Twisted Ni 200 and Kanthal, correcting the DNA 40 temperature setting

[flog]

The short and sweet: Due to the resistance difference of kanthal and nickel, the dna 40 device will need to be set lower than the wanted temp.

To achieve 410 F, with 32 (or 30) gauge nickel and kanthal, set temp to 340 F. Using 30 gauge Ni and 32 gauge Kanthal, set to 370 F (best match I found)

Now the ugly math part

Table 1, Used to calculate Ω's per inch. Data from Steam Engine | free vaping calculators

AWG	Wire Dia	Inches K	Ohms K	Ω/" K	Inches Ni	Ohms Ni	Ω/" Ni
28	0.01264	6.596	3	0.45482	6.642	0.2	0.03011
30	0.01003	6.914	5	0.72317	6.266	0.3	0.04788
32	0.00795	6.957	8	1.14992	6.567	0.5	0.07614

Table 2, Calculates the increased length(resistance is proportional) of wire when twisted (forms a helical)
Multiply the straight wire resistance by the correction factor.
Formula from Math Forum - Ask Dr. Math

Turns/"	28 AWG	30 AWG	32 AWG
10	1.075958	1.048470	1.030717
12	1.107731	1.069101	1.043947
15	1.163956	1.106074	1.067872
20	1.277006	1.182014	1.117816
24	1.381403	1.253756	1.165890

Table 3, coil parameters that I typically wind, gives me a realistic wire length.
Data obtained from Steam Engine | free vaping calculators

AWG	30	32
T ohms	0.2	0.3
Coil ID	0.125	0.125
Leads	0.197	0.197
T Length	4.177	3.94
# Turns	8.73	8.46

Table 5, Data from http://www.specialmetals.com/documents/Nickel 200 & 201.pdf
Handy values for Nickel 200 at various temperatures

Deg F	Ω cmf
0	48
70	58
200	76
400	113
600	164
800	204

cmf is circular mil foot, circ mil = 0.001". Keeping cmf constant, the Ω cmf is the resistance change due to temperature. The ratio from the 70/200/400/600 data points forms the cardinal resistances in the table below for 32 AWG Single Ni. Interpolation fills the rest of that column. The 32 AWG Twisted Ni gets it's factor increase from table 2, at 15 turns per inch, 1.067872 times the single resistance. Yeah, I know the factor does change somewhat when mixing 32/30/28 gauge in the twist, but I don't think it's enough to make much of a change on the final results.

The Single K Ω comes from the single Ni length (table 3) times it's Ω per inch (table 1). Twisted K Ω from single times the same factor used for single Ni (1.067872). K (kanthal) resistance stays fairly constant in the 70-600 F range.

The ## Ni ## K Total Ω = ## Twisted Ni Ω times ## Twisted K Ω divided by sum of ## Twisted Ni and K (Parallel resistance formula).

Setting dna 40 device for left-most column temp, found under "Set device temp". Example: want temp of 410 F, set DNA 40 device to 340 F (for 32 AWG twisted Ni/K).

