Building a Digital Vaporizer (Brain Dump)

[skippymcware]

This post is going to be a schmorgesborg of information relating to what I have been working on over the past few days.

I did some more work on air supply. I kept pushing on air pumps. The most suitable aquarium pump I found was this:

http://www.marinedepot.com/ps_viewi...L38&utm_campaign=mdcse&site=www.shopzilla.com

As I mentioned before, this is a relatively large pump. It isn't really practical, but could be used in a pinch. It would, however, be a great test bench setup. There are plenty of less compact and cheaper ones for this purpose, though.

I also started to look at micro air pumps. Surprisingly, there are tons of these things. The main drawback to these is that they all have high DC power requirements. Given that I am going to be running the cooling fan on the alarm circuit of the controller, it would add a lot of complexity to have a high amperage DC component in the mix. Anyway, here are some of the units I found. The ones in question are almost always the largest units made by the company.

http://www.parker.com/portal/site/P...ERIES MINIATURE DIAPHRAGM PUMP (UP TO 11 LPM)
http://www.airdimensions.com/DiaphragmPumpCategories.aspx?id=5&gclid=CL7QwuCi2poCFRufnAodaWj53Q
http://www.sensidyne.com/products.php?ID=1289
http://www.hargravesfluidics.com/air_pumps.php
http://www.smartproducts.com/pumps_series_ap_micro_air_pumps.php

Note: Some of these may need pump controllers, and that would make the added complexity too costly. Not to mention the added cost.


I also spent a great deal of time looking at enclosures. For once, most of these clearly state that they are RoHS compliant. Here are some of the manufacturers I looked at:

http://www.contextengineering.com/split_body_enclosures.html
http://www.web-tronics.com/exalelen.html
http://www.tekoenclosures.com/enclosures/19.htm
http://www.hammondmfg.com/1455.htm
http://www.newark.com/box-enclosures/b4-220bk/b4-series-enclosure/dp/26K9074
*This last one isn't a split box design.
http://stores.shop.ebay.com/Asia-En...15QQ_sidZ149380788QQ_trksidZp4634Q2ec0Q2em322
*This guy sells a bunch of great and inexpensive aluminum extruded project boxes on ebay. Unfortunately, they aren't quite big enough.

You can also find project boxes on digikey. Digikey is an electronics component wholesaler that functions pretty much like mcmaster-carr. I have yet to find any attractive ones on there, however. My buddy swears they exist.

Finally, even places like radio shack sell project boxes. They suck. Ugly, small, ugly and ugly.

Note: You can see I am focusing on aluminum extrusions. These are pretty much the only attractive option that will withstand the temperatures in this application and also stand a chance at RoHS compliance. You might also have noticed that I am looking mostly at the split enclosure design. Although you can get single piece extrusions with screw on end plates, I would have to assemble the whole shebang on a plate (like a circuit board config) and slide it in. This would be the worst idea ever, and the split design maintains the aesthetics of the aluminum extruded housings while making everything more accessible. One thing that is still evading me is a unit with built in fan mount points and vents. It looks like I will have to do that part myself. Not the end of the world, but it does put a blow in the standard parts goal.


I have been working a lot on the whip. I am really trying to avoid glass components. I can easily see how that would get annoying after the third time I drop it on the floor and it breaks into 1000 pieces. In pursuing this goal, I have looked at all sorts of quick couplings and fittings. I tell you, if it works mechanically, it isn't temperature rated and vice versa. Another thought was to try and use a hookah whip,

http://www.smoking-hookah.com/product/898001.asp

but I cannot for the life of me think of a way to integrate the bowl in an inline configuration. At the moment, I am still determined to use stainless steel whip components with barb fittings for the hose ends and pipe threads to connect to the heater tube. I may end up machining two pieces that are male and female with a small screen catch groove and an o-ring seal (It would end up being very similar to a piston design where the male piece has the o-ring and has just enough of a press fit to hold itself in the female piece). I hate to do this, but I am losing a great deal of my life looking for fittings that may not exist. Let me know if you guys have any ideas on this front.


I did a little more work on the insulation, and I think something closer to this will work.

http://www.mcmaster.com/#ceramic-sleeve-insulation/=21ogkw

I wouldn't insist on this, except that it will really aid in heat up and probably keep the other components in the device cooler as well. The trick with making this ceramic insulation work will be to keep it isolated from the air supply. I looked at lots of heat shrink tubing, and, again, it is hard to find heat shrink that is willing to run at 375 while also being food safe.


On the heating element side of things, I have started calling companies now that I have some idea what I'm talking about. The good news is that I have actually managed to get a pretty good grasp of the commercial heating element market. The bad news is that this is a very strange application and people seem mystified when I explain what I need. Oh, if you are a heating element salesman, this is for a prototype hot air gun for baking. Some more bad news is that my backup plan of using a cartridge heater needs to be tweaked a little. Apparently, cartridge heaters hate being in the open air. Having quoted an air flow of 2 CFM, I was told that I need to keep my watt density below 15 watts/square inch. This really limits the size choices. I was also really hoping that I could use whatever heater I come up with in a non-forced air application. Given that cartridge heaters need to be in a metal sheath of some sort, I started looking at heat exchangers. Here are some pictures of the kind of thing I am talking about:

http://www.vulcanfinnedtubes.com/Htm Documents/Serrated_Helical_Detail.htm

I spoke to the engineer at one of the companies about my application. He said that the serrated helical welded fin design is very hard to make and that they didn't have any lying around, but that a longitudinal aluminum fin design is very common and that they can probably send some over my way. My plan is to try and use this stuff as a heat exchanger for a cartridge heater. We will see what turns up.

