Question about double-coil ohms

[djeaton]

I have a dual-coil 1ohm drip atomizer on order. It's the first dual-coil and rda in my future. But I've got a few newbie questions about it.

1. Because it has two coils, does that mean that each one has 0.5ohm of resistance? Or do they EACH have 1ohm of resistance and you don't add them up?
2. Is there really a benefit of having 2 coils at 1ohm versus a single coil at 1 ohm?
3. Do I need to rebuild this on a regular basis or with every flavor change - or just when the coils stop producing?
4. When I do get around to learning how to rebuild this, do you have to maintain a balance between the coils so that they are roughly the same resistance?

Thanks for the patience and answers.

 

[dr g]

1. Each is 2 ohm resistance
2. Yes, there can be
3. None of the above really. You will probably rebuild when you are ready to try something new.
4. Yes

 

[Ryedan]

1) I believe 1 ohm is what the device will measure. That means it has two 2 ohm coils in parallel. If it had ywo 1 ohm coils, it would meter 0.5 ohms.

3) You will need to rebuild the coils when the wicks can not be successfully dry burned anymore, or when you pop one.

4) It is a good idea to keep the coils the same.

I left #2 for someone who knows these better than I do.

 

[gankoji]

2) I find there to be a slight benefit for dual coils, as you (generally) get more vapor with less vapor temperature, because the power is more spread out spatially.

1) Generally, you'll be connecting two coils in parallel (because series doesn't make much sense). This is why, to get an overall of 1 ohm, you'd need two 2 ohm coils. For a more academic treatment of this principle, see here: Series and parallel circuits - Wikipedia, the free encyclopedia

 

[djeaton]

I don't understand serial versus parallel yet, and barely have a grasp on the correlation between volts, ohms, watts, and amps. So the first time I go to do this, I'll just post what my goal is (say a total of 3ohms) and ask what materials I need to order to do it and how many wraps I should make on the coils. As a fractal artist, I may not be able to grasp all the math behind stuff and can just learn that if I do X it produces Y.

 

[gankoji]

I don't understand serial versus parallel yet, and barely have a grasp on the correlation between volts, ohms, watts, and amps. So the first time I go to do this, I'll just post what my goal is (say a total of 3ohms) and ask what materials I need to order to do it and how many wraps I should make on the coils. As a fractal artist, I may not be able to grasp all the math behind stuff and can just learn that if I do X it produces Y.

Two things: 1) We are always happy to help you understand this stuff, especially as you get started. 2) That said, if you don't understand ohm's law and basic circuitry principles (like parallel resistors), you have absolutely no business rebuilding an atomizer.

Please understand that I am not trying to be snobbish. Atomizers have some inherent dangers (I mean, you're lighting up some tiny pieces of steel to hundreds of degrees, and coming close to igniting liquids that can kill you in too high a dose). I'm also not trying to scare you, or anyone else reading this post. I just want to be clear that the only person who is ultimately responsible for your safety, once you start rebuilding atty's, is you. Thus, the onus is on you to get educated about what it is you are doing.

And, honestly, if you understand fractals, Ohm's law is a walk in the park .

 

[djeaton]

Two things: 1) We are always happy to help you understand this stuff, especially as you get started. 2) That said, if you don't understand ohm's law and basic circuitry principles (like parallel resistors), you have absolutely no business rebuilding an atomizer.

It's definitely nothing I am going to jump right in on. But I figured as long as I had a box coming this way, I'd have them throw a couple of toys in it to play with later. I understand volts, watts, and resistance. And I've heard of serial and parallel before (in more than the context of a breakfast or how to park your car) because my brother and a nephew are (or have been) electricians. But as a programmer and project manager before becoming disabled, my expertise lies more in the software than the hardware.

So you haven't totally scared me off...just added the wisdom of warning that I need not to rush into this (even if I was not waiting a couple of weeks for it to arrive). I'm going to lurk and read a lot and ask lots of questions before I try to tackle this myself.

 

[lctrc]

Assuming identical coils, resistance in parallel is the resistance of one of them divided by the total number of them.

