PID questions

[banditpowdercoat]

Originally Posted by StirCrazy

Dan I just re-read your sugestion and I think I misunderstood, do you mean to use the meat controler PID alarm output to energize the smoker temp controler? so that as long as the meat is under the set value it will allow the main controler to do its thing, but ones the meat reaches the set temp it cuts the power off to the main controler? the only issue with that would be for the first 2 or 3 hours you don't put the probe into the briskit as you want the outside to be cooked a bit befor you insert it to eliminate the possibility of draging bacteria into the inside of the meat where it is going to be at a lower temp for longer.. mind you that is just a set point change.. start it out at 250, then when I stab it readjust it to the temp I want the meat to be.. not a big deal..

so more or less using the meat temp as a limit switch for the cabnet temp.

Steve

Yes, thats what I was meaning. I'm not familiar with smoking meat but ya. Or, what if the meat temp probe stays out of smoker while you cook for the first couple hrs, then it will remain cooler, then put in meat?

Also, I know the PID says it has a 10A capable contacts on it, but do yourself a favor and wire a relay with it. A relay is cheaper, and WHEN it fails(not If, WHEN), it can be replaced easier. Usually the whole PID control has to be changed when the relay goes. and I have had them go. It's not only current, it's current over amount of cycles. And when the cooker is up to temp, the PID will be Pulse Modulating the element on off on off. Doesn't take long to fry contacts that way. In my experience Ive changed a few of them. Companies hate it when you tell them their $5000 PID controller is toast because someone used the internal contacts to switch load.

[StirCrazy]

SO I should get the SSR output one then instead. now the alarm outputs are 3 amp, should I use external SSRs on them also for 1 amp loads? these ones won't be on/off cycling they will be on for the duration of the smoke.

hmm that leaves a spar alarm output.. I could rig up a time based sprayer to bast the meat every 30 min... hmmmm

Steve

[banditpowdercoat]

SSR outputs do last longer for sure. And I wouldn't worry about the alarm output's they will be fine. It's just relays wear out faster when subjected to higher loads and cycles. The PID may in all fact outlast your smoker, and if you just used the relay contacts directly, you may get 20 years use. But it may also crap out in 2 years. I always like putting in cheaper parts for the places that will see the most abuse.

[DiverDude]

Ok, I see -so you want a fairly large unit. I was going to harass you for going electric and suggest that you just get the Webber Bullet (what I have) but you said the magic words "cold smoke". I wouldn't mind an electric smoker so I could cold smoke fish and sausage (not that I make sausage much these days -so much work !) but frankly, I'm almost scared that if I got one I'd get lazy and not use my charcoal unit anymore !

Any interest in rolling your own controller ? I used to sell microcontrollers for a living and if you like electronics, you can have a lot of fun making exactly what you want, yourself !

I figure it's just a matter of time before I design autonomous systems to monitor my tanks' variables, ATO -maybe some dosing in the future.....

[ScubaSteve]

If you want to ramp and dwell, you can go on ebay and get a pretty badass multipoint controller for cheap. I just got 4 of them for my lab this way last week; cost me about $150 but it would have been over $3000 new. University surplus is awesome!

Like DiverDude suggested, I would consider going the microcontroller unit. The easiest to work with is the Arduino. It costs $50 and is EXTREMELY flexible in what is can do. You could make an Arduino do exactly what you want for next to nothing! Hell, you could even control the thing from the comfort of you laptop.

[StirCrazy]

Originally Posted by ScubaSteve

It costs $50 and is EXTREMELY flexible in what is can do. You could make an Arduino do exactly what you want for next to nothing! Hell, you could even control the thing from the comfort of you laptop.

Hmm now that sounds interesting.. would be nice to be able to look at the laptop and check temps on a long smoke while I am watching hockey. but i imagine that getting wireless would make it not so cheep. Does the arduino take any kind of inputs from thermocouples?

Steve

[StirCrazy]

hmm reading up on the Arduino, little bit harder to get probes and such that can be stuck into a roast. might be more simple for me just to use the PIDs and have two of them.

Steve

[ScubaSteve]

Originally Posted by StirCrazy

hmm reading up on the Arduino, little bit harder to get probes and such that can be stuck into a roast. might be more simple for me just to use the PIDs and have two of them.

Steve

Nah, I don't think you'll have a problem. You'd be surprised what probes you can get that can be stuck into a roast. Heck, I could help you find some of the lab grade probes I use at work for cheap. Shoot me a PM and I can help you out. You can even pull the probe off of an old digital meat thermometer.

I found a few links to people using arduinos for smokers if you haven't already found them:

http://www.smokingmeatforums.com/for...?postid=455330
http://techblips.dailyradar.com/stor...e_thermometer/
http://www.casualhacker.net/blog/201...-brown-smoker/
http://qpidproject.blogspot.com/

I say give'r a go. If I can use an Arduino to control my $15K experiment set-up remotely, I'm sure it can do a smoker as well.

If you don't go Arduino route, try ebay for PID controllers. You'd be surprised what you can find.