My mods for unattended smoking

Discussion in 'Electric Smokers' started by fencesitter, Dec 29, 2009.

  1. I'm not too sure whether I got involved in smoking meat for the food or just to fiddle with something.

    I do know that I was inspired by the Cookshack Amerique- just think, set the temperature of the smoker and the temperature you wan the meat done to and walk away. Too bad the Amerique is $1600.

    I figured that it could be made for cheaper, especially if you don't need as large of a smoker. After all, how hard could it be?

    I had a pretty good idea how to start- take an existing smoker, add a new temperature control that you can electronically adjust, add a separate meat probe and put it all together.

    I started with a Cookshack because it seemed that other electric smokers still needed wood added every few hours or so, whereas the Cookshack only needed it put in at the very beginning. Maybe I was mistaken, I don't know, I didn't research it that thoroughly. Anyway, I started with a Cookshack refurb that hopefully would not be cheaper than all the mods I was planning on doing.

    No, actually, I started with the PID control- the smoker didn't come until after I was pretty certain I had all the correct electronics to make this work.

    I mostly started with a lot of pieces from Auber Electronics since they were relatively cheap and it one-stop shopping. I got their 1/32 DIN temperature controller, 25amp SSR, the associated heat sink, a platinum RTD temperature sensor and some connectors- a K-thermocouple and an RTD connector.

    The really important piece was still missing- a temperature controller that could handle multiple set points. A Fuji PXR goes for over $200 which I was really reluctant to invest in. Eventually I found an Ogden ETR-9300 on eBay. It had one aux input that could be used for a second setpoint (among other uses) The only problem was that it didn't have a SSR output, just two relay outputs.

    Taking a chance that I could convert one of the relay outputs to SSR, I bought the Ogden controller for $65. Luckily, it was relatively straightforward to take out one of the relays and have it directly drive the SSR output.

    I figured that all you needed to drive and SSR output, you just needed to take the relay drive voltage and pull it straight out to the terminals. Well, sort of. This is where the manual was very helpful- it indicated that there were 33 ohm resistors in series with the drive voltage. There were even resistor outlines on the PC board under the relay after I removed it.

    So, I had all the parts except for the meat probe and a housing. I picked up a project box (and power switch, fused IEC connector, output plug, and fuses) from my local electronics retailer. I could figure out the meat probe later.

    To test what I had, I assembled the controllers in the project box and used it to control a rice cooker in a sous vide setup (look it up yourself). With the auto tuning, the rice cooker kept +/-1 degree.

    I made a sous vide chicken (160 degrees- way over temperature- next time I'll let it dwell at 150 instead. I could even let it dwell at 140 for an hour if I wanted to kill off most nasties).

    I made a boiled egg (65 degrees C is what the blogs say- the problem is that the white is still too runny for my taste).

    I was ready for smoking, so I bought the Cookshack SM-008.

    Blah, blah, blah, this is getting boring, even for me. Let's get to the pictures.

    Here's the PID controllers in the project box:

    On the top you see the heat sink for the SSR. To the left is the Auber 1/32 DIN temperature controller and on the right is the Ogden 1/16 DIN temperature controller.

    The Auber controller is used to measure the temperature of the meat. It is set to a simple On-Off mode: you set it to the temperature you want the meat to hit- if it's too cool it turns the relay on and when it hits the target temp it will turn its relay off. I put in a bit of hysteresis so even if the meat cools down a lot, it won't turn the relay back on. Right now, the display is showing the SetValue (target temp). The problem with a single line display is that it can't show both the SetValue and the ProcessValue (current temp) at the same time. Normally it will just show the PV, but if you press the up or down arrows, it'll show the SV and allow you to increase or decrease it.

    The Ogden controls the smoker temperature. The relay from the Auber feeds its aux input. When the relay is on, the Ogden will use SetPoint2, when the relay is off, it will use SetPoint1. I'd like SP2 to be the hold temp and SP1 to be the cooking temp, but it will take a bit of effort to make it work that way, until then, this works fine enough.

    Around the back

    you see the K-thermocouple plug for the meat probe, the RTD connector for the smoker temperature, the output plug for the smoker and the input IEC socket (like on the back of a computer) to plug into the wall. Note that the cord pictured is 18 gauge and it resulted in a 2 volt drop. I have since replaced it with a 14 gauge cord though I haven't measured the voltage drop across that one.

    You can't see it but the IEC connector has the fuse below, and of course, the power switch is in the upper right.

    Here's a photo of the Ogden where I'm adjusting SP2 to 225 degrees:

    and here's where SP1 is being shown:

    So, if you were keeping track, the smoker will run at 225 until the meat reaches 180, then it should drop down to 140.

    I was lazy and just hooked the RTD sensor over the smoker's stock temperature sensor in the back:

    it's the little black piece sticking out at an angle back there.

