Love vs. PID for fermentation temp. control

OK, so I want to build something like this:
http://www.gbrewing.com/2009/10/14/fermentation-temperature-control/

one outlet for my chest freezer and one for a small heater fan to be able to raise/lower fermentation temp. I know that one looks like a LOVE controller. Here's the question...is a PID controller better/worse/the same? Correct me if I'm wrong, but would a PID controller effectively "learn" when to shut off power so that you wouldn't over/undershoot temperatures? Anybody set one of these up either way? Please post pics if you have them. Also, I would need separate SSR's with a PID correct? Thanks guys! Oh, and yes I do know that I could buy a dual stage Ranco, but I wanted to build this on my own.

IMHO using very exact temp controllers is a bit of overkill. However the digital output is nice.

To make one from parts you essentially need 4 things:
1) A temp controller (PID) that senses temperature and can trigger a relay.
2) A temp probe that connects to the controller (thermocouple).
3) A relay (SSR, or Solid State Relay) to switch on/off AC from a DC input (from the PID).
4) A 24v, or 12V (depends on PID) power supply to power the PID and DC side of the SSR (via the PID).

The process is actually quite simple in design. It is a probe that becomes less resistant as it becomes cooler. That is connected to relay that opens or closes based upon the resistance of that probe. That relay sends power to the unit where the probe is to cool/heat.

Torg said:

IMHO using very exact temp controllers is a bit of overkill. However the digital output is nice.

To make one from parts you essentially need 4 things:
1) A temp controller (PID) that senses temperature and can trigger a relay.
2) A temp probe that connects to the controller (thermocouple).
3) A relay (SSR, or Solid State Relay) to switch on/off AC from a DC input (from the PID).
4) A 24v, or 12V (depends on PID) power supply to power the PID and DC side of the SSR (via the PID).

The process is actually quite simple in design. It is a probe that becomes less resistant as it becomes cooler. That is connected to relay that opens or closes based upon the resistance of that probe. That relay sends power to the unit where the probe is to cool/heat.

Click to expand...

Sounds like you need to write up a tutorial!

Seriously though, does anyone know of a tutorial around to build one of these?
All of my searches come up with pre-built controllers like Ranco and Johnson.
I'd like to learn how to build one from scratch.

Ok get a PID controller. It should have some terminals on it somewhere. There should be connections for a probe, input power and output power.

Some already have relays in them (i.e. just pout 110V AC to its input and output to a plug). Others have to have just DC voltage. It sort of depends on which one you get.

If it is DC only you need a DC power supply. I looked at the Dwyer page and they make a TSS2 which works off AC power and has a 110V SSR built in. It depends on model. The TSS2-2100 is a dual stage, 115VAC model. So wiring one should be as easy as running some wire from power to it, to socket and to the probe.

--AC Hot---TSS2 input Hot
--AC Neut--TSS2 input Neut

--TSS out Hot---plug hot
--TSS out Neut---plug Neut

Then wire in a temp probe and you are done. It is not really engineering as it is running some wire.

My ferm chamber build in my sig details how I use a TSS2 Love controller.

Here's my "please help me wire my love controller thread":

Pls. ignore the awful photos--I'll get some better ones one day...

https://www.homebrewtalk.com/f11/temperature-controller-wiring-help-129200/

illinibrew04,

You are correct about a PID. Here is a quote from WIKI.

A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly and rapidly, to keep the error minimal.

Click to expand...

The Love Control does not require any SSR and can be ordered for different voltages. A PID is also available to control different voltages. 24 volt is a choice but is not required. 120v can be handled just fine. These are handled through the SSR's.

I also have a PID system controling my brew system. I chose to use the BCS 460 and am a huge fan of the system. It does anything I need it to do and the support for the product amazing. Most PID's will require you to use an SSR for each output. The SSR's can be ordered on Ebay and are fairly inexpensive. (2 for $20 can often be found).

You will get better control of your system using a PID than a simple Love Control. There are lots of other PID system available but I really enjoy the BCS 460 as it was designed for brewing.

Good luck.

I would beg to differ about having better control over the cooling system using a PID controller.

