Why do VW devices even exist?

[SaintDynamicz]

Why do variable wattage devices even exist? This doesn't make sense to me because if I had 0.5 ohms and 30 watts I'd have 7.7 amps and 3.8 volts...
Although if I had 0.5 ohms with 3.8 volts I'd have 30 watts...

When you increase the watts, in reality all you're doing is increasing the volts... so my question is, why not just have 6 volt devices with an amp limit of 15.... then ur getting 72 watts... at only pulling 12 amps.

Are watts only to get more of an exact voltage? or am I just missing something here.

 

[rurwin]

It is power that heats the coil. So the amount of heating that gets done is linearly related to power, but it is related to the square of the voltage. Then the power can be kept constant while the resistance and voltage vary. All of which means that once you find out what power you like to vape a particular type of atty and liquid at, it is easier to find that spot if you are using VW than if you are using VV. In practise it does tend to vary a little as coils with a different resistance have a different surface area and different wicks have different efficiencies, but it varies less if you are using VW than if you are using VV.

In some cases, for example going from a 1.8 ohm a Kanger coil to a 2.2 ohm one, you may be able to use the same power, but you couldn't use the same voltage.

 

[scutterflux]

I kind of wondered the same thing, but in a different way. I think the VW devices provide a constant current and vary voltage (please correct me if I'm wrong), and the thing that gets me is; with the increase in resistance due to the heating of the coil at a constant current the VW would then increase the voltage as the device heats up to maintain a steady wattage. That is that there is an increase in voltage with heat to maintain wattage.

I would think a VV device would be better, the reason why is if it maintains a constant voltage at a lower cold coil resistance it will push more current through initially to heat up faster and the resistor will then start to restrict the current as the resistance increases due to heat. This seems like a better approach to me.

Am I anywhere in the ballpark of correctness?

 

[DC2]

Variable Wattage (VW) first came out so that people could vape at a consistent power level no matter what "topper" they put on.

As for me, I like to vary the power all the time, based on which e-liquid I'm using.
So for me, I would need to dial up or down the wattage just as often as I currently have to dial up or down the voltage.

 

[tchavei]

With vv you need to make some simple math. With VW you don't need to. With VW, each time there is a change in resistance, the mod should adjust voltage. I know for fact that the sigelei zMax will keep measuring the coil even while firing and adjust the voltage x times per second to keep the selected wattage. Not so sure if my evic s does the same as it reads the resistance on boot up but I do know it will stop firing if you start to unscrew the atty during a draw so there is some kind of feedback during firing.


Regards
Tony

Sent from my GT-I9195 through Tapatalk

 

[scutterflux]

Thanks rurwin, you must have posted while I was typing, looks like I'm in the ballpark.

 

[tchavei]

Thanks rurwin, you must have posted while I was typing, looks like I'm in the ballpark.

Not sure it's better. Based on your logic a mechanical would be even better because it would give what it had based on the coil that was mounted... Which is what it does.

We are talking about steadiness and vw is as steady as the electronic permits. Vv is Something in between. Not 100% power steady as the resistance might variate during heat up but also not "all power I can deliver" like a mech... So bottom line... They are different.


Regards
Tony

Sent from my GT-I9195 through Tapatalk

 

[Cullin Kin]

Not sure it's better. Based on your logic a mechanical would be even better because it would give what it had based on the coil that was mounted... Which is what it does.

We are talking about steadiness and vw is as steady as the electronic permits. Vv is Something in between. Not 100% power steady as the resistance might variate during heat up but also not "all power I can deliver" like a mech... So bottom line... They are different.


Regards
Tony

Sent from my GT-I9195 through Tapatalk

This. It's all about what you like as each delivers a different vaping experience.

 

[Derack]

evolv has a patent on variable wattage now(lol). Bring on the death of VW devices(jk hopefully).
This is the best video i found explaining the difference of vv/vw

 

[scutterflux]

I understand completely, the battery in a mech will sag voltage where as a VV device will not, I did not mention direct battery power but a VV device and described its function. Please read my post again.

I stand by my VV theory vs VW as it can be proven mathematically assuming a VW device is constant current as rurwin also stated.

I also understand the benefit of a VW device, but in typical arguments for VW the surface area of different coils does not seem to be accounted for so when switching coils you'd still have to adjust, but it's a difficult parameter to measure, in either case some fine tuning is in order.

To summarize a VV should fire up fractions of a second sooner than a VW device, probably not even noticeable.

