BaKx (heating principle) inspired desktop vape

[CaleidosCope]

Hi.
Now that I'm the happy owner of a BaKx, the functionality, simplicity, elegance and functional principle of it just won't let me go. As I announced in the BaKx thread, I am still trying to make a personal copy of the BaKx - unfortunately I have little time for it and material-finding problems.
But here is a working and Inexpensive desktop version of the BaKx heating principle.
Kudos to Ralph.

- Test tube, glass, 48mm length, OD 16mm, ID 14mm
- Male NS14, OD 13mm, length may vary
- Welding rod, one piece of wood with two holes for the handle / immersion depth adjustment
- Coil, stretched, 16mm (the gaps can also be tightly wrapped with copper wire - better heat distribution)

Uses slightly higher temperatures than normal. I am currently at 280°C. IMPORTANT! let the heater rest for a few seconds after putting it on. Do not pull immediately.

Have Fun

https://imgur.com/mrC8DQS

https://imgur.com/CRSnK19

https://imgur.com/aYdRbxp

I was looking in case anyone else had a similar idea before me...
well, you know, me too now

Translated with www.DeepL.com/Translator (free version)

 

[highvaper]

Hi

Long time reader first time poster here - i have a collection starting with a digital volcano from many years ago which i never really used plus other shit vapes over the past 10 years or so.

I finally switched to vaping fulltime with a dynavap about a year ago. Since then i have had quite bad vas and acquired far too many with my daily driver being a tinymight2 but mixing it up with a screwball.

I have been looking at the various glass test tube type vapes i think all stemmed from the vaponic design - just not keen on the butane torch - the dynavap worked really well once i made a litte ih heater for it.

For some reason my builder itch started up the other week after missing out on the BAKx drop and began to think how to make a similar device. Im only on the initial plan but its very similar to you except i am using an induction heater instead of the coil.

So far i have only used what i have lying about but have put in an order for various steel wire/ribbons to mess with plus im planning on ordering a variety of test tubes and glass tubes to see how thickness and air gap between the outer and inner tube affects things.

@TommyDee has already been so welcoming and given me some decent food for thought.

But presenting my first attempt using a dynavap water adaptor + quartz 20mm insert which fits perfectly in the coil. The steel heater element is some non stainless stuff made from some pc casing so i hade some idea how it would perform (i know not the safest shit to use but over the years i have had a lot worse in my lungs).

https://imgur.com/Aks2gXq

https://imgur.com/njjjf8e

https://imgur.com/a/CNiz5Ed

Hopefully the images work not sure how to link properly yet.

There is a type-k thermocouple which is touching the heater element - when i had it inside the stem i had quite a bit of combustion as it was getting way too hot - i have found i need to pulse the ih rather than just blast it as the metal get hot very fast and takes a while to transfer the heat to the stem. I am going to add a pi pico to arrangement and get it to act as a pid to deal with regulating the temp as its quite hard to do manually.

Its not totally as planned as it doesnt get covered by the quarts cup all the way but the coil itself acts like a tube for the cold air to flow down and over the heating element before entering the tube so works like a convection + conduction vape nicely. The original plan was to have the wire wrapped around the out tube (just like yours with the normal heater) - i will be getting some more ih boards and coils to mess with to see how much wider i can make the coil to fit a an outer wire/ribbon wrapped tube inside so there is only glass in the airpath.

Once it has heated up it does retain the heat pretty well however it takes a while to get the heat into the glass - i think due to minimal surfact contact of the heater element as its really hard to bend the metal so its a tight fit - hopefully some 0.2mm stainless steel wire will work much better - as mentioned i will be trying some really thin ribbon as well which should wrap around the glass really easily.

 

[TommyDee]

You can tame the heater a little by removing one of the black capacitors.

If you want to use a high temp shrink tubing, look for PTFE shrink tubing. This minimizes outgassing.

 

[highvaper]

Thanks - that blue stuff has already been stripped off and getting some more thermocouples with glass fibre protection only - no need for the shrink wrap as i need the probe to be in direct contact with the metal - im hoping i can wrap the ribbon around it without shorting it out or if need be try and give it a little glass fibre insulation so its almost in direct contact.

Im going to get a few of the mini inductor circuits and coils to mess about with things like removing capacitors and making the coil diameter larger to accommodate wider a glass tube with wiring on the outside.

