Most Common Coil Building Misinformation I've Received

[victoryt71]

I'm an electronics engineer and when I first started learning to build my own coils the information I was getting from my local vaping shops did not "click" with me. Until...I figured out the vaping community uses a slightly different vocabulary. As I watched them wrap my coil it dawned on me that what everyone calls coil resistance is what I understood to be impedance.

I kept being told it was the number of wraps, regardless of the wire gauge, that increases or decreases your resistance.

Maybe this was my own hang up, but after several "discussions" with my local store of trying to tell them they were making a heat inductor and not a resistor at all and trying to explain to them the resistance is a result of the length of the wire, not the number of wraps, I finally brought an ohm meter to the store and showed them that 2" of kanthal (gauge didn't matter) has the same amount of resistance whether you do one wrap or 12 it just all made more sense for both of us.

Smaller gauge wire (thicker wire) has less resistance and can give you a much larger heating surface with more wraps than a larger gauge wire (thinner wire) can. To get the same 1.4 resistance on a coil built with 30 gauge wire using a 6/5 wrap with 26 gauge you would have to do a 14/13 wrap using the same diameter wrapping tool. Both these builds will pull the same amps and provide the same wattage. The difference is the 30 gauge coil is only around 1/8" long and does not provide as much heating surface as the 26 gauge coil which will be around a 1/2" or more long.

Sorry, I ramble, but once I was speaking the same "laungauge" I was able to start customizing all my rebuildables for exactly the perfect flavor and cloud.

In short, more wraps does not dictate more resistance. The length and the gauge of the wire you use does.

Anyone else have similar knowledge for us new to rebuildables? (ie. mouth inhalers will get better flavor from smaller diameter drip tips and lung inhalers will get better hits from larger diameter drip tips)

 

[txfordguy]

After reading and thinking (ouch) for a bit I think I get what your saying. Longer wire = higher resistance, and in turn, longer wire = more possible wraps. Vapers just tend to use the term wraps because it's easier to communicate.

Feel free to correct me if I'm wrong. Anything dealing with electricity was never my forte.

 

[Sgt.Rock]

I feel your pain ~lol~

Took me a while to figure out that a "mod" was essentially just a battery holder with a switch and a connection for your atomizer and optionally some electronics.

"Mod" coming from the early days when creative folks would "mod" an existing device like a flashlight tube to be able to use it for vaping.

 

[novamatt]

I think why you're hearing that from people is that when you build a coil, you generally put the ends of it into an atomizer and then snip off the remaining wire. Leg length tends to stay the same. So for every extra wrap you do, your wire length is getting one coil circumference longer. If we used, say 2 inches of wire every time, then number of wraps wouldn't make any difference. But when the length of the resistance wire used is dependent on the size of the coil, then more wraps = higher resistance. A 12 wrap coil is going to use quite a bit more wire than a 2 wrap.

On the other hand, it drives me nuts when people say that it's all about the wraps and then can't figure out why their 24awg wire won't make a coil over 1 ohm to use on their 11-15 watt regulated mod.

 

[bwh79]

I figured out the vaping community uses a slightly different vocabulary. As I watched them wrap my coil it dawned on me that what everyone calls coil resistance is what I understood to be impedance.

You're not wrong, and neither are the rest of us. They're essentially the same thing in our case, since we're using batteries (DC) and not plugged into the wall (AC). From Wikipedia:

Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude. When a circuit is driven with direct current (DC) [batteries, in our case], there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.​

trying to explain to them the resistance is a result of the length of the wire, not the number of wraps

Again, these are essentially the same thing. Presuming the diameter of your wraps remains constant, then you will get more wraps from a longer wire and fewer wraps from a shorter wire. So since resistance/impedance depends on wire length, and wire length is proportional to the number of wraps, it's not incorrect to say that the number of wraps determines the resistance (inasmuch as it dictates the overall length of the wire), as long as the wraps' diameter and the wire gauge remain constant.

 

[White Stone]

Victoryt71,

resistance is a result of the length of the wire, not the number of wraps

Thank you! I will work from there. Get the length that gives me the resistance I want and then coil it to fit my dripper.

