Tweaking temp variances

Hello! I have my brew Pi on a Pi 2 with Audrino. This has been working great for a few months and I love it so much. I am having s few issues with my temp variances and would like to dial it in. All my settings are default right now. You can see I’m having a 1 degree variance and would like to tighten it up.

I am logging every 10 seconds, which I am unable to change. When I change the intervals and apply. If i open setting again it is back to 10 seconds.

I am using chest freezer with SS fermeter with thermo well in front side for beer temp and ambient fridge inside. I am using a 40w fermwrap for heating.

Here are my settings currently:


PID KI 0.25
PID kd 1.5
pid maximum 18
integrator maximum error 0.9 F

temp idle range top 1.801

bottom -1.801

heating target upper .541
“” lower -0.359

cooling upper 0.359
cooling lower -0.541

maximum time in seconds for heating overshoot 600

“” for cooling overshoot 1200

beer fast filter delay 78 seconds

slow filter 159 seconds

slope delay 8 minutes

fridge fast filter 18 seconds

fridge slow filter 159 seconds

fridge slope filter 4 mintues

Another example

Your beer temp goes up when the cooler is enabled. Do you have your heater and cooler mixed up?

I don’t think so. At that time I did not have a heater. I only assigned the cooler outlet spot and relay. I then waited for it to kick into cooling mode and my fridge turned on.

I will double check and make sure.

I am pretty sure this is interference from using mechanical relays.
Please switch to SSRs and those weird spikes will be gone.

This is what I currently use.

How come I have no issue with my heater being inverse?

Here is a zoomed up image of the heater. You can see that it shows it raising the temps.

Here is a zoomed from a cooling one.

What SSR do you recommend? And also how do I hook that up to my current setup does it hook up the same way as the current relay?

Would this work as a replacement.

SainSmart 5V 2-Channel Solid State Relay Board for Arduino Uno Duemilanove MEGA2560 MEGA1280 ARM DSP PIC

never mind I see that this is only 2A. I am not sure how i would hook up the SS to my current setup which looks similar to this.

Also with my current setup like this , I should be using inverted correct? on my relay devices.

Get something similar to this:

But I would avoid Fotek. I have heard too many stories of failed Fotek relays.

You heater is probably not a problem, because it is low power and not an inductive load.
Hooking up the SSRs is very simple: minus goes to ground, plus goes to a digital signal pin.

And I can still use this with my current Audrino setup? So I just buy 2, 1 for heater and one for cooler? Also with the SSR I don’t need to use inverted pin setup like I currently am using with mechanical correct?
With my setup and using SSR what would the red wire I believe it says VCC shown in diagram above going from relay to terminals go to on SSR if it just has the ground and digital.
Thanks for all the help so far.

Yes, you can use this with Arduino too, not inverted.

You connect them to the signal pin an ground. The SSR’s don’t need VCC.

So if I have my current setup like the picture above. Would my new setup look like this with SSR?

I took away red VCC wire.
added 2 10A SSRs to replace 1- 2 channel relay
added another ground green wire for second relay

I shouldn’t need a heat sink for these would I? 1 on cooler 1 for 40w heater? It is just a small 5cubic foot chest freezer.

Looks good. I don’t think you would need a heatsink for these loads.

Perfect. I ordered some of these up. I will test it out and get back to you. My one other question for now is how come I cant change the logging seconds. If i change them and hit apply, when I open the menu back it is set at the default.

I think it is just the field in the web UI which doesn’t get updated (retrieved from the script). The actual value used does change.

i got the SSR hooked up the spikes seemed to be resloved. will let run and see. the one thing i noticed was when i put a outlet test into the socket when the relay is turned off. It still lights up faintly and flickers tiny bit. and then when the relay is ON fully the socket tester lights up full power. Is this wired up incorrectly or is this normal? also the tester indicates correct wiring.

This is over night with the SSRs and it appears that the spikes still appear.

The SSR when OFF also has a very high resistance, but not infinite. It will let through a tiny bit of current. Because the socket tester only requires a tiny bit, it still glows faintly. This is nothing to worry about.

Are you sure the spike is caused by the cooling or the spike caused the cooling?
The spikes are not higher then 1 bit of the sensor, so it could just be a normal bit toggle. Zoom in more to verify.

At first, you had a huge spike of more than a degree, these are not higher than 0.06.

These are the spikes zoomed in.

Looks like the temperature is rising before the cooler turns on.