 

[CaleidosCope]

Oh wow. What a cool idea.
Hello highvaper, and hello TommyDee.

In the meantime, I have noticed that my system cools down incredibly quickly. That's why I've now filled the gaps in the coil with thick copper wire. This results in better heat transfer / heat storage and the temperature sensor works better. Now the PID needs to be set more aggressively. At the moment, when I draw, the temperature drops by 10-20°C (within a few seconds).
Because it is so small and so simple, every single factor has a dramatic effect on the result. Ralf has really built a small masterpiece with the BAKx. Hats off to him.
I can't wait to see how your idea develops.
I'll add two more pictures below. The first is a rough idea of how I could imagine the solution with an induction heater and the second is how I manipulated my coil.
Incidentally, I've also seen the variant where a quartz tube is jet flame heated and then serves as a heating head. I don't think you could even come close to fixing a temperature. But I'm sure it scorches well too. Every vape I own for now has a learning curve.

cheers

EDIT: One idea for getting the test-tube stuck in the metal tube: some rounds of aluminium foil between metal an glas.

https://imgur.com/a/dbBTgTL

https://imgur.com/a/Bml9tmH

 

[highvaper]

Thanks - i did think of the metal tube idea as well just hard to find one of the correct diameter to fit the glass perfectly hence using some wire wrapped around

Using wire would allows for easy adjustment to add a bit more wire on it or maybe in bands so there are gaps to see whats happening - maybe different configurations will work better depending on the material being vaped and just have different tubes to use.

Have just placed an order for a lot of bits including a 18mm and 16mm diameter test tubes (i was only going to get the 16mm ones but the delivery date on them was weeks away) - @CaleidosCope i can only find the smaller length ones like yours in boxes of 100 so went for 125mm length ones instead also i want a lip on them - i have a plan to perhaps use a cork with a grove cut into it to moderate airflow but had a better idea for the lipped tubes.

If you get some wood and countersink the test tube in it then in a similar fashion to the BAKx have the straw part working though a piece of wood with a channel in it - will keep the stem part centred in the test tube and allow for some kind of housing to hold the outer tube in the middle of the induction coil.

 

[TigoleBitties]

Hey all. In the same vein as the last few posts, I managed to get the Vaponic working with the iSpire wand as an induction heater. I had been trying steel wire wrapped around the outside but the best results came from the thread below (not my idea).

https://fuckcombustion.com/threads/vaponic-herbal-vaporizer.6052/post-1703548

It works really well but it's easy to combust. Sipping and testing for vapor while heating works well and I generally remove the Wand immediately upon sensing vapor due to the delay in thermal transfer from metal->glass. With a manual IH like the Wand and no controller, exact temps will never really be achieved so I hope your projects can achieve fine temperature regulation because all-glass vapor paths taste great.

I tried to use the Wand with the Terpedo from TRWW (larger vaponic) but couldn't find an appropriate metal sleeve, not to mention it was too large to fit completely in the Wand. The Wand might've been underpowered as well.

 

[highvaper]

@TigoleBitties thats great! I did think about getting a vaponic but they are just too small bowl wise for me - same goes for the dynavap.

I do think that getting the temps regulated is very important as the ih can get the metal really hot really fast - i do like the idea of a sort of induction version of the TM2 with some stainless steel helixed/spiraled staircased around the inner tube with the test tuber outer layer - allows for much smaller diameter outer tube and that should provide some protection for the ih coil.

I dont see how that is any different from most vapes which use the stainless steel heater elements so should be pretty safe with 316 and be a conductive + convective vape in one as you would draw the air over the stainless steel heater - rather than a wire it would be more of a coil i suppose so would be able to heat the air over a much longer distance depending on how you fashioned the metal.

No reason for me not to mess with both ideas - i have a couple of basically everything on the way so can build two versions one with the metal inside the the larger tube and one with the metal around the outer tube.

The main issue i see with the inner heater is attaching the thermocouple and how to deal with the wire - if its on the outer heater wont need to be moved as the outer tube would be more fixed i suspect.

A little sketch while bored in zoom meeting of how i was imagining the top part to allow for airflow adjustment

https://imgur.com/a/81zgj32

@CaleidosCope - just had a thought how to help increase your heat retention - get a wider longer outer tube - some stainless steel mesh and wrap it into a tube you can fit your inner glass - then put the mesh tube inside the big tube and fill the outer part with some glass balls or if your feeling flush some rubys.

