Resistance wires and TC

How it works, and how we can trick the mods?

All materials have a temperature coefficient. In case of metal wires it describes the relative change of a resistance that is associated with a given change in temperature. It means how the coil resistance changes when it is heating up. Just as all materials have a certain specific resistance (at 20* C), they also change resistance according to temperature by certain amounts. For pure metals, this coefficient is a positive number, meaning that resistance increases with increasing temperature. For the carbon, silicon, and germanium, etc. this coefficient is a negative number, meaning that resistance decreases with increasing temperature. For some metal alloys, the temperature coefficient of resistance is very close to zero, meaning that the resistance hardly changes at all with variations in temperature. Generally the resistance values for conductors at any temperature other than the standard temperature (reference temperature, usually specified at 20 Celsius) may be determined through the formula:

The “alpha” (α) constant is known as the temperature coefficient of resistance, and symbolizes the resistance change factor per degree of temperature change.

Within our interest surely are the most popular "temperature" wires:
* Ni200 - temp. coeff. 0.006,
* Titan - temp. coeff. 0.0035,
* Nife30 - temp. coeff. 0.0032,

Let's go to the practice.

For better understanding of above formula I created a chart showing how the resistance changes with increasing temperature of the coil:

And now, how is it used in TC mods?

Let's say we have the 0.1 ohm (measured at 20*C) coil of Ni200 and set the temperature 200*C. How the mod will work?
a) it fires the voltage, and
b) measures the coil resistance (all the time),
c) when the resistance will reach 0.208 ohm mod "knows" that the temperature of coil is 200*C,
d) if resistance exceeds the 0.208ohm the temperature is higher, so the voltage must be reduced to reduce the power (and of course temeperature).

That's it.

How to use other wires with mods dedicated for Ni200?

Much of the TC mods can work only with Ni200 wires. What is happening if we try to use Ti or NiFe wire on it? Let's look at the figure:

As we can see Ti and NiFe resistance steep less than Ni200. So 0.208 ohm means 200*C in case of Ni200 but for Ti it corresponds to 330*C and 360*C for NiFe wire. So the wire other than Ni200 will burn out immediately or at best will burn our mouth.
But we can trick the mod :-) Let's see at Ti in the above figure again... We have to check what resistance corresponds to 200*C for Ti wire? It is about 0.160 ohm. Then we need to find what temperature corresponds to 0.160 ohm in case of Ni200 wire? It is about 120*C. So in order to reach 200*C using Ti wire on mod dedicated for Ni200 wires we have to set 120*C.
Of course such conversion may be a little uncomfortable, so I prepared the ready to use table with temperatures of our interest:

How to use it?

Let's say we have SnowWolf mod (Ni200 only) and want to use Ti wire at 220*C. So we have to find 220 in first row (the red one) and get down to the Titan row - YES: if you want to wape at 220*C with Titan wire on Ni200 dedicated mod you should set 165*C.

Regards :-)

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Eleaf iStick TC40W

Cheap solution for the start of TC adventure.

1. The FINISH.

Plastic fantastic :-) Typicall at this price (about 30$), however everything is well-fitted with no looses and mod lies well in the hand. And thanks to the plastic finish it is very light. The 510 head is quite decent:

with plus pin on the spring - so each tested atomizer worked with no any problems.
Next to the head we have attached necklace hole. On the bottom:

 

we have only microUSB socket.

The display:

is typicall DNA20-style, with the battery, resistance, voltage and power indication. In TC mode the themperture is shown instead of wattage.


2. FEATURES.

* Output Power: 40W
* Coil Resistance:
- 0.05 - 1.0 ohm in TC mode
- 0.15 - 3.5 ohm in VW mode
* Temperature control: 200 - 600F (100-315 *C)
* Built-in battery capacity: 2600 mAh
* pass-through feature,
* dimensions: 22x36x77 mm.

For the beginners is enough...
The menu is very simple, with additional middle button for mode selection.

NOTE - iStick40 has no wattage regulation in TC mode. Why? Because in this mode the temparature has the PRIORITY - independently of preset wattage mod primarily check the  temperature, and control the voltage so as to ensure that the temp. limit is not undershot. Between us most other TC mods work in a similar way - yes, we can set e.g. 140W in Snow Wolf but so what if mod after half second will have to drastically pull off the power to maintain the temperature?
So do not worry too much about it because generally it works, and the cloud is regulated by changing the temperature limit.


3. VOLTAGE SHAPE.

Measurements were done in my typical test set-up with 1 ohm microcoil on MutationX atomizer and Tektronix TPS2012 oscilloscope.

It is quite well. Although there are some oscillations it is unnoticeable during regular wape.


4. EFFICIENCY.

Having the setup with 1 ohm coil we can also check if we get what we set. Below I compared:
* theoretical voltage what should be on the coil for a given power (calculated according to the P=U^2/R formula),
* real voltage MEASURED on the atomizer pins by use of multimeter.

No comment... Everything is perfect, mod as usual adds a little more voltage than is needed ;-).


5. TEMPERATURE CONTROL

Is VERY WELL - described here. 


6. DRAWBACKS

1. The 510 head is designed so as to leave a gap below the atomizer. In my opinion it is less than half a millimeter and it is hard to see, however it is... One theory is that they did it to avoid scratching the beautifully chromed surface during mounting the atomizer.

2. "Lightness" of the mod. So, when using large and heavy atomizers center of gravity is very high and mod easily falls. 


7. SUMMARY
What can be in case of mod with reasonable power, sub-ohm handling and VERY GOOD temperature control for 30$?
For the start of adventure with TC buy without hesitation!

What I LIKED?
* VERY GOOD temperature control,
* ergonomics,
* 0.05 ohm.

What I DISLIKED?
* built-in battery,
* a bit too plastic.

With others:

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Gallery

Photography is my second hobby after e-cigs, so I'd like to combine pleasantness and usefulness ;-) and to show some more interesting pictures of my stuff. Let's go!

1. My first box mod (dna20).

2. The Orion v2 (do you remember?).

3. The set of 18350's.

4. Dario's wooden box on DNA12 + Kayfun 3.

5. Caravela + Freak.

6. Esterigon+Tilemahos by GG and PAPS v4 + Heron by VaporArt.

7. PAPS v2 + Origen v2 and Neuron+Quasar.

8. Dovpo Mini + Quasar.

to be continued ...

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