Building a Digital Vaporizer (Brain Dump)

[vap999]

Skippy...

I am in the process of ordering parts for a few prototype vaporizers I intend to build (and report about to FC) in the next few weeks.

My starting point or design goals are much different that yours. I intend to make a heavy metal heat sink-based, passive (inhalation-powered), convection vaporizer -- in the classic Eterra/Purple Days class (heating element/resistor heats a metal heat sink through which air passes). I will be using a custom 2-inch low-voltage (12-14 volts) square cartridge heater tightly-fitting (for optimal heat transfer) into a good-sized pure copper heat sink (milled to exact size for the heater by a local machine shop). The cartridge heater will have about 3 sq. inches of contact with the heat sink/exchanger, which will be over >200 grams and, as planned, have >10 sq. inches of heated metal in contact with the air flow. This will be used with either a standard variable/adjustable 12-14 volt power supply; or a wall 12-14 volt adapter will be used along with a solid-state DC dimmer (or motor speed control) switch. The heater will be ;in

Using a heavy metal heat sink allows (or should allow) simple use of input voltage to control the temperature. With your design and presumptions, you appear to be forcing yourself into use of a very rapid-response, very low mass heater (heat sink) design; and use of a PID controller. As an engineer, I suggest you (re)consider use of a metal heat sink, which need not be all that large or heavy. For example, if you used an aluminum heat sink/exchanger, as the Volcano does,

 

[Purple-Days]

This element was in the upper range of models in the early 90s/ Legacy and WRX I think. It was the top end models. Might be an interesting junk yard trip.

Anyway small, low mass, probably fast acting, 12V.

And let me suggest a couple of really big throw pillows and some cool music for next to that test bench. Less math, more in sitro. I know, gotta have the math, believe me.

 

[tuttle]

Hi Skippy,

I really doubt I will need a flow meter. I think what I will need is a heater that has a very quick temperature response (due to a very small heat sink capacity) to applied voltage changes so that the exit temp can be corrected extremely quickly. I could be wrong, but that is what I am gonna find out. A good example of something like this, which I will not be able to use (as far as I can tell) is this:

http://www.sdiohio.com/Documents/Series Op Man.pdf

You may be right and it is not needed, but the reason I suggested it is that every on demand heating device that has a variable powered heater I know of uses flow metering as an input metric for heater power. If you have your thermocouple very close to your heater, this won't be a problem, but if you are tying to measure temperature further away from the heater (at the bowl) to get "weed temp", when no air is flowing the thermocouple is not going to get as much heat and the controller will increase the current to the heater, you then will have a super heated pocket of air in the heat cover. I will admit that I am probably not as much a vape expert as a lot of folks on this board, but I do know if I crank my SSV all the way up, let is sit for a bit, then take a draw, I will get instant combustion. This issue was also addressed in the PDF you linked to:

Always have sufficient airflow through the heater before applying power. Otherwise element will overheat very quickly, and burn out. NOTE: A thermocouple cannot detect temperatures if there is no flow ? turn on flow before applying power, even when a controller with a thermocouple is being used.

Now, with all that said, this is pure conjecture on my part so it is entirely possible that I am completely wrong on all counts, but all I'm saying is keep an eye open for over heating when you have no air flow over the thermocouple

 

[Purple-Days]

Excelent point. Probably why on demand temp control is a bit overboard. But admirable. And why a constant air flow is required for a small themal mass.

 

[skippymcware]

Post Number 3

This post is going to address heating elements and the associated design problems I have encountered.

When I first started this project, I figured I would just go get the ceramic element that is pictured in the Super Vapezilla forum thread I posted previously. Since then, things have gotten significantly more complicated. After reading a lot of user feedback, it became clear that the small ceramic element in the Super Vapezilla could be greatly improved. Not only did it only have a single hole for air to pass through, it took forever to heat up and cool down. This being the case, I have a hard time believing that the controller will be able to quickly adjust the element temperature to account for changing air flow rates. For those that have not been following, the pictures of this heating element are here:

http://www.wrug.net/forum/showthread.php?t=152

I think wickedroots was aware that they were unable to correct exit airflow very quickly, and decided to put their thermocouple on the heating element because of this. In doing this, they negated the purpose of their expensive temp controller. In essence, their controller became a method to change the set point temperature of their heating element. This could easily be accomplished with a dial and a temperature readout (as is done in all the cheaper versions of the digital vaporizers). The other problem with this is that, unlike the volcano vaporizer, they do not supply a constant air flow. Once you lack the ability to quickly change the temperature of the heating element, the only way to guarantee the correct air temp over the bud is to use a designed air flow rate. Many people have mentioned that you have to learn how to inhale properly when using some of the simpler vapes. This is essentially the same thing. The volcano gets around this by using a designed constant air flow rate and collecting the vape in a bag.

