autotuning pid

[paulg]

I have a 70 litre stock pot fitted with a 4500 watt element and recirculate BIAB system
.Today I insulated the hoses and ran autotune with a full load of water and spent grain.The AT took nearly 3.5 hours as the system seemed to take ages to loose any temp after the overshoot faze of the AT.My previous settings gave about 1 degree overshoot
I found on completion that the numbers were drastically different to before and that the system now takes a long time to increase temperature ,say to raise to mash out temp.
I am rerunning AT at the moment but would be keen to learn other peoples settings for p,i,d .I know this will vary for system to system but hope maybe it will give me some idea if my settings are way out. I read that people can control mash temp to very close tolerances with a well setup pid
thanks
Paul

[paulg]

bump come on guys am I the only one to use recirculating BIAB
here are my pid settings set by autotune ,it is a sestos unit

df o.3 default 0.3
m50 500 1000
p 9138 500
t 1645 120
ctl 96 4

is there anyone who understands the effect of these settings please

[mabrungard]

If you are monitoring the system with a sensor in the kettle, you are bound to overshoot the system everytime. The temperature sensor needs to be placed as near as possible downstream of the heating element. If you don't have the sensor there, you will overheat and denature the enzymes in your wort and end up with unconverted starch in your beer. I found this out the hard way.

You will still need to monitor the temperature in your kettle. But do that with another thermometer. Be sure that all of your thermometers and thermocouples are calibrated to an accurate standard.

[Fil]

i will need to dig out my sestos sheet and double check with the auber online manual, but afaik there are 3 control vars the P I and D vars that are the input into the algotithm to alter the behavior..

the defaults plugged into the adruino example i lifted are 5 2 and 1

Code: Select all

PID myPID(&Input, &Output, &Setpoint,5,2,1, DIRECT); //Specifies the PID links and initial tuning parameters

I dint take note of the settings used for my hlt setup and its not wired up right now.

[AnthonyUK]

I use a Sestos PID too for recirculating BIAB.
I put the sensor in the outlet from the pump and have experienced very little if any overshoot.
I have only ran the autotune, no other menu changes but I don't think looking up my values will be of any benefit to you given the differences in setups.
One thing I have changed though is the sensor from the crappy supplied one to a PT100.

[paulg]

ok yes sorry my pt100 is located in a tee with the tap on the output of the pot.previously I had put it at the return to the pot in the lid aka high gravity system ,(but I decided that maybe I would lose too much heat in the pipe work which was at that time uninsulated).I later moved it to the pot below the cake rack I use to support the bag but worried about it being in a dead spot.

I have rerun auto tune again with a brews worth of grain 4 kilos, and my usual mash water quantity 41 litres and the numbers are quite different now the temperature fluctuates about 0.4 of a degree over//under and after a while the mash above the cake rack comes in line ,maybe 0.5 of a degree which could just be the tolerance of the two pids (I placed one in the mash to measure the grain/liquor temp and the out one on output of kettle as described.

what should I be aiming for ? the temp below the rack at target or the grain above the rack at target.Iknow ideally they should both be rhe same and may well be now, I will have to check next brew day when I run system for 1.5 hours mash so everything will stablise .

martin
you mention unconverted starch ,my last but one brew where I had the pt100 in the side of the pot below the rack and monitored high grain temps has been in a corny now for about 1 month, and has so far refused to clear even after the fact I crash cool for 2 days before racking to corny and force carbing.You may have solved my problem re clearing as I saw temperatures several degrees above the 67c I was aiming for

[paulg]

antonyuk
where is your pump placed ,I have about 9" insulated silicone hose before my pump then maybe 20" to my return spray fitting in the pot lid
if it is not too much trouble I would still be interested in your settings as my new ones after running autotune again are vastly different to before

parameter before now default aubin ref
m50 500 195 1000 i
p 9138 1878 500 p
t 1645 263 120 d
ctl 96 96 4 t

[paulg]

sorry another question the parameter ctl on the sestos pid(called t by aubins) is set to 96 I dont remember changing this setting.The aubins manual says for an SSR relay that it should be set to 2 or 20 for a mechanical relay
would AT normally alter this setting or should I set it to 2 as it would appear that the large number could be the cause of inprecise control.


4.6 Cycle time “t”
It is the time period (in seconds) that the controller uses to calculate its
output. e.g. When t=2, if the controller decides output should be 10%, the
heater will be on 0.2 second and off 1.8 seconds for every 2 seconds. Smaller
t values result in more precision control. For SSR output, t is set at the
minimum (2 seconds). For relay or contactor output, it should be set longer to
prevent contacts from wearing out too soon. Normally it is set to 20~ 4 0

[AnthonyUK]

Here is the sestos manual http://www.sestos-hk.com/english/download/d1s-en.pdf
Next time I get the PID out I'll make a note of the settings.
This is how mine looks

[Fil]

have u checked the auber manual, the sestos unit apears to be a slightly feature poor clone of the auber pid described and explained a lot clearer in https://www.google.co.uk/url?sa=t&rct=j ... 7764,d.d2k

++ edit.. yes i see you have.. missed a post..


check the sestos sheet for legal parameters before deciding on setting according to the auber instructions just to be sure

[UpTheToon]

Thread bump!

Just about to set a BIAB recirculating system this weekend with the sestos PID. Do you fellas leave your pump on the whole time or wire it in somehow to only trigger when the element is on?

[AnthonyUK]

I leave it on all the time otherwise you get hot/cold spots.

My PID settings:

df 0.3
Ctrl 3
M50 62
P 308
t 54
Ctl 4
Sn 21 (PT100)
SC 0.5
CF 2
dl 0
run 2

Someone has done some testing with the Ctl settings and it looks like it is buggy. - http://www.homebrewtalk.com/f51/has-any ... ost4389803

Ctl Period
40 = 40s
20 = 20s
10 = 10s
8 = 8s
6 = 8s
4 = 8s
3 = 8s
2 = 70s
1 = 70s
0 = 70s

[UpTheToon]

Great, thanks.

I'll give the autotune a bash to start with then take it from there comparing it to what you have.