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PID CYCLE RATE setting
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Discussions > Espresso > Espresso Mods > PID CYCLE RATE...  
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faster
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Joined: 27 May 2013
Posts: 88
Location: France
Expertise: I live coffee

Espresso: Rancillio Silvia-PID
Grinder: Rossi RR45
Roaster: Homemade drum roaster
Posted Fri Oct 4, 2013, 7:39am
Subject: PID CYCLE RATE setting
 

Question on setting of cycle rate for SSR...

What do you have yours set to?
My manual is translated from Chinese and says: "for relay or contactor output adjust to 20-30 sec (to prevent wearing out contacts in PID) and for SSR set to 2 sec"....
(Isn't relay/SSR same thing?)
I set mine to 25 seconds. Works fine and goes on for 2.5-4 sec when temp drops and 0.5 sec once reaches SV.
I tried the 2 sec setting, but find it a bit odd the constant on/off...What is more efficient? (I know the constant flashing is more accurate.)

The constant flashing makes me wonder if that type of setting is not better at keeping a constant temperature; like in a laboratory environment and longer cycle rate for a boiler with big temp drop for fast recovery, with longer pulses then short flashes...?
Does it make sense?
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calblacksmith
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calblacksmith
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Posted Fri Oct 4, 2013, 8:04am
Subject: Re: PID CYCLE RATE setting
 

The PID has internal contacts, I think these are the ones referenced to with 20 to 30 seconds. There ALSO can be an external SSR in use and either the contacts can be used to trigger the SSR or an output from the PID is often provided to trigger an SSR.

 
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jonr
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Posted Fri Oct 4, 2013, 9:21am
Subject: Re: PID CYCLE RATE setting
 

The two second update rate will be slightly more accurate and doesn't hurt anything.
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faster
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Joined: 27 May 2013
Posts: 88
Location: France
Expertise: I live coffee

Espresso: Rancillio Silvia-PID
Grinder: Rossi RR45
Roaster: Homemade drum roaster
Posted Fri Oct 4, 2013, 10:48am
Subject: Re: PID CYCLE RATE setting
 

calblacksmith Said:

The PID has internal contacts, I think these are the ones referenced to with 20 to 30 seconds. There ALSO can be an external SSR in use and either the contacts can be used to trigger the SSR or an output from the PID is often provided to trigger an SSR.

Posted October 4, 2013 link

Yes, I'm using an external SSR, triggered by PID...but your reply is confusing...


jonr Said:

The two second update rate will be slightly more accurate and doesn't hurt anything.

Posted October 4, 2013 link

I agree, it is more accurate, but is it necessary?... the constant flashing gets on my nerves and I am not so sure that it is good for:
A) the PID
B) the light on Silvia.
Everybody uses the 2 sec. setting...makes me wonder why...
I find the recuperation temp/time with long pulses easier on the PID and in a way more suited for espresso machine where once the SV is set, the flashes are 1/2 sec, every 20 secs...
I'm just wondering if I'm missing something or not understanding?
Thanks
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dana_leighton
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dana_leighton
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Posted Fri Oct 4, 2013, 12:41pm
Subject: Re: PID CYCLE RATE setting
 

faster Said:

constant flashing gets on my nerves and I am not so sure that it is good for:
A) the PID
B) the light on Silvia.
Everybody uses the 2 sec. setting...makes me wonder why...
I find the recuperation temp/time with long pulses easier on the PID and in a way more suited for espresso machine where once the SV is set, the flashes are 1/2 sec, every 20 secs...
I'm just wondering if I'm missing something or not understanding?
Thanks

Posted October 4, 2013 link

There are no hazards to the PID, SSR, light, or any other part of Silvia.

The light merely indicates the heating element is making a circuit and thus heating (or may be the other way around on Silvia). The rapid blinking is good for slowly approaching and maintaining a temperature. If you change the cycle time you run the risk of overshooting/under shooting the set value temperature. However, if you tune the PID and don't have a problem with overshoot or undershoot, the cycle interval can be anything you want. I have mine set at the minimum (.1 second I think). I have my PID tuned so that it approaches the SV temp rather slowly so as not to overshoot.

 
Dana Leighton - Espresso hack and CoffeeGeek moderator
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billc
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Posted Fri Oct 4, 2013, 5:10pm
Subject: Re: PID CYCLE RATE setting
 

faster,
The comment for the 20-30 second cycle time is for a mechanical relay (if you were to choose to use one).  A SSR (Triac) is able to perform millions of cycles so you are able to increase the cycle time to switch more often.  For every cycle the Controller will measure one time and act on the error between the measurement and the set temperature.  