As Tom (Purple-Days), and several others, have mentioned previously, if all you want is a constant temp heating element, just get one with a large thermal mass (that is, one that changes temp slowly with varying air flow rates) and apply a constant voltage that you have figured out with some testing. This eliminates all of the hokus pokus of the temperature controller. Although much of this makes pursuing a vaporizer with a digital controller look silly, I am going to forge ahead knowing that I may end up without a temp controller. I think everyone will agree that this is a worthwhile investigation.

If you have been following this thread, you have seen my attempts at some back of the envelope calculations. Since my previous attempt, I have spoken to a med. student or two and borrowed some books on pulmonary function (lung function). I can now do this with a little more confidence.

As before, I am looking to get a result for the following equation:

Watts = SCFM x DeltaT in F
3

I got this formula from the following page:

http://www.hotwatt.com/airmfg.htm

Although this was the first place I cam across this formula, I later found it on almost every air process heater manufacturer's website. This formula is definitely correct and is not just a copy paste out of a text book. In fact, here is another example from industry where they calculate it for you:

http://www.farnam-custom.com/air_heaters/coolTorch050.php
*On the right side of the page

Looking at the formula, we already know the temperature difference (deltaT) of the air entering the heater and leaving the heater. If the air is entering around room temp. (65 F) and leaving around 375 F, deltaT will be 310. That's the easy part. The next thing we need is the air flow rate. As before, I first needed a good estimate of how much air we inhale when we take a hit. That is this:

Inspiratory Capacity (IC) = 3.5 L (1.24 cubic feet)
* The maximal volume that can be inspired following a normal expiration.

This is a high estimation for a safety factor.

Given a hit takes around 10 seconds, we get a flow rate in cubic feet/second of .0124. Converting to ft^3/min or CFM, we get about .75. Ignoring some small correction factors for atmospheric condition, we can call this SCFM.

So, now we know that, on average, we draw less that 1 CFM of air over a ten second hit. This is a big step. Let's look at 5 seconds and 20 seconds.

5 second hit: 1.5 CFM
10 second hit: .75 CFM
20 second hit: .375 CFM
*all of these are rounded slightly...

Now we have bracketed our flow rate. Note that these are tremendously small flow rates in the world of industrial air heaters.

Moving forward, I am going to choose the flow rate for the 5 second hit so that we will end up with the "worst case scenario" in terms of how much power we will need. Using this, we get:

Watts dissipated by heater into air = 150 watts

Now that we have a ballpark of what we want in a heater, lets look at some heater options:


Cartridge Heater:

http://www.omega.com/toc_asp/frameset.html?book=Heaters&file=cartridge_heater_info
*This is one link, but they are all over the place.

Benefits:
-Cheap (as cheap as $16)
-Easy to get
-Can be purchased in stainless steel, making health concerns a non-issue
-Small enough to fit in a tube
-Lots of performance and requirements data

Drawbacks:
-Might take a long time to heat up like the Super Vapezilla's ceramic heater
-Might not change temperature very quickly
-Possibly hard to mount

Steinel Heat Gun Element:

http://www.howardelectronics.com/steinel/Parts.html

Benefits:
-Cheaper than some ($70)
-Very quick to heat up
-No health concerns due to vriptechs research
-Excess power
-Proven design

Drawbacks:
-Large
-Hard to mount and integrate
-No data on requirements and performance (would need some reverse engineering)

In-Line Air Process Heater Style 1

http://www.hotwatt.com/airmfg.htm
http://www.tempco.com/Catalog/Section 11-pdf/In-Line Air Heaters.pdf
http://www.omega.com/ppt/pptsc.asp?ref=AHP_SERIES&Nav=heaj01
http://www.farnam-custom.com/air_heaters/coolTorch050.php
*This last one isn't affordable

Benefits:
-Excess power
-Cheaper
-Easy to mount and integrate
-Can be purchased with thermocouple attachment
-Lots of performance and requirements data

Drawbacks:
-Has exposed exotic metal heating elements that may pose health risk
-May not change temp quickly

In-Line Air Process Heater Style 2

http://www.sylvania.com/content/display.scfx?id=003684138
http://www.sdiohio.com/Pages/Osram.htm
http://www.convectronics.com/Airheaters3.htm

Benefits and drawbacks are pretty much the same except that this heater may be able to change temperature quickly. I actually have a new one of these already that I found on ebay.

Pure In-Line Air Process Heater

http://www.hotwatt.com/air1.htm
http://www.omega.com/ppt/pptsc.asp?ref=AHPF_HEATER&Nav=heaj01

Benefits and drawbacks are pretty much the same except these have no health concerns but are very expensive ($150 and up as far as I can tell).

