Registered: 1438699145 Posts: 79
Reply with quote
I've recently learned about a new Chinese mod that claims to do TC with Kanthal. Of course it's probably not real TC, and it's not achieved by reading the changes in resistance. There are several "theories" floating about the net, about how this is achieved.
This got me pondering, and now to my questions: One theory is that it uses PWM, and that it measures changes in reactance as the Kanthal heats up. Another theory is that it does not do TC at all with Kanthal, but some sort of dry coil detection: When the juice dries out, the resistance of the coil/wick system increases, because the juice itself has some conductivity. As the title suggests, I only ask this out of curiosity, and I don't expect much precision in the answers. It's more about what the DNA 200 in principle can do, or not. I've come to understand that it's designed to be flexible, and firmware upgradability opens up a whole new world of forward compatibility, but just how far can the hardware be stretched? Does the DNA 200 have enough memory and CPU power to implement completely and radically new features and modes in future firmware versions? (I'm guessing yes plenty.) Is measuring juice saturation even doable in any reliable way? If a good reason to use PWM appears somewhere along the road, will the DNA 200 hardware support it at all, and if so, how well, and what kind of switching frequencies are we talking? __________________ Steam Engine Wire Wizard with TCR
Registered: 1435395843 Posts: 500
Reply with quote
We've seen at least one chinese chip claiming temperature control by the "vape through a tank, then it will stop when you get to that amount of energy next time" which was pretty cheesy.
I know one Chinese manufacturer are experimenting with a thermocouple welded to or pressed into the coil. That's very tricky from a time constant standpoint (I have thermocouples that will do it well, but they're thinner than a human hair so they aren't really suited for a commercial product) but is a perfectly valid general approach. The devil is very much in the details. I know of one who are just running an output power profile and calling it temperature control. There are other ways of measuring temperature too. I imagine we'll see a number of them tried at some point. We went with our method because it has the fastest response time and is compatible with existing tanks and atomizers. In terms of flexibility, we have a fair amount of code space and ram left. So we can (and have been) adding things as they come up. Sure, we could sense dry-out, but if the temperature control is working well would you rather have a device that lets you milk your last few drops of juice at a lower wattage as you drive on a long car trip, or one that says "nope, you're done, refill me." I can't imagine why PWM would be useful. We've been true DC-DC all the way back to the Darwin. The hardware could be made to do it, but it would be a massive step backwards for no benefit I can see.
Registered: 1435413405 Posts: 247
Reply with quote
I'll never live long enough to follow all the way through on every idea I have so here's one I hope to see Implemented one day:
The junction of Kanthal and nichrome is a thermocouple. No need for separate thermocouple of low thermal mass. At vape temps it will produce several milliviolts with a room temp cold junction. I'd envision a coil with a welded junction of the two wires Ian roughly midpoint. Their gauges would have to be selected for equal resistance per unit of length. Might just work