    Here's a shot of the meat probe in a boneless short rib:

  2. So, how did it all turn out?

    Well, I had changed the SP1 from 140 to 180 for the first run. After setting it and starting it, I ran a few errands and came back a few hours later. The meat controller had tripped and the smoker was at 180 but the meat was down to 160 and dropping for some reason (bounce back?). Okay, that was a partial failure. I reset the meat controller to 205 degrees and supervised it as the meat made it up to 200 before I got impatient and pulled it.

    Okay, poor test.

    Let's try a pulled pork: cook at 225 until a 200 internal temp, then hold at 140.
    I put a 7-1/2 pound shoulder in at 6:30pm but had to leave at 7:30. Come back home by 10:30pm and the meat is at 138. By the time I went to bed before midnight, the meat had passed the 140 threshold.
    Check in the morning: meat at 160 or so. Go to work. Back from work at 1:30pm since it's Christmas Eve. Meat at 180ish.
    Go out to my parents'. Get back by 8:30pm, 26 hours after putting the meat in. Meat at 140 since the controller triggered and the smoker was also at 140.
    Pull meat out. Seemed a bit too tender and quite greasy (should have trimmed the fat cap). Pull the meat apart quite easily with forks, drain a bit of fat and refrigerate.

    At the family Christmas potluck the next day the meat is still a bit greasy, even after pulling off quite a bit of congealed fat, but not overly tender this time.

    All in all, I think that's a pretty successful test, considering there was a possible six hour window of time where the meat was done but I wasn't around to pull it out.

    Next up: spare ribs. I want to see if cooking to an internal temperature works even for something so thin.
  3. What did I miss?

    The meat probe- I was hoping that a regular Polder or Taylor probe would work, but upon further research I found that they're usually NTC thermistors which don't work with the controllers I have. So instead I went to Thermoworks and got a K thermocouple oven penetration probe. Only after I ordered it did I find that Auber had one for cheaper. I could have sworn they didn't have it the previous week.

    Wiring diagram- still working on that.

    Did I really trust the meat probe? Well, it was brand new and I did lazily verify calibration. I neglected to mention that I did use my Polder to verify the meat temp when but I did start to worry when the meat temp hadn't changed that much over night.
  4. garyt

    garyt Smoking Fanatic

    Did you install 2 pid controllers on a electric smoker?
  5. danmcg

    danmcg Master of the Pit OTBS Member SMF Premier Member

    Very interesting Fencesitter, but I'm sorry to say I really don't have a clue when it comes to electronics. I wish i did though, because i love to tinker.
  6. morkdach

    morkdach Master of the Pit OTBS Member

    wow ya been busy havent you.
    keep us posted please
  7. beer-b-q

    beer-b-q Smoking Guru OTBS Member

    All of you who understood any of that hold up your hand...[​IMG]
  8. Yes, the bigger controller controls the smoker temperature and the smaller one monitors and controls the meat temp by talking to the bigger controller.

    If the meat isn't warm enough, the smaller controller tells the big one to use it's higher cooking temperature setting. As soon as the meat hits the right temperature, the smaller one tells the big one to use the lower hold temperature setting.

    Even if the meat cools off, the smaller controller is set so that the meat has to drop over sixty or seventy degrees before it'll tell the big controller to use the higher setting again.

    Strictly speaking, only the big controller is a PID controller. The small one is just being used as a thermostat, albeit with a bunch of hysteresis (memory that it was warmer) so the meat can drop down to the hold temperature and stay there.

    If you didn't have a PID controller that could have two different temperature settings, it's possible to have the smaller controller just shut off the bigger controller to turn off the smoker, but then you'd want to pull the meat within a reasonable amount of time before it cools off for too long. That way you'd still have cooking stop without actually having to manually turn off the smoker or pull the the meat- it just increases the window of time you can leave the smoker unattended.
  9. plj

    plj Meat Mopper

    I think we can answer that for you... [​IMG]

    I like what you did, nice job. I put together a pid for my electric - didnt think about a set+forget feature, I was thrilled just to have accurate temp control. Not sure if I would really use set+forget, I think I kinda like the smoking process almost as much as the food. But I agree it would be nice to have the option if I needed it.
  10. flyhigh123

    flyhigh123 Smoke Blower

    now we just need a summary into layman terms...

  11. walle

    walle Smoking Fanatic OTBS Member

    LOL! I tried to follow it, had to chuckle to myself as I installed a Fuji PXR on my smoker this past summer.

    1st call to Manufacturer - How do I wire this damn thing up??
    2nd call to Manufacturer - How do I reset this damn thing after all of the buttons I pushed?

    In laaayyyymans terms, Fencesitter has a very high tech controller that not only tells his smoker if the fire is too hot or cold, but also when his meat is done, then it'll keep it warm for him!

    Way cool - I'm going to have to crack out my 1"+ thick owners manual and figure out how to hook up a meat therm to mine.

