Advanced Atomizer Designs

[hlzr]

I'd post this in the modder's forum, but can't because of my low post count. (Can a moderator maybe move it there for me? I think this is a pretty relevant question...)

Has anybody designed a mod that tries to drive the temperature of the atomizer to an ideal level (with a little control system)? I'd be interested in working on a design in that direction if anybody is working on anything like that.

A friend from UCSD (his name on ECF is makasin...both of us are undergrads in the EE dep't) and I were chatting about possibly designing a mod that would drive the impedance of the atomizer to a particular value using a feedback amplifier of sorts; this might work as an initial design. Efficiency would be an issue, but there are crazy digital amplifiers (super hot field right now in the RF and audio world) that might alleviate some of the issues in later revisions.

Any thoughts on the subject?

 

[Java_Az]

check out the modders section of the forums all kinds of stuff in there about all aspects of PV's

 

[hlzr]

Java_Az: I have scoped it quite a bit. I lurked here a lot before I started posting (past week or two). I didn't see anything quite in that direction back when I was lurking...

 

[Sorrid]

http://www.e-cigarette-forum.com/fo...e-reviews/139697-darwin-really-different.html

Check this out. Pretty dang cool Imo.

 

[capecodjim]

I'd post this in the modder's forum, but can't because of my low post count. (Can a moderator maybe move it there for me? I think this is a pretty relevant question...)

Has anybody designed a mod that tries to drive the temperature of the atomizer to an ideal level (with a little control system)? I'd be interested in working on a design in that direction if anybody is working on anything like that.

A friend from UCSD (his name on ECF is makasin...both of us are undergrads in the EE dep't) and I were chatting about possibly designing a mod that would drive the impedance of the atomizer to a particular value using a feedback amplifier of sorts; this might work as an initial design. Efficiency would be an issue, but there are crazy digital amplifiers (super hot field right now in the RF and audio world) that might alleviate some of the issues in later revisions.

Any thoughts on the subject?

The Darwin above is the the closest thing so far and is kind of what you're talking about. My understanding is that it keep a constant wattage regardless of changes in resistance or voltage or temperature.

Are you talking about the actual temp of the atty coil? I was wondering about that but figured the coil would be too delicate to measure constantly and an infrared temp sensor wouldn't fit....

Hey... Do you two EE's or anyone in the dept have any leads on a nano or micro pump?

Oh ya, and welcome to the forum!! Happy vaping!!

 

[hlzr]

That dawrin is a clever idea; however I don't know if that level of sophistication (namely the screen) is required to do what it does. I'm going to come up with a similar design using a power op-amp that will accomplish variable power output by using feedback for the voltage level across the atty and the current flowing into the atty driving the output.

 

[tybin]

you might be able to post now... i forget if it happens at 15 posts...or????

 

[Xanax]

Try posting in the modders forum now. You have enough posts. Hopefully a mod will see this thread and move it so you don't have to type up the same thing again.

 

[Warped3k]

I moved this to the "Atomizer mods" sub-forum for you. Also, it takes about an hour after you reach the 5 post requirement for the forum to update, so that is most likely why you weren't allowed to post there yet.

 

[hlzr]

Okay, so it should be pretty easy to design an analog constant power source (using a power op-amp and some feedback for prototyping and maybe later some cleverness combined with discrete transistors in a current mirror configuration, or perhaps some kind of pulse width modulation based solution).

Still, I think having a temperature sense line for the feedback would be better; atomizers would rarely (if ever) blow out, and almost as soon as you hit the button, the atomizer would get to temperature and stay there.

Any thoughts from somebody that has thought more about this?

 

[WillyB]

Okay, so it should be pretty easy to design an analog constant power source (using a power op-amp and some feedback for prototyping and maybe later some cleverness combined with discrete transistors in a current mirror configuration, or perhaps some kind of pulse width modulation based solution).

Still, I think having a temperature sense line for the feedback would be better; atomizers would rarely (if ever) blow out, and almost as soon as you hit the button, the atomizer would get to temperature and stay there.

That makes the most sense, the Darwin's basic premise that only watts determine actual heat is flawed and wrong. If consistent heat is the answer you should monitor for temperature, and adjust accordingly, basically ignoring any dissipated watts readings, which may work fine for pristine electric heaters, but certainly not with the atties we use and how we use them. Something as simple as the stiffening of the draw will change the actual heat while at the same resistance/watts. There are a number of things that can alter the heat without any change in resistance, and adjusting the watts based on resistance changes due to gunk build up on the coil will not maintain a consistent vape.

