Temp Control Q&A

Discussion in 'Regulated (Voltage / Wattage / 3.7v/ Temp Control)' started by KingPin!, Jan 29, 2017.

  1. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Hi All
    Thought it would be good to have a dedicated thread for temp control Q & A for newbies (and veterans alike to help us noobs)

    I've recently got into building my own coils one of the things I've noticed is how easy it is to get a dry or burnt hit especially when you put in some of those bigger coil builds. Now I know some will say that's a wicking issue or try turning down the wattage.... whilst that is true, in a lot of cases these chunky heaps of coiled madness just can't cool down quick enough!

    so I started looking into temp control as a means to maintain the flavour...draw for long periods of time...chain vape like a madman...avoid cremating my cotton...and not mash up my coil that I spent bloody ages building!

    What I've learnt so far

    There are 4 main things to remember for temp control

    1) All metals change resistance when heated, but it's those metals that change more that are the best suited for temp control, and its for this reason most temp control mods have Nickel, Titanium, and Stainless Steel as a default ...imagine a hose pipe fully open, now pinch it (resistence in our case), it's harder for the water (current in our case) to get through... that's exactly what's going on here as the metal is heated.
    You will start with a new coil build at say 0.3ohm at room temperature and when heated it goes up to 0.5ohm ...the resistance goes up (some metals change far more than others) this effect is known as Temperature Coefficient of Resistance (TCR*) It's the average amount the resistance changes for every 1 degree Celsius heated

    (*note there is a proper temperature curve some devices can utilise which is different to the average linear line that is TCR but for ease of explaination I'll stick to TCR)

    note 2, Kanthal is usually out of the question for temp control on most mods as its resistance changes so little when heated
    Edit: Hohm wrecker G2 claims to support this metal type thanks @PhantomOp

    2) The type of Metal you choose for your coil changes the correct TCR you use on your mod (I believe I've read somewhere you also need to factor in your own mods internal resistance although on most regulated devices I would assume the chip accounts for this?)
    I'll post a follow up after this of all the metals common TCRs

    3) Temperature - this is what you want your mod to max out at and stay at when it gets there ...meeting all of those things I listed above (avoid cremating cotton etc)... now it's important to note your mod isnt actually detecting the temperature, it's carrying out calculations 1000's times a second based on reading the starting ohm resistance and the resistance while heating this is why TCR is important..(it's also really important you have a good connection on your deck for your coils as well, dodgy ohm readings to start with are bad news, health and safety first people)

    Example:
    • A coil is at 0.10Ω at room temperature (20°C / 68°F)
      • You vape and the chip sees its resistance is now 0.22Ω
        • So it knows its resistance rose by 0.12Ω
      • Then it calculates using the TCR you pre set of 0.006 (NI200) thats a resistance rise of 0.12Ω equals a temperature rise of 200°C (392° F)
        • And therefore the coil temperature is now 220°C (428°F)
        • (0.22Ω - 0.10Ω) / (0.006 * 0.1Ω) = 200°C (392°F)
        • + 20°C (68°F) [starting temp] = 220°C (428°F) [coil temp]
    4) Wattage - This is serving to only get you to the temperature you set earlier because your mod will maintain temperature when it's peaked (that's why you see that temp message on your mod) it's pulsing here to maintain temp rather than keeping going in power mode, it's not turning off like a lot of people think ....
    So set this based on how quickly you want to reach your max temp, if like me your not fussed on the pulsing bit set it lower, if you want it at max level immediately raise it there is no right or wrong

    No doubt there are things I've forgotten or don't yet know so Q&A time guys

    I'd like to take my hat off to Steve @Wingsfan0310 for helping me complete this picture :)

    Edit: found a really useful article which has a very thourough explanation of all the elements affecting TC well worth a read

    https://www.ecigssa.co.za/guide-to-fine-tuning-temp-control-vaping.t18206/
     
    Last edited: May 5, 2017
  2. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Every type of wire has different Temperature Coefficient or TCR and here is the list of the most common and uncommon wires used to vape:

    I will admit that I am stealing this off an article but it has a lot of ToC values. It shows how little we really know about ToC of wires since some of them have multiple values.

