Our vaporizer is on the marginal side size-wise. So a bigger version would be easier to make with all the holes and stuff: 

•  A wood piece of 38x58x105mm (or even bigger).
  
•  20/21mm outer diameter glass test tubes (19-20mm inner diameter).
•  A 16-18mm aluminum smooth rod, 60mm long.
  
•  A 40W heating element.

The easiest way to start with a bigger design is the 16-18mm smooth rod. Drilling a 9,5mm or even a 10mm hole on this rod is quite easy, as you have a 3mm margin on each side.

The same thing goes for the wood. A 28-30mm hole will give you ample space to place the 20/21mm test tube and even more ample space to create a nice thick insulation. The more insulation is always better as you lose less heat to the outside environment.

In this configuration, using a  40W heating element is a better option as the whole heating surface is bigger and at 7,6V it will draw 2A.

Fine tuning the temperature

The whole design rests on the idea that the micro controller can regulate the temperature through the thermistor by turning on and off the heating element. But there are margins of errors in this process. Errors that to our experience are not important. We will list them though:

1) the aluminum heatsink is 5cm long with the heating element on the bottom. The thermistor in the middle while the straw is sucking air through the top. So there is a temperature difference between where the thermistor rests and the 9,5mm hole on the top. According to the measurements we made this difference is usually around 4-7 degrees C. So we have to calculate that in our target temperature.

2) the microcontroller reports the temperature by looking at a table where the values reported by the ADC (0-1023) are translated to human readable degrees C. This table was generated using the reprap thermistor calculator found here. But both the thermistor and the 4,7KΩ resistance have margins of errors (1%) and this adds up to the error margin problem.

3) The ADC table by itself is based on the so called beta of the thermistor, a value you can find on the datasheet of the thermistor. This beta value is usually calculated on the temperature range of 25/85C. The typical vaporizer temperatures on the other hand are quite higher. So the beta is not so precise and adds up the margins of error.

These are the bad news. The good news on the other hand are that:

a) all those errors don't mean much. Actually the vaporizing temperature of each herb is only a value we read in some aromatotherapy book. This value corresponds to a specific moisture content, specific type of herb and many times also the area the herbs come from play a role on the vaporizing properties. So between the lab tested temperature and our real life experience, there is a wide margin of "error".

b) You can hack and change it anytime you want. The vaporizer sketch on the arduino has 3 different temperature sets. Low Med High. These can be changed according to your will and needs and preferences. After all this is all about hacking and tuning the vaporizer to your needs and not some black box some company sold you.

Some of our beta testers preferred to actually see some white vapor coming out of their mouths (mostly those who are already smokers), while others (like me for example) cough when even the smallest amount of white vapor is present. Some may prefer to set the low value for one herb while setting the high value for some other herb. So experiment and play around if you want, or just set it and forget it, if thats your style. My personal 2cents about the issue are, don't be so anal about it. There is no perfect temperature that unlocks the gates of heaven.

Which comes to the part of the temperature potentiometer itself. The potentiometer can actually have 1023 different readings, so in theory you can have 1023 different set temperatures on this vaporizer. We elected to have only three. As you turn the potentiometer counterclockwise: The first third is LOW, the second third is MED, the the last third HIGH. Some may prefer to have even more set temperatures and thats ok. Its fairly easy and straightforward to add LOW1 LOW2 LOW3 etc on the sketch The reason we didnt do it was simplicity.

As the old joke goes. A man with a watch knows the time. A man with two watches is never sure. My first vaporizer was a vapolution I bought some years ago. It was a fairly nice device with a big knob on the bottom where you set the temperature through some analogue circuicity. Well I have to admit it was a hell to tune it. Because the difference between setting the knob on 12o clock and 1o clock was the difference between coughing and running for water or not.

And then some friend comes along and believes thats too low a temperature and kranks up the "volume". Oups all your experiments are gone, you are back on step one.

Yes it gave you more "options" and more "range". But in reality it gave me more frustration. So when we started designing the Lion,  with its nice arduino controlled temperature, we wanted something less tricky. So for my personal vaporizer, I found the temp I like and marked it medium and then gave some more degrees for my smoker friends and set it on HIGH. And everybody's happy.

