Sudden erratic temp control

With the brewpi software I have made about 5 batches, each 5 gallons. My current batch is 3 gallons and while the thermowell is below the liquid, I’m not sure if the smaller batch size (in the same carboy I use for 5 gal batches) is an issue here.

Anyway, last couple of days is showing the beer temp fluctuation while the first few days of fermentation was steady as I usually see.

Any thoughts on this?

Could you please tell me on which hardware you are running? An upgrade to 0.4.1 is recommended anyway.

One very strange thing I notice is that you have little spikes in the temperatures. I wonder what that could be.

Another thing: your fridge temperature seems to rise when he cooler is active and drop when the heater is active. But I am not sure, I can make very little sense of when the actuators are active and whether your temperature is rising or falling.

Some moments the temperature goes up quickly without good reason. Looks like an erratic sensor to me.

That’s weird, mine did exactly the same thing at a similar point in time. I thought it was a dicky temperature sensor so I swapped the room one over but its still see-sawing.

Could it be that fermentation has finished and no longer supplying any heat?
I am using a photon spark btw. I have not updated to the new release yet.


I would upgrade to the new release, but otherwise, reducing the filtering might help too.
Each filter has a delay, so if it is over the target before the algorithm knows it (because of the delay to the input), it will go past the target.

It is still holding the temp to within ± 0.5 a degree so it’s not a problem as such. It just seems a bit odd that it has held very close to set point for ages then wavered a little recently. I will update the software when this batch is finished and see how it goes. The only difference between this and previous batches is the volume I am fermenting ie 10 gallon as opposed to 5.
I will seek your advice with the filtering if the new release doesn’t cure it.



Hi @elco and @Jellyhawk,

I have a theory on this one. This is what I see when I zoom in on the temperature jumps (note: this is a new test):

There is a ~3-4 min. period of time between sensor readings. My fridge is small and the heater inside it relatively huge. My guess is that the problems is a matter of the chamber heating well past the threshhold within prior to brewpi having a chance to confirm the temperature.

BTW, this was both on my arduino Uno and now a Nano. I understand this is not something you can really support, so i appreciate that you answered this thread at all :smile:

The dark red means that it is heating the minimum time. Looks like your heater is a bit too powerful for the volume?

At least on Arduino, on the Spark we can use it at lower power with pwm.

The arduino algorithms in brewpi 0.2 are really built for controlling 20l of beer. It will respond slowly to actuator action, if you have quick response you need to get your sensor inside thr beer so it measures actual beer temperature.