    Edit: added kanthal A1
    Kanthal A1 [0.000002] (steam engine - notice how low this is and why most mods can't support this... the chip has to be very sensitive!)

    Nickel DH: [0.007036]

    Ni80 [0.000112] (according the steam engine.org)

    Ni200: [0.00600] (According to Steam-Engine.org)
    Ni200: [0.00620] (According to @DJLsbVapes and other various sources)

    Nifethal 70 (Alloy120): [0.00525]

    NiFe30 (StealthVape): [0.00500]

    Tungsten: [0.00450]

    Nifethal 52 (Alloy52): [0.004036]

    NiFe (Reactor Wire): [0.00400]

    TitaniumGrade1: [0.00366] (According to Steam-Engine.org)
    TitaniumGrade1: [0.00350] (According to the SX Mini Manual, @DJLsbVapes and other various sources)

    TitaniumGrade2: [0.003525]

    NiFe30 (Resistherm): [0.00320]

    SS410: [0.00155]

    SS430: [0.00138]

    Invar 36 / Nilo 36 / Pernifer 36: [0.001116]

    SS304: [0.001016] (According to Steam-Engine)
    SS304: [0.00105] (According to @DJLsbVapes and other various sources)

    SS316L: [0.000879] (According to Steam-Engine)
    SS316L: [0.00092] (According to @DJLsbVapes and other various sources)

    SS316: [0.00088] (According to Steam-Engine.org)
    SS316: [0.000915] (According to @DJLsbVapes and other various sources)

    SS317L: [0.00094] (According to Steam-Engine.org)
    SS317L: [0.00088] (According to @DJLsbVapes and other various sources)

    SS317: [0.000875] (According to @DJLsbVapes)

    Not all wires we buy are of the best quality, some may contain impurities but this is the generally accepted TCR list for the common materials
     
    Last edited: Mar 12, 2017
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  3. PhantomOp

    PhantomOp VU Donator Gold Contributor Member For 1 Year

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    Last edited: Jan 30, 2017
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  4. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Thanks phantom have edited it :D
     
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  5. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    Nice thread dude!!! Great idea!!!

    One thing for people to consider, is the mass of the material in ratio to the resistance. Because, TC works as a calculation of ∆Rt the resistance and mass has to be large enough for it to accurately read.
    This means that; because a dual coil with two resistors (coils) of identical resistance equates to half the resistance of 1 coil. A dual coil build typically will respond with beading a higher temp setting to get a similar temperature as a single coil.

    In other words 2, 1.0 ohm coils = 0.5 ohms. If you have a 1 ohm build set to 400° degrees and you like the way that temp reacts, when you try a dual coil build, you may have to raise the temp setting to 480-500°.

    This may sound odd, but after using it for so long, this has been my own experience. This is less so with the dna250, than it was with the 200 and drastically less than it was with the dna40 and sx350j but still present.

    When it comes down to it, alot of TC is still trial and error until one finds their sweet spot, but for a tech only 2 years old, it has come a long way in a short time

    Sent from my XT1650 using Tapatalk
     
  6. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Nice @f1r3b1rd I didn't know that! I'll bear that in mind going forward

    Another thing I've been told is that the TCR doesn't change when going for a more complex coil say a fused clapton compared with a simple coil of the same metal type

    How you calculate TCR when mixing metals in your coil I'm yet to learn unless someone knows?
     
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  7. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    Correct TCR remains the same despite build, assuming it's all the same metal.
    Or in the case of say a clapton coil with kanthal and a TC metal, you can use the TCR value for the TC metal.
    If you're using 2 different type of SS or as and To or multiple different TC metals.... You have to calculate it.
    For that I'm unsure, @raymo2u may have an idea.
    I would start with steam engine and see if they have a calculator for it though.


    Sent from my XT1650 using Tapatalk
     
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  8. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Another question I've got is how do you calculate the "sweet spot" for a given coil I understand it's trial an error to a large degree all I know for now is on my H-Priv mod with my beast RTA I've currently got a dual fused clapton coil set up (2 x 28g core,38g wrap all 316L metal) starting ohm at 0.27

    Set the TCR to 0.00088
    Wattage at 40
    Temp at 500.F

    Vapes bloody lovely right there (Air hole open only very little) is there an absolute sweet spot though?
     
