Anyone had a go at making an atomiser?

[MrFog]

Might be a nice little project for someone like trog and co. who has the knowledge. I mean afterall its only a coil of wire, all we are doing is heating a liquid rather than burning it.

I can see it now; "The Spanner by trog". It could run off the mains with a bit of twin and earth for the coil. Killer throat hit

Seriously though, would it be difficult ?

 

[jigtg]

Yes, I can almost imagine trogs shopping list:
-large bucket
-2 gallons of e-liquid
-80 amp arc welding power supply
-2 meters of wire rope

But seriously, why bother when you can take a ruyan disposable or health cigar and wind your coil there?

 

[dc2k08]

would love to but dont have the skillz. was looking to buy a panel heater today and the price on the panel heater with 200% more parts was cheaper than the price of a recently purchased e-cig. soo the sooner i figure out the better. like you say, what's so difficult? its a hot wire, covered in steel wool.

 

[trog100]

he he he..

i dont come in here often.. must have been my ears burning...

but an atomizer is very very simple.. just tooo small and fiddly for my big troll hands to mess with.. little chinese ones do it better..

trog

 

[kmk1018]

Well, i'm working on a proof-of-concept one. Not for an actual cig, just something to test an idea. Maybe i could use it in an e-hookah...?

 

[SuperSteph]

Sorry I'm just throwing things out here, but you should be able to use nichrome wire wrapped around a porous ceramic core, with the ceramic core that inserts itself into the cartridge. Ceramics can withstand much higher temperatures then any fiber, and if it's porous it will act as a wick.
Other ideas include using a thermocouple to provide negative feedback on the atomizer to provide precise temperature control to prevent burning out the element. or precise current control to the element may produce similar results, however if i remember correctly, nichrome wire reduces resistance as it heats up, and could cause a cascading effect.
However I do believe ceramics would be the solution to one issue, and a regulator of some sort to prevent it from burning out. the problem is that a regulator would take up more power, so a redesign of the battery system may be necessary. For that I would recommend a battery of supercaps. High current, long life, and charges in seconds-minuites vs hours. The problem is their capacity does not match with a battery, but their energy density is really good. The solution would be to charge the pack after or before each use using a portable charger.

 

[dazzer1975]

if its just the wick that goes.. hardens over time due to heat, and after looking at the pictures of an exposed wick and coil wouldnt it just be possible to wip out the wick and bang another one in.

ok, it would be fiddly but with some needle nose pliers, some modellers tweezers im sure it's doable.

at least for the first stage where the vape production drops off

 

[trog100]

if its just the wick that goes.. hardens over time due to heat, and after looking at the pictures of an exposed wick and coil wouldnt it just be possible to wip out the wick and bang another one in.

ok, it would be fiddly but with some needle nose pliers, some modellers tweezers im sure it's doable.

at least for the first stage where the vape production drops off

its a lot easier to bung a new one in and let the chinese do the rest... he he

trog

 

[kmk1018]

Sorry I'm just throwing things out here, but you should be able to use nichrome wire wrapped around a porous ceramic core, with the ceramic core that inserts itself into the cartridge. Ceramics can withstand much higher temperatures then any fiber, and if it's porous it will act as a wick.
Other ideas include using a thermocouple to provide negative feedback on the atomizer to provide precise temperature control to prevent burning out the element. or precise current control to the element may produce similar results, however if i remember correctly, nichrome wire reduces resistance as it heats up, and could cause a cascading effect.
However I do believe ceramics would be the solution to one issue, and a regulator of some sort to prevent it from burning out. the problem is that a regulator would take up more power, so a redesign of the battery system may be necessary. For that I would recommend a battery of supercaps. High current, long life, and charges in seconds-minuites vs hours. The problem is their capacity does not match with a battery, but their energy density is really good. The solution would be to charge the pack after or before each use using a portable charger.

A) The ceramic "wick" would have to be really porous in order to provide enough liquid. I've messed with ceramics in the past, and have never seen one that would be porous enough, though I was using ceramics in a different application (dielectrics...)
B) Yes, nichrome changes resistance, though using off-the-shelf components to build a control system would greatly increase the size of the battery. Using a programmed microcontroller would be easier, though it would require some interface circuitry, but could also lead to customization...?

C) Burning out the heating coil isn't much of a concern. It's burning the wick that is the problem.

D) A capacitor array would work, but considering the cost, the fact a portable charger is needed and that you could only get a few good puffs before the charge drops too much, that may be limiting. But those first few puffs would be damn good because the current is STRONG!!

