Wiring PID and SSR = need some help

Discussion in 'UDS Builds' started by flyweed, Aug 23, 2010.

  1. flyweed

    flyweed Smoking Fanatic

    Gene, I am doing OK..I think everything is working...except right now my PID isnt set up to read the RTD sensor...so just trying to figure that out...yeah these dang chinese instructions...make NO sense whatsoever.

  2. dick foster

    dick foster Smoking Fanatic

    Just hang on. I am putting together a care package for you now. Just gotta go snap some pics to finish it off.

    To answer your immediate question, go to settings and select Inty (input type) and set it to PI00 for Pt100 RTD, which is what I think you have for a sensor.

    Be sure you have it wired correctly first, however. Connect the two leads, you should have three, that should test short circuit to terminals 6 & 7 and the last lead which should read a resistance to the other leads that varies with temperature to terminal 8. You might even want to add a jumper between terminal 6 & 7 just to be sure. That will supply a current source to the sensor, the PID will read what comes back on terminal 8 to determine the temperature.

    If you got what I think you did, you have a platinum resistance type of sensor. It's the perfect one to have for smokers as the range in right, they are rugged and they have a very linear temp responce curve. The sensor element itself is a platinum film on a ceramic substrate. 

    BTW if I were you, I'd seal up the junction where the wire enters the probe housing with some high temp RTV. I used Permatex Ultra Copper, . Then I put some heat shrink tubing over that. It's sealed up against moisture entry which would foul the sensor and make things get pretty wacky.  
  3. flyweed

    flyweed Smoking Fanatic

    Dick...good to hear from you.  I didn't want to bother you with all the questions, as I knew you just got back from your trip and trying to get  caught back up..so I didn't email you all these questions.

    Yes, I bought all the items you originally told me to..the XMT7100 PID, SSR 40 amp..which I don't really need now, but still have it wired in..and then the P100 RTD.

    I have RTV'd (high temp siliconed) the end of the sensor already..so one step ahead of you there.  Id' love to see a photo of your RTD connected to your PID..so I can be sure I have it wired right.

  4. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    Dan, I just tuned in and see that you have some problems yet! I believe Dick is going in the right direction. If You indeed got an RTD probe You will have to probally set that up with the setup function. I'll be curious as to how this all turns out.
  5. flyweed

    flyweed Smoking Fanatic

    well I think I got it figured out.  I hooked the RTD wires up to the PID..and plugged her in..it immediately started reading 24...I assumed this was Celcius....so I hit the "set" button then typed in 0089 and got the "Inty"...so I hit the up arrow until it read "P100"..then hit set again....so got the PID reading my temp probe now!  YAHHHOOOOOOOOOOO :)

    Then I had to figure out how to change from C to F....looked on the sheet and just scrolled down with the down arrow until I got to the screen that said "CorF"...I scrolled up to "1" and it switched it over to Farenheit now. COOL

    I think she's working.

    I wanted to see how accurate the temp readout was/is...so I put the probe under my armpit to take my temp...it read a little low..about 95F....so now I have it reading the room temp..it's pretty close..I have our Air temp in the house at 73F..the PID is reading 74F right now. SO that's now bad.

    So now I"ll isntall it into my UDS, and get it fired up to about 250F..then kick on the PID and put it into "autotune" and that should do it.

  6. dick foster

    dick foster Smoking Fanatic

    If you hooked your fan to the relay output like you said you did, the PID auto-tune thing isn't gonna do anything for ya. The PID loop only works on the SSR output and only when using a full on PID control loop algorithm.

    If you're just running a stoker fan the simple on off algorithm should do the trick for ya. The full on PID loop thing is more for controlling something like electrical heating elements like you started out to do.

    A simple on-off control algorithm running the SSR output which you use with your SSR to control your stoker fan. I'd give it a few degrees of hysteresis at HY say 3 or so for a little dead band so it's not going on and off like crazy all the time with one degree of deviation from the target set value or SV. 

    Go to Outy and set that to 3 for an alarm lamp or buzzer relay output and a simple on-off type of control for the SSR output. 

    My set value is 225F and I have 3 degrees of hysteresis set at HY so the fan kicks on at 222F and goes off at 225F.

    My smoker will typically drift up to about 228 or so then start cooling back down. That all depends on now big your smoker is, how big the fire, how much thermal mass you have, damper openings etc.

    Set the alarm relay trip points at AH1 and AL1. I have mine set to turn the low temp lamp on when the temp drops to 220F and it goes off at 224F after I tend to the fire and it heats back up.

    I suggest you get your temp probe sealed up with the RTV and check it in a pan of boiling water. Depending on your altitude you should get 212F when the water is at a rolling boil. You have some correction at register PSb you can dial in if you find it off by much but I doubt you will find the PT100 very far off if any at all. It should be good to go right out of the box.

    Slow down and take your time. Haste makes waste.  Like making good Q, making good equipment takes time.

    BTW that self tuning algorithm runs the temps up way high while it's figuring out the system response times etc. so don't do the auto-tune thing while you're actually cooking food if you use the PID thing at all. If you do you might end up with Q krispies instead of something you'd want to eat.  
  7. dick foster

    dick foster Smoking Fanatic

    You'll get some pics but I used a connector for mine (a 4-pin CB mike connector that I had in my junk box) so you won't see the hook up itself. I have the controller and a small SSR I used enclosed in a small zinc die-cast metal project box. The two outputs are connected to a standard duplex outlet that I broke the isolation jumper on. That I mounted in a low profile Wiremold electrical box that I hang on the smoker. The warning lamp plugs into one outlet which is controlled by the relay output and the stoker fan into the other which is controlled by the SSR. Like I said everything runs on standard 110VAC for simplicity.