Unless this latest plan works out, I may have to go back to the drawing board on heating elements. Of course, I could always just drop the cash and get one of the following:

http://www.abbeon.com/store/item.cfm?code=HT030
http://www.abbeon.com/store/item.cfm?code=2027
http://www.omega.com/ppt/pptsc.asp?ref=AHPF_HEATER&Nav=heaj01

My wallet hurts just thinking about doing that. Oh, also, I called Omega and asked if any of their heaters are food safe other than the one linked above. Nope. I am waiting for a call back from tutco-farnam about the other two heaters linked above. The people at the supplier weren't sure. Moving along...


I think that is it for now. I know none of that is staggering process, but I feel like I am learning by leaps and bounds every day. I have a feeling I just need to talk to the right electrical heater supplier and I will be off to the races.

Lastly, as I mentioned before, I think I am going to build a first generation of this whole thing without forced air or any valving insanity. I am going to use a temp controller so that I can play around with this thing and learn what works and what doesn't with some kind of quantitative feedback. If I can swing it, i would like to have a temperature readout on both the heating element and air flow. I think this will allow me to work the kinks out on a lot of the subsystems before I try and tackle a more complex device. Having decided all this, I still need to sit down with my buddy and mull over what I have done so far. I need to move between then and now, so we will see how quickly I can get rolling on this.

That's it for now,
-skippy

 

[vtac]

I really enjoy reading this thread, wish I had something more constructive to add but things are getting pretty advanced for a simple vaporist like me.

Personally I wouldn't sweat the glass wand/whip components. I guess it depends on the design you have in mind but typical glass wands don't get broken very often as long as basic precautions are taken. That's cool if you want to do something different but just a thought.

That heater you linked on the last page was insane! I know you're trying to innovate here, but maybe it's worth re considering the good old Hakko style ceramic soldering iron elements. Using a bunch of them in some sort of configuration might work really well.

Thanks for keep us updated!

 

[skippymcware]

vtac,

You know, the funny thing is that this project all started when I said to my friend that we should get a decent soldering iron and turn it into a vaporizer... Things have gotten slightly more complicated since then. I guess I just can't help it. I know one thing for sure. Anyone who has designed a vaporizer deserves a pat on the back for sorting it all out.


On another note, I realized I mentioned watt density but didn't define it. For those that haven't been vaping and can stand to look at math, here we go:

http://www.process-heating.com/Articles/Feature_Article/154bd7dd2f268010VgnVCM100000f932a8c0____
http://www.ogdenmfg.com/pdf/tech2.pdf

I have now bored everyone out of their minds... my work here is done.
-skippy

 

[skippymcware]

Quick Update:

When vap999 suggested the Auber temperature controller, he asked me if there was anything different about it. At the time, I couldn't find anything. Since, I noticed that it doesn't have a Ramp/Soak segment feature. For those curious, controllers with this feature have the capability to slowly heat up the element and then pause and let the system heat soak for a period of time before ramping up the heat some more. I think one ramp/soak segment means that it has one soak period in the middle of the heating up process. Honestly, I am uncertain I will need this as I don't plan on using any glass. I will have to talk to some heater guys about it.

Also, I just found out you can run these things on DC power. I don't know how I missed that before. That should make life so much easier.

I talked to a bunch more heater salesman today. One guy owned his company and had designed and manufactured several of the heating elements in the mars lander. Needless to say, that was a good discussion. He asked me to send over some drawings so he can help more. Luckily, I just ordered a copy of SolidWorks to draw this thing up. Things are starting to come together.

More to come...
-skippy

 

[skippymcware]

Ok... calling all vaporists!

I was reading in another thread on here about tubing issues with the SSV. Apparently, it uses vinyl tubing which has several problems related to heat exposure. Many people say that they replace it with Silicone tubing that does much better with heat. So, here i am thinking that I will use silicone tubing when several people start saying that it gets really dirty quickly. Now neither or these options seem just right. What about tygon? Any one have any comments on the pros and cons of high temp tygon tubing? SV users?

Thanks,
-skippy

Edit 1: Another candidate is FDA approved Polypropylene #5 like is used in the PD. Would this work as a whip material, or is it too stiff?

 

[tuttle]

I haven't used Tygon, so I can't comment on it, but I am loving just plain old food grade silicone tubing on my SSV. For me the problem with the vinyl tubing wasn't heat issues, but rather just the smell associated with it (granted, I didn't keep it on there for long, so perhaps over time heat becomes an issue with vinyl). You are right though that the silicone isn't the perfect solution as it picks up odors and dirt fairly quickly (if you accidentally combust, something like that). I end up just keeping extra on hand. It isn't perfect, but it is really good in my opinion.

 

[Hippie Dickie]

Skippy - interesting thread.