Likely you are using the controller to turn off and on the compressor. The tighter you want to hold the temperature to your set point the more PID is going to want to cycle your compressor. There is a minimum amount of time that the compressor needs to run before it actually starts cooling, plus the frequent cycling will cause premature wear.

Basic hysteresis control is ideal for our applications. Turn the compressor on when the temp is x deg above the set point turn the compressor on and then turn it off when the temp gets x deg below the set point. Then have a minimum off time for the compressor to limit short cycling.

Now, were you using glycol to cool the chamber via an adjustable flow control valve that is controlled by the PID. Then YES a PID loop is the ideal solution and you can hold a super tight error on your set point.

If you REALLY want a PID controller type look, I would suggest the SYL-2342 with the following parameters.
At=0 ; Control Mode ON/OFF
Hy=2 ; Turn on and off +/- 2 deg of the setpoint
t=60 ; keeps the compressor from cycling more than once a minute.

Nothing against the BCS, I just think it is way overkill for a fermentation chamber. Unless you want/have the ability to monitor temps from the www then there is no real value add for this application. I am actually considering playing with one for my brewery but that is down the road.

The Auber controller is less than 1/4th the cost and you don't have to buy an external relay.

I agree with Coderage about the mode for cooling and the cost. The BCS 460 is more expensive. You do need to purchase the temperature probe(s) and the SSRs. That is why I am using the Love Control for my cooling needs.

I should have been more specific when refering to the PID device. Most of these devices have other modes. The BCS has four different ways it can control a state; Direct control, Duty Dycle, differential, and PID. The modes I have read about used as refrigeration with the BCS is the differential mode.

Differential - Control the output by associating it with a temperature input and hold the temperature within a defined temperature window (swing)

The cool (no pun intended) thing about the BCS is that it allows you to do temperature ramping. An example would be holding a temperature at 62 degrees for 3 days and then dropping it to 52 degrees over the course of 12 hours (or set ramp time). You could then hold the 52 degrees for a desired period of time.

It is customizable.

With that being said, I am still using a Love Control for my fermentation control. I don't see myself investing in another BCS 460 at this time since I already have one for my brewing and the Love Control handles this process just fine.

I have a Love TS controller hooked up to my fridge right now. I hooked it up to control fermentation temp of my stout, and now the bottle conditioning.
Its my first brew, so I'm not a homebrew expert (haven't even popped a top yet--need one more week minimum in bottles), but I've had a Love controller for about 6 years and a PID for about a year.
I had the Love controller because in the past I used it on my Bradley electric smoker for smoking sausage and other cuts of meat. I now have a PID on the smoker, so the Love has a new use for homebrew.
I'd agree w/ others, that a PID on a fridge/freezer may affect proper compressor operations. As the freezer approaches set temp the PID will turn the compressor on/off several times a minute unless the PID is set to limit on/off cycles. When my smoker gets to set temp, the PID cycles the heat element on/off every few seconds and maintains the temp w/in 1 degree.
The Love controller I have (and I believe the one in this post's photos) is a digital thermostat, not a PID. So it doesn't hold the temp quite as exact, and won't cycle the compressor as often, but still keeps the temp w/in a few degrees of set point. Its a bargain at about $60 retail and includes its own temp probe. I'm sure it can be found cheaper.
If I move into a keg setup and keezer, I'll most likely use another Love controller. I mounted mine in a Radio Shack project box and with a plug-in receptacle too, so the controller plugs into the wall, and the fridge plugs into the project box.
drano

there are a few threads on here from relatively recently about building one yourself. one uses an arduino board and one uses a home thermostat with SSR. the thermostat one is limited by how low the termo can be set, but works fine. but if you want to use the same concept as the thermostat one, you could eliminate the SSR and just use a love controller instead, like the one in the link you posted.

https://www.homebrewtalk.com/f51/diy-temp-controller-build-133364/

https://www.homebrewtalk.com/f51/my-ugly-but-kinda-sexy-temp-controller-136870/

Awesome replies guys! Thanks for all the input. I think I'll build a two stage project box controller out of the love controller.

Thanks.