Has anyone built a PWM style VV mod?

[utak3r]

Thanks a ton CapeCAD for tips When I'm done with this chip I will (hope so) already know what I need. But once again, thanks for equations for inductor's current limit, I didn't know how to choose it. Right now I have 2A one (at 4.7uH).

...and yeah, the duty cycle. It's the biggest problem for me - as what I want is something around 50-70%? It will reduce the current and the efficiency dramatically :/

 

[StrikeEagleCC]

I say give it a try! I'd be interested to see the results.

 

[jrm850]

OP- Have you looked at this thread?
http://www.e-cigarette-forum.com/forum/battery-mods/194095-my-first-pulse-width-modulator-mod.html

 

[jhonutz]

Nothing can beat Step down switching regulators. If you made a PWM regulator simple with mosfet only won`t be different from a linear regulator, but switching it`s the best, Synchronous step down regulator more precisely

 

[jrm850]

Nothing can beat Step down switching regulators. If you made a PWM regulator simple with mosfet only won`t be different from a linear regulator, but switching it`s the best, Synchronous step down regulator more precisely

How do you relate pwm to linear?

 

[StrikeEagleCC]

How do you relate pwm to linear?

I don't think there's any need to. for our application, a steady voltage isn't necessary. Since the coils take time to both heat and cool, if you were to compare a graph of the heat of the coil and a graph of the voltage of the pwm circuit, I think the heat level would be pretty smooth compared to the voltage at frequencies above maybe 100hz. I've spent the last two days going over this post that jrm850 linked to, and I think those guys came up with a winning design.

 

[jrm850]

I don't think there's any need to.

I was just trying to open dialog about the differences for those of us that might not be fully versed in the differences between synchronous buck converters, Linear converters, and pulse width modulation. Dual switch converters like he was talking about are without doubt great, but to say that PWM won't be any different than linear might give people the wrong impression. PWM can be much more efficient than a linear regulator assuming quality components with low on state resistance, an efficient frequency, and fast transitions. This would be especially true when supply voltage is much greater than output voltage.
I would argue that with the nature of the load (Thermal Δ) in this application, and the flexibility of uC driven pwm, that vaping nirvana could be more easily approached by the use of a modulated mosfet.
I'm not an authority on the subject, nor was my intention to disqualify the statement in question, but I do enjoy learning and always welcome the conversation.


Cheers.

 

[bstedh]

I will add that so far in my experience pushing 8+ volts pulsed via pwm to achieve around 4 ~ 4.5 Vrms actually vapes better than anything else I have used to date.

The only drawback with a simple 555 pwm circuit is that its not regulated so you have to continually adjust it as your batteries drain down.

One of these days I plan on doing a 3 battery setup regulated to 8.5V and then pwm'ed to achieve a constant out put. This may seem a bit overboard but my personal opinion is that it just vapes different according to my so scientific experience meter.

Unfortunately all of my awesome pwm boards that I made have been destroyed by my Genesis atty's. I didn't use robust enough components to survive the rigors of occasional mesh shorts. I will have to make a new digikey order and rebuild a couple.

For right now I have an ugly ratshack one with a 30A mosfet that I am going to scab into a box for now until my provari arives.



Sent from my NookColor using Tapatalk

 

[StrikeEagleCC]

bstedh, take a look at this. I was looking into doing a PWM similar to yours, but wouldn't have been able to cram all the stuff I wanted into a reasonably sized box (I wanted a voltage cutout with 200mV hysteris too). Some day when I build a UV exposure bed, I'll try again.

 

[iuseaspork]

I did and it wasn't too bad. You would have to use a low ESR cap to filter it if you wanted because the regular electrolytic that I used warmed up pretty hot. It worked well unfiltered, though. I'm moving to atomizer mods, though so I can use a single battery.

http://www.e-cigarette-forum.com/forum/battery-mods/194095-my-first-pulse-width-modulator-mod-35.html#post5516412