    Last edited: Feb 28, 2017
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  9. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Must admit the calculator on steam engine needs a guide i plumbed in the numbers on the temp control section and didn't fully understand what I was looking at :oops: has anyone done this yet?
     
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  10. gobbly

    gobbly New Member

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    I can confirm the Wrecker G2 works with Kanthal for TC. I'd be curious to hear if anyone knows any details about how they are doing it. I read something a while back that was a bit over my head that claimed to explain it, but I think they were just hypothesizing. I've just assumed they figured out a nifty way to get killer resolution on their resistance sensing. Whatever they do works, best TC mod out there IMO.

    I can explain just about anything on the steam engine, but you'd have to be more specific. If you're talking about the curves, it's just the coefficient of resistance at temps. Different ways of looking at them, like the curve, or a point map for the DNA200. So if a coefficient at 68F is 1, and at 200F is 1.065, and the 68F resistance is 1, it will be 1.065 @ 200F (1*1.065). It's not linear, hence the curves and approximations.

    Mixed metals gets tricky if the curves aren't known. Short of getting a point contact thermometer that supports the ranges we care about (they aren't cheap), there's a bit of trial and error. What works well for me is to keep my cotton scraps and use them to test funky builds, since I know what temps the different shades of brown develop at. From there fine tuning isn't difficult. Works well enough for me.
     
  11. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    By sweet spot I mean the settings that make you say, "holy fuck that's a great vape."

    As to the calculator.... I hope someone has more information for that one, I would love to know myself.
    .

    Sent from my XT1650 using Tapatalk
     
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  12. gobbly

    gobbly New Member

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    Another thing, since we're dealing with rather small numbers, and are limited in our ability to detect small changes in resistance, as a general rule the higher the base (edit: 'cold') resistance the better TC will perform.
     
    Last edited: Jan 29, 2017
  13. gobbly

    gobbly New Member

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    You answered yourself. There is some trial and error. The numbers we're working with are small, and most are approximations on one level or another. As technology improves and gets cheaper this will change, but currently there's no true plug-and-play with TC for someone who has discerning tastes. It's all going to require some tweaking if you want something consistent from coil to coil.
     
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  14. PhantomOp

    PhantomOp VU Donator Gold Contributor Member For 1 Year

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  15. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    @gobbly You mention browning of the cotton though this sounds like an interesting and more definitive way to determine whether a temp set up is right buddy...so what are you looking for and what is the method? Does it matter if you have any cotton strands left behind after you've tested?
     
    Last edited: Jan 31, 2017
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  16. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    @gobbly So taking this as an example apologies but what is it telling me... this isnt the TCR right? I mean if I were to take the difference between 200 and 68 (132) and use that 1.065 number it gives me 0.0081 if I calculate 1.065/132, which seems wrong compared to my second post on the accepted TCR values because we haven't factored in starting and ending resistance....this is exactly the bit I'm talking about not understanding lol
     
    Last edited: Jan 31, 2017
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  17. Iliketurtles

    Iliketurtles Silver Contributor Member For 2 Years

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    Y tho ?
    [​IMG]
    Do the math, TCR is TCR. It should be no different between single or dual coil setups.

    Why is it different.

    Sits back and grabs popcorn.
     
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  18. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Another question do mods always assume starting ohm resistance is at room temp ...so if vaping outside in the winter will that throw off the calculations?
     
  19. conanthewarrior

    conanthewarrior Gold Contributor Member For 2 Years

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    Yes, I have found for me it does throw things off.
    I live in the UK, and it is winter at the moment, and I have found I have had to greatly reduce my set temperature if I am outside in the cold, also when I wake up in the morning if the heating has not yet turned on.

    A few of my friends have also mentioned they have noticed this too, has anyone else here noticed the same thing?
     
  20. skt239

    skt239 VU Donator Platinum Contributor Member For 2 Years

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    I've never had that issue that I can recall. The mods I mainly use for TC is the evic VTC mini, VS DNA200 and hcigar VT75 Nano.
     
