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Thread: PID placement of sensor

  1. #41
    Boolit Buddy
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    Quote Originally Posted by RydForLyf View Post
    ...... all I need to know is that I’m at 3.5 Pink Flamingos and the pot is full. If your situation is different and 3.5 Pink Flamingos won’t work for you and you like 76 Fuzzy Squirrels, then 76 Fuzzy Squirrels it is for you. My Pink Flamingos won’t care.
    I personally am 3 Iguanas shy of a full hedgehog.

  2. #42
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    Quote Originally Posted by Dapaki View Post
    I personally am 3 Iguanas shy of a full hedgehog.

  3. #43
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    There are heat conduction pastes used in industrial non contact controls that would fill the fee space in the head of that acorn nut along with the fact that the nut and probe mount are affixed to the pot in the lead. The unit is then in equilibrium. May find an HVAC contractor that works for food or chem processing to get a small dab of the thermal paste. might also see if electronic heat sink paste would work.
    Shaune509

  4. #44
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by bazzer485 View Post
    Did you use any kind of washer?
    Nope, no washer needed on the two that Iíve done so far

  5. #45
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by shaune509 View Post
    There are heat conduction pastes used in industrial non contact controls that would fill the fee space in the head of that acorn nut along with the fact that the nut and probe mount are affixed to the pot in the lead. The unit is then in equilibrium. May find an HVAC contractor that works for food or chem processing to get a small dab of the thermal paste. might also see if electronic heat sink paste would work.
    Shaune509
    I don’t think there is any lag whatsoever due to the metal contact with the acorn nut with liquid lead. If there is a lag, it’s irrelevant to the process as it’s goin to be a second, or two? As far as pastes I know there’s heat conducting paste for welding processes also and it’s like a clay that would remain stable at temp. But in practice, it’s not needed. But as I said, people try to make this project as difficult as possible lol.

  6. #46
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by RydForLyf View Post
    That sure is a slick way of mounting the TC, but I think the heavy nut will put a significant time lag in the temperature reading and result in temperature swings that you are trying to avoid.

    The thermocouple is designed to respond quickly to temperature changes and in this scenario, it isnít contacting the lead, but is measuring the air temperature inside the nut. It would be interesting to put a wet probe in the lead to observe lead temps being controlled by the acorn nut PID. I do think that is a great idea to seal it out, it fear the response and performance will be muted.
    how quick do you need your temp to read? It takes 20 minutes to even get the pot to temp so, Iím confused why you would have any concern about a two second lag? Also as said, Iíve been testing this for years so itís moved past theory and is proven unless you donít believe me, which would explain some of the resistance to this I guess.

  7. #47
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by hermans View Post
    Very interesting....always wondered how/where in my ProMelt I can mount the sensor, but I sure am hesitant to drill a hole in the stainless steel wall of my beloved ProMelt
    Just do it, itís an upgrade you wonít regret. Night and day, forever change, never look back kind of feeling.

  8. #48
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    You guys have given me many options on placement of TC sensors. Thank you each for your input. Hopefully this will help me as well as someone else.
    Just knowing enough to do it, is not enough to do it right! -Taz

  9. #49
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    Quote Originally Posted by Drew P View Post
    how quick do you need your temp to read? It takes 20 minutes to even get the pot to temp so, I’m confused why you would have any concern about a two second lag? Also as said, I’ve been testing this for years so it’s moved past theory and is proven unless you don’t believe me, which would explain some of the resistance to this I guess.
    Since you're using that temperature reading as input for your PID, you want the shortest lag as possible. As the lag increases, the temperature swings increase. The PID is getting a signal late and is always "behind the curve" in trying to correct. It comes on late, so the lead has cooled more than it knows, and as the temp rises, it shuts off late leading to overshoots in max temp. The MOST important consideration is response time in your measurement.

    A slow reading temperature probe is like closing your eyes while driving and letting a person in the back seat tell you what steering corrections are needed to keep the car on the road. I know it sounds silly, but the resulting oscillations and over-corrections are a good way of explaining it.

    You want your feedback measurement, your temperature probe, to give the PID the most immediate and up to date information available. Throwing a thermal mass, the acorn nut, into the equation and then adding a low-conductivity air space on top of that means your PID will never be able to accurately auto adjust and begin to predict the response cycle of your "system" because it's input is so far "removed" from actual conditions.

  10. #50
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    Quote Originally Posted by Drew P View Post
    I don’t think there is any lag whatsoever due to the metal contact with the acorn nut with liquid lead. If there is a lag, it’s irrelevant to the process as it’s goin to be a second, or two? As far as pastes I know there’s heat conducting paste for welding processes also and it’s like a clay that would remain stable at temp. But in practice, it’s not needed. But as I said, people try to make this project as difficult as possible lol.
    So, drilling a hole in the pot, routing the leads, and mounting the nut/thermocouple and reassembling the pot is "easier" then dropping the thermocouple in the lead? Nothing complicated or difficult about that.

