Tuesday, February 8, 2011

Maiden test brew

Pretty early on in the construction I wired up the heating element, Solid State Relay and got the MCU reading temperatures from the DS1820.

So it would already have been able to do a mash and boil with manual intervention at various points.

Kelly has been wanting to test a Hoppy Red Ale recipe in a small batch for a while and I have been telling her to avoid doing it on the stove (temperature is hard to regulate there by hand). The brewbot can do the temperature part.

Well we finally did tonight.

It was good to get a sense of how the system dynamics are and if the basics are working.

I set up FreeRTOS on the RDK with some simple tasks to monitor temperature and the push buttons.

Up/down would control the temperature set point, and after some experimentation, left/right buttons would control the heating duty cycle. On the LCD was display both those parameters as well as the current temperature in the thermowell.

We did a test boil in the pot the night before and the boil was very vigorous, splashing water out of the pot, so I decided to add the duty cycle adjustment feature before doing a mash.

Kelly had a bag that fit the pot perfectly. Keep in mind that the true bag will be stainless steel mesh and quite a bit smaller.

The test recipe called for a OG of 1.066, so a relatively big beer. We were aiming for a final volume into the fermenter of about 2 gallons. This should nicely validate the volumes and sizing of the pot.

The first step was to setup in the laundry near the 240V outlet.

The laptop is there for final code tweaks and eventually won't be needed.

Then dough-in and some experiments.

Without constant stirring it seems a hot pocket would form and rapidly overshoot but the overall mash temp would slowly drop.

Constant stirring seemed to solve this.

Luckily constant stirring is part of the final design, just not yet implemented.

We also discovered that for the mash I needed to turn the duty cycle right down on the heating. Down near 10% to prevent too much overshoot.

I may also implement the PID control algorithm to help with this.

The boil was run at 50% duty cycle. So about 1750W. This means I probably didn't need to use 240V power, and could probably run this off an ordinary 120V outlet.

The SSR and it's heatsink didn't get warm at all, so I think we are well within spec there (I have heard that these need to be massively overrated and can explode quite violently in some conditions).

The boil causes this rocking of the wort to form.

Post boil, whole hops floating:

 No-chill into a 10 litre sankey keg I got off ebay:
 We did have some problems with hops clogging the tap. Will have to come up with a more permanent solution that the strainer Kelly held over the outlet.
 Some minor caramelisation on the element.

But overall seems to be a successful first test batch.

Now on to build the bag and stirrer. Build the hop dropper. Write a ton more code. And write it all up and submit my contest entry.


  1. Great update Zizzle. Good to see you're not making man cordial anymore :)

  2. Nice work. I'm sure you'll do well in the contest.