Heat Torch

http://www.heating-elements-electric.com/heating_elements_1.pdf

These are an interesting combination of a cartridge heater and an in-line air process heater. They are very small, but you can direct air down the middle of them through that small hole in the base. Unfortunately, they are expensive.


Ok. You will notice that there aren't any simpler heating elements like the ones in the extreme and vapezilla. They aren't here because I can't find anyone that sells anything remotely like them. My feeling is that you have to get this type of thing custom made in bulk quantities or use a heating element from another commercial device already in production. Either way, I haven't found anything similar. This may not be the worst thing because I wouldn't know anything about them if I were to go down that road. LET ME KNOW IF YOU HAVE SEEN ANYTHING USEFUL THAT I HAVE MISSED!

Important
As a final note, I want to throw an idea out there that I came up with recently. What if you setup a system that used constant airflow that would normally vent to the air, but had a valve on the whip that would open when you tried to draw air through it. This way, you could keep your air temp constant and properly calibrated (whether that was done with a controller or not) and yet you could still take hits off of it without using a bag. I think this idea holds great promise and have done a bunch of work to sort out the details already. I will post those details later. Let me know what you think.


A huge thanks to everyone that has gotten involved in this thread. Sorry I disappeared for a while there, but that's life. I will response to some of the posts I missed next.

-skippy

 

[Purple-Days]

Exhausting hot air at a constant rate, AKA Vzila has serious drawbacks in the summer.

 

[skippymcware]

vap999,

Definitely let us know what you end up with. As everyone keeps mentioning, and I agree with but have not settled upon yet, you are using a tried and true method that is sure to bring you success. My only comment is that, without forced air, you will have to learn how to draw the air through it properly to make the system work correctly. I am interested to see if I can make a vaporizer that can be used with a whip, does not require learning how to draw the air through it properly, and maintains a closer to optimal temperature than the ones on the market at the moment. In other words, I realize that the configuration of units like the Purple Days is a successful one, but I am going to try and see if I can create something different. As of now, I don't know if what I end up with will be any better. At best, it seems that if I do come up with a different solution, it will address a different market. Keep us updated!


Tuttle,

Upon further thought, I realize that you are probably right about the requirement of flow control for most heating elements. This was the very thing I was commenting on in my first post in this thread when I commented that the volcano's system worked well and that constant flow may be the best solution. That is, I had already admitted to myself that I may need to have a constant flow, but hadn't put together the idea that this was, in effect, flow control. Although I am still leaving the option open for a very fast response heating element, I am starting to turn towards a valve system that only draws air from a constant flow system when it is demanded. I talked a little bit about that in my previous post and will put another post about it together when I have a chance. Thanks for your advice. I can see you really know your stuff.


Tom,

Agreed. A quick fix for that would be to loop the exhaust back around and make it feed back into the loop. I can't picture how this would work out off the top of my head, but it may be doable. Another point is that the word "exhaust" brings a massive venting of air to mind. We are talking 1 CFM. To put that into perspective, this fan,

http://www.sofasco.com/products/dc_axial/d2510.html

housing and all, is 1" by 1" and can flow almost 3 CFM. The amount of air we are talking about is very, very small.

-skippy

 

[tuttle]

Hi Skippy,

I was thinking about this in the shower this morning and had an idea that may me more trouble than it is worth, but I thought I would throw it out there in the interest of keeping the idea ball rolling.

What was troubling be about the whole arrangement as it stands was finding a heating element that will satisfy all your needs, very fast response, high thermal output, and not a health risk. If you eliminate any one of those three requirements, you selectable candidate list grows greatly. Quick response is probably the most challenging of the three, even a fast element is going to need a second or two to make rather small changes in temperature. Heating elements traditionally are slow, but valves can be very, very fast, and this is where the shower comes back into the story. You could go with a higher thermal mass type heater like a ceramic, apply a constant, high current to it to over heat a small volume of air, then have a thermostatic valve that mixes your overheated air with cool air to the proper temperature.

You can still put a thermocouple near the bowl with a readout of that temperature. The user could run a test draw, set the thermostatic valve to get the desired temperature, from there on out, the thermostatic valve should keep your temps constant regardless of draw speed, as long as the heater can keep up.

The hard part is finding a thermostatic valve that would work. And there may not be such an animal, but in the end it may be simpler, more reliable, and maintain a more constant temperature than trying to regulate with a heating element.

Feel free to disregard everything I have said as it is fairly left field

 

[skippymcware]

tuttle,

It is an admirable idea, but I don't think it is possible. The biggest problem, as you mentioned, is that there probably isn't a small thermostatic valve for air processes. Another issue is that both the heated air and the room temp air would have to be pressurized/have some flow rate associated with them. That being said, I am going to do some looking to see if I can turn up a valve that would do the trick. My last reservation is that I am starting to get the feeling that dynamic control of any part of these systems is overkill. I have been reading user reviews of some of the simpler vapes out there and people seem to be saying they work great. I am starting to wonder if all this high end vape stuff is just feature creep and selling points without any real justification. I think I am going to have to start buying some components soon and sort this all out for myself. Anyway...