    Good to hear on the RTV. I do the same on all my temp probes, Maverick ET73 and all.
  8. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    Dan, I'm gald to hear you have a working PID controller now. Let us know how it's working.

    Dick, I didn't know what you said about the relay tips not being controlled by the PID algorithem. It does make sense though as I ended up using the simple on/off control for my UDS fan. The one I use on my modified Bradley smoker is using an SSR that controls a 1200 watt finned heater. I used the AT function on it like 2 years ago and have been using that cinfiguratiion since. Thanks for the info.
  9. dick foster

    dick foster Smoking Fanatic

    Yeah. while the controller is nice for the price, the instructions supplied with it do leave a little bit to be desired.

    I had the advantage of having worked in a predominantly chinese company for several years and have also had some background in PID control loops for machine motion control. I also spent some time on the web searching for some info on it. There is a lot out there if you look and are persistent about it.

    It seems that two other hobby groups also like to use this little controller. Home brewers for controlling the temp of the brew while it's fermenting. They want it really really close. Also with folks into making their own espresso machines who are kinda nutty about maintaining exactly precise temperatures of the water used to brew a cup. 

    It works well for a lot of things as it turns out.

    Shoot me your email and I will send you some PDFs of what I found. Still not great but a little better than the sheet I got with the unit.  
  10. flyweed

    flyweed Smoking Fanatic

    I've been a homebrewer for about 15 years and never heard of a PID control until I started smoking meats....  The most common temp control we use in the brew fermentation process is a Ranco controller.  It's what I have on my conical fermenters..they are SUPER easy to use, compared to this PID setup....you plug it in...set the temp with an up and down arrow and plug the heat mat into the duplex outlet...put the Thermocouple in the thermo well in the fermenter..and you are good to go.  It's that simple.

  11. dick foster

    dick foster Smoking Fanatic

    This controller can be just that simple too. In fact that is exactly what I am suggesting you do with it as a stoker fan controller. You don't need the fru fru PID filter control loop thing running because it won't do anything at all for you in that kind of a setup.

    Remember when you started you were going to use it to control electric heating elements in an electic smoker. In that kind of a setup a PID controller can control the temps very tightly indeed because the heaters can accept less than 100% on or off power . It can apply power at least duty cycle wise in proportion to how far off the temperature is from the set point.   
  12. flyweed

    flyweed Smoking Fanatic

    it's very cool.....I"ll take some photos of my setup later today, as I am going to get the temp setup with a barrel burn this morning..then tonight I am gonna do something simple, Jamaican jerk chicken drummies.

    Dick can you explain again, in plain english....I want to set the "PID" to turn the fan on at 325F and then off at say 335F...I figured a 10 degree difference would be good so it's not turning off and on all the time with too close of a degree difference.  Can you tell me the steps how to accomplish this..since I won't be using the Autotune...OR...since I do have my stoker fan hooked up to the SSR...will the autotune work just as well??

  13. flyweed

    flyweed Smoking Fanatic

    Just an update....I just got a pot of boiling water going with a good rolling boil..and I put the RTD probe into the water..and let it set for 15 minutes....it worked its way up to 207F and stayed there the rest of the time...so my PID is off by 5 degrees.  Is there a way to adjust this in the PID??

  14. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    Dan, I would'nt worry about 5 degrees. 

    Do you have your UDS going? If so, let's see how your PID will handle it...............we can always correct the unit later...
    Last edited: Aug 28, 2010
  15. flyweed

    flyweed Smoking Fanatic

    yep...I've got the UDS going right now...I have some Jerk seasoned chicken drummies going on it.....I got the barrel up to 240F and then closed down the vents and hit the Auto tune on the PID.....right now my UDS is sitting at 238F..which if it's reading 5 degrees low that's 243F

  16. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    Dan, sounds like you have s winner. If I found the correct instruction manual the parameter you are looking for is pbs. You are low so enter a positive value into pbs then recheck your temp, but wait until after your autotune.
  17. dick foster

    dick foster Smoking Fanatic

    Yes read my previous post. It's in the register settings.

    However, that doesn't sound quite right unless you are at a higher altitude. Also make sure the probe is emersed well into the pan of water so the probe isn't dragging heat out and away from the senor which is down near the tip.

    What is your altitude? Water boils at lower temperature the higher up in altitude you go. By the time to get to space where there is a vacuum water will boil pretty much regardless of temp. As a demonstration, you can put a beaker of water in a bell jar then pull a vaccum on it and the water will boil at room temp.

    This is why food takes longer to cook at higher altitudes. The water is vaporizing at a lower temperature and holding the temperature at that point regradless of how many calories you put in, therefore there is not as much heat avalible to cook the food so it takes longer.

    For example at 5000 feet, say Denver CO the boiling point of water is only about 203F. Depending on the barometric pressure of couse. 208F puts you at about 2500 feet or so above mean sea level with a corrected barometer of 29.92"Hg.

    If your temperature jives with your local altitude then you really don't want to correct the PID because it's reading the actual true temperature.  
  18. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    Hi Dick, I didn't want to confuse Dan with altitude just yet as his boiling water temp test results for me would have just fine. 
  19. ol' smokey

    ol' smokey Smoking Fanatic SMF Premier Member

    By the way I did get those PDF files, although I haven't had a chance to look over them yet. 

    Thanks again
  20. justpassingthru

    justpassingthru Smoking Fanatic OTBS Member

    Dan, congrats my man for gettin' it going, can't wait to see pics.

    I have mine hooked up and running, I set the temp at 120° and it's been holding 123° for two hours, I'm jazzed!

    Joe and Dick, thanks for the help you have posted here, now I have to figure out how to set up the ramp, I hope you don't mind if I pick your brains after I fiddle with it a while.


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