Help With Temperature Settings


#1

I have a 4.4cu mini fridge with a small portable fan heater. My beer temperature sensor is mounted inside my BrewBucket. My beer temp is off by several degrees. I’m just using the default setting and changed the Cooler derivative time constant (Td) to “0” & Heater 1 derivative time constant (Td) to “0” because I will be fermenting. Which settings should I adjust?


#2

Your heater stopped working around 6:00. I don’t know why but the firmware was trying to enable it. You should post your control algorithm output under the maintenance panel to get more feedback.


#3

I replaced my heater with a 25W Heating Mat. Here’s my latest temperature settings. Do these look good or do they need fine tuning? Thanks for your help Elco.

Beer-to-Fridge proportional gain (Kp) 5
Beer-to-Fridge integral time constant (Ti) 1800
Beer-to-Fridge derivative time constant (Td) 0
Maximum difference between fridge and beer set point (= output of PID) 10.8
Beer-to-Fridge Input filter delay time 18sec
Beer-to-Fridge Derivative filter delay time159 sec
Cooler proportional gain (Kp) 10
Cooler integral time constant (Ti) 1800
Cooler derivative time constant (Td) 0
Cooler PWM period (seconds) 1200
Cooler minimum OFF time 180
Cooler minimum ON time 120
Cooler Input filter delay time 18 sec
Cooler Derivative filter delay time 159 secs
Heater 1 proportional gain (Kp) 10
Heater 1 integral time constant (Ti) 600
Heater 1 derivative time constant (Td) 0
Heater 1 PWM period (seconds) 4
Heater 1 Input filter delay time 18 sec
Heater 1 Derivative filter delay time 159 sec


#4

Looks a lot better, but can be improved.

Try this:

  • Beer-to-fridge max temperature difference: 5
  • Beer-to-Fridge integral time constant (Ti): 7200

That will prevent the integrator windup that causes the fridge setting to stay low for too long. It clips to maximum earlier (which will disable the integrator) and it will accumulate slower (longer time constant Ti).

Cooler Kp: 5 (it seems a bit too aggressive).
Cooler minimum on time: 60
Cooler Td: 30 (a little bit to prevent overshoot)

Dead time between switching: 3600 (no need to alternate between heating and cooling this quickly).

It also seems that your sensors are a bit noisy. Does your new heater cable run next to the sensor cable, possibly causing interference?


#5

Yes, My cables are running side by side. Should I try to change it?


#6

Also What setting is the Dead Time Between Switching called? Is it called Cooler PWM?
Thanks again for your help


#7

Yes, try if you get less grassy lines when the cables are not next to each other.
In advanced settings all the way at the bottom you’ll find “Dead time when switching between actuators” .