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  21. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    Yes TCR is TCR, as to the why?
    I don't know for sure, it's something I've noticed as well as alot of other early adopters. To the best of my 'postulation' it's the mass of the metal.
    Correct, TCR is TCR and that variable won't change. TCR is simply the measured ratio of ∆Rt:∆T
    That ratio won't change while the other variables are changing.

    a 0.2 single coil clapton and a 0.2 dual coil simple wire will behave differently.

    If some are not noticing this difference now that are new to it great. Perhaps it's those of us that noticed the huge difference in the first dna40s and then over perceiving.

    I know with the first run 40s a go to build for me was a single coil RDA so that I could both fit a 0.12 ni200 coil but at times trying a dual 30g ni200 build required raising the temp to get satisfactory vape.

    I'm still doing similar, with a single coil clapton I'm sitting around 440° with the same clapton in dual coil I'm sitting around 530 to get that same feeling temp. At 35w, and 50w punch for the single, and 70w and 110w punch for the dual.
    Again this is completely unscientific, but it has been drastically noticeable. Someone with knowledge of thermal dynamics may know more. I know and understand Ohm's law and coulombs law, but those won't dictate heat transfer.... @Wingsfan0310 may have a better answer

    Sent from my XT1650 using Tapatalk
     
    Last edited: Jan 31, 2017
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  22. conanthewarrior

    conanthewarrior Gold Contributor Member For 2 Years

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    I have noticed it mainly on my Evolv mods, (DNA200's and 75), I haven't changed the builds I have been using, but have noticed I have had to adjust the temp settings, otherwise it seems far too hot, even dry.

    I have heard a few people mention it, but others have not. What wire type do you use? I mainly use SS316L now. It definitely has been noticeable for me though, during the day indoors I can run at my normal temp level, but I have had to reduce on cold mornings and outside.
     
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  23. gobbly

    gobbly New Member

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    I just stick scraps of dry cotton through my coil, set a temp, and try to burn it. I've found that around 400-420f I start to see a little brown. That will keep getting darker shades if I move up by 20 degree increments, browning gets fairly dark toward 500. I've got a feeling for the different shades and how deep into the cotton it discolors, and can make educated guesses to the temp. It's not perfect, but works great for what we're doing. This is as much an art as a science, since I'm shooting to stay under where the cotton is browning.

    Keep in mind that the relationship between temp and resistance is not linear, it is a curve. A TCR value is linear, it can't accurately reflect the slope of a curve, it is an approximation. Also you started at 1 ohm @ 68f. So you gained 0.065 ohm with a change of 132f (average of 0.00049242424... ohm per degree when working between 68 and 200f). Does that help? I think in math, but I know for some it's not as clear.

    Yes. It's really the only logical place to start. TC boards will read the ambient (room) temp and assume the coil starts around that (I say around because a good mod will have the chip configured for the case it's in, which has its own thermal properties). They should do OK attaching a coil in the cold (assuming the coil temp matches the ambient temp) because the board will know the ambient temp and assume that is the coil temp. Accuracy varies, but that is the idea.

    You should always make sure your coil is at room temp before use when you first attach it to your device. Also make sure your mod has 'forgotten' the old coil so you're not making assumptions about resistance.
     
  24. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Bet it's got something to with coils not being equal... current will take the easiest or fastest route, when we dry burn we do it by eye does it mean that both coils or multiple wires are going through the heating curve exactly the same (even if everything is using the same metal) ...very doubtful so resistance change isn't linear in this case our mod is reading the overall resistance from the deck not how each coil is behaving...
     
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  25. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    @gobbly so on the resistance curve are you looking for the point of plateau (flat line) when calculating the average up to that point? After this resistance is changing very little if at all ...so reading further on would only scew your result would it not?

    And is this plateau line is the optimal heating point?
     
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  26. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    Agreed ...IE: Coulombs law and resistance in parallel.
    I'm also assuming two identical coils; which.
    1/Rt= 1/R1+1/R2
    Whereas in the case of 1, Rt=R1
    So TCR has nothing to do with it... TCR is constant but total current is divided.