So here is how to fine tune the temperature. Set a temperature on the arduino sketch. Upload the sketch on the arduino and open the serial monitor. On the serial monitor you will see the set temperature and the current temperature. Now you need some external reference. A cooking thermometer can act as one. Most cooking thermometers have a probe that you can stick inside the aluminum heatsink. When the vaporizer hits the set temperature, measure the temperature on the cooking thermometer. Wait for a minute or two for both temperature to stabilize. You will see a difference. This is the actual difference between temperature on the thermistor and temperature on the top of the heatsink. But actually this is just a reference. Because you are not sure if the cooking thermometer is more precise than your thermistor.  Make a choice and set a new temp on the arduino sketch if you dont like the current choice.

Spend the next 5 hours arguing with your friends and family about the CORRECT temperature (I dont want to brag I told you so).

.

.

Actually personalize your vaporizer, using the skills you are good at. You dont have to have our 3d printed case. You can design your own, or you can make a case entirely out of wood.  We can only give you some guidance about some sane stuff and from then on use your imagination and please send us a picture and instructions of your design.

So the guidelines are more or less those.

• Try not to place the batteries close to the heating element. Batteries dont like heat.
• Try to stabilze everything inside as a portable vaporizer means a lot of moving and shaking.
• Try to keep cables insulated so there is no danger of a short circuit.
• Try to use closer to nature elements, materials that people use for thousands of years (like beer). You dont want to breath funny chemicals.
• Too much space is better than too little. That comes from bittersweet experience.

Ok and here comes some picture porn.

Leather cover (need to finish my laser engraver).

heating up

Ready

The only apple device we have is an old laptop charger used as power supply

The first hippier portable version. 

T. did create an alternative base, more forgiving with mis-aligned holes. (the part is named alternative desktop base.stl). The style is no-nonsense minimalism

 D. used also the alternative desktop base but decided  to go with a more fluid style

P. is a master wood worker so the finishing and quality of the wood piece is salivating. He also added a cover for the more fragile glass part that protrudes.

That was our first breadboard prototype.  Pretty flimsy but it was a proof of concept mostly. Meaning that you can make a vaporizer that's working. And it worked, but its success was also its demise. After so many people wanted to beta test it, the cables started breaking down. So it was apparent that some kind of case was needed (duh). The setting was also not portable as we havent found yet the elegant solution of the 3pdt switches.

This is our first naked case. And actually the first portable vaporizer we made. We elected for a bigger piece of wood as most of the beta testers (ie our friends) were holding the vaporizer not as a bottle of soda (our first thought) but as a flask. So we went for the flask (ie more rectangular) type of wood. The thermistor cables were also coming out of the wood the cables running down to the 3d printed box. And there was also one more hole were the fixing screw was fixing the glass the heatsik and the wood in place. That created a less than pleasing aesthetic result which we tried to cover by using the blue thread as you can see. The blue thread was also serving as an insulator as the thinner parts of the wood were becoming warm to the touch after prolonged use.  

One more problem was that the 3d printed case was a bit constrained. Well actually it was damn too small. On FreeCad everything looked perfect, but in real life, the cables were longer, the case door had to be forced to close (hence the duct tape) and the hinges were the wood screws had to go, were not accessible by a screwdriver after all the electronics were in. Hot glue solved this problem (hot glue and a dremel can solve ANY problem).

Well it worked quite well and it is still working but there was space for more improvements.

One of the improvements was actually to cloth the whole damn thing. A striped pantyhose was cut and placed by k on the second vaporizer we made (no photos for the moment sorry), and then m knitted a small glove for the first (pink) vaporizer. This pretty much also solved the whole "issue" of the warm wood (pleasant for the winter but unpleasant for the summer) ..

This is the current portable version. The wood is screwed on the door which makes life easier and convenient. The thermistor cables are running on the inside (thanks to a suggestion from R) and the setting screw doesn't need to go through the wood. The whole insulation on the glass makes a snug fit in the wood.

The 3d printed case is now wider which means more space for the electronics. The batteries are placed further away and there is even space for the 1/3 of the wood to fit inside. So the whole device became wider but lower.

The electronics board was redesigned (more rectangular than square) and fits under the wood without protruding much. So now the wood, heating chamber electronics combo rests on the inside of door making everything accessible, repairable and hackable.

This was the first desktop vaporizer so there is room for improvements. The 3d printed front and bottom panels were fixed with hot glue, but the force applied to the front panel is greater than the hotglue solution. So a skirt comes to the rescue. The front panel will have an outer skirt to actually press against the wood, so no amount of finger force and unset it. Same goes for the bottom panel, were also two screw holes were placed in order to have better access to the electronics compartment.