Top it all off with a cork with a hole for the stem to go down and perhaps the edge of the mesh in place as well. I think cork can go to about 300C before you have issues.

 

[CaleidosCope]

@CaleidosCope - just had a thought how to help increase your heat retention - get a wider longer outer tube - some stainless steel mesh and wrap it into a tube you can fit your inner glass - then put the mesh tube inside the big tube and fill the outer part with some glass balls or if your feeling flush some rubys.

Top it all off with a cork with a hole for the stem to go down and perhaps the edge of the mesh in place as well. I think cork can go to about 300C before you have issues.

The sandwich idea is not bad. But it would need a huge heating coil. Or did I miss something?
Air intake IMHO (speaking of BAKx or my attempt) is not so important. You can influence that with draw speed, and how deep you adjust the bowl in the test tube. And surprisingly (Jerry mentioned it in the YT-Video with Troy) the hot spot is not all in... more in the middle.

 

[highvaper]

The sandwich idea is not bad. But it would need a huge heating coil. Or did I miss something?

As long as the coil can wrap around it and pump in more heat than it looses while heating up you should be all good - may take a while to get up to temp though.

The balls are there just for heat reserve like a ball vape - with the screwball i need to leave it on for a good 5 mins before rubies inside the injector get up to temperature and that has a massive heating element/coil


Thanks for the airtake info on the BAKx - may have gone down an unneeded rabit hole there - never actually tried a BAKx and was just assuming you needed to restrict the draw somehow - i suppose just by having a seal with the top part over the tube you can just tilt/hinge it slightly to let in as much air as you want.

 

[highvaper]

While i await my deliveries I have been doing some research and looking at some code to control it all - looks like the glass bits may take a while to arrive but I only need a few bits more of the electronic parts to make a start on the pid/temp control stuff.

Seems there are some hard limits - the thermocouple sensor controller will take about 1/3 of a second to return a value so that would be the finest resolution possible if the K-Type sensor reacted to the temperature change with no delay. There is also some thermal delay so suspect the closest reading to the heater element real temperature will be about 0.5 to 1 second behind the real value at a guesstimate.

I had a thought of maybe using 2 sensors at the same time and interleaving the readings - that would give double the resolution and some redundancy but after some research on switching the induction heater on and off really fast i dont think the higher temperature reading resolution is required - plus there may be some difference between the sensors temp reading at a stable temp so that would need to be compensated for if too much but i dont think a few degree C will matter in this case.

The issue with the induction heater and pulsing it on and off to regulate the amount of induction may be an issue if i try to do it really quickly (aka pulse width modulation for techie speak) - from what i have gathered i do not think it will work as depending how fast its done it may mess with how the ZVS circuit works also it may blow the mosfet switch. Hence the need for higher resolution temperature reading may not be needed and switching the induction coil on/off every 0.5 of a second will be a limit.

There is a possibility of using a DC-DC convertor and adjusting the voltage applied to the coil instead - i quite like this idea but from my initial searches any component is going to be quite pricey, bulky and not sure how easy to get one which can be easily controlled by a micro controller which can handle the current needed.

I have had some other thoughts like how to protect the coil in case it gets hit by the hot element like maybe encase in ceramic of some kind but tbh at the moment the goal is to get a simple set of off the shelf parts together so anyone can replicate this easily without any specialist tools or equipment - like a kiln or glassblowing setup.

Also checked out the non contact thermometers - they wont work for stuff inside the big tube but maybe useful for reading the temperature of the glass outer tube - they are a bit pricey and also are a bit slow like 1/3 of a second to take a reading as well but once I have something up and running i may mess about with one and see if they are of use - but again that is for another time along with integrating some kind of battery setup as at the moment im using a chunky mains to 12v 10a power brick so have a nice constant power source to do tests with.

Other point i didnt realise is that if the heater element is on the outer tube then it doesnt need to be 316/316L stainless steel so just some normal steel wire should be easier to source and cheaper plus easier to work with - not looking forward to messing with the 316 wire/ribbon and not sure how well the induction will work with it now so may have to use something like 304 instead - i realise the 316L is lower carbon so at high temps is safer but if the temp is being kept under 400C im not actually too worried about using the 304.