I've been working on my own vape design since about 2002. On Overgrow (RIP), i called it the Bud Toaster (and The Perfect Cube) and on PlanetGanja (also RIP) it had evolved to be the Black Leather Vaporizer. Rather than hijack your thread, i'll start my own thread since the design is significantly different from your approach -- all glass, i.e. no plastic or metal in the air flow, and battery powered with 30 minute vape time on a charge, 20 seconds to go from room temp to 420F vape temp -- using the Tesla car batteries which can deliver 60 amps continuous and recharge in 15 minutes. No fan. Like i said, a different set of design goals.

But there may be some ideas you can incorporate into your effort. In particular, i designed a pulse width modulator to digitally control the current to the heater. There is a type K thermocouple feeding a MAX6675 to read the temperature of the heater and a 12F683 PIC processor to talk to the MAX6675 and drive its built-in PWM to maintain the desired Setpoint temperature. The program on the PIC is 42 pages of code (so far). Total cost of the electronics is about $10 in units quantity.

i'll post up the circuit diagram when i do my thread. i'm redoing the PCB(s) to use surface mount devices and i changed the voltage regulator from 5v to 3.3v to run the electronics - which may allow a little longer run time. And a new approach to the enclosure that i've been kicking around for over a year. It could be running this weekend.

 

[skippymcware]

Hippie,

Thanks for the reply. I just ran into pulse width modulation as a method of heater control about 2 days ago. I forget where the article was. Very interesting stuff, though. I will definitely follow your thread. I can't wait to see how it turns out.


On another note, I am getting confused about alumina ceramic. I read somewhere that the dust can be an irritant to the lungs, but then I was just reading about the SSV and how it has an aluminum ceramic heater. Now, I know there are different kinds of aluminum ceramic, but what is the deal? Anybody have any info on this?

Thanks,
-skippy

 

[skippymcware]

Alright. I have created a new set of goals that reflect what I have learned. I will have to edit these some, but this is the gist. Also, I sat down and laid out the first device. My main goal was to see how compact I could get it. I picked an enclosure off of one of the sites and ended up with the H:1.38" x W:5.23" x L:8.66". Granted, this is as compact as I could get away with given my new set of requirements. There are several concerns with this device that are still bothering me, but I will have to sort that out in testing. The trick to getting it to be a great unit will be to insulate the crap out of the heater portion of the unit. I will post CAD drawings once I finish them. That should take me a week or so. I have to drive across the country first.

Remember Step 5
Here is what, I think, many of you have been gnashing your teeth in anticipation for. In this post I will make a more realistic set of design goals that apply to the first generation device I plan to make. Here are the design steps I laid out in my second post. This is going to be step 5. So close to choosing components, yet so far.

Design Steps:
1. Survey market.
2. Do as much reverse engineering and information gathering as possible on the good products.
3. Put together a list of design goals. (bag/whip, digital display, temperature controlled, glass on glass, blah blah blah)
4. Identify best case scenario for each design decision.
5. Modify design given that money, time, and resources are not infinite.
6. Start choosing components.
7. Modify design to fit said components.
8. Build and test.
9. Iterate step 7 and 8 until satisfied.

Editing the previous list:
Design Goals
-Stay healthy... same

-Durable
This used to say "built like a tank." Since then I have seen that the PD can be put in a dryer. I have no fantasies that whatever I build would be destroyed if I did this. That being said, I am going to try and avoid glass and make it so that a 4 foot drop is no problem. If I leave out the forced air, valves, and glass, this should be doable.

-PID
This first generation device is going to be an extremely compact whip device. It will probably have a temp. controller in it, but it may just have a temperature meter.

-Isolated Electronics
RoHS compliance if I can. Electronics will have to be isolated just to keep them from burning up.

-Whip design
If I can swing it, it will be an unbreakable whip design. The first gen. will almost surely be a horizontal setup.

-Insulated
If I insulate the heater element and put some cooling air into the enclosure everything should be fine.

-Stealth
Shouldn't be an issue on the first gen device. This will get much harder once things start to get Frankenstein on me in the more complicated configurations.

-Fan Control
Built into controller as an alarm function

-Standard Components
Still a goal. Looking like I may have to deviate a little here and there.

-Attractive
Still a goal.

-Quiet
The first gen device should be very quiet. The fans that people mentioned were loud on the vapezilla were 28 dB. I should be able to come under 20 dB. Given that the decibel scale is exponential, this is a significant gain. This whole thing gets more complicated because it really depends on what kind of noice (what frequency noise) the device is generating. It sounds like those fans were making high pitched noises which are very annoying and much worse even at the same sound pressure level (dB).

-Affordable
Well... I have been running a BOM and updating it as this whole thing evolves. If I don't have to shell out huge bucks for the heating element, I think I can build the first one of these things for around $300. A lot of this will be muddled due to failed concepts or implementation. I will post a full workup when all of this is over.

Removed Items:
No bag design consideration.
No active carbon.
Durability scaled back to something more realistic.
Glass on glass is now going to be avoided

 

[skippymcware]

I am getting close to having something that resembles a final product. Here are some CAD pictures and dimensioned drawings. I also threw in a BOM. I haven't really focused on cost cutting. If I bought everything on that list I would have 100 O-rings when I only need one, and a foot of stainless steel stock when I only need 5 inches or so. The cost of this thing wildly fluctuates from $250 one day to $450 the next. It is kind of a balancing act with all the compromises that need to be made. Anyway, cost cutting comes later. Let me know what you think.














