Why do NI200 builds increase in resistance during use?

[conanthewarrior]

Hi people, hope you are all OK.

I thought I would give TC another go, and got a 0.07 dual coil build. As I am using it it is raising to up to 0.18. I have let it cool and it is dropping.

As you can guess, this is mildly annoying as it will continue to rise if I chain vape, and then be out of TC range.

Does this happen to everyone, or is it just me building wrong? Im good with kanthal, but TC wires are quite new to me. I use tempered Ni200.

 

[conanthewarrior]

Ahh, this does NOT happen on the xcube as it reaches temp immediately I guess. It is only on the sigelei and IPV D2.

Ok, the Xcube actually does it much better than the IPVD2 and SIG 75. I am getting real vapour, and the resistance is not changing on the device!

I am actually enjoying this for the first time ever!

EDIT: I was enjoying it untill I realised I was using it on the worst clone that I own that leaks even if you drip fairly moderately. Thin metal, uneven sealing.

I WILL get this working like it was tonight, 16 wraps a side, In my el cabron clone by tobecco. That is my favourite RDA along with my velocity.

 

[bijou]

I thought that was normal? It's the reason why you have to lock in the resistance (on a DNA40, for example) when the coil and mod are both at room temperature.

At least, that's what I've been led to believe.

 

[danb]

The resistance increases with temperature, this is the basis of TC. You can't heat up the wire without increasing its resistance.

The mod does not directly measure the temperature of the coil, it measures the resistance, and from that it calculates the temperature. Not sure what you mean by going "out of TC range".

 

[Jake O]

I thought all tc devices locked in the resistance. Thats how it can accurately measure temp. I thought this feature was a must with nickel coils as the ohms fluctuate so much when heated. The sig 75 has a lock feature.

What device you got mate?


Sent from my iPhone using Planet of the Vapes

 

[nacmacfeegle]

Some mods indicate the current resistance of the coil, I believe other mods indicate the locked in resistance. Resistance of the coil must be locked in for the device to function correctly.

Most metals change resistance with temperature, to a varying degree. This is known as the TCR (temperature coefficient of resistance) of the material. This TCR is the rate of change of resistance over a temperature range, and is different for different materials.
Kanthal hardly changes resistance at all at normal vaping temps, and its why we have to use 'exotic' material such as Titanium or Ni for temp control. As The TCR is different for each metal, you have different presets for each material, and its why you will get a different vape temperature at the same setting on the mod for different coil materials.

As mentioned above, the mod senses this change of resistance and calculates the resistance (which equates to temperature) at which to control the coil power. Some mods will supply power, then cut it off which results in a pulsing or rattlesnaking modulating type power feed. My IPV D2 does this, if I set to a fairly low temp and a high power I can hear it pulsing.
Other mods may, I believe, lower the power input to the coil once it is at temperature to maintain a smooth-ish power delivery to the coil.

At least, that's how I understand it, I'm an engineer, but I do fluid flow, not electron flow.

 

[TuX93]

If your mod has the capability, make sure you are locking the resistance of your build while it is cold.

 

[scrumpox]

Some mods indicate the current resistance of the coil, I believe other mods indicate the locked in resistance. Resistance of the coil must be locked in for the device to function correctly.

Most metals change resistance with temperature, to a varying degree. This is known as the TCR (temperature coefficient of resistance) of the material. This TCR is the rate of change of resistance over a temperature range, and is different for different materials.
Kanthal hardly changes resistance at all at normal vaping temps, and its why we have to use 'exotic' material such as Titanium or Ni for temp control. As The TCR is different for each metal, you have different presets for each material, and its why you will get a different vape temperature at the same setting on the mod for different coil materials.

As mentioned above, the mod senses this change of resistance and calculates the resistance (which equates to temperature) at which to control the coil power. Some mods will supply power, then cut it off which results in a pulsing or rattlesnaking modulating type power feed. My IPV D2 does this, if I set to a fairly low temp and a high power I can hear it pulsing.
Other mods may, I believe, lower the power input to the coil once it is at temperature to maintain a smooth-ish power delivery to the coil.

At least, that's how I understand it, I'm an engineer, but I do fluid flow, not electron flow.

This is a great reply, thanks. I have a question though.

The predictability of Ni and Ti make them suitable for TC. ie the software calculates the likely temperature at the coil by sensing the resistance and looking up the TCR graph/values. They can hard code the TCR for each metal used.

If kanthal hardly changes resistance at normal vaping temperature, then there is no useful TCR graph to look up. What the Asolo mod does is "learn" and copy the vaper's own form of TC ... the duration of fire. Without TC we control the vape by how hard we draw (airflow) and for how long we take a draw. We sense the coil heating up, we sense the presence of liquid and we stop before the coil burns the wick. The Asolo is just copying this draw pattern to create its own graph. This has been called Taste Control rather than Temperature Control.