Two 2ohm coils in parallel results in a resistance of 1ohm. For your 3ohm dual coil, you'd need two 6ohm coils. That's a lot of wire.

Just to be pedantic - the actual formula is:

1/r₁ + 1/r₂ + ... = 1/R

where r₁ is the resistance of the first coil, r₂ is the resistance of the second coil, etc.

coil1 = 6 ohms
coil2 = 6 ohms

1/6 + 1/6 = .166 + .166 = .333

1/.333 = 3

 

[djeaton]

Thanks, KTRC! That is some great information. I had noticed that when I was looking around at different supply options that the resistance is measured in ohms per foot based on the type of wire you have. So I "get" that the total length is important. And I'm assuming that there is really a limit to the number of wraps around the wick that you can make since you are not supposed to let them touch and the total wick distance you have to work with is limited. If wanted to double the length of wire to increase my total ohms, could I take what is typically a dual-coil setup in parallel and turn it into a single coil setup? I'm not asking if it is SMART to do this, mind you. I'm just curious from a mechanical standpoint what would occur if I only used one of the positive terminals for a long coil before grounding it. Would it even work?

 

[ScottP]

Since no one else has actually shown you the difference maybe this will help. The + and - represent the positive and negative leads from the power source and the 000000 represents a coil.

Single Coil - Total resistance is that of the coil
+000000-

2 Coils in series - Total resistance is the SUM of both coils
+000000 000000-

2 Coils in parallel - Total resistance is calculated using the formula posted by Ictrc
+000000-
+000000-

Another example of two coils in parallel can you figure out why this is parallel?
+000000--000000+

If you have an android device or can download an android emulator, I would also definitely recommend getting Vaper's Toolbox from Google Play. It's free, and it will help with some of the math by calculating wire length and number of wraps to use.

 

[lctrc]

Wraps can touch each other - with the caveat that if any touch then more should be touching than not. Having only one wrap touch its neighbor while the rest are spread out will cause a hot spot. Check the micro-coil thread for lots of pictures.

Coils shouldn't touch each other - not entirely true either, but it can be tricky to get right. Usually a piece of silica is placed between them to insulate them from each other (in a Odysseus or Ithaka for example).

If you are asking whether you can wrap two lengths of wire into a single coil but in parallel (both are connected to both the positive terminal and the negative terminal) - yes. However, it's much more difficult for the single wick to keep up. You're probably going to be better off with each coil having its own wick.

 

[djeaton]

Thanks for the further help/confirmation, Scott. I'm a graphical leaner so all those OOOOO's really helped! I had kinda figured that was what was going on when I started thinking about why the parallel coils actually decreased resistance. And, to answer your question, the current going through the coil doesn't change between having +00000- and -00000+. Direction doesn't matter.

My earlier question about what would happen could be illustrated as +000000 000000-. If I put that in a dual-coil rig, and made sure that something that long didn't ground itself of course, would it work? I'm just curious because the battery would still be sending power to that other positive terminal that didn't have anything connected to it.

I appreciate your advice about the Android app. I'm already using eLiquid Recipe Manager Pro to calculate ejuice recipes. It has a simple calculator already in it. I was playing with the toolbox app that you mentioned last night on my tablet. There is a Sweet Spot app that does something similar that I really like because it gives a "thumbs up" when you are in the range between producing good vape and not burning stuff. Are there any other Android e-cig related apps that you would recommend? I'm a huge android fan.

 

[gankoji]

Thanks for the further help/confirmation, Scott. I'm a graphical leaner so all those OOOOO's really helped! I had kinda figured that was what was going on when I started thinking about why the parallel coils actually decreased resistance. And, to answer your question, the current going through the coil doesn't change between having +00000- and -00000+. Direction doesn't matter.

My earlier question about what would happen could be illustrated as +000000 000000-. If I put that in a dual-coil rig, and made sure that something that long didn't ground itself of course, would it work? I'm just curious because the battery would still be sending power to that other positive terminal that didn't have anything connected to it.

Yes. The battery would still be sending voltage to that unconnected pos terminal, but it would be drawing no power . Which means that you effectively turn your dual coil setup into a single coil atty. NBD.

