Adventures in smallscale geek cooling (homeassistant, ESP32s and micropumps)

[Agentgonzo]

Pretty-much universally, all the beers I brew are ales so fermenting in the utility room provides decent-enough temperature control, sitting at 19-21 degrees year round except hot summers. I've swamp-cooled my fermenter before.

I've been playing with electronics for a while now, and don't have the space (or inclination) to get a separate fridge just to take a fermenter. I use a heat-belt, combined with automation and a smart plug to automate warming the beer, but there is no simple equivalent for cooling the fermenter.

So I set about playing with stuff to see what I could come up with, and here is what I came up with. Similar to many low-tech lagering/cooling approches, I don't need a separate fridge if I'm prepared to move cool blocks once or twice a day into a cold reservoir.

Simplified setup
Basically similar to low-tech lagering. Run a tube around the fermenter with both ends of the tube in a reservoir. Have a pump in the reservoir that pumps cold water around the fermenter when it's too warm. Lots of people use an inkbird, but thath's big and chunky, so I set about building my own

The reservoir
As mentioned, I don't have a lot of space and my fermenter is in the sky

But there is a small space next to the fermenter, where I can keep a small reservoir.
This 3L LocknLock tub fitted nicely next to the fermenter

I have a bunch of cool blocks. Some silicone tubing was bought from ebay.
The next thing was the pump. I didnt' need a big one, nor a powerful one. As long as water flows at a moderate speed, it'll cool the fermenter.
As it turns out, you can buy teeny tiny USB-powered pumps! The photo doesn't really show how small it is. It's 2.4W and only 6cm long. Plenty small enough to sit inside the tub. Apparently in shifts 2L of water a minute, which is plenty.

I wrapped the tubing around the fermenter 4 times, froze some tupperware tubs of water in the freezer, filled the fermenter with water and put the pump on. It dropped the temp by about 2 degrees in an hour. Plenty fast enough - no points for cooling too fast.
It turns out that 1L of ice does a lot of cooling

The controller
Obviously, having to turn the pump on/off manually is not going to work. So I needed some sensors and control software.

A tiny dallas DS18B20 temperature probe (which I'm pretty sure is what most things like inkbirds etc use anyway) costs about a dollar when got from AliExpress. Plus, it'll go into the fermenter thermowell. Bonus

I wired some dupont connectors to the end of the probe.
To control it, I got an ESP32 C3 microcontroller for about $1.50. Wifi included!

I then set about wiring it all up, in short wiring/soldering together:

1. The ESP32 microcontroller
2. 2x Dallas temperature probes (one for the fermenter theromwell, one for the cold reservoir)
3. A USB socket, so I can power the pump
4. Some protective diodes/resistors
5. A MOSFET to turn the pump on/off based on the output from the ESP32 (thanks to @The-Engineer-That-Brews for helping me out understanding the electronics, protection circuits and even sending me the MOSFET!)

I might get a wiring diagram set up, but here's a photo instead:

Red = 5V rail
Black = Neutral
Yellow = the 1-wire data protocol for connecting the two Dallas temperature probes
Blue = control signal to turn the MOSFET (white/black rectangle at the top of the blue wire) on/off
Bottom white plug = USB-C power
middle two cables: temperature probe connectors (dupont connectors)
Top USB cable is the power to the pump

Control software
I didn't want to write my own control software, because I already run homeassitant at home so can just use this for the control logic. So all I needed to do was install the ESPHome software onto the ESP32 chip, connect it to WiFi and home assistant, configure the ESPHome to have 2x temperature probes and 1x switch and away I went.

Then it was just a case of writing an automation in home assistant to go "when the temperature changes, if it's above the target temperature then turn the pump on, otherwise turn it off"

With a bit of finessing, it looks like this

The temperature will remain stable at the target temperature until the ice blocks melt and the reservoir heats up, so I have to swap out the blocks about twice a day. But the overall temperature swing is ~1-2 degrees if I lose the windo and it's actively fermenting and the yeast is being exothermic.

The last thing to do was to chuck the reservoir in a cool bag to keep it cooler and prevent condensation going everwhere

The final thing I need to do is onder and wire up a new temperature probe because they're not as waterproof as I had thought, and the one that I put in the ice bath stopped working shortly after I submerged it in water , which is why it reads as "unknown".

It's certainly not beefy enough to lager inside on a hot day. And If I use about 2-4 frozen 1L cubes of water it can get the temperature down to about 5 degrees before racking, but TBH I'm not that fussed as I just leave it a week and it clears up nicely without needing to chill hard. It takes the heat away during summer months, and was a fun project.

 

[Agentgonzo]

All-in-all, the kit cost me about ~£25 and hours of fun. And that £25 is less than an inkbird costs. And my controller is way tinier. And I made it

 

[MashBag]

I have a vaguely similar setup. Have you considered an alarm or alert for the reservoir temp?

 

[Agentgonzo]

Yes. I had one of those set up initially the sent a notification to my phone (using home assistant notifications) if the reservoir went above 10°C.

Then I broke temperature sensor so am waiting on a new one being delivered

 

[Twostage]

Yes. I had one of those set up initially the sent a notification to my phone (using home assistant notifications) if the reservoir went above 10°C.

Then I broke temperature sensor so am waiting on a new one being delivered

I buy them 5 at a time. Some seem to work most of the time but not all and I just swap it out and bin it.

Good project. There is a lot of pleasure when it all comes together. Active fermentation is only a few days really which is when it needs cooling so swapping out ice blocks shouldn't be too onerous.

 

[Agentgonzo]

Good project. There is a lot of pleasure when it all comes together. Active fermentation is only a few days really which is when it needs cooling so swapping out ice blocks shouldn't be too onerous.

Indeed. I'm sure the novelty of swapping cool blocks will wear of eventually, but it's not too hard. I work from home so it's a good reason to get me out of my chair for a break.

 

[Buffers brewery]

The final thing I need to do is onder and wire up a new temperature probe because they're not as waterproof as I had thought, and the one that I put in the ice bath stopped working shortly after I submerged it in water , which is why it reads as "unknown".

I used a nylon cable gland to fit a probe in my mash tun. Got one suitable for 6mm dia. cable. The rubber sleeve of the gland fits snug on the metal body of the probe and when the gland nut is fitted it's watertight. Just need to drill suitably sized hole in the reservoir (and seal that too).
Good to see a cat skinned differently!