Needed hardware for a glycol powered 4-fermentor system?

I have 4x 175L stainless steel tanks that I’ll be using as fermentors. I’m planning on using 150W reptile cords for heating, and glycol for chilling, pumped through a 3/16" coppar tube on the outside. Both are about 15m long, enough for it to go around about 10 times. Isolation on the outside of this of course, but exactly what is not yet determined.

Initially I think I’ll set up individual pumps for each tank, may switch to a valve system at some point thou. So I reckon I need 4 SSR:s for pumps, another 4 for the reptile cord, 4 sensors for the tanks, 1 ambient, 1 glycol, 4 extra shields to connect to SSRs and sensors.

Simple sketch, numbers show what port the sensors are connected to:

So for this build, here’s my shopping list:
1x Base system
8x SSR
6x Sensors
4x Shields

Does this look right in terms of what I need?

If you are using a glycol setup you will need to have the code for PWM (not yet 100% complete) and then only a single sensor per fermentation vessel (ambient/fridge is not required). If you want to control the glycol system itself with the BP I don’t think the code is there yet as that would essentially be a second chamber (focus now is on completing the HERMs ability multichamber will come later). This also raises the question are you looking for different temps across all the fermenters if so that is multichamber support and you will be waiting a bit. Once that support is there the setup should be pretty straight forward:

1 probe 1 SSR controlling the cooling of the glycol chiller
1 probe per fermentation vessel
2 SSR per fermentation vessel (heat/cool)
1 shields per fermentation vessel (controlling the 2 SSR attached to each vessel)
1 SSR for glycol chiller
1 shield for glycol chiller

Again at this time the support for this is just not there, but it’s coming.


The way I have it in my head now actually is that each PID is entirely independent.

You’ll have a list of sensors, which you can name.
You’ll have a list of controllers, which take a sensor as input
You’ll have a list of actuators, which take a PID as input

If you set up multiple pids for multiple processes, why not. I think PIDs should be the center, not chambers. It is more flexible this way. For the gylcol system above, I just see 9 independent PIDs.

Another idea I have is that you can define actuator groups. Actuators belonging to the same group cannot be active at the same time, or would even require an interval between switching.

If the minimum switching time is zero, they can just not overlap. The main application I see for this is that you make the BK element and HLT element mutually exclusive. But if they are both running at 50% or 10% 90%, they can just alternate their PWM cycles. You would be able to run 2 16A elements on a single 16A electrical group.


I’m not sure what part I would use the PWM for. I saw your experiements and the quick cooling, but this is with a submerged coil right? I’m having mine on the outside. You think it will chill as quickly?

As for the multichamber, reading through older posts I was convinced this was in already. If not, yeah, that will be an issue. I’m not sure what kind of chiller I’ll have yet, so it’s best to assume I would need 5 chambers then.

Any idea what the timeline would be for that?

Can the arduino version run on Nano? I believe I have enough of those laying around to get started, just need the sensors and SSRs, which will then be re-used when I can plug in a Spark instead.

With actuators this sounds like a good idea. Even if you don’t need to share an electrial group, safe-guarding against heating and cooling at the same time would be good.

Is there no resource penalty from running more PIDs?

Yes, each PID will take up quite a bit of memory. There is a reason I am moving away from Arduino. It doesn’t have the resources to run a lot of PIDs.