For 32 gauge Ni wire

	32 AWG	32 AWG	28 AWG	28 AWG	30 AWG	30 AWG	32 AWG	32 AWG	32 Ni	Set	32 Ni	Set	32 Ni	Set
Deg F	Single Ni	Twisted Ni	Single K	Twisted K	Single K	Twisted K	Single K	Twisted K	28 K	device	30 K	device	32 K	device
	Ω	Ω	Ω	Ω	Ω	Ω	Ω	Ω	Total Ω	temp	Total Ω	temp	Total Ω	temp
70	0.300	0.320	1.792	1.914	2.849	3.043	4.531	4.838	0.274		0.290		0.300
200	0.393	0.420		1.914		3.043		4.838	0.344		0.369		0.386
210	0.403	0.430		1.914		3.043		4.838	0.351		0.377		0.395
220	0.412	0.440		1.914		3.043		4.838	0.358		0.385		0.404
230	0.422	0.450		1.914		3.043		4.838	0.365		0.392		0.412
240	0.431	0.461		1.914		3.043		4.838	0.371		0.400		0.421
250	0.441	0.471		1.914		3.043		4.838	0.378		0.408		0.429
260	0.451	0.481		1.914		3.043		4.838	0.384		0.415		0.438
270	0.460	0.491		1.914		3.043		4.838	0.391		0.423		0.446
280	0.470	0.502		1.914		3.043		4.838	0.397		0.431		0.454
290	0.479	0.512		1.914		3.043		4.838	0.404		0.438		0.463
300	0.489	0.522		1.914		3.043		4.838	0.410		0.446		0.471
310	0.498	0.532		1.914		3.043		4.838	0.416		0.453		0.479
320	0.508	0.542		1.914		3.043		4.838	0.423		0.460		0.488
330	0.518	0.553		1.914		3.043		4.838	0.429		0.468		0.496
340	0.527	0.563		1.914		3.043		4.838	0.435		0.475		0.504
350	0.537	0.573		1.914		3.043		4.838	0.441	220	0.482	260	0.512	290
360	0.546	0.583		1.914		3.043		4.838	0.447	230	0.489	270	0.521	300
370	0.556	0.593		1.914		3.043		4.838	0.453	230	0.497	280	0.529	310
380	0.565	0.604		1.914		3.043		4.838	0.459	240	0.504	280	0.537	310
390	0.575	0.614		1.914		3.043		4.838	0.465	240	0.511	290	0.545	320
400	0.584	0.624		1.914		3.043		4.838	0.471	250	0.518	300	0.553	330
410	0.598	0.638		1.914		3.043		4.838	0.479	260	0.528	310	0.564	340
420	0.611	0.652		1.914		3.043		4.838	0.486	270	0.537	310	0.575	350
430	0.624	0.666		1.914		3.043		4.838	0.494	270	0.547	320	0.586	360
440	0.637	0.680		1.914		3.043		4.838	0.502	280	0.556	330	0.597	370
450	0.650	0.695		1.914		3.043		4.838	0.510	290	0.565	340	0.607	380
600	0.848	0.906		1.914		3.043		4.838	0.615		0.698		0.763

For 30 gauge Ni wire

	30 AWG	30 AWG	32 AWG	32 AWG	30 AWG	30 AWG	28 AWG	28 AWG	30Ni/32K		30Ni/30K		30Ni/28K
	Single Ni	Twisted Ni	Single K	Twisted K	Single K	Twisted K	Single K	Twisted K	Total Ω		Total Ω		Total Ω
70	0.194	0.217	4.659	5.208	2.930	3.276	1.843	2.060	0.208		0.203		0.196
200	0.254	0.284	4.659	5.208		3.276		2.060	0.269		0.261		0.250
210	0.260	0.291		5.208		3.276		2.060	0.276		0.267		0.255
220	0.267	0.298		5.208		3.276		2.060	0.282	200	0.273		0.260
230	0.273	0.305		5.208		3.276		2.060	0.288	200	0.279		0.266
240	0.279	0.312		5.208		3.276		2.060	0.294	210	0.285	200	0.271
250	0.285	0.319		5.208		3.276		2.060	0.300	220	0.290	210	0.276
260	0.291	0.326		5.208		3.276		2.060	0.306	230	0.296	220	0.281	200
270	0.298	0.333		5.208		3.276		2.060	0.313	240	0.302	230	0.286	200
280	0.304	0.339		5.208		3.276		2.060	0.319	250	0.308	230	0.291	210
290	0.310	0.346		5.208		3.276		2.060	0.325	260	0.313	240	0.297	220
300	0.316	0.353		5.208		3.276		2.060	0.331	270	0.319	250	0.302	220
310	0.322	0.360		5.208		3.276		2.060	0.337	280	0.325	260	0.307	230
320	0.328	0.367		5.208		3.276		2.060	0.343	290	0.330	270	0.312	240
330	0.335	0.374		5.208		3.276		2.060	0.349	290	0.336	280	0.317	250
340	0.341	0.381		5.208		3.276		2.060	0.355	300	0.341	280	0.322	250
350	0.347	0.388		5.208		3.276		2.060	0.361	310	0.347	290	0.326	260
360	0.353	0.395		5.208		3.276		2.060	0.367	320	0.352	300	0.331	270
370	0.359	0.402		5.208		3.276		2.060	0.373	330	0.358	310	0.336	270
380	0.366	0.409		5.208		3.276		2.060	0.379	340	0.363	310	0.341	280
390	0.372	0.416		5.208		3.276		2.060	0.385	350	0.369	320	0.346	290
400	0.378	0.422		5.208		3.276		2.060	0.391	350	0.374	330	0.351	300
410	0.386	0.432		5.208		3.276		2.060	0.399	370	0.382	340	0.357	310
420	0.395	0.442		5.208		3.276		2.060	0.407	380	0.389	350	0.364	310
430	0.404	0.451		5.208		3.276		2.060	0.415	390	0.396	360	0.370	320
440	0.412	0.461		5.208		3.276		2.060	0.423	400	0.404	370	0.376	330
450	0.421	0.470		5.208		3.276		2.060	0.431	410	0.411	380	0.383	340
600	0.549	0.613		5.208		3.276		2.060	0.549		0.516		0.473

