mani -

Very nice project!  I have been thinking along similar lines, and have actually made quite a bit of progress.  So it is nice to see a successful, completed installation.

For sensing temperatures, I assume you are using the AVR's 10-bit ADC.  By my estimates, this would give a temperature resolution of around +/- 0.5C with the LM35AH, right?

If you don't mind sharing, can you post a little more information about the plastic enclosure for your LCD display?  I am spinning my wheels badly on this part of my project.

Jim
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mani
Senior Member


Joined: 7 Mar 2011
Posts: 8
Location: Stockholm
Expertise: I love coffee

Espresso: Rancilio Silvia
Grinder: Campak K3 Touch
Posted Tue Mar 8, 2011, 2:28am
Subject: Re: Yet another Silvia mod..
 

Yes, I am using the 10-bit ADC with the internal 2.56V reference voltage. This gives a resolution of 0.25 deg C.
But! The big improvement I made was to let the ADC sample all the time and then once per second calculate the average of all samples from the last second.
This gives the impression that the resolution is better than it actually is. For example when the temperature is rising slowly, the calculated average value is rising smoothly 0.01 degrees at the time.

Regarding the plastic box. The electronic supplier here in Sweden has a lot of different plastic boxes and I just bought one that had the right size. I guess it would be even easier to find one in the US. The one I bought is called 1591MBK from Hammond. http://www.hammondmfg.com/dwg2XX.htm
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JGG
Senior Member
JGG
Joined: 31 Mar 2006
Posts: 1,357
Location: Kentucky, US
Expertise: I like coffee

Espresso: PID Silvia; PID Alexia
Grinder: Mazzer SJ
Roaster: Hottop D w/HTC+TC4C
Posted Wed Mar 9, 2011, 5:49pm
Subject: Re: Yet another Silvia mod..
 

I was not aware of the internal 2.56V reference voltage.  I thought it was 5V.  I guess I need to get the book out!

Until you had answered my question about the box, I did not realize that the plastic bezel around the LCD display was a loose piece.  Where did you get that?  I think the bezel might be what I am looking for.

Thanks again.

Jim
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JGG
Senior Member
JGG
Joined: 31 Mar 2006
Posts: 1,357
Location: Kentucky, US
Expertise: I like coffee

Espresso: PID Silvia; PID Alexia
Grinder: Mazzer SJ
Roaster: Hottop D w/HTC+TC4C
Posted Thu Mar 10, 2011, 6:19am
Subject: Re: Yet another Silvia mod..
 

JGG Said:

I was not aware of the internal 2.56V reference voltage.

Posted March 9, 2011 link

Turns out that my AVR chip (ATmega328P) provides a 1.1V internal reference, not 2.56V.  Apparently, this value is different for different AVR series.  Now I know something new :-)

Jim
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