As I mentioned before, I think the following solution may hold some water. Let me draw a quick flow diagram here:

|-------> Exhaust to Air (ignoring the heat problem for now)
|
Fan ---> Heater ---> Thermocouple ---> Y Joint ---> Herb ---> Valve ---> Whip ---> Enjoy

So, if I used this valve [7838K54] from www.mcmaster.com, would it work?

With this setup, you could get the benefits of a constant flow system, without needing to use a bag vape. Because you don't have changing air flow rate over the heater element, you no longer need to quickly change the heater output or air flow. Since the "cracking pressure" on the valve is only 1/3 of PSI, it would be easy to draw air through it once you sucked on the whip, but it wouldn't let air through otherwise. I did a little looking around to figure out our maximum inspiratory pressure. This link describes it:

http://www.medal.org/visitor/www\Active\ch8\ch8.01\ch8.01.11.aspx

With a little calculator action, we get about 1.7 PSI. Given this, 1/3 PSI shouldn't be a problem.

Ok... I am starting to get a little buried in this and am losing sight of the big picture. Is this a completely hair brained idea? I feel like I might be going way off course here.

-skippy

 

[Purple-Days]

Skippy,

I wrote something then hit the worng button, Damn. HOpe this comes close.

What you are doing is unique and very positive. Immediate control of temps to eliminate learning curves is an admirable goal. Maybe Immediate is to far toreach, but I think you can come closer than others have.

That saidI think the last idea, a valve might be a new approach. A manifold design fresh air in one, mixed with heated air from another. Hw this might be done id abviously open to conjecture. But I might take a mechanical aproach, bi-metal thermostatic controled louvre of some sort. Noelectronics, just a spring type bi-metalic valve,.An example, and I have used them, is a foundation vent sontrolled by this very idea. Opens when warm, closes whem cool. Primative , but properly calibrated it might fo the trick.

Old wall thermostats might be a start for salvage material for bench tests of bi-metals in this application. For those interested, the bi-metal I refer to is two different metal strips of different composition mated and fused. As temperature expands the metals at different rates the fused combination bends. How this might be applied is for skippy, but I think it is interesting.

Tuttle the shower or bath is probably the place formany inspirations. Right On, as they say here.

 

[stickstones]

skippy...your thread is very interesting but reads like you don't have much experience with vapor. I can't imagine trying to build a better bike without having ever ridden one. How much experience do you have using vaporizers? If I'm right, my first order of business would be to go out to some vapor bar in Cali to try a bunch of different vaporizers or something like that.

 

[tuttle]

Yeah, finding a valve that will work is going to be the (impossible?) trick. I may have to be something that needs to be engineered, which could be fun if you had a few years The lack of pressure on the supply side shouldn't be a problem though as sucking on the delivery side creates relative pressure on the upstream elements. The relative pressures on the hot side and cold side probably won't be the same, (unless the valve is mixing at something very close to 50/50), but I don't think this would be an issue.

As for the constant flow with exhaust idea, it certainly seems quickly attainable, and seems like it should work. I think you may need to rearrange you valving slightly something more like this (lets see how clear my ascii art is ). The one thing that would need to happen in my set up is that you would need to make sure that your thermocouple and the herb is equidistant from the heater, so the exhaust side would probably need some extra, otherwise unneeded tubing just to maintain proper distance.

---Thermocouple->Check valve->exhaust
/
Fan->Heater->Y Joint
\
---Vacuum break valve->Herb->Whip->Enjoy

The check valve on the exhaust can be something like the McMaster valve you spec-ed, which would prevent cold air back flowing through the exhaust to the whip. The vacuum break valve on the whip side _should_ (I haven't worked a lot with these valves, but it seems exactly what the doctor ordered in this case) will keep the air from exhausting through the whip when someone isn't sucking on it. I haven't done an exhaustive search, but look at something like McMaster #4817K63

Ok... I am starting to get a little buried in this and am losing sight of the big picture. Is this a completely hair brained idea? I feel like I might be going way off course here.

It sounds to me you are at that point in any engineering project where you start realizing that it is going to take twice as long, cost 4 times as much, and deliver on half of you hopes. Of course you are overthinking it, you can vaporize off a light bulb, but isn't that the whole fun of it, and really the point of this exercise? The reason you don't see something like this on the market now is because as you are discovering, it is a difficult nut to crack. That doesn't mean that it shouldn't be investigated or explored. I think if you are still getting enjoyment out of it, then why not? You have a cool little project to keep you brain spinning, and you might get something cool out of it in the end. If it is driving you crazy and just getting you down, then I would say call it a day and enjoy one of the fine vapes currently available.