 

[SuperSteph]

I'd need to experiment with ceramics but you could get a ceramic cylinder about 3-4mm diameter and drill down the middle with a 0.5mm bit to act as a conduit. We all agree, the wick has gotta go.

As for controlling the circuitry, I'd suggest an Atmel ATtiny13a. Very small size. Add in a driver like a mosfet to power the atomizer, and use the ADC to measure current draw through a 0.1 ohm sense resistor. The other method would be to use a low dropout LM317 voltage regulator in constant current mode, however that would be more wasteful as the lm317 is inefficient. Or, the other method is to use a 555 timer in monostable mode to provide a cutoff of how long the atomizer should be on. I still think a thermocouple might be the best way, but like you said it might be a non issue if the coil doesn't burn itself out.

The supercap might work, though I just did extensive research and you'd need at minimum a 5 ferad, which i can't find at a reasonable price or size.
So for power it seems your best bet is to use off the shelf lithium batteries.
I've already ordered some Nicrome wire, and I'm thinking I'll use a flashlight for the housing, just need to find out how to design the atomizer and the cartridge.

 

[SMILIN]

Good luck, we really need to bring these up a few notches

 

[SuperSteph]

I have most of the parts I need ordered. Maglite Solitare, 3.6v aaa 500mAh Rechargables, Nicrome wire. I need to figure out how to rig a switch, and design an atomizer and cartridge. I'm unimpressed with the performance of the "Suck" switch So I'm thinking that a contact switch, like those seen on those lamps that you could touch anywhere to turn on. press lips to mouth piece, atomizer turns on.

 

[Josiah]

I have most of the parts I need ordered. Maglite Solitare, 3.6v aaa 500mAh Rechargables, Nicrome wire. I need to figure out how to rig a switch, and design an atomizer and cartridge. I'm unimpressed with the performance of the "Suck" switch So I'm thinking that a contact switch, like those seen on those lamps that you could touch anywhere to turn on. press lips to mouth piece, atomizer turns on.

That's a nice idea. What gauge nichrome did you buy, and how did you pick it? I'm a bit more on the mechanical side than electronic (something I plan on changing) so had problems finding the right wire. I do, however, have an atomizer idea I want to try.

 

[SuperSteph]

I bought 42ga nichrome wire, considering that it was 82ohms a foot, and i would use maybe 2 inches = 13 ohms = 277mA. Considering I purchased a 500mAh battery it means roughly 2 hours of nonstop (continuious) use which equates to about 4-5 hours nonstop use, or 24x 10 minuite vap breaks, at 1 watt power usage. I couldn't tell you how many watts are needed to get the right temp, thats going to be trial and error. Temp is a calculation of surface area vs watts and i haven't found the calculations for that yet.
Search google for an Ohms law calculator to figure everything out yourself.
I'm also looking up things like Insulated wire, which will allow for a more complex atomizer design without risk of shorting the wire. Other ideas include encasing the wire in a ceramic (maybe epoxy depending on toxicity reports) to keep out impurities and for electrical isolation. That will alow encapsulating the element in steel wool to aid in wicking abilities.

 

[Josiah]

You're a good man. That was mostly over my head, sadly. Pulled the electronics book off the bookshelf and I'll read it until my pen gets here (hopefully Saturday).

 

[SuperSteph]

Ok So i did more research, and got my trusty multimeter out. The atomizer in my 901 is 3.1 ohms. The battery puts out 3.7v. that puts the power output of the atomizer at 4.4 watts, significantly more then i guesstimated.
so to get the nichrome wire at that resistance to put out ~ 4 watts power we need to shorten it... a lot. for 4 watt output, we enter the formula: Current=Watts/Volts. I=4/3.7=1.081amps Ohms=volts^2/watts=3.4225ohms
so we need a resistance of 3.4225 in the wire. so to get that length we have 82ohm/12 inches. we need to convert that to 3.4225/X (X is the length in inches. that's just some fun algebra. 82*x = 12 * 3.4225. x = 41.07/82 = 0.5inches. We'll need .5 inches of 82ohm per foot at 3.7v power supply to get 4 watt output. .5 inches may be long enough for the wire and the power density will be good. If i wanted something longer i'd need to find some wire at a thicker gauge, and thus lower resistance which means it would need to be longer to meet the same 3.4225 ohms.
now with 1.08 amps with a 500mah battery we'd get 30 minuites (1800 seconds) of continuous running. We'll assume that you'd take 5 second puffs= 360 puffs. Now assume 10 seconds between puffs=3600 resting seconds. add that to our total runtime, 1800 and we get 5400 seconds (90 minuites) of a really long smoke break. Lets take a norm of 10 minuite break = 9 "breaks". thats our runtime equivelant. 18 breaks if they're only 5 minuites each. if you take 15 seconds between we get 12x 10 minuite breaks, or 24x 5 minuite breaks.
for a light user like me, i would take maybe 4x 5 minuite breaks a day. 24/4=6 days of use.
Hope the math helps you can use it to determine everything you need.

