David_
Advanced Member level 2
Hello.
You who are regulars here on edaboard are probably aware of my other thread(s) dealing with a MCU based DC-DC converter with the intended application of driving an personal vaporizer.
I have just heard some for me completely unheard of things(not that it is surprising I haven't heard of it before), I stumbled upon a thread on another forum posted few years ago by a guy who had a long career in... I can't recall exactly but it had to do with heating and welding.
And he wrote that it is a fact that if a heating element is driven by DC current then 2/3 of the heating will take place in the heating coils most positive portion(I am trying to get a hold of him to ask more, but he was mentioning this in a personal vaporizer forum and he was writing about such coils as I will use with my device).
So there will not be equal heating through the hole coil, which doesn't sound as something one would prefer in a device for those purposes, and he went on to say that by using AC that effect was cancelled due to obvious reasons(current direction changing direction so the heating becomes equal over the hole coil).
Does anyone here know about this effect?
Is this true... Someone wrote something more in that thread that I interpreted as pointing to this affect in some way has to do with reactance but I can't understand how this would work.
Before I come to the point of it all I have also realised another thing, the reason why I wouldn't use unfiltered PWM was because it have been shown in early devices for personal vaporizer purposes that such an waveform isn't pleasant to use, however those devices used really low frequencies. Something like 800Hz, and so if I would use a unfiltered PWM signal but at 100kHz then I would think it would be another situation entirely(I didn't realize all this my own though).
So that leads me to wonder, how would one use a µC generated PWM signal to generate a PWM waveform spanning equal values above and below 0V?
My other design would use two Li-Ion batteries to create 8,4V-6,4V so I would think that using those two series 3,7V Li-Ion batteries to generate ±3,7V to generate a dual polarity supply could work.
But it depends on what sort of circuit one would use to level-shift the PWM into a dual polarity signal.
I recently started to think about this but so far I haven't found out anything, but if I am not mistaken isn't this exactly what a Full-Bridge switching circuit is used for?
Regards
You who are regulars here on edaboard are probably aware of my other thread(s) dealing with a MCU based DC-DC converter with the intended application of driving an personal vaporizer.
I have just heard some for me completely unheard of things(not that it is surprising I haven't heard of it before), I stumbled upon a thread on another forum posted few years ago by a guy who had a long career in... I can't recall exactly but it had to do with heating and welding.
And he wrote that it is a fact that if a heating element is driven by DC current then 2/3 of the heating will take place in the heating coils most positive portion(I am trying to get a hold of him to ask more, but he was mentioning this in a personal vaporizer forum and he was writing about such coils as I will use with my device).
So there will not be equal heating through the hole coil, which doesn't sound as something one would prefer in a device for those purposes, and he went on to say that by using AC that effect was cancelled due to obvious reasons(current direction changing direction so the heating becomes equal over the hole coil).
Does anyone here know about this effect?
Is this true... Someone wrote something more in that thread that I interpreted as pointing to this affect in some way has to do with reactance but I can't understand how this would work.
Before I come to the point of it all I have also realised another thing, the reason why I wouldn't use unfiltered PWM was because it have been shown in early devices for personal vaporizer purposes that such an waveform isn't pleasant to use, however those devices used really low frequencies. Something like 800Hz, and so if I would use a unfiltered PWM signal but at 100kHz then I would think it would be another situation entirely(I didn't realize all this my own though).
So that leads me to wonder, how would one use a µC generated PWM signal to generate a PWM waveform spanning equal values above and below 0V?
My other design would use two Li-Ion batteries to create 8,4V-6,4V so I would think that using those two series 3,7V Li-Ion batteries to generate ±3,7V to generate a dual polarity supply could work.
But it depends on what sort of circuit one would use to level-shift the PWM into a dual polarity signal.
I recently started to think about this but so far I haven't found out anything, but if I am not mistaken isn't this exactly what a Full-Bridge switching circuit is used for?
Regards