  12. kozmo

    kozmo Fire Starter

    Alright this is pretty neat, do you have a wiring diagram for one to peak at for this hog?
  13. scarbelly

    scarbelly Smoking Guru OTBS Member

    So does anyone who knows how to do this to a SmokinTex need a place to stay in San Diego for a few days?
  14. the dude abides

    the dude abides Master of the Pit OTBS Member

    That's cool. I wish I understood all of the technical aspects but awesome build. Have you figured out how much $$$ you've got in it?

    [​IMG]for a sweet build
  15. bbqhead

    bbqhead Smoking Fanatic

    I guess that's why I just got cookshack FEC with IQ4. not smart enough to figure all that stuff out. and yes I know I spent far more than I should but it makes life easier with all those controls. i just let cookshack figure all that out for me.
  16. Oh yeah, I said I'd get to that, didn't I?

    Here's what I've cut and paste together:

    I think that's mostly complete. I didn't include the various plugs, illuminated switch, etc. but the erm... meat of it is there- the connection from the Auber to the Event Input of the Ogden, highlighted with the red wiring.

    Actually, I bought an Ogden ETR9300-411110 off eBay (I notice the seller still has them there) and I modified it so it was effectively a -412110. The nice thing about the ETR9300 is that the event input comes pretty standard with the thing, vs. the Fuji PXR where the event inputs are something like a $40 option.

    As mentioned before, the Auber has a K-thermocouple meat probe in it and the Ogden uses a platinum RTD for measuring the smoker temp. There wasn't any real rationale behind the choices of thermocouple vs. RTD.

    So, the Auber is set as pretty much a thermostat control- when the meat is not hot enough, the J1 output relay is shorted, telling the event input on the Ogden that it should use set point/temperature #2. As soon as the meat gets hot enough, J1 opens telling the Ogden's event input that it shoud use set point #1.

    You can program the Auber to allow the meat to drop a given number of degrees before it should be heated back up again- that's the hysteresis. So, if you're looking to get the meat to 200 degrees but want to have it hold at 140 degrees, give it something like 70 degrees of hyteresis. If the meat drops below 130 degrees, the Auber will tell the Ogden to use set point #2 again until the meat heats back up to 200.
  17. nickelmore

    nickelmore Smoking Fanatic

    What is the mod? A picture is worth a thousand words. This is sort of what I thought you were talking about.

    Very nice set up, I have to go back and look at your build to see what you are controlling with it.

  18. nickelmore

    nickelmore Smoking Fanatic

    Just found that you are using SSR instead of a relay output.

    May have to keep your name on file, to ask about hysteresis settings,

    I was thinking about adding a PID just to monitor meat temperature to double check my ET73.

    This is a great idea for long sausage smokes.
  19. Okay, here goes...

    So, I figured that a controller with a relay has to be driving the relay somehow- say something like 5-10 volts. SSRs use something similar, so all I have to do is pull the relay out and have that relay drive voltage wired directly to the output terminals on the controller.

    Simple, right?

    So, here's a shot of the back of my Ogden ETR9300-411110 controller:

    (sorry about the lighting)

    And here's a better view of the back.

    Press the tabs on the sides and wiggle the back plastic piece out and you've got two pieces:

    There's PCB tabs sticking through the plastic case both top and bottom:

    Flex the plastic and slide the inner bits out:

    Simply slide off the upper board to get to the backs of the relays:

    Remove the relay that corresponds to the output you want to put an SSR on:

    Hey, look, there's a silkscreen image for the locations of two resistors.

    From the manual, it says that there are 33ohm resistors on each of the lines, so put 33ohm resistors in the indicated areas:

    And put it all back together. (picture omitted since it looks no different except for the lack of a center relay barely visible through the plastic.

    Note on that last picture: the resistors are there for illustrative purposes. Not only are they the wrong values (if you read the color code) but one isn't even attached. I really would prefer to install them better than is shown, but I didn't have a good soldering iron handy at the time.
  20. Okay, I was going to elaborate on this but then the kids started fighting so I had to finish the post up pretty quickly. They're asleep now so here goes:

    I initially got an RTD for the smoker temp since it is supposed to be more accurate (better than tenths of a degree) and I also wanted to use it for immersion cooking (sous vide) and that particular RTD was good for use in liquids.

    The meat probe is a thermocouple since it's cheap. I was pricing RTD meat probes and they were >$100. Yeah, they're probably better quality than what I've got, but I figure I'd get this meat probe (from Thermoworks, but Auber has a better price, had I known about it at the time).

    I figure if the thermocouple loses accuracy by more than a few degrees, then I'll get the RTD, but if something else goes wrong, like a wire breaks or the shaft bends, then I'll just keep to the cheaper, more disposable thermocouples.**

    Yeah, this may be something for the Thermometers forum, but it fits this thread and I'm never there, so maybe they've hashed this out already (even if they've probably disproven all my assumptions).

    **Conversely, if the RTD breaks a wire, since this is pretty much permanently installed in my smoker, I'll probably just put in a thermocouple.

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