Fridge Internal AC Fan Control

I wired my fridge to have three SSR: one for heat, one for cooling, and one to run the internal AC fan. I am trying to program BrewBlox to run the fan any time either the heating or cooling is running.

Things I Tried:
First i tried two separate PIDs for heat fan and cool fan, but that does not work and the PID outputs seem to offset each other. Then i tried PIDs with separate PWM blocks, but the blocks fought for control of the fan actuator. The only other way i see is to use a manual actuator and leave the fan on constantly. However, wouldn’t this prematurely wear the fan out?


  1. How do most people control the internal AC fan in their chambers?

  2. Is there a way to implement a If/Then for the Fan actuators? (i.e. IF Cool = 1 OR Heat = 1, THEN Fan = 1)

This functionality still has to be added. A logic block has already been added to our features to be implemented.

I would set up a PWM actuator and run the fan on low speed continuously.

Can’t you create a cooling AND heating PID hooked up to their own PWM hooked up to the same actuator? So have both two heating and two cooling PID and PWM’s. Not the nicest way, but it does do what you are trying to achieve afaik

(I tried hooking two PWM’s to the same Actuator on my brewpi and that at leat was possible in the software)

I see that you tried this after re-reading your post. And putting a mutex between the PWM’s?

Technically it’s possible to mirror the heat/cool chains, but with no guarantees that the on-off cycles match.

It’s highly likely the PWMs have a comparable duty setting %, but you’re missing any cycle stretching caused by min/max on/off constraints on the digital actuator.

Hardware-wise you can slave it to either the heater or the cooler by putting the SSR on a power strip with both the element and the fan. This is of course not perfect either.

Software-wise it’s a high priority feature. Firmware dev time is constrained by Elco also having a company to run, so we can’t pin a definite ETA on it yet.

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