I’m running Brewpi Spark in a mini fridge (no fan or heater yet, 30C here in Brazil now) which doubles as a kegerator.
As soon as I got everything set up I tested the fridge constant mode with the one sensor through the fridge door:
Then I wired everything following the fridge hack guide and then decided to test the beer constant mode with 20L of water in a carboy (thermowell included):
That’s when I noticed I had a overshoot problem and after reading a couple of threads decided do incr
ease Kp from 2 (default) to 12.
The overshoot problem was beautifully resolved but now I think I have two problems:
- Wildly oscillating fridge set point, and;
- Big lag between frige temp and set point.
Right now I have a 5 gal corny keg which I’m holding at 16C for one more day before I crash it to lagering temps:
When holding at 16C I tried to decrease the ‘Maximum difference between fridge and beer set point’ from 10C to 5C but the beer temp started to deviate from the set point.
I’ve seen a suggestion to increase both the ‘Beer-to-Fridge filter delay time’ and that’s what I just did.
Other suggestions are increasing Ti or trying a Kp less aggressive. I’d really appreciate some directions.
Here’s my settings:
{
"kind": "Control",
"pids": [
{
"kind": "Pid",
"name": "heater1",
"enabled": true,
"setPoint": {
"kind": "SetPointSimple",
"name": "fridgeset",
"value": -8
},
"inputSensor": {
"kind": "TempSensorFallback",
"onBackupSensor": false,
"sensor": {
"kind": "TempSensor",
"name": "fridge",
"sensor": {
"kind": "OneWireTempSensor",
"value": 1.1875,
"connected": true,
"address": "28822DC2070000CA",
"calibrationOffset": 0
}
}
},
"inputError": 9.1563,
"Kp": 10,
"Ti": 600,
"Td": 60,
"p": -91.5625,
"i": 0,
"d": 0.3125,
"actuatorIsNegative": false,
"outputActuator": {
"kind": "ActuatorPwm",
"value": 0,
"period": 4,
"minVal": 0,
"maxVal": 100,
"target": {
"kind": "ActuatorMutexDriver",
"mutexGroup": {
"kind": "ActuatorMutexGroup",
"deadTime": 1800000,
"waitTime": 1799929
},
"target": {
"kind": "ActuatorNop",
"state": false
}
}
}
},
{
"kind": "Pid",
"name": "heater2",
"enabled": true,
"setPoint": {
"kind": "SetPointSimple",
"name": "beer2set",
"value": null
},
"inputSensor": {
"kind": "TempSensor",
"name": "beer2",
"sensor": {
"kind": "OneWireTempSensor",
"value": 27.5625,
"connected": true,
"address": "28C6A5C007000091",
"calibrationOffset": 0
}
},
"inputError": null,
"Kp": 10,
"Ti": 600,
"Td": 60,
"p": 0,
"i": 0,
"d": 0,
"actuatorIsNegative": false,
"outputActuator": {
"kind": "ActuatorPwm",
"value": 0,
"period": 4,
"minVal": 0,
"maxVal": 100,
"target": {
"kind": "ActuatorMutexDriver",
"mutexGroup": {
"kind": "ActuatorMutexGroup",
"deadTime": 1800000,
"waitTime": 1799860
},
"target": {
"kind": "ActuatorNop",
"state": false
}
}
}
},
{
"kind": "Pid",
"name": "cooler",
"enabled": true,
"setPoint": {
"kind": "SetPointSimple",
"name": "fridgeset",
"value": -8
},
"inputSensor": {
"kind": "TempSensorFallback",
"onBackupSensor": false,
"sensor": {
"kind": "TempSensor",
"name": "fridge",
"sensor": {
"kind": "OneWireTempSensor",
"value": 1.1875,
"connected": true,
"address": "28822DC2070000CA",
"calibrationOffset": 0
}
}
},
"inputError": 9.1563,
"Kp": 10,
"Ti": 1800,
"Td": 200,
"p": -91.5625,
"i": -26.2539,
"d": 0.9766,
"actuatorIsNegative": true,
"outputActuator": {
"kind": "ActuatorPwm",
"value": 100,
"period": 1200,
"minVal": 0,
"maxVal": 100,
"target": {
"kind": "ActuatorMutexDriver",
"mutexGroup": {
"kind": "ActuatorMutexGroup",
"deadTime": 1800000,
"waitTime": 1799784
},
"target": {
"kind": "ActuatorTimeLimited",
"minOnTime": 120,
"minOffTime": 180,
"maxOnTime": 65535,
"state": true,
"target": {
"kind": "ActuatorPin",
"state": true,
"pin": 17,
"invert": false
}
}
}
}
},
{
"kind": "Pid",
"name": "beer2fridge",
"enabled": true,
"setPoint": {
"kind": "SetPointSimple",
"name": "beer1set",
"value": 2
},
"inputSensor": {
"kind": "TempSensor",
"name": "beer1",
"sensor": {
"kind": "OneWireTempSensor",
"value": 8.375,
"connected": true,
"address": "286BE2C00700003F",
"calibrationOffset": 0
}
},
"inputError": 6.4141,
"Kp": 12,
"Ti": 7200,
"Td": 1200,
"p": -76.9688,
"i": 0,
"d": 3.75,
"actuatorIsNegative": false,
"outputActuator": {
"kind": "ActuatorSetPoint",
"targetSetPoint": {
"kind": "SetPointSimple",
"name": "fridgeset",
"value": -8
},
"targetSensor": {
"kind": "TempSensor",
"name": "fridge",
"sensor": {
"kind": "OneWireTempSensor",
"value": 1.1875,
"connected": true,
"address": "28822DC2070000CA",
"calibrationOffset": 0
}
},
"referenceSetPoint": {
"kind": "SetPointSimple",
"name": "beer1set",
"value": 2
},
"output": -10,
"achieved": -0.8125,
"minimum": -10,
"maximum": 10
}
}
]
}
