Number of wraps for resistance

[Danny55]

Thanks for all the replies guys. I'm not much the wiser at the moment though.

Unless I am completely missing something here that still doesn’t equate. According to Steam, a 3mm ID, 7.5 wraps of 26awg SS317 comes out to 0.596 ohms per coil or 0.298 ohms for dual coils in parallel. There is usually a small variance between actual readings and what Steam calculated but I have never seen anything as great as a 0.4 ohm per coil. Even taking into account the long leads on the build still does not make up for the difference. Something else must be at play here.

I've absolutely no idea what's going on. I just unwrapped those coils and made them 5.5 wraps and according to the calculators, it should be 0.22 ohms but it's reading 0.34 ohms.

 

[Skunk!]

Thanks for all the replies guys. I'm not much the wiser at the moment though.



I've absolutely no idea what's going on. I just unwrapped those coils and made them 5.5 wraps and according to the calculators, it should be 0.22 ohms but it's reading 0.34 ohms.

Picture?

 

[puffon]

Be sure you are reading the ohms when the coils are cold.
SS rises in ohms, as they heat up.

 

[Skunk!]

I have never used a coil calculator. They simply weren't available back whenI was learning. I wouldn't stress too much about what the calculator says. If the resistance is stable and the coils are glowing evenly from the inside out, then you should be fine. The resistance of stainless fluctuates quite a bit, so keep that in mind.

 

[papergoblin]

I have found variances in ss and ni80, depending on brand (not a huge amount though). Generally the calculator is going to be close but not spot on. Then there is also the length of the legs to contend with, some RDA's I use I have to S shape the legs to get the width I want, to center the coils.

I skimmed over the posts and may have missed but it also depends on if the coils are spaced or contact. I think a lot probably comes down to what you count as wraps.

How I count wraps:
- The jig in my left hand, the tail faces me on bottom (kuro style coiler)
- I wrap clockwise (over the rod) so with tail facing me and going over rod I wrap till the opposite end faces away that's 1 wrap (on top)
- I count this way till desired amount which leaves legs going opposite ways

Then depending on the atty I leave alone or bring the wire down to both legs facing same direction.

 

[Punk In Drublic]

I reference Steam quite a bit but tend to focus more on Heat Capacity and Surface Area as a guidance oppose to the amount of wraps - even though the later plays an important role in the former. Steam uses known properties of specific wire so it’s calculations will be correct. We do not know the properties of the wire we use therefore a variance can be expected. However, with every coil I have built or even pre wrapped coils that I have purchased, I have not once encountered a variance as great as what the OP has experienced. Personally I think this should be investigated further. If one has purchased Stainless Steel wire for a specific purpose, say allergies for instance, then they should have confidence that what they purchased is in fact is what is labeled on the spool. A discrepancy this large does not leave me with that confidence. Not trying to discredit the retailer in which this wire was purchased from – it is quite possible the manufacture got it wrong and the retailer has no idea. A discrepancy this large could also point to other issues such as lose connections within the deck or foreign debris. Food for thought.

 

[Danny55]

Thanks for the replies guys. Punk In Drublic, yes I suppose there could be an issue with the deck, good point. I'm going to build on another tank and see if that's closer to the calculator. This is the reel. What they wrote is in black, everything else is my writing. 'TMC' stands for the mesh company, their old name. I'm guessing the 'S' is Stainless steel.



I've just been messing around with some fresh 26 wire to see how many wraps would actually give me around .2 ohms.

3 and a half wraps per coil is giving me 0.27 ohms. Weird eh, because Steam says 7 full wraps. I'm not keeping these coils, they're messy, only for testing.

 

[Punk In Drublic]

@Danny55 – I have noticed from time to time that Steam does not always refresh once a change has been made. Not saying this is the reason behind your discrepancies, just bringing it to light.

I also prefer to use the Wire Wizard app on Steam over the Coil Wrapping app. They are both accurate, but the Wire Wizard tells you the actual resistance of the coil vs the Coil Wrapping trying to match your preferred resistance. The Wire Wizard also only works on a per coil basis but just divide by 2 if using a dual parallel. It also allows you to build Clapton style coils if thats your thing

 

[louiesquared]

What are you using to measure the resistance?

 

[Danny55]

Sorry for the late reply guys. Thanks Punk In Drublic, that Wire Wizard is handy.
louiesquared, I should probably buy one of those CoilMaster meters, but I just read the ohms on whatever mod I'm using. In the last couple days I've built a variety of different resistance coils from 1.17 up, but for whatever reason none of them match the amount of wraps reported from Steam. So I'm just finding out through trial and error how many wraps I need for whatever resistance I'm going for.

I found a 4 year old reel of Kanthal A1 32 gauge so decided to test with an arbitrary amount of wraps. I did a single coil with 10.5 wraps and 2mm ID and it came out at 3.2 ohms. Lol, imagine trying to vape at 3.2 ohms. Anyway, it read that on two different mods, and I also transferred the same coil from my OBS to my Tobeco Velocity Mini and it read the same. But according to Steam, that should give 3.8 ohms. So, I don't know, I give up on Steam. It's easy enough to experiment and discover how many wraps I need.

 

[Punk In Drublic]

Don’t know what to tell ya. As mentioned Steam uses known metal properties to perform its calculations – based on these properties Steam is pretty accurate, probably 100%. Metal resistance can vary depending on their grade and the variance of alloys used. So unless there is another factor influencing your readings, it is obvious your Kanthol and SS wire is of a different grade than what Steam uses.

