# PID for dummies



## 3timesaday (Nov 11, 2021)

Hi,

Does anyone have a link that clearly explains PID parameters and their effect on the machine behavior?

I've seen a few site proposing different values than the default ones, with short description. I understand there is a trade off between "speed" and "precision", but I'm not really sure how it works, and which set would suit me best.

Thanks!


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## MediumRoastSteam (Jul 7, 2015)

3timesaday said:


> Hi,
> 
> Does anyone have a link that clearly explains PID parameters and their effect on the machine behavior?
> 
> ...


 Good luck with that. It's not simple, and there are so many factors to consider that your best bet is experimenting.

I for one have done some testing:

https://www.coffeeforums.co.uk/topic/53045-new-upgraded-lelit-on-the-block-elizabeth/?do=embed&comment=810985&embedComment=810985&embedDo=findComment

https://www.home-barista.com/tips/coffee-guys-oversimplified-guide-to-setting-your-pid-t11027.html

https://en.wikipedia.org/wiki/PID_controller


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## Gagaryn (Oct 21, 2021)

This explains it quite well : https://www.omega.co.uk/prodinfo/how-does-a-pid-controller-work.html

"

*
PID Controller Working Principle
*

The working principle behind a PID controller is that the proportional, integral and derivative terms must be individually adjusted or "tuned." Based on the difference between these values a correction factor is calculated and applied to the input. For example, if an oven is cooler than required, the heat will be increased. Here are the three steps:



*Proportional tuning* involves correcting a target proportional to the difference. Thus, the target value is never achieved because as the difference approaches zero, so too does the applied correction.


*Integral tuning* attempts to remedy this by effectively cumulating the error result from the "P" action to increase the correction factor. For example, if the oven remained below temperature, "I" would act to increase the head delivered. However, rather than stop heating when the target is reached, "I" attempts to drive the cumulative error to zero, resulting in an overshoot.


*Derivative tuning* attempts to minimize this overshoot by slowing the correction factor applied as the target is approached.


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## 3timesaday (Nov 11, 2021)

Thanks all, definitively, fiddling with PID settings will not be my cup of tea&#8230;


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## woodbar (Aug 28, 2020)

3timesaday said:


> Thanks all, definitively, fiddling with PID settings will not be my cup of tea&#8230;


 Well actually that is the whole idea behind PID that you don't have to fiddle with it - you tell it what temperature you want and it does its best to maintain it - nothing can be 100% accurate but PID is the best attempt probably.

Compared to a thermostat or a steam pressure sensing device (correlates steam pressure to temperature) it is far more accurate as they will likely have far greater margins of overshoot and hysteresis than an electronic PID controller.


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## MediumRoastSteam (Jul 7, 2015)

Thing is, the whole thing is as good as the tuning of the PID controller for that specific environment. If badly or incorrectly tuned, the overshooting is dramatic. For instance, try using Lelit Elizabeth's default settings. It overshoots like mad.


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## woodbar (Aug 28, 2020)

MediumRoastSteam said:


> For instance, try using Lelit Elizabeth's default settings. It overshoots like mad.


 I understand that, but if Lelit have chosen unsuitable defaults then, once you have put in corrected settings from an experienced user on the forum for example, surely you would no longer need to "fiddle" other than selecting the temperature you require for your particular brew?


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## MediumRoastSteam (Jul 7, 2015)

woodbar said:


> I understand that, but if Lelit have chosen unsuitable defaults then, once you have put in corrected settings from an experienced user on the forum for example, surely you would no longer need to "fiddle" other than selecting the temperature you require for your particular brew?


 Not sure why you are saying this, but yes... I've key'd in @DavecUK settings, I also have tried others too (see first reply to OP). My remarks were generalised in trying to have a "generic" setting that works for all coffee machines. Impossible. 🙂

I'm using Dave's settings. It works a treat.


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## woodbar (Aug 28, 2020)

MediumRoastSteam said:


> My remarks were generalised in trying to have a "generic" setting that works for all coffee machines.


 Ah, I think I understand - I suppose those settings will work for all Lelit Elizabeth but obviously not ALL other models or manufacturers, which would be logical?


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## MediumRoastSteam (Jul 7, 2015)

woodbar said:


> Ah, I think I understand - I suppose those settings will work for all Lelit Elizabeth but obviously not ALL other models or manufacturers, which would be logical?


 Correct. PID parameters are for a specific system, as heating elements, boiler size, group type, internal architecture, pipe size, are can be different.

on my example above (2nd post in thread, see link) I experimented with the settings suggested by Clive Coffee for the Profitec 300. It works and it works well, and the recovery and warm up types are faster than the parameters provided by Dave. However, the temperature does fluctuate a bit more.


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## woodbar (Aug 28, 2020)

So, going back to the OP's original concerns, he might maybe have to "fiddle" a bit with settings - if the OEM ones are off and someone has suggested better ones - but after that he would be good to go with just selecting temperature most of the time. So, only half a "fiddle" then😉


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## 3timesaday (Nov 11, 2021)

woodbar said:


> So, only half a "fiddle" then😉


 🤣


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