I suppose if this doesnt work out for vaping i should still have a much simpler way to control temperature for purging bho/qwiso or maybe even decarbing small amounts.

 

[highvaper]

Initial setup of control stuff pretty much done - pi pico and other bits arrived yesterday afternoon - took a hr or so to get connected and familiar with it as never used a proper microcontroller before but its so nice and easy to develop/prototype with that by the time i went to bed i had finished most of it.

All of the code i have done by timers or irqs when buttons are pushed so no main loop and its possible to inspect whats happening really easily - again blown away at how easy and FAST it is to get something going with one of these little things.

Currently its using the temperature sensor built into the pi controller chip - its keeping its self warm by turning on/off an led controlled by the pid - all i need to do is now remove the led and connect the mosfet in its place and get the temperature from the thermocouple instead of the pi chip.

https://imgur.com/KdNYBfx

The only thing missing is the MAX6675 K Type Temperature Sensor Module to connect the thermocouple to the micro controller and we should be ready to try out a pid controlled induction heater.

Even the test tubes arrived - the biggest 16mm diameter is too small - i was hoping to get my tinymight stem in it but no chance - i think the min diameter of the tube will need to be closer to about 30mm. So that means messing with the coil - as the coil wire needs to be a fixed length for the mini zsf cuicuit i need to reduce the number of turns so did a quick calculation on the assumption the length of the wire is about 70mm and diameter is 2mm (can anyone confirm the length?)

diameter = length / (pi x number of turns)

coil height = number of turns x diameter

no turns diameter coil height 1​ 22.3​ 0.2​ 2​ 11.1​ 0.4​ 3​ 7.4​ 0.6​ 4​ 5.6​ 0.8​ 5​ 4.5​ 1​ 6​ 3.7​ 1.2​ 7​ 3.2​ 1.4​ 8​ 2.8​ 1.6​ 9​ 2.5​ 1.8​ 10​ 2.2​ 2​ 11​ 2.0​ 2.2​ 12​ 1.9​ 2.4​ 13​ 1.7​ 2.6​ 14​ 1.6​ 2.8​ 15​ 1.5​ 3​

So looking at about 1.5cm coil height when no air gap - currently i have about 0.2cm gap between the wire and its quite aggressive so maybe it will be ok with the wider tubes. Maybe worth looking at other coil shapes as perhaps not having a coil shape the tube sits in (which tbh seems the most sensible) but there are other shaped coils which are used from having a quick read.

Spend so far is minimal and all components are easy enough to get.

 

[highvaper]

I was itching to get the coil and micro controller working together and remembered I had some DS18S20 1-wire thermometers so decided to see if I could get a low temp test working. Again it only took under and hour to get it all wired up and coded - the tests took much longer. For the testing I also attached a thermocouple to the setup so i had an independent reading to check.

Some pics of the whole setup.

https://imgur.com/a/fKvVKpS

In action - as you can see the metal glowing when doing the initial heat up from cold.

https://imgur.com/a/42jDLYp

A little burning to the cork mat it was sitting on - and thats with the quarts banger insert in the bottom of the coil



First test was when i had the "power threshold" set to 9 - the PID function will output a value (power in this case) between a given set range - useful for analogue or if you are going to use something like pwm to regulate a motor so similar - for the heater im using a range of 1 to 10 and have to decide at what point to switch on/off the heater.

https://imgur.com/a/gfAyjqf

Test where the power threshold set to 5 - i think the sensors moved in the tube during the heat up time hence the gradient increasing after about 100 secs. Not sure why it overshot so much compared to when the power was at 9 or 1 - this is where the art in tuning the initial PID values come into play i believe.

https://imgur.com/a/AxlUEur

And a final one where the setpoint temp was adjusted higher and lower and power at 1

https://imgur.com/a/O8WOVoU

The PID performs and self tunes nicely i think considering the DS18S20 is very slow - it takes about 0.7 seconds to get a temperature reading but what is worse is it is enclosed in plastic which takes a while to respond to any temperature change, like a few seconds or more and with the induction heater thats a loooonnnnnngggg time. The thermocouple attached to the DS18S20 in the test was much faster at updating the multi meter so im hoping it will work as expected.