Just rebuilt the coils for one of my RDA’s, 6.5 wraps, 3mm ID N80 fused Clapton made with 4x 30awg cores and a 40awg wrap with a 5mm leg. This is a complex coil in comparison to a single gauge wire. Steam calculated the coil to be 0.446. Cheap ohm meter read 0.44, Rage Squonk mod read 0.45, a Lost Vape DNA250C read 0.472.

 

[Danny55]

Yep Punk In Drublic, I don't doubt that Steam is correct. I must be doing something wrong but I wish I knew what.

 

[dripster]

Don’t know what to tell ya. As mentioned Steam uses known metal properties to perform its calculations – based on these properties Steam is pretty accurate, probably 100%. Metal resistance can vary depending on their grade and the variance of alloys used. So unless there is another factor influencing your readings, it is obvious your Kanthol and SS wire is of a different grade than what Steam uses.

Just rebuilt the coils for one of my RDA’s, 6.5 wraps, 3mm ID N80 fused Clapton made with 4x 30awg cores and a 40awg wrap with a 5mm leg. This is a complex coil in comparison to a single gauge wire. Steam calculated the coil to be 0.446. Cheap ohm meter read 0.44, Rage Squonk mod read 0.45, a Lost Vape DNA250C read 0.472.

Personally I don't believe Steam is accurate. For example, it reports that the heat capacity of Kanthal A1 is lower than that of Nichrome 80, when we all know Kanthal heats up slowest...

 

[Zakillah]

Personally I don't believe Steam is accurate. For example, it reports that the heat capacity of Kanthal A1 is lower than that of Nichrome 80, when we all know Kanthal heats up slowest...

Specific heat of N80 is slightly lower then Kanthal (450 vs 460); however N80 has a higher density (8,4 vs 7,1), making the coils heavier. Therefore the heat capacity of a Kanthal coil is in the end lower compared to a same sized N80 one.

Its not like Steam is the only site to look up these properties...

 

[Punk In Drublic]

@Zakillah is correct (BTW, ur profile pic…awesome band!)

Use Wire Wizard and adjust your coils so that the mass is close to matching and you will see that the Heat Capacity of N80 is lower than Kanthal

 

[dripster]

Specific heat of N80 is slightly lower then Kanthal (450 vs 460); however N80 has a higher density (8,4 vs 7,1), making the coils heavier. Therefore the heat capacity of a Kanthal coil is in the end lower compared to a same sized N80 one.

Its not like Steam is the only site to look up these properties...

I've already looked up the numbers myself a while ago, and so I know you're right (and in fact at room temp the datasheets I found online seem to suggest the difference between the specific heat of Kanthal A1 and that of Nichrome 80 is actually even much bigger than the numbers you gave...), but this still doesn't change the fact we all know that Kanthal heats up slowest, watt for watt. So that's another example of why I don't rely on Steam, i.e., theory vs practice just doesn't always add up, and often times the theoretical side isn't even remotely accurate.

 

[dripster]

@Zakillah is correct (BTW, ur profile pic…awesome band!)

Use Wire Wizard and adjust your coils so that the mass is close to matching and you will see that the Heat Capacity of N80 is lower than Kanthal

Something just doesn't add up because, why would I need to adjust the mass? When I want to compare apples to apples, doesn't it make proper sense to keep the volume the same for both coils, i.e. use the same wire thickness, number of wraps, inner diameter, and leg length, thus changing only the metal type itself?

 

[Punk In Drublic]

Something just doesn't add up because, why would I need to adjust the mass? When I want to compare apples to apples, doesn't it make proper sense to keep the volume the same for both coils, i.e. use the same wire thickness, number of wraps, inner diameter, and leg length, thus changing only the metal type itself?

It’s because Heat Capacity is related to mass. N80 for the same dimension wire has more mass than Kanthal therefore Steam reports a higher Heat Capacity. If Heat Capacity is your objective, then other parameters have to be changed. Similar to if resistance is your objective - a N80 coil will have different dimensions than Kanthal for the same resistance.

 

[Zakillah]

I've already looked up the numbers myself a while ago, and so I know you're right (and in fact at room temp the datasheets I found online seem to suggest the difference between the specific heat of Kanthal A1 and that of Nichrome 80 is actually even much bigger than the numbers you gave...), but this still doesn't change the fact we all know that Kanthal heats up slowest, watt for watt. So that's another example of why I don't rely on Steam, i.e., theory vs practice just doesn't always add up, and often times the theoretical side isn't even remotely accurate.

Yeah; I found either 435 or 450 specific heat for N80. Greater difference, yeah; much greater, not really. Taken density into account, Kanthal still wins overall, at least in theory.
However I´ve not found detailed numbers on how heat capacity changes in the temperature range that matters to us (20-250°C)

I don't "know" if Kanthal heats up slower then N80 or SS. All I hear is some people say this, others say that. Someday, maybe, I´ll order a roll of 0,3mm N80; SS and Kanthal and find out if I can feel a difference.
But in the end; idk if it matters all that much. If you´re unhappy with ramp up; using thinner wires will have a much bigger effect then changing coil material.


Punk In Drublic, Yes; good taste in music.
I (obviously) love Bolt Thrower. Shame about their drummer; would have loved to see more concerts of them.

 

[DaveP]

I've had variances in coil readings from time to time. Screw connections, loose bottom contact screw (threads into positive side of deck), and coils touching before a dry burn are just a few of the reasons. Wire diameter variances can also be an issue at a minute level.

Compressed coils vs spaced coils can make a difference, especially before the coil is heated for annealing and the wire forms an insulating layer from the heat.