# STC-1000 - Avoiding fermentation overshoots



## idzy (5/10/15)

Hi Guys,

Was talking to a guy the other day and he mentioned he has a heater in his fridge and has the temperature on it set to 25c or something and it got me thinking...

The STC-1000 has on or off and that's it. By controlling his heater he can avoid a large overshoot as the fridge warms up beyond the fermentation temperature and warms up the fermenting beer.

Just wondering if anyone has done this or something similar. I was thinking that you could control it pretty accurately with 3 STCs:

Maximum external temp (heater belt)
Minimum external temp (cold fridge)
Fermentation temp (controlling hot and cold)

Wiring diagram would look a little like this:


|- [Hot out] - [STC - Set to 25c] - [Heater Pad/Belt]
[240v outlet] - [STC (set to 19c)] - | 
|- Cold out] - [STC - Set to 15c] - [Fridge]

Does this have merit or am I on crack? I have never actually monitored the maximums and minimums of my fermentation temps, but thinking this would avoid large drops when the deep freeze goes into freeze mode pushing the temps down too far or vice versa.


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## growler (5/10/15)

Hi idzy,

The STC1000 has both heat and cool relays. the differential can be set from 0.3 to 10C.

You're over complicating........ or on crack!

Just try 1 to start with 

G.


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## idzy (5/10/15)

growler said:


> Hi idzy,
> 
> The STC1000 has both heat and cool relays. the differential can be set from 0.3 to 10C.
> 
> ...


If you have your fermentation set to 19c, it will only be active between 18.7 and 19.3, yes that is true. However, the difficulty is, if you have the probe set inside the beer, then the external temperature of the fridge/freezer could be quite different. This is most likely going to occur on initial pitch however (e.g. pitching at 25c and setting at 19c)...


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## Benn (5/10/15)

I use an STC-100 to run a little deep freeze with a heat pad stuck to the rear wall, I only seem to get over shoots in temp when fermentation is over and I drop the temperature right down to cold crash so now I drop to 3 degrees until it's all balanced out and then make the final drop to 1.5 degrees. My only real concern with my current method is the accuracy of the STC's temp probe that I insulate with cut up stubbie holders taped to the outside of the ferm vessel. One of my next purchases will be the NTC probe that goes into the actual wort. I've tried the longneck full of water method but the temp seemed to swing around all over the place. Works well for some people but doesn't seem to work too well with my setup.


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## Benn (5/10/15)

Another thing I'd like to add to my setup would be a small 12v fan to circulate the air (Co2...) inside my deep freeze just to even the ambient temperature a bit more.


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## growler (5/10/15)

idzy,

Hysteresis...i.e Over/Under shoot will always occur with an on/off type controller. Thats why people here use PID's for temp controll. If the probe is in the wort obviously the air temp will be lower/higher in order to change the temp.

If you are worried about the air temp then just controll that. Eventually equliberium will be established with the fermenting wort.

I personally use a styrofoam block behind the probe & taped to the FV side. Other brother brewers (FCBB) use the probe measuring the air temp.

Why not experiment.

Cheers G.


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## trevgale (5/10/15)

When I used to use an STC, I found that the temperature would hold pretty well within the control band when the probe was in a thermowell within the wort. When it was taped to the outside I would get a bit of a swing. I never really found the need for a heater, a fan and active fermentation were enough even in winter.

If you were going to buy 3 STC's you would be better of control wise to buy a Raspberry Pi, an Auduino and a few cheap extras and build yourself a BrewPi. It holds temps within 0.06degC, you can set temp profiles, check temperature logs and program it from anywhere over the internet. It would be a similar price to 3 STC's.


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## idzy (5/10/15)

I have the temp probe dumped in the beer itself.


trevgale said:


> If you were going to buy 3 STC's you would be better of control wise to buy a Raspberry Pi, an Auduino and a few cheap extras and build yourself a BrewPi. It holds temps within 0.06degC, you can set temp profiles, check temperature logs and program it from anywhere over the internet. It would be a similar price to 3 STC's.


Sounds awesome, but not a real coder or anything too technical.

Would be interested in seeing someone that has something fancier


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## DJ_L3ThAL (5/10/15)

Even in my chest freezer, which has the largest potential for overshoot due to extremely cold walls from running on the cool setting, only seems to overshoot by -0.1C that I have ever noticed.

Having your probe in the beer itself is the best, measure the variable you want to control directly. Having said that I opt for the tape and insulate on the FV wall.