The bottom line here though is that TC, in whatever current (!) form, is a mathematical prediction game and cannot really work until the atty contains a temperature sensor that delivers information to the software in the mod. The atty has to become smart, fully integrated. After all, if the software can operate off reasonably accurate temperature data it would render the type of metal used in the coil irrelevant.

We have already seen some reviewers using temperature probes to check the accuracy of TC. I would assume that Evolv and Yihi do the same thing in R&D. What are the technical blockers to adding a temperature probe or sensor in the atty?

 

[nacmacfeegle]

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We have already seen some reviewers using temperature probes to check the accuracy of TC. I would assume that Evolv and Yihi do the same thing in R&D. What are the technical blockers to adding a temperature probe or sensor in the atty?

I personally don't really worry about the accuracy of the temp setting, but I do rely on it being consistent, which to me is the biggest bonus of TC. IE I don't care if it 398 degF or 410, or 450 degF, what I want it to do is keep the temperature fairly constant at whatever I set it at, and to come up to vape temp quickly. I've actually found that I use different temps for different liquids to accentuate certain flavours.

That aside, technical blockers to getting the device to control the actual coil temp...a very good question.
I think the main one would be the requirement to keep the temp detection signal separate from the power supply to the coil, right now we only have two connectors in the 510 (pos and neg), so the brains or the temp controller would have to be built into the atty or a completely new connector is developed with three poles (pos and two negs, one for power, one for temp detection).

In my industry we use sensors based on 4-20 mA signals to send varying parameters (pressure, temperature, flow etc) to a controller (normally a PC baesd arrangement) which then sends a signal back out which opens and close valves etc. Variation in the 4-20 amp signal is computed into actual variables by the PC based on known sensor parameters.

If the temp sensor could be built into an atty, and the control system could built into a small device that would sit between the mod and the atty (I'm visualising something like a heat sink in terms of size) we might have something that would fly, but the connection between the controller and the atty would have a 3 pole connection and would be non-standard as we currently know it. The control 'base' would simply be a std 510.

Given the sensitivity of the temp sensor I think we would be looking at a factory coil that houses the temp sensor within it, think a big and expensive Kanger OCC. Rebuildable coils would be out due to sensor/ coil geometry constraints, I think, but the coils themselves could be replaceable within the head.
We all know from our coil building that two similar coils can heat up differently and need a bit of love to remove hot spots, so coil manufacturing tolerance might have to be high.

Finally, the sensors we use take a while to 'boot up' and stabilise when power is applied, certainly longer than the average puff time. Processing time and response of the controller is relatively fast once its up and running and self calibrated etc, though.

I think temp control based on resistance reading of the coil itself is the way forward, and its where we are at currently. It works, and can be used on virtually any RTA/RDA without the need for new hardware, apart from the mod. WE have all used our TC mods in non-TC mode, so we have flexibility and variety in our devices.

On the upside, there are probably much smarter, cunning , and inventive guys working feverishly to prove me wrong, and I genuinely hope they do. We live in interesting times.

 

[scrumpox]

Great reply again, thanks!
I totally agree with you on a real world vaping experience rather than absolute accuracy. I believe the vaper would prefer to set a variable linear value between low and high temp rather than precisely 385F for example. We all know the temperature is approximate, precise settings are inappropriate.

So it's the 3 pole connection that's the major obstacle?

I don't see why the heatsink control/connector that you imagine could not be part of the mod, maybe with integral 510 connector. There's a decision around backwards compatibility of course ... the mod should ideally accept non-smart atties. But if this new kit was not backwards compatible, would that be the end of the world ... a deal breaker? We do like to swap our atties and mods around, though we're already used to using TC mods for TC built atties. There would be an argument based on principle against something too proprietory and maybe a battle would ensue over which "standard" would get accepted if multiple proprietory solutions emerged simultaneously. This is a watershed rather than a blocker. Potentially.

How about a 3 or 5 pole connection between atty and mod (with controller integrated) instead of the 510 screw? Or maybe the mod could have both connectors?

The end of rebuildables? Yeah, why the hell not, there's a very small percentage of us hobbyists who are into rebuilding ... the vast majority of vapers want plug and play simplicity, they're not into messing about with wire. As much as I like rebuilding I can see a future without it, buying OCC heads with temp sensor on board ... they'll become economically viable after an expensive start.

That said of course, you can put an OCC head into a tank and use a TC mod today. It's only the user interface (menu) that's needs sorting out because of the legacy issue, ie TC and non TC in the same mod. Imagine:-

You put the OCC coil and juice into the atty - all the user needs to do is set the variable airflow.
The mod detects the coil - all the user needs to do is set the temperature on a scale from low to high.

That's about as complicated as vaping needs to be, isn't it? Of course, it won't stop the minority of us dinosaurs messing about in our vape dens ...