White Stone

 

[KenD]

Misusing resistance for impedance I get (because I do it myself, and I don't really get the difference ), but the idea that wraps are what determine the resistance (see, I'm doing it) is outright dangerous (and quite common). You frequently see new coil builders asking "how many wraps do I need for x.x ohms", never even considering coil diameter. People really need to get it into their heads that wire gauge + wire length are what determine resistance (sorry, impedance ).

 

[Jockamo]

Why don't micro coils with the wraps touching have bigger impact on resistance? It seems it would create a much shorter path between the poles.

 

[readeuler]

Why don't micro coils with the wraps touching have bigger impact on resistance? It seems it would create a much shorter path between the poles.

Good point, and it turns out the magical Kanthal is the answer. As it gets hot (dry burning) it forms a layer of oxidation that insulates the surface of the wire, preventing the electrons from taking any shortcuts - and they'd try it, too! The oxidation stays, even after the coil cools down.

You can even see for yourself. If you measure a coil before a dry burn, it's often a couple tenths of an ohm lower (for 1.8ish ohm coils). It's not as dramatic as you may think, because it's rather hard to wrap a coil that's touching more than slightly.

 

[Jockamo]

Interesting. Thanks.

 

[Jockamo]

I just assumed there was little if any contact especially with the round wire()(). So I guess the power we are talking about isn't enough to bridge the gap or push through oxidation?
Oxidation never entered my mind. Not much does.

 

[eyerhere]

Yes it is true people tend to tell you half the details needed to make a coil. More wraps = more resistance (or impedance) holds true assuming the dia and awg remains constant. which is true when building 1 coil. I am sure we could get way more technical with this stuff but as long as we get a safe and good vape, who cares?

 

[charlie1465]

Hello all

This is absolutely right as a discussion but for me we have to then think about heat capacity. A higher number leading to slower firing and cooling. It is crucial for me that I find a responsive relationship between firing my mod and inhaling some vapor.

I am new to building and have been trying lots of different builds. What I am looking for is a high surface area low resistance build which equally has a low enough heat capacity to fire quickly.

Any suggestions would be appreciated?

C

 

[Firestorm]

I kept being told it was the number of wraps, regardless of the wire gauge, that increases or decreases your resistance.

You are absolutely correct that the length and diameter of the resistance wire determines the resistance (or impedance). If I have a given length of Kanthal I'm going to wrap it as many times as I can around a wick and then attach the leads directly to the terminals - say 6 wraps. A vaper would not take the same length of wire, do two wraps, and then have excess wire leads not going directly to the terminals (any resistance wire that is not touching the wick will be wasting power and might result in a burning taste). If you understand this you might appreciate why someone might say that more wraps equals higher resistance (regardless of the wire diameter).

 

[HecticEnergy]

In theory this all makes sense to me, but in practice it seems 24ga wire takes longer to heat than 32ga. to do anything with 32ga you have to wrap around like 5/64, which is a tiny coil, and seems to burn up any wick i put in it (narrow heat tube with intense heat).
For a better comparison 28ga vs 24ga with the same inner diameter, 24ga seems to take longer to heat. Even when building around .3 ohms. I guess that is due to the surface area of the microcoil - with more surface area, the heat is dispersed along a larger area meaning it takes longer to heat..? I admit I'm no electrical engineer, but I do like to know how things work
I stick to 28ga for the most part, seems to be responsive (heat quickly) and produce a decent vape. I usually build single coils around 1.4-1.6 ohms - which is about 6 or 7 wraps around 7/64... check steam-engine.org if you want to know the actual length of the kanthal When doing dual coils, i build the same coil, which brings me to .7-.8 ohms net. I have a .3build with some twisted 26ga, but that was just being ridiculous with my little boy atty


Sent from my iPad using Tapatalk

 

[Cavenerd]

I also am not an electrical engineer. I'm actually a geologist by education and rocks are not famous for their electric effects. So if there are smarter folks out there please correct my analogy and/or science.

On an 8-lane highway (thicker wire) it would be pretty easy to get 100 cars (electrons) through a 100 yard segment of road in a few seconds, but on a 1-lane highway (thin wire) it would be it would be much more difficult to get the same amount of cars through the same distance in the same time. In the second case, Road Rage (resistive heating) would grow much faster.

Please realize that this is a rough explanation and it leaves out a few of the actual mechanisms for resistive heating.