Your approach would not be influenced by any of the various atty problems, instead it cuts right to the core... actual heat regulation.

Get on it.

 

[tdh]

Any idea how to actually go about the temperature measurement?

A thermistor inside of the coil or just above would give the most useful readings. You could just put a pot in series with it to make it variable but on the other hand, you would need an extra pair of contacts on the atty, so the threaded and rca jacks that we mostly use wouldn't work. If the temp sensor and atty coil shared a ground, you could use a stereo headphone jack.

 

[tdh]

I have been parts searching all day and the best I have found so far is

prt08100w (free samples from ti)
kty83 series ($1.16 from digikey either option should work)
any 100ohm pot
a fixed resistor ~250-280 ohm

Using the attached schematic will give significant power variation with temperature, but not a constant temperature. This spreadsheet shows the actual output voltage for different temperatures and pot settings. The bottom and right numbers indicate how much the power (i.e. watts) will vary in different circumstances. Actual wattage will, of course, depend on the atty selected.

I will keep looking for better options, including amplifiers , ntc thermistors, boost regulators, etc. It would be nice to have a truly constant temperature mod, but I think that the responsiveness of the heat sensor will make that basically impossible.

 

[kjj]

Reading a thermistor with a PIC (or whatever) is pretty damn easy. Getting the thermistor into the coil is going to be the tricky part...

I still have a batch of DO-35 sensors (103JG1J , digikey #615-1016-ND) sitting around from a past project. I'll give it a shot when my wick material shows up.

On the other hand, they are only rated to 300 C, and I've seen my coils glowing before, so I'm not sure they can take it.

 

[rannox]

This sounds rather interesting.

A shot in the dark: If you had information on how resistance changes inside nichrome wire according to heat, you might be able to read those changes to get an educated guess on the temperature. Of course it would be different for different gages of wire, and might be so minuscule that it wouldn't be feasible, but worth a shout out.

 

[kjj]

It isn't the wire gauge, it is the wire composition.

You can take a cold reading, and then a hot reading and look at the difference to find the change in temperature. It doesn't matter if the 2 ohms (at room temp) worth of Nichrome A is a 32 gauge wire 2.36" long, or a 40 gauge wire 0.354" long. They will both show up as 2.126 ohms when heated to 538 C. On the other hand, if they were made of Nichrome C, they would be 2.172 ohms now.

Nichrome - Wikipedia, the free encyclopedia

Take a look at that last table. The change in resistance with increasing temperature is different by a factor of nearly 2 between two alloys of Nichrome, and there are many other alloys for heating element wire beyond those two.

Stranded Resistance Wire

 

[AttyPops]

Yeah, kjj, but what rannox (and maybe hlzr) is saying (I think) is to use the resistance change to measure/manage temperature... it would have to be calibrated for different atties/esp gauges. But, the resistance change could be a "plug in" and the resistance used to calculate temp. This is all regardless of composition. Although, as you point out, composition effects calibration. This is similar to a "thermistor". It's easy for a processor to monitor an atties' resistance. Getting an accurate temp reading with an additional device is another matter entirely.

You post #16 is very informative tho, but you missed his point (I think). No matter the composition, it would still have to be calibrated somehow. Once calibrated, the resistance change is a thermistor. No need to put another thermistor inside the atty. And you're correct... not rated to sit next to a hot coil like that. I'm sure they make em, but not sure it is necessary. Hell, you could probably use a probe from some industrial instant-read thermometer...... it's all lipstick on a pig IMHO. But I digress.....

In other words, the atty is a thermistor of sorts. Calibration is an issue, and varies with wire composition as well as construction.

What I don't know is whether or not this is a good indicator of vaporization. One could theorize that a gunked atty needs a higher temp to work as well as an un-gunked atty. So do we accomplish anything with a constant temp? Better regulation with battery voltage drop off? The voltage regulators do a pretty good job, at least initially. Over time, with use, maybe resistance/temp regulation is better. IDK. Interesting discussion. In the end tho... gunk is gunk... and a thermal insulator. So consistent performance of the heating coil is only one factor, albeit an important one.

Good luck!