Pulse Width Modulation or PWM a simple explanation, I hope ;

[robby]

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]

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]

bleedin thing wouldn`t rotate

[Brambles]

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]

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]

mmm, I thought RMS was irrelevant to square waves. Enlighten me.

[VapingBad]

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]

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]

I stand corrected. Brambles you are bang on in your mathematics. DiscoDes the voice of reason as always

[robby]

May 31, 2014 13:53:10 GMT Brambles said:

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