Backyard Poultry Forum • View topic - PID for temperature control

Backyard Poultry Forum

Chickens, waterfowl & all poultry - home of exhibition & backyard poultry in Australia & New Zealand
Login with a social network:
It is currently Sat Nov 25, 2017 2:53 pm

All times are UTC + 10 hours [ DST ]




Post new topic Reply to topic  [ 30 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Tue Jan 06, 2009 7:32 am 
Offline
Dapper Duck
Dapper Duck

Joined: Mon Nov 10, 2008 8:46 pm
Posts: 21
Location: Tassie
Hi,
Has anyone fiddled with PID's (proportional–integral–derivative controller) for temperature control. These are a "learning" thermostat that are able to maintain a very stable temperature. Read on them on wikipedia. http://en.wikipedia.org/wiki/PID_controller. They are pretty cheap on ebay these days and are very versatile with the ability to set temperature, temp swing between on and off cycle, and have the ability to "learn while operating to control temperature overshoot and undershoot. I like "plug and play" things, but they can be limiting at times, with their lack of control and adjustment. My current thermostat is working okay but I can only change st temperature by units of 1 degree C at a time and resolution by 1 degree C units. From reading they look interesting, but maybe too complex for me, and maybe overkill for controlling temperature in an incubator ?.

Mark and Karen


Top
 Profile  
 
PostPosted: Mon Mar 02, 2009 5:48 pm 
Offline
Dapper Duck
Dapper Duck

Joined: Mon Nov 10, 2008 8:46 pm
Posts: 21
Location: Tassie
Hi,
I bit the bullet and set up one of these PID controllers in the incubator, pretty straight forward and very simple to set up.
I am very happy with the accuracy of control, +/- 0.2 degree farenheit. The unit "auto tunes" to learn how to control the heating element to all but eliminate temperature fluctuations, and overshoot and undershoot problems.
I highly recommend one of these PID units and I got mine from these guys http://auberins.com/index.php?main_page=index&cPath=1 (the universal one). Also got a SSR relay that is needed because of how frequently these units switch, and a PT100 temperature probe from the same guys.
If you are frustrated with normal thermostats, try one of these !

Mark


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 8:54 am 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
Will the SSR cope with wattage up to - say 300 Watts that is required for the heating unit? Also is the smallest one - 25A SSR, sufficient for the job? I think it should be but I'm not sure.

There are two universal PIDs on the site, The first one is a bit smaller. The second one has dual display - both set temp and process temp. It can also switch between F & C which I like. Which one did you get? I think that having the process temp as well might be useful.

About the PT100 sensor - Do you think the faster response one is the way to go? There's a variety on the site - about 8 I think and I'm not certain about the benefits of each. What about this one:

Quote:
The miniature Pt100 RTD sensor has very small thermal mass for fast response. It is also suitable for places that large sensor can’t get into. Accuracy: Class A. +/-0.15C at 0.0 C. Alpha: 0.00385 Click Here for Temperature Vs Resistance Table Cable,...

Haven't bought anything yet, but I'm going to give it a go. It sounds like a good thing to play with. Thanks very much for the info & the link.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 9:18 am 
Offline
Prime Pekin
Prime Pekin
User avatar

Joined: Sun Apr 03, 2005 9:48 am
Posts: 3292
What did you use as a senser?


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 9:21 am 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
David, I'm not sure if you're asking Mark & Karen, or me. If it's Mark & Karen, he says in his first post that he got a PT100 temperature probe from the same guys. If it's me, I haven't used the system yet and am working out what sensor is appropriate. The thermostat that I'm current using is a 'plug & play' system with sensor built in.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 1:20 pm 
Offline
Superior Bird
Superior Bird
User avatar

Joined: Wed Aug 16, 2006 3:13 am
Posts: 3059
Location: Bendigo
The 25Amp is the cheapest I think. There is a 10Amp one (new) which is not appropriate for switching 240V.

300W would be a little over 1Amp and I would imagine the 25A SSR would handle that OK without a heat sink.

A SSR is pretty much the same triac output I use in my circuits but in a discrete package.

The website has some plug and play units including a Precision Temperature controller which is designed for incubators. It uses the RTD type sensors presumably the PT100. Pretty expensive, but with all the other units at their disposal you can assume this is probably the best for incubators.


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 2:57 pm 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
Thanks Denis, I thought the 300W would bit a little over 1 amp, but wasn't sure I was right.

I like the look of the plug and play models, but the cost is more than twice the price of buying the three components separate. I've ordered the three now, so I'll wait and see how it goes. By the time it gets delivered via international post, I should have some early results from the incubator running on the existing thermostat.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 5:18 pm 
Offline
Dapper Duck
Dapper Duck

Joined: Mon Nov 10, 2008 8:46 pm
Posts: 21
Location: Tassie
Hi Guys,
I was a little unsure of the combinations myself, so I asked the people from Auberins and I went with their recommendations. The Pt100 sensor is more precise and responds much quicker than the other options. With a normal thermostat a slow acting sensor is sometimes an advantage but because of the predictive nature of the PID, this is not a problem, nor is a heating element that is slow to heat and slow to cool. The PID seems to work by pulsing the power to the element at a rate that keeps it at the target temperature and only kicks in continous if the temperature drops dramatically (eg, opening the door of the incubator. As such a PID would not work properly with a light globe type heat source. Because of the frequent switching the SSR relay is needed. I went with the 25 amp one as it was ample for my needs. I am sort of using a heat sink as it's bolted to the aluminium lining on the heater compartment and has the fan blowing over it that also blows over the heating element. I went for the universal PID at $41 USD as that was the one they recommended. Its very simple to set up.
Mark


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 5:31 pm 
Offline
Dapper Duck
Dapper Duck

Joined: Mon Nov 10, 2008 8:46 pm
Posts: 21
Location: Tassie
Postage from the guys in the link was pretty good. Took 8 days from placing the order.