 

[skippymcware]

Thanks for the feedback guys. I am used to getting buried in projects, but normally I have someone to bounce ideas off of. Since my partner in crime is wrapped up in his day job at the moment, I am flying solo. It is always good to be able to check with someone to make sure you haven't left the building completely.

I definitely started this project for a challenge, but I didn't expect to build an entirely new kind of system. The fact that we are going down this road at all sets off warning bells. In any case, it should be interesting, and that's the point. I'm glad I gave myself a few months for this, because I am going to use all of the time I have and more. That being said, my goal is a working and clean example by the end of the summer. I think my best plan of action now is to start nailing down some of the other details and ordering components so I can start testing configurations. I will put a list together of some basic components for everyone to take a look at.


Tom,

The valve is definitely interesting. I spent a bunch of time looking for thermostatic valves, but they all seem to be for very large hydraulic applications. I am starting to wonder if there isn't a reason for this. If I can't find a valve that I can buy, I am not going to make this solution my main plan of attack. One of my biggest goals is to stay with standard parts. I don't want to finish this project having resorted to spending a week or two in the machine shop and end up with a sweet vaporizer that is impossible to make two of. I will do some more searching while I move forward with this other plan.


slickstones,

I have very little vaping experience. I ran into them when I was in college, but it was always a friend of a friend kind of deal. Furthermore, I wasn't exactly in "engineering mode" when I ran into these things. I have tried to find head shops around me that have them, but they aren't exactly try before you buy kind of places. It has crossed my mind that I should just buy a PD so I had a solid example, but I think this has drawbacks. If I were to just buy a commercial vape, you can be sure that the drive to keep this project rolling wouldn't be as great. As I mentioned a while back, I think the smart thing to do is to build this whole project in steps. First, I will build a simple vape with no forced air and no temp control. This should give me a solid idea of what works and what I am looking for. It will also help me evaluate all the extra work I will do from that point on. As everyone keeps saying, all this extra wizbang stuff may be giving very little to the experience. Once I have done this first step, I can then start to build the more complicated configurations and try some different things. The only reason I haven't done this already is that it is usually a bad idea to start a project without knowing where you are going with it. The more work I do before I start this, the better.


Tuttle,

Much better layout on that design you drew. You wouldn't need that complicated a check valve on the exhaust side, though. I was hoping to use that check valve instead of a vacuum breaking valve. I figured, and maybe wrongly, that it would actuate even though it is supposed to be for positive pressure applications. I can't really figure how it would know the difference between negative pressure on one side and positive pressure on the other. Anyway, you could use something simple like this for the exhaust valve on your drawing:

http://www.hookahcompany.com/mya_check_valve_adapter_3283_prd1.htm

As for the vacuum breaking valve, I was looking at that same one on mcmaster, but it only goes up to 365 F and has rubber in it that I don't know much about. It may work for this application, but would need some looking into. I will keep digging around for other more suitable vacuum breaking valves. Also, I had the bowl before the valve in my diagram because I figured there would be no flow down that leg as long as there was no where for the air to go. This is mainly relying on the fact that the flow will have almost no pressure associate with it, so it shouldn't try and go up the whip side if there isn't an opening. This is all just conjecture, though. The best thing to do is buy a bunch of parts and try some stuff out. The main question is whether or not this is a solution worth pursuing. I still need to mull that over for a while. Right now I picture it being about 2 feet from end to end without some special care taken to package it nice.

Thanks for the input and encouragement. Don't let me thrashing around fool you, I am in this for the journey and challenge. Not being able to come up with a solution gets to me sometimes, though. Anyway, off to do some more thinking.

-skippy

 

[skippymcware]

Here are some ideas that really aren't that spectacular, but interesting, nonetheless:

I have come across these before in labs...

http://www.mcmaster.com/#flow-control-orifices/=1z20wc
*you are probably starting to think I only look at mcmaster. The truth is I always spend a long time searching at random and then bump into what I was looking for in mcmaster later. If I were smart I would just check there first.

Anyway, these things just use a small orifice to limit the maximum flowrate that can be passed through them. I haven't been able to find any really good performance graphs or data, so I can't say for sure that this would be of any use. My understanding is that the flow remains the same above a certain pressure. My thought was that you could use something like this to limit the flow above a very low pressure. If it worked, the vape user could suck as hard as they wanted and they would get the same air flow rate.


Another thing I cam across was PTC (positive thermal coefficient) heating elements...

http://www.dbk-usa.com/products/ptcheaters/ptcheaters.htm

To summarize, these things are self regulating heating elements. They change their resistance around a predefined temperature to regulate the wattage dissipated in them.