    Unfortunately for me, I'm lazy and just adjusted to taste rather than digging any further to see where this falls with the thermal properties, to give any in depth mathematical answer.



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  27. skt239

    skt239 VU Donator Platinum Contributor Member For 2 Years

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    316L as well.
     
  28. gobbly

    gobbly New Member

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    If I understand you correctly, no. The curve may have a (theoretical) asymptote, but not a plateau (no slope. Edit: keep in mind that once you get to a melting point I'm not as solid on the physics, so there may be a plateau, but it's not relevant here. The idea of a superconductor implies a plateau, but that's going the other direction in temp). An average is a basic approximation (like I did to get the average resistance change per degree above), and there are other methods (if you're curious, research for least squares approximation, it's a popular method). If you look at the curve for something like Ti or Ni200 (easier to see as the curve is sharper), you will notice that even in the ranges our graphs are in, you see an increase in the growth of resistance as temp increases, in other words the rate of resistance change per degree is accelerating (in math terms the derivative is increasing and the second derivative is positive). If you bound your growth between two points lower on the chart, and use that start and end point to average, your approximation will be closer to the curve than if you were to analyse a broader range using the same methodology.

    Another way to put it is that TCR will be the linear solution that is near a minimum average distance from each point on the true curve (limited by the methodology used to determine it), with a higher [correction] deviation as the range of inputs increases.
     
    Last edited: Jan 31, 2017
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  29. Iliketurtles

    Iliketurtles Silver Contributor Member For 2 Years

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    I have seen a few 'discussions' on this subject. Never seen a good answer so I don't expect to see one now. I have experienced this with a DNA mod single coil works as expected but dual coil does not. On FSK mods both single and dual coils work as expected with no adjustment of settings required in my experience. The odd thing with the DNA is you would expect it to produce more vapor as you have 2 coils at x temp rather than one but you get a weaker output and 'temp protected' almost straight away so like you I put the temp up or just use single coils which it works perfectly with.
     
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  30. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    With the DNA 40, yes. This was a huge problem!
    I chocked it up to early adopter syndrome.
    With the fsk, I have VERY limited experience. I mostly use DNA and Yihi boards. I've used the fsk, but don't own one; and, it's been a long while.
    If memory serves, fsk works very well, it just needs a more attractive box for my taste.
    The newer gen DNA boards, the issue is drastically less present. I have noticed that the more mass, the less likely.
    In other words a single round coil vs dual round coil. Will have more difference in temp setting than a single clapton or alien.

    The ratio of mass is increased



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  31. Iliketurtles

    Iliketurtles Silver Contributor Member For 2 Years

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    I am not going to worry about it as there is a simple remediation vector...those buttons at the bottom :)
     
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  32. gobbly

    gobbly New Member

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    I'm going to do a little theorizing. Keep in mind that it's been 10+ years since I took my last EE course, and I've been working on the software side since. Forgive me if I overlook or misstate something, this is getting a little past where I can speak with authority.

    I don't know that the mass is really impacting the resistance/temp relationship much, if at all. There are a few things I can think of that would lead one to think this was the case. For one, the more mass the lower resistance (all other things equal), and the lower the resistance the harder it is to detect the small changes as temp fluctuates. So it may be that the lower resistance is interfering with the accuracy of your TC (the resolution with which you can detect resistance).
    Another idea of what is happening is that with a dual coil you're really working with two resistances. If the coils are not precisely the same resistance then one coil is going to heat up faster and have different thermal properties (at a given time) than the other.
    Edit: I guess it's also possible that your wire has impurities vs a generic curve for that wire type so your TC may be off to begin with and that would become much more apparent at lower resistances.

    Again, I could be totally off base about how mass impacts this, but the above is extrapolation based on my understanding.
     
    Last edited: Jan 31, 2017
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  33. gobbly

    gobbly New Member

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    The FSK and the DNA are very different. I have a very good understanding of how the DNA works, but haven't found those low level details for the FSK. My suspicion is that the FSK just has far better resolution with their resistance sensing. IMO the FSK does work better for TC.