Bit stuck at this point until i get the last component for the thermocouple link to the micro controller but I do have a couple of spare zvs circuits and coils so may try and make a 3cm wide coil and see how it works.

 

[CaleidosCope]

Wow! You're taking this seriously. Are you sure you want to roll this out "under or in" my thread? You should start your own! Cool stuff!
Good progress. I want to see more.

 

[highvaper]

Glad to know this is of interest to other people. Im hoping once i prove the initial idea is a runner other people will give it a go. There are so many tunables and other people trying stuff out would be great maybe ill start a new thread once the initial list of needed bit and pieces, I hope you dont mind me using yours for the experiments?


Speaking of experiments, they continued today with a basic 30mm coil and an old glass bho blasting tube with the larger 160mm test tube and some wire.

https://imgur.com/a/XTXYKBO

I have added a tiny extension to the coil to make it easy to change to test different configurations. However I did notice a little bit of smoke coming from the coil extension wire when it was on for about 60 secs so decided to keep an eye on its temperature with the thermocouple -will be sensible to add a extra thermocouple sensor to the coil to back off heating when its temperature rises to fast or is too high.

Once the glass is up to temperature all is fine as it only gets turned on for a few seconds and the wire temperature settled around 30 when the tube temperature was at 60 and even lower when there was more wire around the inner tube.


Graph for 1 wire

https://imgur.com/a/F508juN

Graph for 2 wire

https://imgur.com/a/eOqb9Od

The combination of the extra metal and slow sensor makes it shoot so far past the setpoint that it is better to heat up manually for a few secs before turning on the PID to keep it at the desired temperature but with the faster sensor i think the issue will be much less. Also the extra thick outer tube really keeps the heat in nicely unfortunately not a standard test tube size - the closest i can find are some 30mm outer diameter 165mm long ones which i think will work.

I now understand that it is impossible to stop the overshoot on the initial heat-up with the PID if using the standard way to update the proportional via the error, i tested using a method where its calculated on the measurement instead but the heater never gets switched on long enough for it to get up to heat - its a much gentler heating but think the slowness of the sensor just messes up the maths and need to try again when the temperature reading resolution is higher and closer to the true value.

Also tried to unsolder one of the capacitors as @TommyDee has suggested but my pre RoHS soldering iron just doesnt cut the mustard and couldnt get it to melt the solder - i amused myself by trying to use a screw driver heated in another induction heater coil to do it but it didnt work. I had a chuckle when looking at various soldering stations as they are all pretty much a PID - they really are everywhere.

 

[CaleidosCope]

they are all pretty much a PID - they really are everywhere.

Yes they are

... have you tried temps in direction 200-230°C?

And for your smoke problem... I used the same wire as for the coil. Or way thicker wire. But we are talking about frequencies so I don't know if that helps.

 

[TommyDee]

My iron is a 20/40 watt RadShack special with a 1/8" chisel tip. Solders 12 gauge coil wire to the plane with ease.

 

[Hippie Dickie]

@highvaper - i have been using the MAX6675 for my design. i love it. finding it was totally unexpected, it was so perfect for my need.

i went with a PIC 12F683 instead of Arduino - one was on a PWM board i found on eBay and is perfect for my design. i finally evolved a PID algorithm, table based for coefficients, that is very stable regardless of air flow volume. the control program is sampling the MAX 3 times per second - as i recall the read rate is 0.22 seconds, so a little margin. using a 100 msec loop, reading the MAX every 3rd loop.

for startup, i go full power until a threshold temperature is reached, then go to PID algorithm - a bit of undershoot, so takes an extra 20 seconds to stabilize at setpoint.

i use a k-type 0.010" bare, plugged into the MAX6675, against the middle of the heater tube under the ribbon. i use polyimide tubing to insulate the k-type from the heater ribbon - no melting point - i still am amazed by that material.

i use a 1/8" wide nichrome 80 ribbon - 13" wrapped around the outside of 15mm test tube. all glass, only glass, airflow.

my code is assembler but i am happy to share. lots of comments. i will eventually put it on github.

if i can ever get back to this project (i've been mesmerized by biology for the last 4 years), i want to use AI to tune the PID coefficients. i figure if i show it several runs with different table values it should be able to zero in on the correct settings. my heater heats at 20°F per second and cools at 2°F per second - roughly.