If you want "fancier", I'd say rather than looking at the control philosophy, look at the method of applying heat/removing heat. Using still air (therefore natural convection) in an enclosed spacer and cold fridge walls is not a great method for cooling, not is a heat belt applying heat at a fixed point on a FV wall. Perhaps a coil immersed into the wort/beer that cycles warm or cool media through a control valve proportionally to the load and set point would be the ultimate. But is it overkill for homebrew? Yes! Do I want you to do it and report back, hell yes!

ED: Incorporate a Beer Bug into the above?! https://www.thebeerbug.com/products/ then you could incorporate a D-rest based on a actual current gravity without even needing to take a sample. Well you could still take taste samples


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## AJS2154 (5/10/15)

Hi idzy,

I have an STC mate, I find it incredibly good,l especially when you consider the huge outlay was $22.

I use mine summer and winter. I have a couple of heat pads on the side walls of a large fridge, and use it to brew some reasonably good lagers. I run the STC taped the the outside of a stainless fermenter, and can run 2 fermenters at the same time. The STC is set at 12 degrees plus or minus 0.5 degree. Runs well.

When the weather changes I move on to ale production and ferment at between 18 and 21 degrees (or more for saisons).....plus or minus 0.5 degrees. The system works well if you use the ambient temperature as your friend; lagers in winter, ales in summer. Go with the flow, man!

I would like the abiity to data log, but that is more my curiorisity than a necessity. Controlling fermentation to plus or minus 0.5 degrees is pretty tight.

I think we have the tendancy to overcomplicate things by thinking too much. Beer has been made for a very, very long time and it has been achieved without an STC.......30 years ago I would have been at cutting edge and in reality I am just using a $22 STC and a fridge which cost me $10 on Ebay....... $33 for the kit, and they work fine in producing good beer.

See you, Anthony


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## anthonyUK (5/10/15)

Don't overthink it Idzy. Many, many people use a single STC and it just works. 
For best results as mentioned above fit a fan or two, I have one on both heating and cooling in a 6ft fridge, have a low wattage heater and measure the wort temp with something to insulate the sensor from the air temp.
I have logged the temps using other methods but this is the most accurate.


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## mudd (6/10/15)

Hey Idzy,
Let's face it your not going to half do it are you? Brewpi will give you the bast accuracy and you'll learn a lot more about temp control.
If you want to get something up and running quickly stc is a great option.
Not sure if there is any difference when you are fermenting in hectolitres though.D Theoretically principle is the same. 

Cheers Mudd.


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## Crusty (6/10/15)

idzy said:


> I have the temp probe dumped in the beer itself.
> Sounds awesome, but not a real coder or anything too technical.
> 
> Would be interested in seeing someone that has something fancier


This is much fancier.
I use a single STC via a thermowell on a sanke fermenting kit as I ferment in stainless kegs but before that, I just insulated my temp probe against the fermenter using a piece of stubby cooler. 17.7 the heat comes on, 18 it goes off & 18.3 the fridge comes on. 18deg of course being the average temp. Works perfectly & pretty simple.


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## TheWiggman (6/10/15)

Took my head a bit to get around what you meant but yeah, it has merit. I have a single STC-1000, a fermenting fridge with a fan and a chest freezer for cold crashing. Two problems I find are -

Hunting when the ambient temp is similar to the ferment temp. It'll overshoot by up to 0.5°C, which means if I set the hysteresis too tightly it'll turn the heat on after the cold has finished and vice versa.
Overshooting in the chest freezer, consistently. By about 0.6°C.
One observation is that the fridge's thermostat results in funny things when crash chilling. It is locked on the coldest setting, so when I'm 'crash chilling' it actually takes about 2 days to get to 0.5°C (as cold as it will go). So for a fermenter sitting at 17°C with an ambient temp of 0.5°C, the chilling process is very slow - albeit more rapid to start with - which is ideal for my lagers so I'm happy to leave it like that.
With your proposal it will definitely address overshoot. The only issue being it's 3 different units to rig up, which all need to be set to one another, in a box etc. etc. and there are other alternatives in that price bracket. But hey, if you have them lying around then it's a free upgrade. I would have the two settings a bit tighter though, with a heat belt it's possible the brew will soak up more heat than the ambient air.

DO IT.


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## idzy (6/10/15)

Guys, the other factor I forgot to mention and the real genesis of the thinking is multiple fermentation vessels within the one chamber...

For instance, in my big deep freeze I have 3x 60 litre fermenters that have been in for about a month, fermenting out a RIS. I have the temp probe in the middle fermenter, but I always wonder if they go out of sync with one another somehow.

In my little chest freezer, I have 2x 30 litre fermenters getting a Vitus ready for Oktoberfest and a couple of Demijohns of mead. Same thing, I wonder about hot spots and cold spots. If the temp is ramping from 18.7 to 19.0, the fridge may get upto 23 degrees by the time it is ramped.