 

[r77r7r]

It was psychological for me

I miss my "66

 

[The Cloud Minder]

Why does VW exist?

I blame the Nazis, they funded the dang company.

 

[tchavei]

If this is becoming a pissing contest about which one is better and why, I am out.


Regards
Tony

Sent from my GT-I9195 through Tapatalk

 

[Dampmaskin]

To summarize a VV should fire up fractions of a second sooner than a VW device, probably not even noticeable.

I suspect that some VW regulators measure the resistance as you push the button, adjust the voltage accordingly, and fire, keeping the voltage constant until you release the button.

Other regulators measure the current and voltage (in effect the power) continuously, so they would even be able to compensate for a coil that changed resistance mid draw.

The first ("cheaper") type of regulator could introduce a noticable lag. I should probably mention that I am speculating at this point.

 

[tchavei]

The sigelei chip measures continously that I know, the evic s, not so sure... It takes like two seconds to detect the resistance and display the calculated voltage needed to the chosen wattage... Kinda doubt there are two circuits / methods whatever to measure resistance... Like one slow at boot up and a fast one during firing so probably it doesn't care about the resistance once you hit the fire button but I could be wrong


Regards
Tony

Sent from my GT-I9195 through Tapatalk

 

[scutterflux]

Dampmaskin, that's another interesting point you raise there, if the VW has to measure first it may create a lag.

Myself I could have been more clear, I was trying to make the point of VV firing up to full power faster not the initial start time.

I'm not trying to start a pissing contest or say which one is "better" (perhaps I should not have used that word). Everyone will have a preference, and myself I'm just making statements from an academic perspective only. However I do have a couple VV devices if that matters.

I was making the assumption that the VW device measures and adjusts in an instantaneous analogue fashion in a steady current state, reacting to the change in resistance with heat.

I'm thinking of VW as a reactive power supply with a choke or inductor styled filter and the VV power supply provided by capacitance filtering. Now I understand these devices might not work exactly as such, like perhaps VW uses a gyrator instead, but the principals should be relatively the same.

 

[crxess]

I do not play the which is better game either.

VW is one of my tools.
It is extremely handy for someone that has 1/2 dozen or more clearos, all with different resistances and likes to swap flavors quick.

Yes, I may still adjust........a whopping .2-.4w depending on the device/flavor. Still the VW setting plants things smack in the ball park, not the adjoining parking lot.

My Mech Mods are all Tank dedicated.

 

[tchavei]

Well, like I said, a good vw chip shouldn't come behind vv. My sigelei is almost instant, just as my I taste vv3 but my evic has a built-in ramp up so it's slower to fire. If I however change the curves to have a hot start (starting at say 16w for 0.5 seconds and then hold 10w for 5 seconds, the lag seems to disappear.


Regards
Tony

Sent from my GT-I9195 through Tapatalk

 

[Ed_C]

I understand completely, the battery in a mech will sag voltage where as a VV device will not, I did not mention direct battery power but a VV device and described its function. Please read my post again.

I stand by my VV theory vs VW as it can be proven mathematically assuming a VW device is constant current as rurwin also stated.

I also understand the benefit of a VW device, but in typical arguments for VW the surface area of different coils does not seem to be accounted for so when switching coils you'd still have to adjust, but it's a difficult parameter to measure, in either case some fine tuning is in order.

To summarize a VV should fire up fractions of a second sooner than a VW device, probably not even noticeable.

Current is the amps. It's not held constant. It moves in relationship to voltage and resistance. I=V/R. So, the wattage is held constant in a VW PV, by altering the voltage, but the current (amps) won't be constant. Example:

8W=(4^2V)/2 ohm 2A=4V/2 ohm or ~8W=(~2.83^2V)/1 ohm ~2.83A=~2.83V/1 ohm

 

[jjk1]

It’s the same thing and I don’t get it. I bet most people like to vape at 3.5 to 5.5 volts.
If you are into low resistance and high watts you are still needing to vape without frying your lungs. You can do that just fine with VV.
You can put a .3 ohm coil on your PV and set to 4 volts and have a nice vape at 53 watts.
You can then put a 1.8ohm coil on and set it 4 volts and have a nice vape.
So you think you like 53 watts and pop on a 1.8ohm coil and you fry your juice at 9 volts.

It really doesn’t matter because the next big thing that will make all these VV VW mods turn into junk will be mods that let you set your wire temp (again – same thing)
I have both and change to taste with both - all day long..
JJK