Along these same lines is a thermistor:

http://en.wikipedia.org/wiki/Thermistor

Both of these are interesting, but I'm not sure they achieve something we can't achieve easily by other means.

-skippy

 

[tuttle]

The only reason I had bowl downstream of the check valve was accessibility, as if it where upstream you would probably have to be unscrewing something to get at the bowl, and stoned + trying to thread something usually isn't a good combo

As for the check valve on the whip side, the reason I was inclined to swap that in favor of a vacuum break is because with the check valve you are relying on the cracking pressure of the valve to keep air from exhausting out of it instead of the planned exhaust, and I was worried if you had a check on the actual exhaust and one on the whip that you would have to fine tune your selections of the valves based on just their cracking pressure (if this makes sense). The MYA check valve looks like a good candidate!

Of course the easy way around all the valving is to have something like the Silver Surfer or Vapor Brothers whip where the user has to hold it up to draw. That way you can always just run your exhaust through one path. You would then need to have the thermocouple at the end of a probe that would stick some way into the bowl to get a more accurate bowl temp, which may just open another can of worms that isn't worth getting into.

Those heaters look very very interesting. I'll have to give them a perusal when I have a chance.

 

[DeepFried]

"or for example on an air heater application, the air flow could be slowed down to increase the exit air temperature" this worries me that the PTC heater like any made with ceramic will react way too slow to temp variations. I think that by using a very fast valve to mix outside air with overheated air can work very well and is definitely a great idea.

 

[vap999]

skippymcware:

Regarding PIDs, Auber Instruments has units at the cheapest prices I've seen. See http://auberins.com/index.php?main_page=index&cPath=1 Their basic unit is about $36. They also have an Ebay store. Do you see any reason that these units are not comparable to those often costing much more (any reasons to avoid them)? Auber appears to be an established U.S. company.

A major problem I've seen with most PID controllers (for your design requiring a fast-response heater) is that their response (cycling) times are generally every 500 milliseconds (.5 seconds). This is going to be too slow, even before considering the heating lag time of any heater. Faster-responding controllers are much more expensive.

For fast-responding vaporizer heaters, check out the VAPIR portable vaporizers (www.air-2.com). Although not discussed much on FC, they use a very fast-reacting heater with digital control and readout. I recall looking at some of the related patents (listed on www.vapir.com/about_us.php), and they included rather detailed information about prototype construction, parts used, etc.

If you are looking for constant flow rate air pumps, consider aquarium air pumps. They should have no toxicity problems (with fish generally very sensitive to most anything toxic).

 

[skippymcware]

OK, lots of good stuff here...

Tuttle,

"The only reason I had bowl downstream of the check valve was accessibility, as if it where upstream you would probably have to be unscrewing something to get at the bowl, and stoned + trying to thread something usually isn't a good combo"

I struggled with that for a while as well, but I realized you could put it in the whip. Depending on what temperature the valve would see, you might even be able to get away with something that isn't stainless. There are lots of great medical breathing valves. Another reason i wanted to put the bowl before the valve is that you could get it closer to the heater.

I'm sure you have a good point about putting a check valve on both ends of this thing, but I don't quite follow what you are saying. In either case, I think one of those ball bearing purge valve things would work wonders on the exhaust side.

The vapor brothers whip design is definitely a possibility, but I think we are going down slightly different paths here. My goal is to avoid having forced air on the whip side. The only reason I wanted to create that exhaust side was to have a ready supply of air at 375 degrees. If you ran the air flow on the exhaust side slightly above our figured maximum inspiration rate of 1.5 CFM, you could get it so that no matter how hard you sucked you didn't draw more air through the heater than was already flowing through it. By doing this, you are guaranteeing a constant air temp and inexhaustible supply to take hits off of. I actually noticed this when you did your ascii art like this:
____ _____
_____/ and I did mine like this _________|_____
\____

That 90 on mine was actually intentional. I am trying to discourage flow down the whip side unless it is demanded by the user. I actually thought about doing this:
_______
_____\_______

Man... I rarely feel as nerdy as when I am drawing this with forward slashes and underscores. Coming from me that means something.

Anyway, like I said before, all of this is more easily figured out once I get the components. The trick is deciding whether or not this is worth pursuing. An interesting point is that the Steinel heat gun element can heat up to temp in a claimed 20 seconds. If this is the case, there would be no reason to leave this thing running, and, if I can avoid glass, cool down may not be an issue either.


DeepFried,

You are right that PTC heaters may take a while to heat up. There are several other problems with them that prevent me from going down that road. If I wanted to make a simpler device for mass market I would pursue this further. I agree about the valve. Gotta find something that is even remotely close to practical before I discuss this further.


