# PID programming questions

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#### sgebbie

##### Newbie
Original poster
Alright so I'm comfortable enough after looking up information about PIDs to possibly pick one and or wire it up.

I'm having difficulty understanding some of the concepts of the programming. I ultimately want to run my fridge with both cooling and heating capabilities

Lets throw a random number out to start with. Lets say 55F as my starting fridge temp. For example say cooling I want to keep a cooling high temp of about 48F and maybe low temp of 38F. (keep in mind these are just random temps )

Since the fridge is starting out at a cold temp higher than both the high and the low does the cooling still kick on to get it down to that level or is that another setting?

Once the fridge gets down to the cold low(I would assume it would do that first much like a house thermostat?) does it just turn the cooling off and wait for it to reach either a target temp in between or the cold high point temp of 48F before turning back on? I know something should be limiting how much it cycles the compressor to not damage it so there has to be somewhat of a range or timer preventing that from happening too rapidly.

Next how does heat tie into this? Lets say for example 70% of the time it will be operating in the cold ranges and not using the heat. How do I basically set it to start heating up when I want it to? How do you set a hot and a cold range without making it fight between which to use?

If it's sitting between 38F and 48F and that's where I want it to be most of the time, how do I just suddenly tell it I want to boost up to say 160-180F? If I set the hot low settings in  between the cold range how do you keep it from trying to do both? If heat low is set to come on at  45F how does it ever get there if cold turns on at 48F since it has to cross that to keep going hotter?

Is there a logical way to program that I'm not seeing? It seems to me that type of a change would have to be manually programmed or a switch to flip from whether I want to do hot or want to do cold also like my house thermostat. I feel like I'm missing something incredibly stupid or obvious with this.

I would be very grateful if someone could help me break this down a little

Yes u need a manual two position switch and two pids. The switch will be set to either heating or cooling with one pid set up to control your heating element/device and the other set to control your cooling device.

Yes u need a manual two position switch and two pids. The switch will be set to either heating or cooling with one pid set up to control your heating element/device and the other set to control your cooling device.
Do you know of any companies that make one that's prebuilt this way or in a way that not a ton of modification would be needed?

I was looking at this but after reading your post I'm thinking it's not going to work right. Any particular device or devices you would recommend?

http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=334

Any ideas on how to set something like this up with the above or if not possible something else? I believe I'm understanding PIDs a bit but not sure of what all they are capable of or how to tie them together if I have two that are say switched.

That should work for what u want. Scroll to the bottom and click on the link for the instruction manual.

That should work for what u want. Scroll to the bottom and click on the link for the instruction manual.
I read that manual and it mostly makes sense. I just wasn't sure how the hot / cold on off part works. The manual is a little bit cryptic / incomplete for someone who doesn't really know what they are doing Lol. It pretty much looked like there are several ways to set it up. I almost kind of wondered if it would be easier for me to set up like you said 2 separate PID controllers and just rotate them as needed. I mean it wouldn't be that big of a deal if I had to unplug one and plug in another to do hot smoking vs. cold smoking or just straight up fridge mode. One single device would be cool and cleaner but really not a necessity.

I almost need to find a tutorial on how to program one for the desired temps and why or with an example of how it actually works when set properly. If nothing else maybe I'll get that one and play with it. It would be nice though to do it cheaper than \$80-\$90 and I could maybe do it with 2 more basic PIDs. I really would prefer F over C reading and from what I've seen the ones that have the F reading are a little more expensive. \$90 for one that does it all isn't that terrible just have to hope I can get it configured right.

I'm thinking a solution to my understanding may lie within using Hysteresis but I don't fully understand that yet. From what I've read and understood so far, it's a different mode than actual PID mode but not quite as accurate? Do you by chance have any insight regarding the use of hysteresis?

I have this controller... http://www.auberins.com/index.php?m...ult&search_in_description=1&keyword=SYL-2352P

in the manual it has directions for hooking up hot and cold to one controller... look for figure 5.6 on page 7 in the link below

http://auberins.com/images/Manual/Manual version 3.4.pdf
I was looking at that model too. That's the one I was planning to get before I saw the other one. Do you have yours hooked up that way? I looked at the manual and I'm kind of stupid when it comes to electrical wiring diagrams. I do fine with actually looking at the wiring but the diagrams don't always make sense to me. I think I understand how this should be wired up but I don't really understand how to program it right.