I should also say that there are still a few things missing. The power plug, for example. I haven't decided on the fan either. At the moment, I have the biggest fan I can wedge in there. I hate the fact that I might have to vent out the top of the unit, but I don't have a good idea how much air flow I will actually need to keep everything in there cool. Also, the bigger the fan, the quieter it will be for the same flow rate. I really want to run a blower type fan like this so that I can push air out the back of the unit:

http://www.mechatronics.com/IndividualModelWebPDFs/DC/B5015_7.6.05.pdf

But blowers are very loud (usually around 30-40 dB) and you can't really get more than 7 or 8 CFM out of them in the very best case. A good 80mm axial fan can push over 20 CFM at less than 20 dB. As far as I can tell 15 dB is ambient, and anything less than 17 or 18 dB is silent.

As for AC fans, I took a long hard look at them, but they pretty much suck. The motor that drives the fan has to be much larger for one reason or another which makes the fan blades very small. Because of this, they end up being much louder for the same flow rate. This goes for AC blowers as well.

Anyway, the next step is to go back to heater manufacturers with a sketch in hand. I can't nail down the controller, fan, or power supply until I decide what type of heater I am going to run.

-skippy

 

[tuttle]

Let me know what you think.

...At the moment, I have the biggest fan I can wedge in there. I hate the fact that I might have to vent out the top of the unit, but I don't have a good idea how much air flow I will actually need to keep everything in there cool. Also, the bigger the fan, the quieter it will be for the same flow rate. I really want to run a blower type fan like this so that I can push air out the back of the unit:

Do you have enough room that you could put a fan shroud on top of the fan to direct the exhaust out the back? I couldn't find one that would be and exact fit for what you want, but you could by a regular shroud and cut off the side that would mount on the back then seal the top, or just make one out of sheet metal / aluminum to spot weld or pop rivet to your enclosure.

Looking good though, if you have an OBJ / IGES (going into Rhino), I can render it out in V-Ray for you

 

[skippymcware]

Tuttle,

I thought about putting a fan shroud on there. I am just very attached to a slim profile on this thing. I have worked so hard to fit it into that 1.37x5.3x6.3 box. It would kill me to throw a big shroud on there. I am hoping that an 80mm fan is going to flow so much air that the temperature of the air it is exhausting will actually be relatively low. That is, you could put your hand in it without a problem. As shown on the bill of materials, I have two types of insulation going in the heating "chamber." One goes around the heating element (a ceramic sleeve) and the other goes on the walls surrounding it. My hope is that this will keep the temperature in there pretty constant and avoid heating the rest of the box. I had never heard of v-ray before, but it looks awesome. Despite it being completely unnecessary, I may just take you up on that offer once I finish the drawing.


In other news:
One interesting thing I came up against while I was working on this is that air has a tremendously low thermal conductivity. This is also called the R or K factor. One is the inverse of the other. Anyway, here are some thermal conductivities:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

The thing that you always hear people yammering on about is how "air is a perfect insulator." Well, this is true, as you can see in the link. It has a k factor of 0.025. Wood by comparison has one that is twice as much. The only problem is that air moves! The heat differential between the heater and the wall creates natural convection and before you know it you have 450 degree air right next to your very conductive aluminum wall. Anyway, that's why I am going to use insulation which, although it is much more thermally conductive than air, will end up being more effective than air. Honestly, I felt like I understood all this before I started this project, but it messes with your head once you actually start looking at insulation.


On a final note, do these drawings make sense to people? I realized that after staring at this thing for a week straight I may be incorrectly assuming that the purpose of all the items in the pictures may be clear. Should I post something that outlines what everything is? I kind of assumed it was possible to go back and forth from the bill of materials and figure it out, but this may not be the case. Let me know and I am happy to write something up so people feel more comfortable commenting.

 

[DeepFried]

Instead of a fan, how about using the peltier type cooling internals of this
http://www.coolitsystems.com/index.php?option=com_content&view=article&id=10&catid=14&Itemid=6

 

[skippymcware]

DeepFried,

A very good point. I ran across a selection of these at digikey.com a while back.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1180573

My concern is that these are made to be used in places where they are in direct contact with the thing they are cooling. That is, they are built to be conduction based cooling devices. One thought is to wedge one of these in there with a finned heat sink on it and then use a very small fan to pull or push air across it and onto the controller. I have three concerns with this. First, I am trying to keep my costs down and things add up quick. It looks like a decent size peltier cooler is about 15-20 beans. A heat sink would probably go for around the same. Second, I'm not certain I have the room in there. I went to a great computer store today where they had an entire wall of all the best cooling fans on the market. After looking at all the fans on the internet for so long, I was blown away by how small a 40mm fan is in person. That thing is freaking tiny. Despite this, however, I think I would run out of room pretty quick if I started trying to cram a heat sink and a pelitier cooler in there on top of a fan. Third, those little guys draw 6 amps. Most controller devices have dc alarm outputs that have a max current of around .15 amps. Therefore, using one of these would only be possible if I wire the whole device for dc power. That is still an option, but it makes this solution contingent on a lot of other things.