It's interesting to note that 30 gauge Nickel and 32 gauge Kanthal twisted, gets the smallest correction factor to the DNA 40 setting. Makes sense, as in parallel resistances, as the larger value gets further away from the smaller resistance, the less effect it has on the total resistance.

Well, there you have it. Most likely there are some mistakes here, I've tried my best. I did make some measurements on wire resistance, single and twisted and they did come out in the ballpark of instrument accuracy. Only thing I didn't have was a thermal gun to check actual generated temperatures.

That's it, thanks for your time.

 

[maleasdf]

This is great, this should be informative for most trying to build sturdy coils. From my experience only twisted wires are strong enough to handle dry burns and rewicking without any deformation.

I had made some plots also for composing temperature differential between pure nickel and hybrid coils. Will post some later as don't have them handy right now.

From my notes the difference using two single strands of 32g nickel and single 32g kanthal had around 50F@500F difference (the difference changes nonlinear so noting difference at a reference set point).


However if doing a hybrid of single 28Ni and 32g kanthal has 20F@500F difference, hence much closer to pure Nickel coil. This is what most users have reported in their buidls to be the most successful.

Two strands of Ni 28 along with one stand of28g kanthal also seems to have 20F@500F, however the ohms are low and would make a huge coil and longer to heat up.

Like to hear what other users experiences are.

 

[flog]

Appreciate the insight maleasdf,

The 2 strands of 32g nickel would make it appear electrically as a single 29g nickel, using the Steam Engine | free vaping calculators site (they both come out as 0.038 ohms per inch).

I didn't make a table for 28g nickel with kanthal, as I found that that gauge nickel holds up fine in the post hole type capture.

Your experience might make me ambitious enough to include some other sizes.

Question, is there a way to include the actual excel spreadsheet on ecf, or do I need to look at a link from google docs?

Laters and enjoy the new year.

 

[qorax]

^^Well done Flog√

 

[flog]

Got a revised spreadsheet that's a bit more user friendly, try it out!


https://docs.google.com/spreadsheets/d/1VRmTbfy9Owsj-bRTIEwvi46LKnQyLxYNzy8Q-H9zaPo/edit?usp=sharing

 

[bwhitt]

thanks, trying my first single coil build using 30guage nickel and 30 gauge kanthal. The kanthal wire really holds the heat in a lot more then nickel wire. Set the temperature to 370 and it does not burn the cotton. Temperature protection seems to be working well. 8 wraps on a 3mm screw gave me 0.2 ohms. Should make it a lot easier to run a dual coil setup in my current RDA’s

 

[flog]

Definitely don't take the values as gospel, I believe there's plenty of wiggle-room in the numbers. I saw the same thing on my 30g Ni/30g K twisted coils, running 370 F and the washed wick came out clean (no burning). The kanthal definitely let's you snug the holddown screws or use post holes.

