Rapt Temperature Controller + Pill - PID Settings

[RichardM]

I was given a RAPT Pill and Temperature Controller for Christmas. My first brew with it is almost at FG and I have been very pleased with the set up.
However, I haven't enabled the PID functionality. Does anyone have any advice for setting the PID parameters?

 

[hoppyscotty]

Just use default levels initially as ideally you'd tune it for your specific system characteristics. Not sure PID is really needed especially for fermentation or for the kettle. Works well with the Mash in my experience using an Inkbird PID on the default settings.

 

[RichardM]

Just use default levels initially as ideally you'd tune it for your specific system characteristics. Not sure PID is really needed especially for fermentation or for the kettle. Works well with the Mash in my experience using an Inkbird PID on the default settings.

I did wonder if it is worth it, but I have it, so want to play with it.
I agree that starting with the default settings is a good idea, but I have no idea where to start when it comes to tuning it.

 

[hoppyscotty]

Well I guess in theory you need to track the trend of the temperature response and depending on if you overshoot, undershoot, how quickly the response is once you're at set temperature will depend on whether you need to tune the P, I or D parameters. Some units have an autotune, but whenever I've tried using these they seem to take ages to run through their tuning cycle and the result is often not an improvement.

Again depends on the accuracy of maintaining your set temp. For fermentation a +/- 1 degree is perfectly fine so long as you're within the recommended temp range for the yeast and not dipping in and out of the recommended limits...really the yeast wont care if their temperature fluctuates a degree or so.

For the boil, well you can see when its boiling and ideally you want a vigorous boil so that is dead easy to manually manage.

Not sure what the tolerance is for temperature in the mash in terms of denaturing enzymes...how many degrees over the desired set temperature do you start to denature enzymes...I've always been paranoid if, during the mash, the system throws a wobbly and the temp overshoots by a couple of degrees for a few minutes but not really had any detrimental impact of this so think its more of a measurement issue rather than an actual temperature issue as the temperature response and lag of the full volume of the mash isn't that fast at all. These all in one systems often have the temperature probes located in sub-optimal' positions so can be affected by local effects. E.g. with my Brewzilla the temp probe is located under the mash basket and you can get wild temp swings of upto 10 degrees or so, but clearly this is just a 'cloud' of warmer wort sitting on top of the temp probe and as soon as it moves the measured temp will suddenly and immediately drop. This is why I like to maintain a good overflow down the overlflow tube to ensure you get good movement of the wort over the bottom with no wort stagnation.

I've moved onto a single infusion mash now without recirculation so I'll see about a degree temp drop over the course of an hours mash and its just massively simplified the mash process without having to monitor the system and worry if the readings go a bit haywire.

 

[aero-spaced-out]

I have both the Temp controller and 2 pills.

If it's any help...
I took my temp controller into work and carried out a 2 point adjustment at -5°C and 35°C and it changed some of the settings in the temp controller.

I don't use the temperature of the pill unless I really need to (fermenting in a 20L oxebar keg in my chamber)

Followed up with calibration readings (as found) every 5°C between my set points so that I had an idea of my non linearity in the reading that I can make corrections for. These extra incremental readings weren't used to change anything on the device, they were just for my own reference.

Never touched any of the PID stuff though. Considered it mind you but don't wanna play with something I'm not overly familiar with if what I have right now is working and doing what I need it to. If my temp goes too high, my cooling is quick to correct. Usually stabilises within an hour or two which I'm okay with.

On my temp controller I have tight hysteresis tolerances on my readings and haven't really seen anything greater than ±0.5°C from my setpoint. Do I need my deviation that small? No. Do I like it my deviation being that small? The engineer in me screams yes lol.

I use a thermowell in my all rounder lid with the probe tip submerged in sanitising solution as the thermal transfer fluid.

Currently considering getting a second bluetooth RAPT probe to get an idea of the temperature difference across the liquid from the vessel wall to centre of the solution as I've been reading and come to find that the lag in thermal transfer from the exterior of the all-rounder could mean the outer sections of the ferment could be hotter than I want them to be... I won't know unless I start tracking it.
It'll probably be at that point I'll start to look at my PID settings if I can't correct it with other settings first

 

[RichardM]

My temperature controller settings are still at the defaults. I am seeing larger swings in temperature than I did using an STC1000.
I think the default hysteresis settings are much larger on the RAPT controller than on the STC1000. I might have a play with them next time I ferment.
However, as @hoppysays, it probably doesn't matter, the swings are about +- 1 centigrade