  11. #51
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by jsizemore View Post
    So, drilling a hole in the pot, routing the leads, and mounting the nut/thermocouple and reassembling the pot is "easier" then dropping the thermocouple in the lead? Nothing complicated or difficult about that.
    Ya, because it’s a one and done solution and won’t have any (in my opinion) fussing around later on like your method. But if you feel like I’m being too assertive it’s only because I’ve tried several methods and I’m pretty sure this is by far the best and I want you brothers in arms to enjoy the feeling I’m getting by my method. So if you must go your own way just know I have your back and love you anyway.

  12. #52
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    Quote Originally Posted by RydForLyf View Post
    Since you're using that temperature reading as input for your PID, you want the shortest lag as possible. As the lag increases, the temperature swings increase. The PID is getting a signal late and is always "behind the curve" in trying to correct. It comes on late, so the lead has cooled more than it knows, and as the temp rises, it shuts off late leading to overshoots in max temp. The MOST important consideration is response time in your measurement.

    A slow reading temperature probe is like closing your eyes while driving and letting a person in the back seat tell you what steering corrections are needed to keep the car on the road. I know it sounds silly, but the resulting oscillations and over-corrections are a good way of explaining it.

    You want your feedback measurement, your temperature probe, to give the PID the most immediate and up to date information available. Throwing a thermal mass, the acorn nut, into the equation and then adding a low-conductivity air space on top of that means your PID will never be able to accurately auto adjust and begin to predict the response cycle of your "system" because it's input is so far "removed" from actual conditions.
    Have you used a pid before? They approach set point gradually and slow down before hitting the set temp, so lag in the sensor will only delay pot temp by however many degrees that’s worth which in my opinion, having used it for years, is about 2į at most? So, I understand your concern but I don’t think it applies to a big bath of liquid lead. I’m not sure how faster lag time would make it better or faster or more accurate at all.

  13. #53
    Boolit Master Drew P's Avatar
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    Quote Originally Posted by jsizemore View Post
    So, drilling a hole in the pot, routing the leads, and mounting the nut/thermocouple and reassembling the pot is "easier" then dropping the thermocouple in the lead? Nothing complicated or difficult about that.
    You added a few more steps to seem dramatic there too. It’s a 1/4” hole, and a nut. No “reassembling” the pot or “routing” the leads lol. See, you really are making it more complicated.

  14. #54
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    seems like a PID is a bunch of high tech hassle

  15. #55
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    Quote Originally Posted by barnabus View Post
    seems like a PID is a bunch of high tech hassle
    Honestly, they can be a little frustrating to program but downloading a "cheat-sheet" and watching a YouTube video makes sorting it all out pretty easy in the end.

    Drew has a pretty good handle on this, (I would love to see your setup) you want the 'lag' to be long enough so that your not firing the SSR all the time, they bleed off power by making heat and do best when the duty cycle is moderate. Better SSR's do better but I have a 30A SSR running my brewing boil kettle for 6 years now with no signs of failure.

  16. #56
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    Quote Originally Posted by Dapaki View Post
    Honestly, they can be a little frustrating to program but downloading a "cheat-sheet" and watching a YouTube video makes sorting it all out pretty easy in the end.
    Most PIDs by default are set up to be used on heaters, so it's pretty much just set the temp and forget it. We really don't use all of their bells and whistles, but they really are a game changer and take over 100% of the temperature baby sitting.

    The truth of the matter is that they are NOT necessary nor a "must have". We all used to get along just fine with a fan speed control and temperature slider in our cars for AC control. However, I won't ever give up my automatic climate control now that I've got it. It just makes life easier and everyone needs to determine if the convenience (luxury) is worth the price.

  17. #57
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    Quote Originally Posted by barnabus View Post
    seems like a PID is a bunch of high tech hassle
    It's as simple as sticking the liquid tight probe in the lead, turn your original thermostat/control wide open, plug your pot into the PID AC output, turn on the PID and set the temp. Easy. No drilling holes. I have an alligator clip with a piece of coat hanger wire attached that clips to the thermocouple probe to adjust height in whatever casting pot I choose to put it in. You get a direct read of the actual lead temp at a glance. As long as the tip of the probe is submerged your golden. When your lead reaches temp the first time, hit AT (autotune) and the PID figures what rate it needs to energize/de-energize power to the pot as your lead level decreases with casting (or dripping if you own a LEE 4-20). Simple. Easy. Cast bullet dimensions are very consistent.

  18. #58
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    I wish the Inkbird ITC-308 Digital Temperature Controller was compatible with the LEE pots, it would be good to just have a plug-n-play option for those not wanting to do the programming.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check