 

[DeepFried]

I was thinking you could create almost a little fridge with a tiny aluminum enclosure around the electronics with the peltier on the top inside the fridge enclosure, cool air will fall naturally onto electronics with the hot side of the peltier facing vents cut into your main enclosure above it. This would eliminate the fan and large heat sinks but of course you still have the 6 amp draw.

 

[vap999]

The thing that you always hear people yammering on about is how "air is a perfect insulator." Well, this is true, as you can see in the link. It has a k factor of 0.025. Wood by comparison has one that is twice as much. The only problem is that air moves! The heat differential between the heater and the wall creates natural convection and before you know it you have 450 degree air right next to your very conductive aluminum wall. Anyway, that's why I am going to use insulation which, although it is much more thermally conductive than air, will end up being more effective than air. Honestly, I felt like I understood all this before I started this project, but it messes with your head once you actually start looking at insulation.

There are now several types of insulation better than still (no convection current) air, i.e. have lower thermal conductivity -- silica aerogel and microporous insulation.

This stuff in expensive (but then you only need about 1/4 to 1/3 or less than other types of insulation). I've contacted every company that sells this stuff in the U.S. These companies are the worst to deal with. Hardly any would even respond to my E-mails requesting prices, and I had to call and chase after their sales reps just to get prices. And then nearly all, particularly those with the insulation in board or other rigid forms, have minimum purchase requirements, generally around $300-500.

Silica aerogel is the better known of the two types, with this being hyped by NASA for many years as a spinoff from space R&D. The most available and accessible aerogel insulation is the granular form from Wacker distributed in the U.S. by Solar Components Corp., with a gallon (231 cu. inches) costing about $50. If your design allows (or can be deisigned) for voids that can be filled with granular aerogel, that should work well.

However, for my own vaporizer prototypes I am slowly building, I've decided to primarily use microporous insulation in the board form. Using this, unlike the granular aerogel, with my design the insulation can also support the heater on its bottom and immobilize it to prevent lateral movement (i.e., I box-in the heater with insulation board).

 

[skippymcware]

Vap999,

Very interesting info. You definitely have more experience on this than I do. Aerogel is really cool material, but I moved on from it after hearing that it was extremely fragile. Strangely, mcmaster actually sells sheets of it:

http://www.mcmaster.com/#9590k8/=28we7b

I just bumped into it when I was looking for ceramic insulation. The aerogel that mcmaster sells is reinforced with carbon fiber. So, here is my question to you. How do you work with this stuff? Can it support itself if I attached it to a wall? I have absolutely no idea what the texture/surface of aerogel is like. Watching videos and reading articles about it, everyone always talks about how fragile it is. All that kind of scared me off of it.

For those following this discussion, here is a link to the company and their aerogel product:
http://www.solar-components.com/aerogel.htm
http://www.solar-components.com/Nanogel.pdf

Well, this stuff actually looks very useful. I wasn't aware you could buy it in granular form. Again, I wonder how I would service the unit (replace the heater, for example) if you can't really handle aerogel. Let me know if it is more durable than my previous investigation has led me to believe, as I would love to look into this a little more.

Thanks!


DeepFried,

I agree that it is definitely a viable option. The power consumption is only a minor bump in the road if it is the proper solution. I think I am going to have to look deeper into the whole cooling issue with all of my options open. Thanks for the idea!


I wanted to throw one idea out there. It just came to me. I could put the switch in the back of the unit, move the controller over to the left as far as it will go, and then create a channel in the middle of the unit with another piece of aluminum angle. This sealed off channel could either be filled with insulation of one sort or another, or I could move air through it. I feel like using standard insulation around the heater is a better idea because it would allow easier access (although I still need to look into that other material that vap999 brought up), and I could fill the channel with aerogel. This would prevent any natural convection from occurring and give an excellent insulating barrier. The only problem is that it would once again significantly raise the total cost of this thing. More thoughts to come. I will mess around with the model and see what I can do. Honestly, I really need to nail the heater down before I can go much further. I am waiting on a reply from some heater companies. Keep the ideas coming.

EDIT: just cleaned up a sloppy post.

 

[vap999]

Hippie,
On another note, I am getting confused about alumina ceramic. I read somewhere that the dust can be an irritant to the lungs, but then I was just reading about the SSV and how it has an aluminum ceramic heater. Now, I know there are different kinds of aluminum ceramic, but what is the deal? Anybody have any info on this?

Thanks,
-skippy

Ceramic dust, just like any other kind of particulate dust, is an inhalation hazard. Glass, stainless steel and anything else used in vaporizers is an inhalation hazard as a dust. But here, we are dealing with vaporizer and heater parts, composed of solid material.

Any ceramic being used to encase a commercial heater, much less a vaporizer, obviously is not a dust-forming hazard.

The main types of ceramic likely to be used in heaters are composed of alumina (aluminum oxide), silicates (silicon dioxide; quartz) and mixtures. Any ceramic being used with a heater is almost certainly made from very precisely quality controlled particle size, pure, probably synthetic, versions of these materials. This is far removed from common ceramic made from ground clay and fired. High-end ceramics, such as would need to be used in a heater encasement, don't contain asbestos or other fibrous inhalation hazards. And even if you somehow inhaled dust from a ceramic heater encasement, it's contents (alumina and silicates) would be biologically inert or non-toxic (but like sand, the particles would be irritants).