All the applications I've seen were more for something else (brewing / fermenting)  and I was having a hard time from those examples how I would configure it to do what I wanted it to do. Would you be able to explain how you have yours programmed if you have yours set up in a similar way?

No.. mines not set up that way.... mines just a regular hook up for my smokehouse.. i bought it for the ramp feature.... I also read in that manual the controller you want if you don't need the ramp feature ....

No.. mines not set up that way.... mines just a regular hook up for my smokehouse.. i bought it for the ramp feature.... I also read in that manual the controller you want if you don't need the ramp feature ....
So I must have been reading the manual for a different controller that looked similar. Page 2 and the Step features are VERY different for this controller and exactly what I was looking for to make some kind of sense out of this. Honestly having worked with code this makes a lot more sense now and I am positive this is exactly what I want / need to make this work.

Basically set it in an endless loop of do this temperature forever for refrigerator mode until I want to hot smoke. Press one or two buttons when I've got everything prepped for hot smoking to execute a step and ramp up to hot smoking temp. Run another step to hot smoke for desired duration then perhaps a cool down step ending in a fridge loop again or even manual back to fridge mode when I'm ready. VERY cool thank you. Also sounds like this thing can do like a million more things than I want to make it do too! lol

Only part I have left to figure out is the compressor control when ready to ramp up to desired hot smoking temp and control again when ready to turn it back on for fridge mode. Looks like auber instruments has a pretty decent forums area so hopefully can get some help on fine tuning the programming there.

Thanks again to both you and ElginPlowboy for your input here. I feel like I'm actually getting somewhere with this project now that I've somewhat figured out the harder part.

JckDanls 07

Couple last questions for you about your 2352P . What is powering yours? 120 or 240? and do you use the SSR output feature? I'm debating if the SSR output or Relay output (model 2342P) would be better for what I'm doing with it or if it even matters. It may not based on how I'm planning to run it but was curious about yours.

I have run mine on both 110 and 220 when experimenting.. going to run it on 110 while my heating elements will be 220.... Yes, i do use SSR's for the heating elements (1 for each element)... as you know mechanical relay's are ether on or off, probably better for cooling ... SSR's work much better for heating ... as they are on and off MANY times a minute .... good luck with your venture (whatever it is... ya haven't said yet)

I have run mine on both 110 and 220 when experimenting.. going to run it on 110 while my heating elements will be 220.... Yes, i do use SSR's for the heating elements (1 for each element)... as you know mechanical relay's are ether on or off, probably better for cooling ... SSR's work much better for heating ... as they are on and off MANY times a minute .... good luck with your venture (whatever it is... ya haven't said yet)
I'm not incredibly qualified or even claim to know a lot about what I'm doing  to be messing with electricity so LOL hopefully I'll figure out how to power this PID without blowing myself up. I think a concept I read on another message board with some good pictures of how to wire one of these up for a standard outlet should work OK.

As far as the SSR vs. relay I'm going to have to think on that one a little before I buy one or the other. I'll be doing hopefully a lot of both. My project is a mini fridge smoker that will operate as a cold smoker, hot smoker or just plain old regular fridge for pop, beer or whatever when I'm not smoking anything. Ideally I want to have it in my basement and be able to route it outdoors so that I can smoke year round. Here's the link to the thread I have going for it so far. It's going to be a long one with probably a fair amount of failed attempts at this or that before the good end result. Hopefully most of the failed attempts help other people like me and don't cost me a fortune in the build while I learn stuff.

I'm still in the REALLY early stages of this whole project but I think I at least have the smoke generator part figured out and am getting along nicely with the info on the PID to control it all. This whole thing is kind of based on a smoker that dcarch made about a year ago. I got curious one day and did a web search for running a smoker indoors. I guess I have the winter months fever right now and was desperate to get something going when I can't realistically get out the barrel smoker in this terrible weather! lol

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