Vap999,

Good work. Holy crap. Not only are those temp. controllers cheap as hell, but I read some reviews and people aren't screaming bloody murder after owning them for a while. Strangely, this controller, like the fuji I mentioned a long time ago, is also favored amongst espresso aficionados. Anyway, I am going to take a closer look at this line in comparison with some of the more expensive ones and also in comparison to the CN7533 from Omega. It looks like it is just trimmed down a little but still has autotune PID, thermocouple input, an alarm function, and a dc pulse output. That is pretty much all I need. Also, valid point on the response time of the controller itself. For the moment, I have given up on correcting the temperature of a varying rate air flow with just the heating element. (That's in bold so everyone knows that) Our only hope is in some version of constant flow rate or mixing flows. Unless some other idea that hasn't come to light thus far pops up or I get a nice surprise when I bench test all this, of course.

I just spent some time surfing around the US Patent Site. Wow... that site is great. Lucky for me I don't care who patented what, so I am having a field day. Here is the volcano's patent:

http://patft1.uspto.gov/netacgi/nph...)&OS=volcano+and+storz&RS=(volcano+AND+storz)
*I feel like I am breaking the law reading that stuff. Crazy.

I read over some of the patent for the vapir devices. It looks like they use a ceramic honeycomb heating element. They call it a UF ceramic heater. I searched UF but couldn't figure out what that stands for. It any case, to the best of my knowledge, that is what the Steinel heat guns use. Good stuff. Again, you have to find people that will sell you 1 or 2 in the size you want. Something tells me that is a little tougher.

Lastly, I have looked into air pumps for fish tanks once or twice during this process, but I have a few concerns. Do they create obvious pulsations in the air supply? Are they noisy? Will a pump large enough to suit my needs be massive? The fact that Vapir used one in one of their patent applications is encouraging, but that may have just been for a test rig. Given that they are cheap, I may copy this move.

Thanks guys,
-skippy

 

[skippymcware]

I did a little more looking and found this video of a UF Heater:

http://www.youtube.com/watch?v=KWEHko51rws

I still need to find out what UF stands for, but it is definitely some kind of PTC heater self-regulating heater. There was some discussion in the last post that these may take a long time to heat up. This video contradicts that claim for sure. If you watch you will see the temperature skyrocket. Don't forget, it is in degrees C.

HOLY HELL, look at this one...

http://www.youtube.com/watch?v=sAPECDgfkx0&feature=channel

He mentions that it is a coating in this video. That must be expensive, that is all I have to say.

-skippy

 

[tuttle]

I got nothin' right now - just wanted to say how much I love this tread

 

[Purple-Days]

Me too. It'sa funny thing.

Experience is relative. Heck, the Pope gives advice on SEX. I can see this as a purely engineering project. But also advised testing 'on the piillows'. The bike analogy was similar to to what I was thinking.

What happened to that vape? The one that was instant on , and portable? Hand sized? Not kidding, can't remember, might give him a goal. Don't make me search,I'm blind...

 

[vap999]

I just spent some time surfing around the US Patent Site. Wow... that site is great. Lucky for me I don't care who patented what, so I am having a field day. Here is the volcano's patent:
skippymcware:

http://patft1.uspto.gov/netacgi/nph-Par ? AND+storz)
*I feel like I am breaking the law reading that stuff. Crazy
-skippy

Patents, by design (in the Constitution), empower the government, on behalf of the inventor or his sponsor, to enforce a time-limited monopoly on commercial use of (stop others from using) a qualifying invention (what's claimed by the patent). In exchange, the patent fully, publicly discloses the invention; and anyone can use or improve upon patented inventions, particularly for research and non-commercial purposes. So, if there is no money being made, if it's for your own and friend's use, for research, etc., don't worry about patents.

Patents are probably the best single information source for anything technology (know how; how to)-related, if only for new ideas. Much better than the scientific literature. And there are many free patent and full-text databases. For a much larger patent database, covering the U.S. and most other developed countries, check out ESPACENET (from the European Patent Office), e.g., at http://ep.espacenet.com/advancedSearch?locale=en_EP. And don't forget the U.S. patent office's database of pending patents (the newest stuff), e.g., at http://appft.uspto.gov/netahtml/PTO/search-bool.html

 

[Purple-Days]

Man, you guys want some fun get to a library that has the big thick books of patent synopsis. Very few libraries have them, but when you get your hands on one of these 10 pound 4 inch thick wonders... well you can spend hour after hour just looking at crazzzzzy ideas. Some so silly you wonder at the patent departments reaction to them. Some just amazing ideas too, of course. I was going through some of these when I was developing a 'quit smoking' device around '82. No internet then.

I think instant control of heater temps was never going to happen, but it was a good starting point.

