MVP, or vv,vw question: How do you vary volts and watts at the same time?

[Markgm]

Hi,
I'm still getting started on this vaping journey...

I know that ohm's law cannot be violated. OK, so the coil(s) have the R, and it is what it is. So how does a person vary both the voltage and the wattage at the same time? Or, does one set the wattage which varies the voltage, and vice versa?

Thanks. - Mark

 

[daveid777]

You can only set one variable, the other is mathematically related to the first and the resistance of the coil. In wattage mode the device calculates the voltage to supply in order to attain the desired watts. Conversly, in voltage mode the watts provided are a direct result of the voltage set and resistance of the coil (provided this falls within the limits of the devices max output).

 

[Markgm]

Thanks, Dave

 

[MrPlink]

Ohmslawcalculator.com

play with this and you will figure it out

 

[yzer]

With a atomizer of the same resistance when you change the voltage you also change the wattage. It works the other way around, too.

Now, if the resistance of that coil is changed and you are operating with variable voltage then you must adjust the voltage to get the same wattage you were getting before the coil resistance changed. If the resistance of the coil changed and you are using variable wattage then you won't need to change the voltage or the wattage you were using before the coil resistance changed. That's because you have already dialed in the wattage you want with VW operation and the device will adjust voltage automatically to provide the wattage you chose. VW rigs do this by reading output voltage to the atomizer and the resistance of the coil and calculating the desired wattage every time you hit the fire button.

This advantage of VW operation becomes useful if you change coil resistance occasionally (like changing out different atomizers) or if the coil you are using is aging and the resistance is rising. All coils age over time.

 

[Markgm]

Actually, I got a really interesting reply in a personal message, and it makes VW more attractive to me. It included mention of the coil resistance changing during its use. Under these circumstances, I would prefer the VW approach, because if I'm using VV, then the wattage could change while this is happening. So, if the coil resistance is going down, then the voltage will be brought down so the current doesn't jack up, and vice versa. Sounds pretty neat!

 

[yzer]

I have VV/VW operation on the Sigelei telescopic V3s and V5 I use. I always run on VW. It's just as easy to bump the power up or down a bit to suit your mood on VW as it is with VV. Besides, when you get VV/VW you have both available to you for the same price. Win/win.

 

[daviedog]

Watts = Volts • Amps..

 

[MrPlink]

Actually, I got a really interesting reply in a personal message, and it makes VW more attractive to me. It included mention of the coil resistance changing during its use. Under these circumstances, I would prefer the VW approach, because if I'm using VV, then the wattage could change while this is happening. So, if the coil resistance is going down, then the voltage will be brought down so the current doesn't jack up, and vice versa. Sounds pretty neat!

On a healthy coil and setup any change in impedance is rather small to the point where most VW mods wont even detect it NOR will they adjust for it.

 

[Markgm]

On a healthy coil and setup any change in impedance is rather small to the point where most VW mods wont even detect it NOR will they adjust for it.

I'm curious... From these links at Kanthal, which are FeCrAl types, if I'm reading it right, the resistance at 20°C is 20-25% higher than at temperatures from 100°C on up. ? What is clear is an 8% variation from 100°C to 1300°C, which doesn't seem as significant. Also, it's funny if the resistance rises a little with temp, which might provide a little current protection with rise in temperature.
Kanthal D
Alkrothal 14

 

[livinlarge]

Yep just set them to VW set the power to 8.0 to 9.0 and then Vape away. It will automatically adjust no matter what normal resistance atomizer you put on it.

 

[Markgm]

I want to add a correction.... There is no 20-25% variation 68°-200°F. There is no variation.
http://attachments.temcoindustrialpower.com/Data_sheet/kanthal_wire_ribbon_data_sheet.pdf

I think the most variation in resistance by temperature alone is going to be around 6%.