 

[highvaper]

@TommyDee cheers i have decided to treat myself and ordered one of those pen like ones plus a set of 510 heads in case i need extra heat.

@Hippie Dickie wow - your build is class thanks for the link! Also thanks so for confirming my suspicion re the thermocouple being fast enough - im using micopython on a pi pico board and still cant believe that you can prototype something so fast, I have used the simple-pid libary to do the heavy lifting for me and not had to actually get my head fully round the maths. I did also think about using my results with AI and get it to help me figure out the tuning.

@CaleidosCope just been doing some tests without the controller to see how the 30mm coil performs with just me manually switching on and off with a thermocouple - plus a little something in the bottom of the tube - unfortunately my coil extensions were the weak point with the cable insulation and plastic white connectors and blue connectors on the zvs board melting and only hitting about 200C inside the tube.

I think my windings arent great and need to be closer together. Also if the heating wire wrapped around the tube is touching rather than having an air gap between winds as the current i think will build up more in a more solid lump of metal either way im now not so sure the little zvs are going to be able to do a 30mm coil safely - i have some 30mm and 24mm test tubes on the way and will get some more coil wire to mess with as unwinding and winding up the existing ones its really hard to get them uniform. Note for anyone else rebuilding a coil - i checked and the coils are are 28" in length so my 70cm estimate was pretty good.


Just did a quick test with a 8 turn coil and some qwiso - seems to do the trick - the main issue is the inner staw type tube i have is closed at the bottom so not the best airflow.

https://imgur.com/a/xTI9hr0

I think my dogey extensions may have caused the heating issue as the coil bits near the board arent too hot.

Have had the idea to add an extra induction coil into the setup so have one above the other - i will get the controller to switch between them so the magnetic fields dont interfere with each other and the power draw will remain the same but a large amount of metal will get heated and the induction circuits will only be on for 1/2 the time and not get as hot plus should speed up the heating of the tube. Also will allow the coil to be tighter so should heat should be more concentrated over a smaller area.

 

[highvaper]

Well work cut in to the experimentation today but i did get 2 zvs coils lines up next to each other and have the code to switch on/off the heaters

I decided to get the code going first and finished off a really nice class

class InductionHeater(object):
    def __init__(self, coil_pins=None, timer=None):
        self.coil_pins = coil_pins
        self.coils = []
        self.switched_on_coil = None
        self.switch_coil_period = 990 # Time between switching coils
        self.timer = timer # Store the external timer
        self.timer_running = False # Flag to track if the timer is running
        self.coils_init()

    def coils_init(self):
        if len(self.coil_pins) == 0:
            raise ValueError('No coils defined')
        coil_no = 0
        for coil_pin in self.coil_pins:
            self.coils.append(Pin(coil_pin, Pin.OUT))
            self.coils[coil_no].off()
            coil_no += 1

    def on(self):
        if self.coils:
            self.coils[0].on()
            self.switched_on_coil = 0
            # Initialize the timer if it's not already running
            if not self.timer_running:
                self.timer.init(period=self.switch_coil_period, mode=Timer.PERIODIC, callback=self.change_coil)
                self.timer_running = True

    def off(self):
        for coil in self.coils:
            coil.off()
        self.switched_on_coil = None
        # Deinitialize the timer if it's running
        if self.timer_running:
            self.timer.deinit()
            self.timer_running = False

    def change_coil(self, timer):
        for coil in self.coils: # Ensure all heaters are off
            coil.off()
        if self.switched_on_coil is not None:
            self.coils[self.switched_on_coil].off()
            self.switched_on_coil = (self.switched_on_coil + 1) % len(self.coils)
            self.coils[self.switched_on_coil].on()
        else:
            self.coils[0].on()
            self.switched_on_coil = 0
        print(self.switched_on_coil)

    def is_on(self): # Returns True if the heater is on, False otherwise.
        return self.switched_on_coil is not None

However when i came to wire up and actually test the two coils together i hit an unexpected issue

https://imgur.com/a/B7DqB0i

I had both connected to the power and switched on one of them but the other one turned on as well - i was wtf - so double/triple checked my wiring only to realise the first coil was powering the second one!

So now not 100% sure what to do - i think i may just continue with 2 coils and see what happens - i will setup measurement of temperatures on all coils to see how it affects things. Maybe a copper sheet with a hole in will reduce the effects between the coils.