    Edit: The FSK takes a TCR value and the DNA takes a curve. The DNA may just approximate a TCR or it may approximate the missing curve (I'm not certain), but either way it's starting from a different point. All things equal, using a curve would be more accurate than a TCR, so if you accept that the FSK has better TC, it gives you some indication of how much impact the approximation makes vs other factors. How different devices get you to your temp and limit you once there is quite different as well, which has a significant impact on your experience using it. DNA gives you a lot of control in this regard, FSK not so much.

    For dual coils, they are not identical resistances, so the curves that you are using won't quite model the temps for both coils. The closer your two coils are in resistance the more accurate I would expect your TC to be.
     
    Last edited: Jan 31, 2017
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  34. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    I thought that as well. I got my first DNA40 my last year of the EE program and it really was a nice way of combining some other technologies. (IE: some welding equipment uses similar techniques)

    I would certainly agree with that to some extent.

    Also bearing in mind not all wire is created equal, either.

    Another thing that is famous for causing general issues are contact issues: 510 not seated well, bad ground, coils not screwed down well......




    Sent from my XT1650 using Tapatalk
     
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  35. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    So what about the point the linear TCR and non linear curve line intersect starting from 0.C? Could this be used as a potential sweet spot for temp setting?

    Other than just using steam engine to find the Linear TCR which I already gave everyone in my second post I'm struggling to understand if there is anything else in that temp section that's of any use?
     
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  36. f1r3b1rd

    f1r3b1rd Phantom Pilot Staff Member Senior Moderator VU Donator Diamond Contributor Member For 2 Years

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    Right, that and the fact that I can go in to formulate how I want the mod to behave in escribe or the yihiapp, has led me to the same conclusion. I used to bang my head on the wall trying to get the performance I want, then came TC mods with enough power, programming and material options to compensate.

    Just glad I don't have to build with nickel anymore.

    Sent from my XT1650 using Tapatalk
     
  37. gobbly

    gobbly New Member

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    Yeah, so from an accuracy point of view that would be a sweet spot, because ideally you want to hit the point on the curve, and if the approximation runs through that curve it's no longer an approximation at that point, it has converged. However, we're not staying in one spot, we're changing, so that only helps give you a starting point to fine tune from. And of course, if the convergence is outside the temps you want to target, it's of limited use.

    Again though, this is great for understanding how things work, but I wouldn't get too focused on it because of all the other factors that can have a significant effect on your experience.

    And don't be afraid of approximations. We use them constantly everywhere. The safety of your car is based on them, we sent people to the moon with them, airplanes stay in the sky with them, they are everywhere. It's basically the standard when it comes to applied math. Also be aware that though we may have an approximation, often we are bounding that and can tell the exact margin of error. Rarely do we shoot in the dark, usually there's a lot we know about what we don't know :)
     
    Last edited: Jan 31, 2017
  38. gobbly

    gobbly New Member

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    TCR is probably good. You could copy the point map for the DNA, edit it to a single line and post that, but it may make your post a bit cluttered.
    For most mods, having a TCR or a curve is about all you need as far as wire config. From there it's adjusting whatever other options the mod gives you, but that is independent of the thermal-resistance properties.
     
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  39. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    @Whiskey

    Hi Whisky is it worth sticking this post? Might help people new to temp control?
     
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  40. Whiskey

    Whiskey Diamond Contributor Member For 3 Years

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    Sure it is, Done :)
     
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  41. gakudzu

    gakudzu Gold Contributor Member For 1 Year

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    :nothingtoadd: :popcorn:

    Thanks, @KingPin! for this thread. And Thanks to those contributing knowledge!
     
  42. Gregjl

    Gregjl Bronze Contributor Member For 1 Year

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    Can a resistance be too low for tc? I got some fused clapton ss, 2x 24 inside 34, 316L. And I want to know what to do with it. I kept adding wraps in the vape tool app to figure out how many I should do and stopped because 10 is a little ridiculous. And that only brought me up to .15.
     
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  43. PhantomOp

    PhantomOp VU Donator Gold Contributor Member For 1 Year

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    3mm ID @ 8wraps us x2-24g/ 34g SS316L would be .223ohm --- dual coils would be .110ohm.
    That is usable on some mods. The build decks would have to be pretty good size though.