 

[skippymcware]

Not to deviate from the present discussion, but I wanted to address why I am using a temperature controller in this device. Several people have pointed out, and very correctly, that their benefits are questionable at times, and their drawbacks are obvious. Well, there are several reasons why I settled on using one.

No More Expensive:
I definitely want a digital temperature display. This of course does not necessarily mean that I need a an entire controller, but, interestingly, temperature meters are actually just as expensive as many controllers. From what I have found, a digital temperature meter runs about $50. I was blown away by this. How is it possible that an entire controller could cost less than just a thermocouple amplifier and an LED display? I have no idea, but, as far as I can tell, that is the reality of it.

Faster Heat Up:
I suppose this isn't entirely true because you can turn a heater control all the way up to warm the system up and back it off when you are ready to use it. This, however, has risks when you are talking about high wattage heaters. If my unit ends up with a relatively high wattage heater (600 watts or so), you could easily ruin the heating element by cranking the voltage and leaving it/forgetting about it. A controller allows for fast heatup without monitoring the unit. You can even automatically ramp up the voltage to gradually warm the system. The best news is that, so long as you have a thermocouple on the heater, you can forget about it and it will take care of itself.

Built in Fan Control:
Controllers have integral "alarm" functions. These alarms usually power an actual speaker or light that warns the user of out of specification conditions. Luckily, the output signal can almost always be set to either of the 2 outputs on most controllers. At least on of these outputs is a dc pulse signal. When you set the alarm you can say turn on alarm when temperature is greater than X degrees. With this function the controller will be able to automatically start and stop the fan when the unit is too hot or too cold. Rejoice, no more button mashing.

Durability:
Given that I want a temperature display, having a controller really doesn't make the thing that much less durable. It will be able to take a short fall either way and any amount of digital electronics makes a device prone to certain types of failures automatically.

Experimentation:
A controller will really allow me to use this device for experimenting with temperatures and setups. You can see that the air path goes all the way through the element and has pipe threads on either end. My hope is that I am creating a heating unit that I can use as the basis for further development by attaching more stuff on either end when I am ready to try other things. Meanwhile, the controller will allow my heater to be adjustable while still giving me some idea of the scale of the changes I am making when I change the temperature.


A lot of bad things have been said about the vapezilla and its controller setup in this thread. Many of those things by me, but a temp controller really is the best option for what I am trying to do. This excludes a custom solution. An example of this would be something like pulse width modulation or making my own PID control circuit and temperature meter. All of that would require too much engineering on the parts of the system that I am not really interested in spending a great deal of time on.



On another note, I wanted to bring up air turbulators. My design has the heater outside of the air path, and the air travels a straight shot through the stainless tube all the way through the unit until it hits the whip. Given this, I am a little concerned that there won't be enough mixing in there to get the air evenly heated to the target temperature. In an attempt to fix this, I started looking into air turbulators. Here are a few links:

http://www.taaming.com/turbulators.htm
http://www.sunheattransfer.com/turbulator/wire-turbulators-specification.html

Now that I know I don't have to fear alumina ceramic (Thanks Vap), I could also use an alumina ceramic tube like this:

http://www.mcmaster.com/#alumina-ceramics/=28zqkt
*this, of course, isn't big enough

What do you guys think? Given that my tube ID is only 3/8" is it even necessary? Can you think of any other simple solutions? I think it is going to be a bitch to try and get a small piece from one of those two companies I linked to. They never want to sell you a foot. They are more on the scale of 300 feet of the stuff. Anyway, I will call them and see. It would be an interesting experiment, even if it isn't necessary.


One more thing. I looked into Tygon. It is really just a brand name silicone tubing. I guess they use a proprietary process to create their tubing so it has a very smooth inner surface. Supposedly, this prevents crap from sticking to it. I found a few people who swore by it for their fish tanks, but I'm not convinced. For now, I am just going to get the regular high temp silicone tubing and I will try Tygon when I have less other crap to sort out. If you ask me, Tygon sounds like a gimmick.

 

[Hippie Dickie]

Skippy -

Lots to comment on here.

My experience shows me that air is indeed an adequate insulator. Virtually anything else (except the aerogel, and thanks for those great links guys, i've been trying unsuccessfully (so far) to find any purchase info about it) just sits there, next to the heater, and is a thermal mass that absorbs and holds heat that doesn't assist the vaping process. So i use a very thin aluminum foil shroud around the heater, and use air as the thermal barrier.

A custom pulse-width-modulator for digital temperature control is really quite simple and quite cheap:
(1) K-type thermocouple @ $5 ea
(2) 12F683 PIC processor @ $1.35 ea
(3) MAX6675 (cold junction compensated K-thermocouple-to-digital converter) @ $7 ea ($3 in 1000s)

This technique requires writing some code to control the PIC (which i will post if there is interest). i'm able to maintain set point within a degree.

The PWM also solves the "minimum time to vape temp" requirement. i slam the heater coil with 12 amps @ 6vdc (72 watts) until the temperature (as reported by the MAX6675) hits a "trip" temp, at which point i kill the current until the temperature peaks, and adjust the "trip" temp. Then turn on and diddle the PWM to keep the temp at the setpoint. This works amazingly well.