 

[E_DeCastro]

Is it better to use 32g and less turns or 28g and more turns? I'm going to build my first dual coil . i'm shooting for .7 To .8 Ohms.

This will be micro coils not std coils.

 

[ScottP]

Thanks for the further help/confirmation, Scott. I'm a graphical leaner so all those OOOOO's really helped! I had kinda figured that was what was going on when I started thinking about why the parallel coils actually decreased resistance. And, to answer your question, the current going through the coil doesn't change between having +00000- and -00000+. Direction doesn't matter.

My earlier question about what would happen could be illustrated as +000000 000000-. If I put that in a dual-coil rig, and made sure that something that long didn't ground itself of course, would it work? I'm just curious because the battery would still be sending power to that other positive terminal that didn't have anything connected to it.

I appreciate your advice about the Android app. I'm already using eLiquid Recipe Manager Pro to calculate ejuice recipes. It has a simple calculator already in it. I was playing with the toolbox app that you mentioned last night on my tablet. There is a Sweet Spot app that does something similar that I really like because it gives a "thumbs up" when you are in the range between producing good vape and not burning stuff. Are there any other Android e-cig related apps that you would recommend? I'm a huge android fan.

Always glad to help. I had not heard about Sweet Spot, but I had heard about the Recipe Manager. I put mine together because I have not seen any other app that calculates the exact wire length and number of coils to use to achieve the desired resistance.

Now for your question, mathematically there is no difference between two coils in series: +000000 000000- and a single coil with the same number of total wraps: +000000000000- so there would really be no reason to ever mess with two coils in series, just wrap a single coil more times if you want the higher resistance. Would it work? Sure, but why make things more difficult for the same result?

 

[gankoji]

Is it better to use 32g and less turns or 28g and more turns? I'm going to build my first dual coil . i'm shooting for .7 To .8 Ohms.

This will be micro coils not std coils.

This is really a question of preference, but I'll wager an answer that hopefully is illuminating. When considering single coils, I generally prefer 28g and more wraps, as more wraps leads to more surface area, and generally more clouds of lower temperature vapor. That said, 28g is more wire material, meaning it will take longer to heat up to vaping temperature. In the case of .7-.8 duals, meaning two 1.4-1.6 single coils, that 'performance' issue of heating speed might be noticeable enough to be a drawback.

Wrapping 1.4-1.6 with 32g, on the scale of a micro, is going to take you probably 6-8 turns each coil. this should be plenty of surface area, and it should heat up much more quickly than the 28g alternative. In fact, wrapping 1.4-1.6 with 28g is liable to take you anywhere from 12-16 wraps each coil, which is a TON of wire.

IMO, go with 32g if you are gonna do dual coil micros at .7-.8. 30g, if you have it, might be a nice compromise in this case, though .

 

[E_DeCastro]

Thanks that was my concern the time to get to full temp. I'll try out the 32g and order some 30g to add to my supply. Thanks again.

 

[djeaton]

Would longer time to get to max temperature produce less vapor and more flavor until it reached that maximum temp?

Sent from my Nexus 7 using Tapatalk 4

 

[ScottP]

Would longer time to get to max temperature produce less vapor and more flavor until it reached that maximum temp?

Sent from my Nexus 7 using Tapatalk 4

Not sure but my guess would be less of both.

 

[LeoRex]

Would longer time to get to max temperature produce less vapor and more flavor until it reached that maximum temp?

Well, we're not really talking a long time. I have a 1.4 ohm 28g microcoil in an IGO-l.... on my Vamo running 10w, there is about a second of lag between when I fire and when I hear the coil start doing it's thing. Now, I believe there is a pause inherent to the device, so not all of that is the coil heating up.

In general... think of it this way.... two pans on a stove. Both burners put out the same amount of total heat (BTUs). One burner has a small little pot and only a couple of flames that are REALLY hot that will blast the center of the pan and get it hot really quick. The second burner has a large pot and a burner with a bunch of flames that aren't as hot and might take a little bit longer to heat up.

The little pot might heat up quicker, but I can cook a lot more chili in the larger pot (and I'd be less likely to burn it).