    However --- TC mode can usually run very low resistance coils. You won't be able to run them in VW mode though.
    Example: SMOK Alien can run TC as low as 0.06ohm. Wismec RX200s as low as 0.1ohm and the sweet Hohm Wrecker at 0.007ohm
     
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  44. gobbly

    gobbly New Member

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    Yes, but I'd look at what your mod suggests. The higher you can get the resistance the better TC is going to work, but it's going to impact your vape experience as well (it changes your current), so keep that in mind.

    I went into the why in posts above, but the basic idea is that we need a certain threshold of change in resistance to detect it (and limited in how low a total resistance can be detected). A coil at 0.1 ohm that goes to 0.1001 ohm @ 200f wouldn't be detected on a device with a minimum sensing resolution of 0.0002 ohm, but throw in a 1.0 ohm coil and now you're at 1.001 ohm @ 200f, a change easily detectable with your 0.0002 resolution.

    There's really no demarcation point, every mod is going to be different (and is impacted by the atty as well) and TC will continue to work to some degree, just will become less and less accurate. If you build super low, get a good TC mod, and put in the time to configure it for your builds. I regularly run a SS 0.2 ohm coil on an FSK chip and the TC works fine once I tweak the TCR a little. I don't go lower often, but never had an issue down to .1 with SS. Haven't tried a build that low on the DNA yet.
     
  45. Gregjl

    Gregjl Bronze Contributor Member For 1 Year

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    Thanks, I did try to change the math with a 3.5 mm I.d. the mod is a tempest and the deck is a lynx so pretty forgiving all the way around. The resistance just seems nuts though.
     
  46. PhantomOp

    PhantomOp VU Donator Gold Contributor Member For 1 Year

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    Going up a .5mm ID doesn't change a whole lot.

    3.5mm ID @ 8wraps us x2-24g/ 34g SS316L would be .246ohm --- dual coils would be .123ohm.
     
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  47. Gregjl

    Gregjl Bronze Contributor Member For 1 Year

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    Thanks, my new mod will tell me if the res. Is too low. I. Guess I'm in the habit of trying to be sure from mech mods. Good habit.
     
  48. HondaDavidson

    HondaDavidson Gold Contributor Member For 1 Year

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    The mass of a coil is why it heats faster or slower.... NOT the OHM rate. It takes longer to heat a lot of metal vs a a little metal. Or so I would think.. A 1ohm coil from 28awg is much faster and hotter than a 1ohm coil of 26 and slower colder than than 30......

    My question is which wire should be best for TC???? If Higher ohm is better. Accepted..... IS bigger or smaller coil/wire size, better??????
     
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  49. gobbly

    gobbly New Member

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    It shouldn't really matter to TC, with the caveat that you have a time resolution for how often you check resistance (I hear 1ms thrown around for the DNA), so if you heat up faster than you are checking resistance it could impact your TC. Under normal use, the vape characteristics would be different, but I don't think your TC would suffer (ie: The resistance/temp relationship wouldn't be impacted). I haven't tested it with any rigor though.

    This relates to the heat flux and heat capacity values in steam engine (heat flux is how quickly heat travels, and capacity is what temp an amount of heat energy will raise an object to; basically).
     
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  50. KingPin!

    KingPin! Senior Moderator Staff Member Senior Moderator Gold Contributor

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    Other threads ive read suggest that metals that change ohm resistence more substantially when heated are overall better for temp control as its easier for your mod to detect the changes and make the temperature calculations more accurately

    Check out my second post on this thread for the common TCR numbers ...the higher the number the more the ohm resistence will change for that metal. Know that you might not like the taste of all metals, also some are safer than others at high temperatures so bear this in mind with your decision about what to go with ;)

    in terms of thickness of gauge it's something to experiment with... what's right for one person might not be right for the next I don't think there is such a thing as best it's subjective... however avoiding hotspots and going for spaced coils is seen as the better option for temp control

    As a side note to this it's very important your starting ohm resistence is stable so checking coils are tightly screwed in the posts occasionally taking off your tank and resetting it on the mod are equally important
     
    Last edited: Feb 10, 2017

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