For digital temperature display i use a $10 digital thermometer from Amazon. This is because driving the typical LCD display takes like 20 output pins, and the 12F683 PIC i use only has 8 pins (including power and ground). The 12F683 PIC talks to the MAX6675 with only three pins, leaving pins for (1) user input (3 buttons on 1 pin), (2) user output (green LED), and (3) PWM output. i also like that the temperature display is an independent subsystem, and it can't be fucked up by a software error.

And, from my research, LiIon batteries are the cheapest way to deliver the current required for the heater. The A123Systems batteries can deliver 70 amps continuous. Heater temp increases 15F per second (and cools 2F). 15 minute recharge.

And managing current flow is the biggest problem i've had over the 7 years of working on my vape. But i think i've finally got that nailed.

 

[skippymcware]

Hippie,

Wow, if you are willing to post that code or email it to me I would strongly consider using it. The main question is what are you writing it in? The majority of my experience is in C and C++. The code is really the biggest part of the that project that scares me off. I just wouldn't know where to start if I had to do it from scratch. A cool side benefit of using it is that fans can also be controlled with PWM. If you are uncomfortable posting it on the forum, you can email me at skippymcware@gmail.com. If I cannot share it with this forum, however, than I might not use it just to keep within my project goals. If you don't mind sharing it, I would develop a fan controller part of it and post any revisions I made to it. After a few minutes of searching here is what I found on PWM controllers for fans:

http://www.bit-tech.net/modding/2001/12/03/pwm_fan_controller/1
*Here is a schematic for the fan controller
http://www.coolerguys.com/pwmfans.html
*It's good to see Nexus makes a PWM fan. Their fans are very quiet. The one I saw has a 16 dB sound level and flows 32 CFM. That is absurdly good.
http://www.nomad.ee/micros/pwm555.html
*Another circuit
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1242516621
http://www.acousticpc.com/pwm_cooling_fans.html
http://www.boondog.com/tutorials/2993pwm/2993pwm.htm

Anyway, I will keep searching. I am definitely interested in pursuing this if I can get a kick start from your work.

As for insulation, I guess I will try using just air as an insulator first, but I have my doubts. Again... it depends on what wattage heater I end up with and the heater guys aren't calling me back.

Alright, thanks for the input! Let me know if you are willing to share your code/schematic. I would definitely appreciate it.

 

[Hippie Dickie]

Sure, i've always posted the design and construction details of my vape -- first on OverGrow, then on PlanetGanja (i wonder if that's why they tanked???) -- i want the design to be in the public domain as open source hardware.

Two people have made their own copy of my designs and both said it was the best vape they had ever used. For what that's worth. that was several years before this most recent temp control model. imho all glass rules.

The code is currently running 42 pages of Assembly Code. i got Microchip's simplest PIC programmer board ($35) and that comes with a macro assembler that is pretty good. Posting that much code might be problematic.

i've only used 50% of the 2k bytes of program space. there's a few more features to add: (1) reset to factory defaults (2) detect battery depletion imminent and warn user to recharge.

And i've got some ideas to improve temperature drift - there is a bit of wandering around the setpoint that can be nailed down, i'm pretty sure.

Also, i just realized that this website doesn't allow uploading images, so i need to figure out where to upload the JPG of the circuit diagrams. Throwing extra steps into the process just slows me down.

 

[skippymcware]

ARRRGH, assembly code. Brutal. Well... I do have my EE friend. He knows some assembly. You can use imageshack.com for your images. I will find a hosting service to post the code and then link to it. Anyway, I will see what I can do with it after you send it over.

On a more basic note:
Wait... I am suddenly confused. All the controllers I am looking at do is send voltage pulses of varying lengths to the heater. I realize that this isn't quite the same because, to my knowledge, the pulses are not fast enough to generate a lower effective voltage, but I am struggling to grasp the fundamental benefits of PWM. Hippie, any thoughts on this? I need a little help wrapping my head around it. Thanks.

EDIT: I looked into it and am starting to see what is going on here. Here is an intro to PWM:

http://www.netrino.com/Embedded-Systems/How-To/PWM-Pulse-Width-Modulation

Here is a summary of PID control:

http://www.omega.com/temperature/Z/pdf/z110-114.pdf

The gist is that PWM switches the load in the range of 1000 times to 200,000 times a second in order to simulate an analog signal. (Compare this with a PID controller which switches the load once every several seconds.) From what I gather, PWM is great because it is cheap on the control end, eliminates any digital to analog conversion, and is very resistant to signal noise. My problem is, it is just the basics of what is needed to properly control a heater. You still need to develop a control algorithm that tells the controller what to do when the temperature is too cold or too hot by varying amounts. That's the hard part. That's what Hippie has spent all that time on (I think, correct me if I am wrong) Once all of this is done, of course, you have a very slick temp controller in a small package that is capable of holding a the heater temp very very close to the target temp because of the fine resolution it can achieve. Given all this, it certainly does seem like the best way to accomplish the task.

That being said, I don't think this is a proper project to layer on top of what is supposed to be a first gen. vape. I am pretty tempted to stick to my guns here and not get too far off on a track that I could very easily get bogged down on. I will have to think it over.