Hope this makes sense. Good conversation nonetheless.


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## Pogierob (6/10/15)

idzy said:


> Hi Guys,
> 
> Was talking to a guy the other day and he mentioned he has a heater in his fridge and has the temperature on it set to 25c or something and it got me thinking...
> 
> ...


I think what you would find is that the two external STC's would wear out fairly quickly, I don't believe they are designed to turn on and off that often, the relays themselves are obviously designed to turn on/off but the whole device?


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## simmo1972 (7/10/15)

mudd said:


> Hey Idzy,
> Let's face it your not going to half do it are you? Brewpi will give you the bast accuracy and you'll learn a lot more about temp control.
> If you want to get something up and running quickly stc is a great option.
> Not sure if there is any difference when you are fermenting in hectolitres though.D Theoretically principle is the same.
> Cheers Mudd.


Plus one for brewpi. Didn't take too much to build and read a good learning experience for me. Quite cool being able to check the brew from anywhere.


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## idzy (7/10/15)

Okay, brewpi is starting to pique my interest. Time for some google.


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## simmo1972 (7/10/15)

Mine can be viewed at http://rednblue.ddns.net you can see where i must of turned it off by accident! I have a different address to access maintenance page. 

It gets it to the right temp quick and then holds it. When you ask it to start to ramp down it gradually does it so not to shock although you can crash and once saved it can be repeated. 

My beer probe is against fermenter with bubble wrap and other is loose on fridge. 

I use a light bulb in a tin for heat.

Good luck


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## anthonyUK (7/10/15)

idzy said:


> Okay, brewpi is starting to pique my interest. Time for some google.


You can build one with parts from Amazon/ebay/Aliexpress.
I tried using a standard mechanical relay but it causes the Arduino to stop so I'm going to use SSRs.
If you need a parts list I can post what I used.


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## Mattrox (7/10/15)

I have been reading about the 2 temp probe mod of the STC 1000+.

That looks like a cost effective way to prevent overshoot. The 2nd probe has a hysteresis setting which cuts out the heating/cooling if the ambient temp becomes to different to the wort temp.


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## simmo1972 (7/10/15)

Simmo1972 said:


> Mine can be viewed at http://rednblue.ddns.net you can see *where i must of turned it off by accident! I* have a different address to access maintenance page.


Turns out from the logs that there was an error but because I can change online I changed it while on the train to work.
This was error:
Oct 06 2015 17:00:19 controller debug message: ERROR 10: Expected { got END OF INPUT

but soon sorted 
Oct 07 2015 07:07:54 Setting profile 'Wheat!' as active profile
Oct 07 2015 07:07:54 Notification: Profile mode enabled

If you do go down the BrewPI route it looks like Tony will help and I will also point you to the Aussie ebay people I use. Will also point you to the places to change your BrewPi to have some security when accessed across the internet.


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## idzy (7/10/15)

Simmo1972 said:


> Mine can be viewed at http://rednblue.ddns.net you can see where i must of turned it off by accident! I have a different address to access maintenance page.
> 
> It gets it to the right temp quick and then holds it. When you ask it to start to ramp down it gradually does it so not to shock although you can crash and once saved it can be repeated.
> 
> ...


Yeah, I'm game Simmo, lay it on us...

I have been googling a fair bit this evening and it seems like there are a number of options. The most compelling thus far is the following: https://www.youtube.com/watch?v=WUme8oTLxs8


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## idzy (7/10/15)

Mattrox said:


> I have been reading about the 2 temp probe mod of the STC 1000+.
> 
> That looks like a cost effective way to prevent overshoot. The 2nd probe has a hysteresis setting which cuts out the heating/cooling if the ambient temp becomes to different to the wort temp.


Looks interesting... I am guessing you need to buy it modded? Or has someone done this DIY?


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## Mattrox (7/10/15)

idzy said:


> Looks interesting... I am guessing you need to buy it modded? Or has someone done this DIY?


Directions on how to do the DIY are on the stc 1000p github page.

Also you can download the sketch for dual probe functionality with your fermentation temp profiles preloaded from his web-based profile editor snd sketch generator, link on github site.


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## idzy (14/10/15)

Problem solved. Why use 3 when you can mod 1. Will get it done when I have some time. Thanks gents


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## Mardoo (14/10/15)

Be sure to get the right version Idzy. Source is in the STC-1000+ thread.


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## idzy (14/10/15)

Mardoo said:


> Be sure to get the right version Idzy. Source is in the STC-1000+ thread.


Cheers man, will check my current ones off against the literature and buy from there in the future.


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