 

[MrFog]

I'd need to experiment with ceramics but you could get a ceramic cylinder about 3-4mm diameter and drill down the middle with a 0.5mm bit to act as a conduit. We all agree, the wick has gotta go.

As for controlling the circuitry, I'd suggest an Atmel ATtiny13a. Very small size. Add in a driver like a mosfet to power the atomizer, and use the ADC to measure current draw through a 0.1 ohm sense resistor. The other method would be to use a low dropout LM317 voltage regulator in constant current mode, however that would be more wasteful as the lm317 is inefficient. Or, the other method is to use a 555 timer in monostable mode to provide a cutoff of how long the atomizer should be on. I still think a thermocouple might be the best way, but like you said it might be a non issue if the coil doesn't burn itself out.

The supercap might work, though I just did extensive research and you'd need at minimum a 5 ferad, which i can't find at a reasonable price or size.
So for power it seems your best bet is to use off the shelf lithium batteries.
I've already ordered some Nicrome wire, and I'm thinking I'll use a flashlight for the housing, just need to find out how to design the atomizer and the cartridge.

5 fared ? Surely not.

 

[SuperSteph]

we can calculate the discharge time by using the RC time constant. t=R*C
My old calculations would have been ok if the coil was 13 ohms we'd get 65 seconds of continuous use. which would equake to 13x 5 second puffs, the equivilant to 1 use. considering a caps ability to charge nearly instantly with low input resistance, this would have been reasonable. but now that i know the required power output, we would need nearly 4 times the capacitance. that comes out to nearly 20 Ferads. Unfortunately in this size it's nearly impossible and uneconomical. It might be possible If I made my own capacitor, but that can get tricky.
anywho I'm making progress on a chassis, I'll post pics after i find a solution for a power switch.

 

[jigtg]

we can calculate the discharge time by using the RC time constant. t=R*C
My old calculations would have been ok if the coil was 13 ohms we'd get 65 seconds of continuous use. which would equake to 13x 5 second puffs, the equivilant to 1 use. considering a caps ability to charge nearly instantly with low input resistance, this would have been reasonable. but now that i know the required power output, we would need nearly 4 times the capacitance. that comes out to nearly 20 Ferads. Unfortunately in this size it's nearly impossible and uneconomical. It might be possible If I made my own capacitor, but that can get tricky.
anywho I'm making progress on a chassis, I'll post pics after i find a solution for a power switch.

I don't know how you calculated that but I got 2 watts*30 seconds/2.85 v = 21.053 F . 30 for 15 2 second puffs. Capacitor set like that would be 10mm in diameter and 60mm in length. Around $8 for 2 pcs. Anyway, it would suck since it wouldn't be able to give off voltage high enough when half-full.

@Stepth: you didn't take account the fact that battery voltage drops when loaded. It probably only gives off around 2-3 watts. Haven't checked any minis so don't know for sure. Yeah, attiny13a should be the way to go. I had a go with older attiny15l that I think is pretty much same but without sram. Made a mistake of placing coil on source side of fet and it didn't switch on fully and started to overheat. Haven't gotten new version to work yet. There seems to be some magic force pulling gate up when trying to pull high amps through it.

 

[SuperSteph]

I've been looking for a capacitor in that range size but I couldn't find one. I am assuming that the power draw is 4 watts but you're right I didn't account for voltage drop from the battery under load. unfortunately it would be very difficult to measure this. However with the larger power batt i plan on using i think the voltage drop would be much lower and keeping the voltage near 3.7. In addition, using a cap, you get a steady and predictable voltage drop, starting at whatever you charge it to (3.7) down to the cutoff voltage, which is typically considered 63.2% of the original voltage which would be 2.33v
I might be able to help you with your problem with the FET over heating, but it's been a while since i've done something like that. Beautiful PCB though, I can appreciate work like that.