The Heating element that I'm using are a dime a dozen, old defrost units from frost free fridges. They come in all shapes and sizes, and wattages .... usually stamped on the element itself. Cruise around the local tip shop and there are any number of elements of low wattage that can be used, or adapted.
I overengineer everything, and I made an aluminium sandwhich with an air gap all around the heating element to reduce the direct radiant heat to areas of my cabinet, and a fan blows over the element continously. Sort of like a heat shield around a wood heater flue. Heat sources like this are a fire risk, and 240 volts is not something to be messed with unless informed. "One flash and your ash !". If unsure .... don't even contemplate it.
The PID's do require some 240 volt wiring.
I don't claim to be an expert but I am more than happy to help anyone out that wants to play with one of these PID's, in any way that I can.

Mark


Top
 Profile  
 
PostPosted: Wed Mar 04, 2009 6:09 pm 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
Thanks for the info. It sounds like I'll have to get my inhouse sparky to cast his eye over it before I wire it up. My incubator does have globes in it, but that can be easily switched if necessary.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
PostPosted: Thu Mar 05, 2009 12:03 am 
Offline
Superior Bird
Superior Bird
User avatar

Joined: Wed Aug 16, 2006 3:13 am
Posts: 3059
Location: Bendigo
kaz1104 wrote:
As such a PID would not work properly with a light globe type heat source.


Why not.?


Top
 Profile  
 
PostPosted: Thu Mar 05, 2009 8:33 am 
Offline
Dapper Duck
Dapper Duck

Joined: Mon Nov 10, 2008 8:46 pm
Posts: 21
Location: Tassie
Denis wrote:
kaz1104 wrote:
As such a PID would not work properly with a light globe type heat source.


Why not.?



Hey Dennis,
Please correct me if I'm wrong Dennis but I don't think light globes would last very long with the constant pulsing/switching that the PID uses for maintaining stable temperature (around once per second). Initially I had the fan that blows air over the heating element, switching with the element, but the PID switches so frequently the fan would not even come up to running speed before being switched off again. The fan is now wired to run continuously.
Mark


Top
 Profile  
 
PostPosted: Thu Mar 05, 2009 11:32 am 
Offline
Superior Bird
Superior Bird
User avatar

Joined: Wed Aug 16, 2006 3:13 am
Posts: 3059
Location: Bendigo
I haven't had any major problems switching at about once a second with light globes. They do blow occasionally but no more often than ones in a brooder which are left on all the time.
I just use Phillips brand and always have 2 in the incubator.

Lights usually blow in the first instant they are turned on due to a higher current with a cold filament. Dimming the lights is ideal as it just keeps the filament at the right temperature. Dimming however is just switching the power on and off faster than the eye can tell, about 50 or 100 times a second. I think switching at about once a second also keeps the filament pretty warm.

I certainly like the look and price of this one.


Top
 Profile  
 
PostPosted: Wed Mar 11, 2009 12:39 am 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
Well the electronics arrived today and they are now installed. At the moment we've just auto tuned it, and set it to turn off at 100F and turn back on at 99.5. I know it's supposed to work even more accurately than that, but that's what I'm trying first. While it's auto tuning it's coming on at 99.5 and going off at 100.1F. As soon as it finishes auto tuning the temp gradually drops down and the light flashes, but it doesn't keep up the temp. I think we've set it wrong. There must be a PID setting to alter. Too tired. Will try again tomorrow.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
PostPosted: Wed Mar 11, 2009 8:13 am 
Offline
Site Administrator
Site Administrator
User avatar

Joined: Sun May 11, 2008 8:44 am
Posts: 31464
Location: Morayfield, SEQ
Update: well last night we didn't give up. We changed the HY setting (for those who have these) from .3 to .5 and it worked. I'm not sure if it was already set correctly and was just taking a long time. Anyway, changing the HY setting seemed to allow it to get to temp quicker. We kept reading the instructions and just trying things. It was a bit random really due to my ignorance, but in the end it's sorted. It's now holding 99.8 almost constantly. I set it at that point so that it doesn't go over 100, but it only fluctuates by 0.1 degree F. It is very, very accurate. Now hopefully the bulbs won't blow, but at least there are two of them. Sticking the eggs back in now.

The parts took 7 days to get here from the US. It wasn't cheap. The total cost of all three parts plus postage was:

$155.22 AUD
($96.85 USD)
Exchange rate: 1 AUD = 0.623953 USD

I am sure that I'm going to love using it though. No more stressing about temp, this is just too easy once it's set. Thanks for the tip Mark.

Some pics in case anyone is curious:

First: PID Unit - quite small isn't it?
Image
SSR connected to PID:
Image
Image
Display on PID:
Image
I haven't bothered photographing the sensor. It's very small and just gets an in and out wire connected to the back of the PID. Just like a smaller version of what comes on a 'plug & play' thermostat.

_________________
image
Backyard Poultry Forum


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 30 posts ]  Go to page 1, 2  Next

All times are UTC + 10 hours [ DST ]


Who is online

Users browsing this forum: Yandex Bot and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group
©2004-2014 Backyardpoultry.com. Content rights reserved
freestone