The real mechanism that causes your wire to heat up is a transfer of energy between moving electrons and the atoms of the wire. It's almost like an atomic level friction. As the electrons "bang" into the atoms of the wire they leave behind a tiny bit of their energy. That "left-behind"/transferred energy is what causes your wire to heat.

If the length of the wire(s) and the number of moving electrons (current) across that length are constant:
-Narrow wire will offer a smaller cross section through which the electrons might travel... The wire will heat faster because there is a smaller mass through which to distribute the transferred "heat".
-Thicker wire offers a larger cross section for the same number of electrons. The same number of collisions as before (remember, same number of electrons moving through the same type of wire, only thicker this time) will transfer roughly the same amount of heat but there is a greater mass of wire to distribute the heat through... Slower responding wire. In order to make this thicker wire respond as quickly to the resistive heating we will will need to add more electrons (i.e. increase the wattage which increases the current = more electrons).

If you look below at the 22g (.11ohm/inch) and the 30g (.7ohm/inch) you'll see that the resistance of the 30g is almost seven times the resistance of the 22g. What that means is that if I wanted to build a coil at .7ohm I would only need 1 inch of the 30g while I would need (almost) seven inches of the 22g!

AWG 22: Low Resistance (0.11 ohms/inch)
AWG 24: Low Resistance (0.175 ohms/inch)
AWG 26: Low Resistance (0.28 ohms/inch)
AWG 28: Low - Standard Resistance (0.44 ohms/inch)
AWG 30: Low - Standard Resistance (0.70 ohms/ inch)

Wire with a bigger cross-section (thicker) = more "room" for electricity to get through un-impeded. Lower resistance to flow.
Wire with a smaller cross-section (thiner) = less "room" for electricity to get through un-impeded. Higher resistance to flow.

So, what does this mean to us as vapers? That big slow responding coil we've built is going to resist the flow of current only a little bit (and the resistance is what is causing the heat) so it will take longer to heat to a given temperature, but it has a much larger surface area (compared to a thinner wire coil at the same resistance) to vaporize juice on. More power applied to that same coil will allow it to heat faster.

Anyway, I hope this helps. I "might" be a little hung-over today so this is probably not my best work.

Happy new year

BTW,

I am new to building and have been trying lots of different builds. What I am looking for is a high surface area low resistance build which equally has a low enough heat capacity to fire quickly.

C

I use a kanthal A-1 dual-coil twisted 28g with 7/6 wraps on 1/8" bit for about .4ohm. At ~30 watts it's nice and smooth but I pulse it for a second before I inhale to preheat the coil a bit.

Before you do anything though:

1. Know your battery's limitations
2) Use the correct tools, including an ohmmeter
3) Know your battery's Limitations!!
4) Use this tool to help you plan your next coil: Steam Engine | free vaping calculators

 

[skoony]

i have heard that some regulated and VV or VW PV's use pulse-width DC.
would this not cause inductive reactance in a coil?
i know its a square wave as opposed to a sinusoidal wave.
it does put frequency back into the equation.
regards
mike

 

[Bunnykiller]

i have heard that some regulated and VV or VW PV's use pulse-width DC.
would this not cause inductive reactance in a coil?
i know its a square wave as opposed to a sinusoidal wave.
it does put frequency back into the equation.
regards
mike

inductive resistance occurs in AC circuits... the flow of electrons need to be reversed and then sent back in the opposite direction. the faster the reversing cycle, the higher the inductive resistance will become
in pulsed DC there isnt a reversal of electron flow to deal with

 

[coilwrapper]

Hello Victoryt71...The shops talk to 100 people and 99 of them may know nothing about volts ,watts, ohms. but one of them does...thats you...they are trying... love your post...you nailed it...happy new year and good vapes.

 

[tj99959]

I too am an engineer, just not an electrical engineer. It has always fascinated me that often different engineering fields will use different terminology for the same thing. So saying resistance instead of impedance is no big deal to me.

I can sure think of some funny things about vaping tho'.

Resistance (sorry, impedance) doesn't matter all that much, it's what you do with it that makes a difference.
Understanding the thermodynamics allows us to easily make a 0.2 ohm coil run to cold, or a 2 ohm coil run to hot.
Resistance/volts/watts is only one small part of the formula for a good vape.