A simple yet informative guide to vaping. Ch1 Ohm's law

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MattyTny

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I've seen many threads where people are just getting into vaping and it seems now that it's growing popular at an extremely fast rate. vaping as opposed to smoking has always been a great alternative, but now that more satisfying equipment is readily available and popular, it would be great to have an ongoing guide for someone brand new. If you're just getting into vaping now you're going to be hit with a million different devices, a trillion different atomizers, and an infinite amount of ways to rebuild. All of this information can seem very intimidating and overwhelming, but having communities like ECF to get advice are very helpful.

I remember when I first started learning about how devices work and how sending current through a coil with different resistances at different voltages can yield different results, and then add in different ways to get to that same resistance, the possibilities go on and on. It's not easy to someone brand new, but with proper information it is easy. If we all had a single ongoing information source referring to device capabilities and ohms law available to members and the public a lot of questions would be answered everyday and thoroughly.

I say ongoing because vaporizer equipment is expanding so fast. The amount of gear and vape related things are moving so fast. I remember seeing a good amount of youtube videos with Phil Busardo visiting vaporizer headquarters and manufacturing stations across seas and here. We also see a lot of expanding on the site. I have only been a member since 2013, but the amount of stuff coming out today is much more than before. There is also a lot of traction on this forum, but that's what makes it good.

I've read a lot of good information on the forum before and some of the posts are really spot on, I feel it should be compiled to one source. I've seen Baditude and Susan~s both have readily available links for solid information multiple times. It would be great to access all the detailed information from all the great posts I see on threads all in one place, like a ongoing source with everything like: battery safety, hybrid top cap mechanical, cleaning a mechanical, coils, example chips in regulated devices and how they work, liquid and the ingredients, the effects vs cigarettes, the proactive community and the apposed laws. For someone brand new they see so many new things at once. It wouldn't have to be a day to day updated guide, just a compiled, easy to understand with examples, information source about vaping up to now. I've seen a lot of good posts and wish I could quickly pull up the same posts without searching. I think we deserve some sort of guide, vaping isn't an underground type of thing.

Ohm's law

With all that I want to present a small guide I prepared as a response to a few questions I see on the forum.

I feel the most common question is about Ohm's law and about understanding resistances for devices. Ohm's law is the most important piece of information pertaining to vaping since it's what we use all the time. There are four variables to know in the equations, but an easy way to help understand it is with the Steam engine online tool. In the online calculator you see resistance, voltage, current, power. The units are ohms, volts, amps, and watts respectively. An even easier way to understand it is thinking about it in an example.

The water pipe analogy
Think of the resistance like a pipe and you have water flowing out of the pipe and the water is amperage. There is also a valve on the pipe that you can turn to make the water(amperage) come out faster and that valve acts like a voltage control. The end result of the water flowing out the pipe is expressed by power, also known as wattage. You can increase the wattage by either decreasing the resistance or increasing the voltage.

Let's say you have a pipe set up with a certain width and water is flowing at a constant rate. Lets also say the pipe has a resistance of 1ohm and our valve to control the speed is set to 4volts. You can use Ohm's law and see that amount of water coming out is 4amps and the pipe's power is measured to 16watts. Now if you widen the same pipe more water(amps) can flow through it and you didn't touch the voltage valve. Adjust the pipe's resistance to 0.5ohms and as a result we see we just doubled the amount of water to 8amps and doubled the power to 32watts with a constant voltage.

Take the same pipe you started with, 1ohm, and instead of making it wider you just turn the valve and double the pressure or speed from 4volts to 8volts. You see 8amps of water flowing through the pipe and the power by the pipe went up to 64watts by adjusting the voltage only. Now put the two examples together and lower the resistance to .5ohms and increase the voltage to 8volts, you see even more power at 128watts and 16amps.

This can be applied to our coils and devices. Mechanical mods work like the first example in which we just made the pipe wider because that's the only thing you can adjust on a mechanical. You have a fixed battery voltage, and can only change the resistance. The second example is more like a variable voltage/wattage mod where you can keep the pipe the same resistance and just turn the voltage valve.

Understanding how these variables work will give you a better understanding of ohms law and how to build for specific devices.


Ohm's law and a regulated PV

Lets talk about personal vaporizers, or mods, a little more. Each device has: a resistance range it can read, an amperage limit it can push, a voltage range it can fire, and a wattage range it can fire. When you look at a device you want to know all of these things because it will determine what resistances will work the best on top. Some devices work well with a wide range, some work very well within a small area within that range. Lets look at an example.

vdU9MSy.png


Here is the DNA40(kanthal) and it's specs given by Steam Engine. I don't own one so I don't know the actual performance, but I want to use the numbers as an example. You can see the max voltage, max wattage, resistance range, and amp limit on the left. On the right there is three boxes, these three boxes is where all the information comes together.

