robby
Super Member
International Bargain Master
WISMEC? Check out the Member`s Only thread.
Joined:September 2012
Posts: 13,815
Location:
Likes: 8,652
Recent Posts
Last Online Jun 24, 2013 9:58:00 GMT
|
Post by robby on May 31, 2014 12:47:38 GMT
PWM or Pulse Width Modulation is used in the vast majority of VV/VW mods to control the voltage/wattage available to the atty. In the diagram above, there are two elements.
One element (DCBoost) changes the battery voltage to a steady 6V until the battery reaches a voltage level that is safe to stop at. Usually about 3.2V. Much lower than that would damage the battery so that it would not take a charge. The 6V is then changed into a pulsed format by the PWM, so it is switched on and off thousands of times a second. The voltage will be either 0V or 6V. The timing of when it the electrically switched voltage is on or off is determined by what voltage you want for your atomizer. This is called the DUTY CYCLE.
In order to change the voltage to what you require the DUTY CYCLE is changed. If you want for example 4V, the DUTY CYCLE will be two thirds ON and one third OFF. It is a simple process. If you want 4.5V the DUTY CYCLE will be adjusted to 75% ON and 25% off.
In the 5 different waveforms on the right (from the top down), you would produce 0V (off all the time), 1.5V, 3V, 4.5V, and 6V(on all the time).
There, didn`t hurt too much, did it
Please let me know if I have got it wrong anywhere, I dont think I have.
The main reason for PWM over normal regulation is that PWM is a more efficient way of getting the required voltage and cheaper than other methods.
|
|
Ripshod
Super Member
Music Man
Hug A Veteran!!
Joined:May 2014
Posts: 4,863
Location:
Likes: 3,469
Recent Posts
Last Online Mar 19, 2022 8:18:25 GMT
|
Post by Ripshod on May 31, 2014 13:30:17 GMT
Great work again robby Only one little error that probably only you and me would see - the battery symbols' the wrong way round (larger plate positive). Don't think it'll matter to anyone else though. Good work!!
|
|
robby
Super Member
International Bargain Master
WISMEC? Check out the Member`s Only thread.
Joined:September 2012
Posts: 13,815
Location:
Likes: 8,652
Recent Posts
Last Online Jun 24, 2013 9:58:00 GMT
|
Post by robby on May 31, 2014 13:31:57 GMT
bleedin thing wouldn`t rotate
|
|
Brambles
Super Member
Joined:October 2012
Posts: 1,746
Location:
Likes: 1,071
Recent Posts
Last Online Dec 14, 2022 15:16:58 GMT
|
Post by Brambles on May 31, 2014 13:37:37 GMT
Notice the deliberate mistake with the Battery polarity not matching the +ve PWM . Think of the battery symbol making up the + and the -. The short bar makes the negative -. The long bar is cut in half and the two halves make a + sign.
Or the _ is the base of the battery (negative - ) and the long bar | is the carbon rod in an old carbon battery cell which is positive.
p.s. someone beat me to it.
|
|
Brambles
Super Member
Joined:October 2012
Posts: 1,746
Location:
Likes: 1,071
Recent Posts
Last Online Dec 14, 2022 15:16:58 GMT
|
Post by Brambles on May 31, 2014 13:53:10 GMT
Good write up though robby You have explained the mean voltage but the effective voltage is actually different, You need to calculate the RMS voltage value which is in effect squaring the 6 volts to make 36. Then say for 2/3 rds on/off time take the mean so it will be 2/3rds of 36 = 24. Then take the square root which is 4.9 volts which is the effective voltage and equivalent to a constant DC voltage of 4.9volts.
This is why when you set a vamo to mean voltage and select 4 volts it seems too powerful, that is because you have actually set it to 4.9 volts RMS equivalent for power purposes.
Am I over complicating this for people with a basic understanding to follow - I suspect I am.
|
|
Ripshod
Super Member
Music Man
Hug A Veteran!!
Joined:May 2014
Posts: 4,863
Location:
Likes: 3,469
Recent Posts
Last Online Mar 19, 2022 8:18:25 GMT
|
Post by Ripshod on May 31, 2014 13:55:12 GMT
mmm, I thought RMS was irrelevant to square waves. Enlighten me.
|
|
VapingBad
Mod Maker
Mr Fix-it
Joined:January 2014
Posts: 13,798
Location:
Likes: 14,172
Recent Posts
Last Online Aug 19, 2023 21:23:33 GMT
|
Post by VapingBad on May 31, 2014 14:00:37 GMT
RMS (Root mean square) is just a type of average, commonly used where the wave form is not alternating around 0 V as in this case the voltage is always positive. Just a more realistic way to compare apples and pares DC to PWM.
|
|
DiscoDes
Super Member
Perp's Personal Aide
Joined:April 2011
Posts: 11,588
Location:
Likes: 6,099
Recent Posts
Last Online Oct 24, 2022 6:13:15 GMT
|
Post by DiscoDes on May 31, 2014 14:02:07 GMT
I think for a "general" explanation it's fine for people to get a grasp as to what's going on and why you get the "Rattlesnake" sound from some vv/vw mods. Well done
|
|
Ripshod
Super Member
Music Man
Hug A Veteran!!
Joined:May 2014
Posts: 4,863
Location:
Likes: 3,469
Recent Posts
Last Online Mar 19, 2022 8:18:25 GMT
|
Post by Ripshod on May 31, 2014 14:12:22 GMT
I stand corrected. Brambles you are bang on in your mathematics. DiscoDes the voice of reason as always
|
|
robby
Super Member
International Bargain Master
WISMEC? Check out the Member`s Only thread.
Joined:September 2012
Posts: 13,815
Location:
Likes: 8,652
Recent Posts
Last Online Jun 24, 2013 9:58:00 GMT
|
Post by robby on May 31, 2014 14:33:51 GMT
Good write up though robby You have explained the mean voltage but the effective voltage is actually different, You need to calculate the RMS voltage value which is in effect squaring the 6 volts to make 36. Then say for 2/3 rds on/off time take the mean so it will be 2/3rds of 36 = 24. Then take the square root which is 4.9 volts which is the effective voltage and equivalent to a constant DC voltage of 4.9volts. This is why when you set a vamo to mean voltage and select 4 volts it seems too powerful, that is because you have actually set it to 4.9 volts RMS equivalent for power purposes. Am I over complicating this for people with a basic understanding to follow - I suspect I am. Didn`t want to confuse anyone at this stage I`m confused enough for all of us lolol
|
|