 

[Alexander Mundy]

flog, don't know if this is useful to you or not but here is the math I used for NI200.
I found these equations in several places online so they should be good.

For high precision:
R(t) = R(0)*(1 + a*t + b*t^2+ d*t^4+ f*t^6)
Where a=5.485x10^-3 b=6.650x10^-6 d=2.805x10^-11 and f=-2.000x10^-17
t is measured in C
R(0) is the reference resistance at starting temp
R(t) is the new resistance at the new temp.

For low to medium precision:
a = alpha = 0.00672 ohms / ohm / °C
R(t) = R0 (1 + a*t )
Inverted for temperature:
t = (Rt / R0 - 1) / a

 

[flog]

Fantastic Alexander,

I do love fooling around with the technical aspects of things, this will add some bling to the current assumptions. If you do run across the source, send the address to me please. I try to document where all this stuff comes from, giving others confidence that it didn't come out the other end ;-)

I did enjoy your 3 videos on the magic ribbon, the close up views were awesome, kind of like how nature expresses her beauty. Keep up the good work, Ribbon Master.

 

[Alexander Mundy]

Nickel is used as an RTD (Resistance Temperature Detector) quite a bit in industrial and laboratory settings. Here's one, but Google "Nickel RTD" and you will find it multiple places.

Capgo - RTDs

 

[foliagegreen]

Awesome info here. Quick question for you guys, I've been building nothing but spaced ni200 coils. I was wondering if micro coils are possible with the twisted kanthal/ni200 method. Also is it advisable to pulse these coils? If so, at what wattage?

 

[flog]

Due to the uneven geometry (conductor not making contact continiously around the coil turns), i would think it would be an iffy situation. I'd look in http://www.e-cigarette-forum.com/forum/coil-builds/613433-dna-40-nr-nickel-builds.html

 

[flog]

I'm not sure why I can't paste the colored excel spreadsheet bits like I did when opening this subject, but wanted to let ya'll know that with the more precise formula given by Alexander Mundy, the resistance values came out a bit higher, but the over ratio pretty much stayed the same, that is, for a 30g Nickel twisted with 32g Kanthal, the 410 F wanted for the coil temp, still came out as a setting of 370 F, same with either means of calculation.

https://docs.google.com/spreadsheets/d/1c7ZtQ_xDjv-4Q-lodrS0PrLeJFKsrfPRNqt16NFucsI/edit?usp=sharing
here's the updated spreadsheet.

 

[Mylt1]

so quick question, how are you twisting Ni200 and kanthal? are you doing it by hand to count the wraps or just using a drill till its tight like you would with 2+ strands of kanthal?

 

[flog]

drill method, usually coming up with 20 something full twists per inch. Basically until it breaks from the drill bit.

 

[Mylt1]

thats what i was thinking. thanks for the help. will be ordering some 30awg Ni200 tonight, already have the 32awg kanthal. just got a vaporshark rDNA 2 days ago and want to try the temp control.

 

[Ryuukon]

Thanks for this great info. Subscribed so I can come back to it when I get my grubby mitts on an SX Mini M Class.

 

[slipr]

hi, i am mathematically challenged, would it be a pain for you to put together a 26K/30Ni twisted chart for me/us? I couldnt get flavor out of the 28ni so i went to 30 to minimize the NI and brought in my 26K and the flavor is restored. Only problem is i have no idea what the real temps are. Will redo water boiloff temp and compare result to standard boil (210F) to get a reading and report back. tnx OP

 

[flog]

Don't take these value as gospel, just somewhere in the ballpark.
Hope this helps, all values are for a correct temp of 410 deg.

 

[slipr]

Flog, i can see that you are busy, really really busy but could you apply these values to to say 420F as well so we can see what the increments are between steps??

greatly appreciated