Current limit 16 A vs 40 W
The box labeled “Current limit 16 A vs 40 W” measures the lowest possible resistance you can use to get all 40watts. When you decrease your resistance you are able to push more amps through your coil with available voltage and get more wattage. This is done by using ohms law calculator and plugging in the max amp limit along with the max wattage it can fire. You can see that the lowest possible resistance to get all 40watts while using all the amps is a bit lower than what the device can read. This means the DNA40 devices can fire it's lowest reading while still getting 40watts and it's starting to bump the amp limit. Not the best place to be, but it works as advertised.

Voltage limit 9 V vs 40 W
The next box “Voltage limit 9 V vs 40 W” measures the highest possible resistance you can use to get all 40watts. When you increase your resistance you are able to use more voltage to get to higher wattage without using as many amps. This is done by plugging in the max voltage for the device and its max wattage it can fire. You can see that highest possible resistance to get all 40watts while using all the voltage is a bit higher than what the device can read. Now you're starting to hit the voltage limit, but it's still firing 40watts.

Optimal resistance
The last box “Optimal resistance” sums it all up by giving you the resistance range along with it's median resistance. Then it gives you a “sweet spot”. This is the median from the original median and the high limit. Basically it's telling you that if you want all 40 watts and you want to keep your battery life in good shape to use a resistance around the “sweet spot”. You don't have to use the sweet spot, but keep in mind the less amps you pull, the more battery life you get while taking advantage of the device's voltage.


These numbers are unique for each device that uses a different chip. If you start looking at the higher powered devices like the Sigelei 150W you'll see that you can only get all 150 if you build within a certain range that it can fire. Too high of a resistance and you'll use all the voltage before you start taking advantage of it's available amperage by lowering the resistance. This doesn't mean the device doesn't live true it it's specs because the it can fire all 150, but there is limitations. In order to to fire all 150w within it's 0.1-3.0ohm range the power source would have to give 20+ volts which is impossible for safe portable devices we have now.

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Ohm's law and a mechanical PV

Check out how mechanical devices work, you only use the specs from the battery along with your resistance.

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Take the Sony VTC4 for example. I used a resistance of 0.5ohms and a voltage of 4.1volts charged on this page. The page tells you how many amps you are pushing along with the wattage output. The amp limit is advertised to be 30amps, but the box under shows the “headroom” or I like to call it the buffer. In this example you only use 8.2amps, this is safe for the battery. You really shouldn't use all the battery's amperage on an unregulated mechanical, it's not very safe. A lot of people agree on only using about 75% of the batteries amp limit, leaving a 25% headroom to be considered safe. This works out to be about 22amps used and around 0.18-0.19ohms. You should only do this if you are aware of the risks.

Finding your resistance

Now that you looked at the devices, look at choosing a coil for your device. This should be easy now because you just saw what will work well on your device. Take your resistance you feel you would be comfortable with and go to the coil calculator.

SIhMGlih.png


I used a 0.5ohm resistance, selected the kanthal of choice, selected dual coils, and picked the coil's internal diameter. I also calculated the wattage with 0.5ohms and 4.1volts I want to use to get around 33 watts to plug into the heat flux(under results) to get an estimate of the vape temperature.


You want to pay attention to number of wraps, the coil width, and surface area. This will give you an idea of how big your potential coil is. What you can do from here is change the diameter, you’ll notice the surface area stays the same, but the width will change because the number of wraps change. You can also change the resistance and use a fixed diameter to change width and surface area. Try selecting different gauges too.


This is my first shot a making a simple guide. Please let me know what you think and feel free to comment. I wanted this to be as simple as possible and the Steam Engine is extremely helpful in doing so. I really think it would be a great idea to have the most popular questions to vaping with answers available to anyone new. I'm not saying people are not getting the right information, because they are and the time people take to make posts explaining things are greatly appreciated. I still think having a detailed, but easy to follow guide with examples would answer most of the questions. I've seen other great guides on the forum, but the technology moves so fast and having one ongoing source explaining everything would be awesome. There is so many things to learn besides battery safety and Ohm's law and all the information is here, but only for those who take the time to ask for it.


Thanks to Lars Simonsen who made Steam engine calculator. Also thank you to ECF member Dice57 for helping me with figuring out how most of this works.


A few links I visit:

Steam Engine | free vaping calculators
E-Cigarette Forum - Baditude - Blogs
E-Cigarette Forum - State O' Flux - Blogs
http://www.e-cigarette-forum.com/forum/ecf-library/661383-basic-coil-building-safety-beginners.html
The ECF Library (this strongly represents the type of guide I'm talking about)
I would really like commentary on the idea of a single comprehensive vaping guide. I think the members here could easily do it, let me know what you think.
 
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MattyTny

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Thank you for the comments.

I realize the post is a little on the long side and may be a lot to read at once, but I feel thorough explanation works the best. I would like to know what you all think about he single ongoing information source I mentioned in the post. That's my main goal of this post, like a sample of all compiled vaping information that we should have readily available and is easy to read. Kind of like a vaporizing handbook. I feel like a lot of vaping information isn't so available, unless you ask for it.

I added some headings to paragraphs for easier navigation. I want to post a "Ch2" next, I'm thinking making the topic about how to choose a device.
 