Now, depending upon how your controller are designed and made will determine the min for cycle time.  The more expensive you get the lower cycle time you can achieve (typically).  The ideal case is the lowest possible so essentially instantaneous control.  There is a trade off to account for the durability and longevity of the components in the system.  The larger the cycle time the longer things last.  in the case of the Electronic Controller (with PID) and espresso machine a cycle time of 1-2 seconds is usually a good enough to balance components and reaction time of the controller.

Concerning the components in the system, the controller and SSR will be fine at 2 second cycle time.  The only unknown would be the Sylvia light.  If it is an LED light then no problem, if it is a zeon light then the life will be reduced with switching but I presume it would last 5-6 years instead of 15 years so it will probably not matter.

Not sure of the reason that everyone used 2 seconds but I presume that this was the lowest number recommended by the controller manufacturer.


BillC
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faster
Senior Member


Joined: 27 May 2013
Posts: 88
Location: France
Expertise: I live coffee

Espresso: Rancillio Silvia-PID
Grinder: Rossi RR45
Roaster: Homemade drum roaster
Posted Sat Oct 5, 2013, 3:31am
Subject: Re: PID CYCLE RATE setting
 

THANK you ALL for your explanation on the subject. Really appreciate it:-)

dana_leighton Said:

The rapid blinking is good for slowly approaching and maintaining a temperature. If you change the cycle time you run the risk of overshooting/under shooting the set value temperature. However, if you tune the PID and don't have a problem with overshoot or undershoot, the cycle interval can be anything you want. I have mine set at the minimum (.1 second I think). I have my PID tuned so that it approaches the SV temp rather slowly so as not to overshoot.

Posted October 4, 2013 link

That's a conclusion I came to with the slow/fast cycle rate setting.
Some overshoot-yes, by few Fahrenheits on 1st shot. 2nd shot gets corrected.


billc Said:

The comment for the 20-30 second cycle time is for a mechanical relay (if you were to choose to use one).  A SSR (Triac) is able to perform millions of cycles so you are able to increase the cycle time to switch more often.  For every cycle the Controller will measure one time and act on the error between the measurement and the set temperature.  

Now, depending upon how your controller are designed and made will determine the min for cycle time.  The more expensive you get the lower cycle time you can achieve (typically).  The ideal case is the lowest possible so essentially instantaneous control.  There is a trade off to account for the durability and longevity of the components in the system.  The larger the cycle time the longer things last.  in the case of the Electronic Controller (with PID) and espresso machine a cycle time of 1-2 seconds is usually a good enough to balance components and reaction time of the controller.

Not sure of the reason that everyone used 2 seconds but I presume that this was the lowest number recommended by the controller manufacturer.
BillC

Posted October 4, 2013 link

Yes, I didn't think of the mechanical relay, only SSR (and I wasn't worried about the SSR switching on/off)....more about PID...
I thought, since it is an industrial instrument the 1-2 sec. setting is to KEEP a temp XXX from deviating, and 20-30 sec. pulses were better for fast recuperation time on the boiler...

I am still not sure if I want to look at the PID/Silvia light flashing constantly, besides the overshoot of 3-5 F is still within range of acceptable temp, SV=208.4F
Will experiment and see;-)
Thanks again and you all have a good weekend.
cheers
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,672
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 Sat Oct 5, 2013, 6:18am
Subject: Re: PID CYCLE RATE setting
 

Yes, I'm using an external SSR, triggered by PID...but your reply is confusing...

A PID can have built into it a mechanical relay that can switch the load AND it has a different connection that is designed to trigger a SSR , you choose which you want to use.

 
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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billc
Senior Member


Joined: 15 Jan 2009
Posts: 129
Location: Seattle, Washington
Expertise: Professional

Espresso: CC1 - GS - GS3 - GB5
Grinder: Baratza - Mazzer-Marzocco
Drip: My own Creation
Posted Mon Oct 7, 2013, 11:44pm
Subject: Re: PID CYCLE RATE setting
 

Rarely will you find a temperature controller that has PID control containing a mechanical relay inside.  And if you do you the PID control will be deactivated if you choose to use the mechanical relay inside.  The PID Control would be rendered useless if you were to increase the cycle time to a time that would allow the mechanical relay some lifetime.  

BillC
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