 

[skippymcware]

Alright. Hippie Dickie's solution really threw me for a loop there. (Thanks for pushing the envelope, Hippie) I have spent the last several days bashing my head against the wall trying to think of a better solution where I can still use AC power to control the heater. As Hippie said, if you don't want to use batteries (I don't) you are going to have to pay $150 or more for your AC-DC converter. Plus, that's only for a 150 watt heater. Lucky for me, I have been slowly converging on a solution without even knowing it. I spent a bunch of time looking around at pulse width modulation controllers and what would be needed to implement that. Like I said, the DC power for the heater was really a killer for my application. Then, just as I was going to walk away from the whole idea, I came across a forum where some guy was using something called a triac in a digital circuit to control an AC motor. A triac is two silicone controller rectifiers back to back. If you don't know what that means, that makes two of us. All I know is that they are in solid state relays as well and act like a switch for AC power. But, more importantly, you can use them to control the power output on an ac signal with phase angle control all through a digital circuit. Granted, the response time isn't as good as pulse width modulation, but it is .08 seconds. On top of this, it can also infinitely vary the power output at each time step. That is a whole lot better than the .5 seconds that all the other temperature controllers give you. Here is a summary from the link below (I am interested in phase angle control):


"A silicon controlled rectifier (SCR) is a solid state switching device which can provide fast, infinitely variable proportional control of electric power. Not only does this give maximum control of your heat process, but it can extend heater life as compared to other control methods. Since the SCR is solid state, it can cycle on and off over a billion times, if properly used. SCRs can be used in the following ways:

On/Off Control works like a mechanical or mercury relay. When the SCR is on it fires full voltage into the heater until the command signal turns it off.

Phase Angle Fired controls proportionally turn on a percentage of each power cycle. This gives smooth, infinitely variable application of power to the heaters. Phase Angle Fired SCRs provide the most precise control of heaters, quickest response to load changes, and maximum heater life. Only Phase Angle Fired SCRs can have options such as Voltage Limit, Soft Start, and Current Limit.

Zero Voltage Cross Switched controls proportionally turn on and off each full power cycle. The SCR controls power by varying the number of AC power line cycles. A variable time base determines the optimum number of cycles to be turned on or off. The switching is done at fractions of a second during the zero voltage crossing of the power line cycles. For fast responding elements (e.g. a T3 infrared heating element), the element may flicker. For heaters with greater mass, temperature can be controlled within very tight tolerances.

Normally, SCRs are controller by a linear input from a temperature controller. This input can be 0-20mA, 4-20mA, 0-5 VDC, or 0-10VDC."


This realization makes fast acting heaters a possibility again! I won't get into any of this for this current design, but it renewed my hope that a more elegant solution is out there. Here is a link to a description of SCR based temp controllers, a 5amp SCR that costs $10 , and a control circuit diagram for a SCR based heater controller for an electric range.

http://www.sdiohio.com/Pages/Power Control.htm#Silicon Controlled Rectifiers (SCRs)
http://ww1.microchip.com/downloads/en/appnotes/00958a.pdf
http://www.nteinc.ca/specs/5500to5599/pdf/nte5511_13.pdf

Alright, moving on. I have ordered an Auber controller, a 25 amp (overkill) solid state relay, a thermocouple, a 4.5" wide 300 watt .5" inner diameter heater element with an integral thermocouple and an hagen 5 L/min aquarium air pump. Since I have linked to everything else at one point or another, here is the aquarium pump:

http://www.marinedepot.com/ps_ViewI...lies-Saltwater_Aquarium_Supplies~vendor~.html

I have to order a few more bits and pieces to make this pile of stuff a working test bench, but I should have all that sorted out by the end of next week. After I do some testing I will put up some pictures of what is sure to be a ridiculous looking test bench and whatever I find about it.

Just for the sake of trying to predict the future I am going to guess at what the results will be:

Since the 300 watt heater was the only thing this heater manufacturer had on the shelf, I had to take it. On a side note, I actually have a few suppliers working with me now. Hard earned win for sure. This guys coil heaters are much cheaper because he is small, and, thus, I am getting a 300 watt heater. He thought I would need something between 200 and 300 watts, so this will be an upper bound. Anyway, since I have a relatively high wattage heater (read: more mass to heat up), I should have a quick heatup time but a very slow reaction time. The slow reaction time will be all but guaranteed due to the temp controllers .5 second sampling time. We will see what happens! I think there is a lot for me to learn regardless of how good the setup is in the larger picture.

-skippy

 

[Hippie Dickie]

i was only suggesting the $150 AC power supply value if you want a decent amount of amps - say 20 amps or so. This amount of current is so the heater gets to vape temp fast. You can certainly do it with a 4 amp power supply - cost about $10, but it takes about 15 minutes to reach vape temp (400F) ... based on extensive testing.

i really like the 20 seconds to vape temp, which i can get with the 12 amps the batteries pump out with a 0.5 ohm nichrome wire heater coil.

i also like getting rid of the power cord. i spent the last 7 years vaping with an AC adapter and it was a hassle to move the vape around on my desk, knocking things over when i drag the power cord around. using battery power for the last 6 months or so has been very liberating.