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DingerCPA

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Matty, this is fabulous! In a future chapter, can you help explain REGULATED mods and input current v. output current? I've put my foot in my mouth (on MANY occasions, and not just on ECF) and I need some clarification. I'm REALLY comfortable with the UNregulated mod's current draw math, but on a regulated mod, Power In must equal Power Out, so what's really going on with the current draw on the battery? If one presumes 3.7V on the input circuit, then what current should one use to make sure to pick an appropriate battery?

{Inquiring minds.....}
 

MattyTny

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Matty, this is fabulous! In a future chapter, can you help explain REGULATED mods and input current v. output current? I've put my foot in my mouth (on MANY occasions, and not just on ECF) and I need some clarification. I'm REALLY comfortable with the UNregulated mod's current draw math, but on a regulated mod, Power In must equal Power Out, so what's really going on with the current draw on the battery? If one presumes 3.7V on the input circuit, then what current should one use to make sure to pick an appropriate battery?

{Inquiring minds.....}

I myself am still learning and I'm not 100% sure about figuring out a regulated device's input current. I may not be the best source for that info right now, but would love to hear if anyone else has something to share. I will say what I do know, and I think it's right.

Like you said power in and power out must be equal. In the case of a regulated device let's look at a number example to help.

Let's say we have a 1 ohm resistance and our device is set to 4 volts. Using ohm's law we see 4 amps and 16 watts. But our device's input nominal voltage is 3.7, assuming non stacked batteries, so using those 4 same amps we get 14.8 watts. Not the same wattage.

Now adjust the equation. Power in is power out. Take the 16 watts and our input voltage of 3.7. We now see more amps, about 4.3 amps for our input current.

I'm pretty sure your input current will always be more than your output current on a regulated. There is also efficiency loss on the output side. This means you'll have even more amps drawn on the input side since more power will be needed to keep up. This is only the case where your output voltage is greater than the nominal.

I'm not absolutely sure which current to use when choosing a battery. I would say both when looking at these high wattage regulated devices. Being that some of these devices are dual 18650 I also have to consider battery orientation. I would definitely want high amperage rated batteries for a parallel.

I would end up always getting the most reliable high amp rated battery for any situation. Considering we usually leave a percentage of the amp rating unused, say pull 20 amps with 30 continuous rating on mech I would do the same for a regulated. These regulated devices have protection and limits for unreasonable use too, so that helps in being safe with a battery not capable enough. I suppose you'll end up killing the battery faster. I really feel like it depends on the device too like if I had a mod using RMS or Mean to deliver there's different things going on. At the end of the day I feel like the current drawn is somewhere in the middle. All the devices aren't spot on accurate and we have efficiency loss.

I'm not 100% sure on it, but if someone could clarify that would be great.

I also added more links to the bottom of the first post. Those are really great sources to check out.
 
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OldBatty

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Thrasher

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Things were different just a few years ago batteries varied wildly, as did their mah ratings.

Many of the batteries today are very similar both in output and may. It used to be we thought do I choose the 1500 man 16 amp battery or should I use the 2900mah 10amp battery.

Now batteries vary by just a few 100 man for the same power outputs.if you want to really get technical you can dive into charts and say I'm going to draw 16 amps and this battery has the best curve for that range. Or luckily just pick one of the wildly popular and recommended batteries for a general range and be done with it. There are still some better then others but in most regulated mods this usually amount to a few minutes more or less.

Power curves and load graphs become more importaint when moving to a mechanical where the curve needs to be as flat as long as possible for best results and you can build accordingly.

And your pretty spot on with v in v out most chips today are around 80% efficient some higher so the conversion usually need just a touch more to make up for lost power. I cannot speak for current chips I have not studied them enough but there was a time when provari was king at 90%+ efficiency

Then there's the whole pwm vs DC flat but that's another post all its own lol
 
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MattyTny

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Things were different just a few years ago batteries varied wildly, as did their mah ratings.

Many of the batteries today are very similar both in output and may. It used to be we thought do I choose the 1500 man 16 amp battery or should I use the 2900mah 10amp battery.

Now batteries vary by just a few 100 man for the same power outputs.if you want to really get technical you can dive into charts and say I'm going to draw 16 amps and this battery has the best curve for that range. Or luckily just pick one of the wildly popular and recommended batteries for a general range and be done with it. There are still some better then others but in most regulated mods this usually amount to a few minutes more or less.

Power curves and load graphs become more importaint when moving to a mechanical where the curve needs to be as flat as long as possible for best results and you can build accordingly.

And your pretty spot on with v in v out most chips today are around 80% efficient some higher so the conversion usually need just a touch more to make up for lost power. I cannot speak for current chips I have not studied them enough but there was a time when provari was king at 90%+ efficiency

Then there's the whole pwm vs DC flat but that's another post all its own lol

That's good information, thanks.

There seems to be a lot of different batteries that can be used in different applications, probably good to have a high mah capacity batt for lower amp draw.

I found a post in ECF with this link explaining PWM and the DC flat:
http://www.escoglobal.com/resources/pdf/white-papers/True_G2.pdf

Seemed to answer the question and was easy to understand.
 
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