Mmmmm and here i was thinking how nice and even the heating was going to be over a large surface area - maybe i do need to look at other coil shapes which can be place near to each other without causing the same effect.


A cut up can and some time later:

https://imgur.com/a/w9WDghD

And in action - if you look closely you can see the PID values updating

https://imgur.com/a/ISpqHn7

 

[highvaper]

Heating testing with various metals - i got some stainless steel 316L strip wire i think the same the TM2 uses in its heater - a nightmare to work with but managed to wind some around my glass inner tube and get it to stay there which was the hard part - unfortunately it got hot and i droped it so the end broke but in a good place so i now have a glass straw.

https://imgur.com/a/T0ICx7u

i could only get the temp up to about 160 when measuring the outer layer but inside the tube it got to about 180.

i did a test with the thin non stainless steel wire in the bottom of the tube and it got to about 250C a similar test with the SS got to 150C - so having a SS heater inside the tube i think may be a non-runner which is nice to know and also defeats the point of pure glass air path. Well at least i have about 50m of spare tm coil now.

One thing i noticed is the bigger 8 turn coils got the SS to the same temp as the standard 11 turn one - so maybe my not so perfect coils are ok - btw if anyone is trying to redo a coil boil some water and dunk it in every now and then to keep the copper warm as its much easier.

 

[highvaper]

Well i had a thought when going to bed i had to give a quick test to see if i could make a very basic heated tube with the SS and a mod box. I dont know much about custom coils and hit an issue with too long wire and to higher resistance for my little mod box. But hacked something together in about 30 mins.

https://imgur.com/a/Hgujgx6

I managed to get temps up to about 130 when the ribbon was wrapped better and touching the glass compared to the video - maybe with a better mod and careful wiring to it may be possible to make one with the most basic materials - SS wire and a dead coil head plus some heat shrink stuff.

https://imgur.com/a/A7S4etB

Just a bit of food for thought but there is a lot of fiddling to do i suspect to get a mod + ss wrap up to temps and even with tcr isnt going to regulate temps as well as a PID.

Very seful calculator: https://vapinghardware.com/calculators/coil-wrap-calculator/

 

[CaleidosCope]

@TommyDee
While we're on the subject... Do you have any experience with extending the coil? I'm thinking of a 30-50 cm long extension cable. Would that be possible?

 

[highvaper]

I dont think it is possible to increase the length of the coil wire in the circuit with out adjusting other components as there is an oscillation back and forth so any change in the coil length will mess with that.

The larger tubes arrive 30mm and 24mm outer diameters - the 24 is a great size for the 8 winding coil and when inserted my coils look pretty professional

https://imgur.com/a/rRcD9Rf

The above pic was when i did a test with some about 1 cm wide pc casing wrapped around a smaller test tube. Wasnt a problem getting up to needed temps - i used the controller to flip between the heaters - i have a watt meter and it was only pulling about 30W per coil so i went for it and fired them up at the same time to see what would happen - all good power draw went to 60w and temps zoomed up even faster and the coils are not getting very hot at all.

So i think i comes down to the metal element being heated and that there needs to be a decent chunk - one benefit is once it got up to over 200 and i switched stuff off the heat was retained for ages.

The build is looking positive - if only those thermocouple controllers would turn up now and the 11mm x 15cm glass straws - i forgot some rotary dials turned up which i think will be a lot nicer to adjust the temp with - plus if you push it then it can act as a button/switch so if i make a little menu you can scroll through and select with the button - think perhaps of pre saved settings ...


Well a few hrs later and rotary encoder working and updating the desired temp - i do need to add some assertions and error checking in the code but for the time being its pretty stable and have left it running over night without any hiccups.

 

[TommyDee]

@highvaper - coil wire impedance can be modified with limitations. If you are staying with the 12 awg magnet wire, it is pretty easy: The stock coil is 33" for 3S operation (12V). The stock coil is 10 turns; This equates to approximately 1V/turn, or 10 watts increase for each turn removed.

By the same token, you could go 22" for 2S operation. Haven't testing this 2S arrangement but the coil wire length determines the current draw for any specific cap you put in the coil. Tweaking a good coil by one turn is perfectly fine. Just know it will couple harder with less wire length.