Well that definitely helps put it into perspective I don't need to worry about ohms with my regulated devices I can save that worry up for when I start using my luxotic and then after that the Armageddon LOL I'm really tempted to start using that lux bf because I love it it's by far my favorite mod as far as feel and looks go that I have of course I need to preemptively fix a certain downfall it has of leaking juice from the squonk pin into the mosfet chip *am I using the term mosfet correctly I think that that's a universal term it's not only a vaping term but I think that's what describes the chip that is placed in unregulated mods that have some limited safety features...
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The term MOSFET may not be exact, would depend on circuit design. But for simplicity, I think the term is fitting.
I agree there's no safety concern, but there are some concerns with efficiency and accuracy of TC.
The lower the resistance of your coil, the more current you need to supply to that coil to get obtain a given wattage. But the more current is flowing between the output of your regulator and the coil, the higher the losses are in all the wiring and connections between the regulator and the coil. In fact, those losses will be proportional to the square of the current flowing. Since a regulator board only knows voltage and current at its output, and not at the coil itself, it cannot compensate for those losses. This can definitely affect the accuracy of TC.
This is also why some TC regulators (e.g. modern DNA boards) have a calibration mode that requires one to screw a solid slug of copper in place of the atty. This allows them to learn (and then compensate for) the resistance in the wiring between the board and the 510, as well as in the 510 itself. That helps, but it's still not a 100% cure, since they still don't know the additional resistance added by the the atty, or the connections between the atty and the coil, nor do they know how much all of this stray resistance changes as the conductors and connections heat up under load.
Obviously whatever stray resistance exists between the regulator and the coil will have a greater effect on a lower resistance coil. Let's say the stray resistance adds up to 10 mΩ That's 10% of a 0.1Ω coil, but it's only 2% of a 0.5Ω coil. Now think about how much 10% is when you're looking for the relatively small resistance change in a material with a low TCR such as stainless steel.
All of this is why I think titanium is probably the optimal material for a TC coil. Nickel has a higher TCR, but extremely low resistivity, meaning nickel coils will have very low resistance. All the other commonly used materials have a TCR that's substantially lower than titanium. Titanium lets you build coils that have reasonably high resistance, with reasonably high TCR...
Efficiency can go both ways and is not dependent on how low or high your resistance is. That would assume all else being equal and the only contributing factor being coil resistance. That said, all else is not equal - we can’t have the same coil properties but different resistance therefore the same applied power resulting in the same output and outcome but with higher/lower current. The additional factors involved can sway the results to favour either low or high resistance.
Efficiency within a regulated circuit does not always scale in terms of applied current, meaning the higher the current output the less efficient the board is. It is entirely possible higher current output is more efficient with a lower resistance coil than one of a higher resistance that requires more voltage in order to achieve that same prescribed wattage. Either or can have diminishing returns - It’s all down to design which will require detailed measurements in order to conclude.
Fully agree on your points with stray resistance. It is an unfortunate factor that plagues the accuracy of temperature control - as with many other variables such as getting the TCR or in more detail, the TFR values correct. It’s far from a perfect system.
Excellent post
I use Temco's RW0499, 26ga titanium Grade 1 Annealed. Grade 1 is surgical grade titanium and the annealing makes it very easy to work with. Coils will last a long time. I usually rewick 4-5 times before rebuilding and clean each time with a small screwdriver. Used exclusively since Oct. 2018 but only halfway though a 50ft spool. Preferred coil is 3.5mm ID with 8 wraps and rayon wick.
If I note any inconstancy in TC (and batteries are well-charged), tightening the 510 pin or brushing the pin and threads lightly with Deoxit brings everything back to 100%.
Enjoy!
If I note any inconstancy in TC (and batteries are well-charged), tightening the 510 pin or brushing the pin and threads lightly with Deoxit brings everything back to 100%.
Enjoy!
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It's possible I'm being pedantic here, but nothing I wrote in my previous post was intended to address the efficiency of the regulator itself; only the conductors and contacts between the regulator and coil.
If you're vaping at 50W on a 0.5Ω coil, you only need 10.0A (albeit at 5.0V)
If you're vaping at 50W on a 0.1Ω coil, you'll need 22.4A (at 2.24V).
The losses between the regulator and the coil in the latter case will be ~5x as much as in the former, because the losses are proportional to the square of the current.
28ga ss316l is my favourite for TC mode. Heats fast and cools quickly, which is perfect for my chain vaping style.
Though I'm going to look at ss430 and titanium after reading this thread
I bought a boatload of premade ss430 coils from avs on clearance. They were going to stop selling them for some reason. Honestly I can’t tell the difference in ss316l and ss430 when using tc. I know there’s suppose to be but everything seems the same- wattage, temp, ramp up/down times etc... maybe I’m just oblivious lol!!
There would be no difference in the vape... SS430 has a higher TCR than SS316L so it is a little easier for the mod to detect the resistance rise using TC.
Also SS430 is nickel free, so those that have a problem with nickel can use it.
Oh good so I’m not as oblivious as I thought lol!! I bought A LOT of those coils for the higher TCR just for bettter TC “accuracy”. Wasn’t sure if there would be a noticeable difference or not when vaping.
Thanks sara
Never stated you mentioned anything about the efficiency of a regulator, I threw that in for the sake of conversation. But what losses are you referring to? Give an example?
Regardless, you are still assuming all else is equal which is not the case. Why does the 0.1 ohm coil require the same power as the 0.5 ohms? I do not see it as cut and dry as that - the values are not static therefore it is difficult to conclude that lower resistance will always equal a greater loss in efficiency.
I gave an example on the first page of a Ti coil of lower resistance requiring approx. 40% less power than a SS coil of the same dimensions and of a higher resistance. The power difference which is a requirement based on the coils properties equates to the higher resistance coil drawing more current.
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