Aquarium pumps: Most are AC operated. Most use an electromagnet to operate a flapper that moves a rubber diaphram.The fluctuation of AC provides the back and forth movement. The problem I see here is the diaphrams are all black rubber. Absolutely safe. Real rubber. Rubber has a smell. Stick your nose next to exhausting air from a tire and get an idea what I mean. The fishing department might be a good source of DC air pumps. Bait aerators for boat use? Probably still a diaphram of rubber.

Not sure how well it might hold up but with some reverse casting and making a mold you might come up with your own 100% silicone diaphram.

Yes pumps, the ac type I am familiar with, using a diaphram, have a noticable pulse. And really don't pump much volume either.

 

[tuttle]

I'm sure you have a good point about putting a check valve on both ends of this thing, but I don't quite follow what you are saying. In either case, I think one of those ball bearing purge valve things would work wonders on the exhaust side.

I actually noticed this when you did your ascii art like this:
____ _____
_____/ and I did mine like this _________|_____
\____

That 90 on mine was actually intentional. I am trying to discourage flow down the whip side unless it is demanded by the user. I actually thought about doing this:
_______
_____\_______

Yeah, rereading what I wrote I wasn't very clear about the valving. What I was trying to say is that on the exhaust, the check valve is doing exactly what it is designed for, allowing flow in one direction (allowing exhaust to flow out) but not the other direction (back flow through the valve when the user is drawing on the whip). On the whip side, there is never a chance of back flow. You are only trying to keep air from flowing when someone isn't sucking on it. If you use a check valve instead of something like a vacuum break in this situation, you are relying on the cracking pressure of the valve to make the system work. My concern was if you have a check valve on the exhaust, it will have some cracking pressure, and if you use another check valve for the whip, you will have to make sure the whip valve has a higher cracking pressure than the valve on the exhaust.


As for the divergent angle on the whip, I'm not sure it will make a big difference unless the fan can't move enough air to pressurize the whole system, but the nice thing is that it seems you are getting close enough that you can just test it out to see.

Looking good.

 

[skippymcware]

Alright,

I have been lost in patents for a day or so. Honestly, I can't say I found anything earth shattering. Most of the details I really want to know are left out, and the general device concept is always very similar. I will keep going back and poking around more every once in a while.

I also spent a bunch of time reading about fans. After looking around at Aquarium pump flow rates I realized it was a totally hopeless endeavor. A good size pump puts out about .1 CFM. Although this may change, I can't see getting away with less than .5 CFM. Interestingly, the vapir patent specifies that they use 0-10 L/Min. 10 L/Min is about .35 CFM. I could be overestimating how much flow I am going to need. This will all have to be sorted out under testing. Anyway, I found a few great sites that deal only with quiet PC case fans:

http://www.silentpcreview.com/article63-page2.html

Here is the fan I will probably end up with:

http://www.heatsinkfactory.com/nexus-80mm-real-silent-case-fan-sp802512l-03-p-16283.html

I will also need one of these:

http://www.heatsinkfactory.com/zalm...-speed-controller--noise-reducer-p-16300.html

and a filter and grill seen here:

http://www.heatsinkfactory.com/80mm-grills.html


mmmm, feels good to make progress on at least one front. That case fan was rated around 21 dB. From what I understand that is damn near silent. Considering it makes that much noise while pusing 22 CFM, I think it should be fine for what I am trying to do. I may have to step down to a smaller fan to get the necessary level of control, but I am hoping this will work since it looks like the Extreme uses a very thick 40mm fan. If I have to step down to 40mm I can use this scythe fan that generates 19.6 dB and 4.96 CFM at full speed.

http://www.quietpcusa.com/Scythe-Mini-Kaze-Ultra-Quiet-Computer-Fan-40mm-x-20mm-P459C6.aspx


On the heater front. I was getting close to gauging my eyeballs out with my thumbs because I kept going in circles. I am desperately trying to figure a way to use the Steinel heating element because it would guarantee a quick heat up and long life. It is a really awkward shape though and doesn't really offer a lot of options. I am starting to think I should just use a cartridge heater. I didn't mention this before because I am selectively blind/stupid, but Hotwatt makes a ceramic cartridge heater:

http://www.hotwatt.com/ceramic.htm

This would end up giving me a very similar system to the SSV or the heat wand from vriptech. I was thinking of putting it in an alumina insulating tube like this:

http://www.mcmaster.com/#alumina-ceramics/=204439
*Anyone know the health concerns surrounding these?

EDIT: Alumina ceramic is not an insulator... small problem with that plan. Oh well, I will look into another way of insulating the heater portion of the system. Alumina is also an irritant to lungs in ceramic glazes. So... that's out the window.

I could also put a stainless steel spring around the heating element to "turbulate" the air. The drawbacks to this setup would be a longer heatup time, but it would make it more practical to build and maintenance.

That's it for now... Thanks, guys.
-skippy