Replacement for nichrome coil...

[Quit4myKids]

I think I may have found the holy grail here, but I'm trying not to get too excited. I originally saw Sun Rod heaters, and upon further research here I was told that it had been tried and they didn't work. I searched a bunch of threads, but couldn't find exactly why it didn't work. Based on the probability that someone else had tried and failed with the Sun Rod devices, I sourced a different supplier that I've been talking with for several days now. I sent him pics of a BE112 atomizer in various stages of disassembly, and a few tutorials on e-cigarettes in general. Here's what we came up with.

They can manufacture a ceramic rod heater that meets the following specifications:
- The heating circuit is encased in non-porous ceramic that measures 3.8mm in diameter, and as short as 10mm in length (top 6mm is heating area, bottom 4mm reserved for spacer and lead wire routing). It can be as long as we wish, and any section (heating area, or bottom section) can be longer. He can also add a non-heated area at the top of the atty, although I'm not sure why we would want to do that.

- The heater will produce roughly 100-120C at 3.7V in less than a second. It cools off equally fast. The temperature can be adjusted up or down. Without a thermistor, it is impossible to regulate exactly, but he said they could adjust the embedded circuit to compensate.

- The resistance of the heater is around 3 ohms. This can be adjusted up or down.

This is a custom job, and he is willing to manually process 10 of them as samples for $250 USD total ($25 each) including shipping. They will create the custom mold for free on a minimum order, but a minimum regular order is 2000 pieces, for $2,500.00 USD ($1.25 each).

I tore apart an old BE112 (801) atty, and have posted some pretty bad photos here on my web site. The ceramic pot containing the coil is larger than the rod, and the lead holes in the bottom correspond with exiting the heater right at the edges of the base, which means it could sit flat in the pot. The base of the pot is 4mm from the bottom of the atomizer, and the entire atomizer is 17mm long (from the base to the tip of the atty bridge). I envisioning re-using the same ceramic pot, wrapping the entire heating rod in a 1mm thick stainless sleeve, and it would fill the ceramic pot. A 10mm heater would bring the tip to the exact position of a low bridge 801 atty, and an 11mm heater would match a high-bridge atty, such as the bestecig.com BE112 attys that so many folks here (including myself) love so much.

Now I'm not an electronics expert, but if what he says is true, he is offering a direct replacement for the weak link in our beloved e-cigarette. Can anyone come up with a reason why this shouldn't work? I'm willing to front the cash for purchasing the sample lot and will do the research that I am able, but I'm looking for some help with funding and guinea pigs. I am not trying to make any money from this, but would probably start offering atty rebuilds if this is as plug and play as it seems. Anyone else want to share the cost of this experiment and pony up $25 for one of these heaters to experiment with?

I'm hoping to make a decision by Sunday night, so I can draft a final list of questions for him and/or place the order for the samples. Please PM me if you would like to purchase one of the heaters, and post if you have suggestions on questions I can ask the rep, or issues that I haven't considered.

Thanks for all the expert help, I hope I don't end up throwing away $250.00 on a wild goose chase.

Q4mK

[roadkilldeluxe]

Nice. Just a few thoughts:
1) Boiling point of VG is at or slightly below 200C, I believe. Having a little bit of water in the juice will lower the boil point by a decent amount, I would almost think that you would want to aim for ~160C at least, and 100C i'm not sure would work at all. Is the quoted temp the internal coil temp or outer surface temp?
2) Safety--what material exactly are they using? What chemicals will the liquid be exposed to? Is the nichrome welded or soldered? What are the leads made of?
3) Size--personally, i'd go for the shortest possible. You could put spacers under them to raise the height for specific models, or use it as it is to create even shorter ecigs. How simple of a design can we use? Can we get rid of the ceramic pots, wick, or bridge?
4) Durability--any info on life expectancy? Will dry burning for too long kill it?

Great work, though. I'll probably have more questions as I mull it over. Might be able to invest some money in this. Any chance of getting sample pics or scematics?

[Ralph Hilton]

Sounds very interesting. Could you find out the coefficient of resistance change with temperature? I'm working on a temperature regulator circuit at the moment measuring the atomizer resistance.

[Quit4myKids]

Nice. Just a few thoughts:
1) Boiling point of VG is at or slightly below 200C, I believe. Having a little bit of water in the juice will lower the boil point by a decent amount, I would almost think that you would want to aim for ~160C at least, and 100C i'm not sure would work at all. Is the quoted temp the internal coil temp or outer surface temp?
2) Safety--what material exactly are they using? What chemicals will the liquid be exposed to? Is the nichrome welded or soldered? What are the leads made of?
3) Size--personally, i'd go for the shortest possible. You could put spacers under them to raise the height for specific models, or use it as it is to create even shorter ecigs. How simple of a design can we use? Can we get rid of the ceramic pots, wick, or bridge?
4) Durability--any info on life expectancy? Will dry burning for too long kill it?

Great work, though. I'll probably have more questions as I mull it over. Might be able to invest some money in this. Any chance of getting sample pics or scematics?

RoadKill,

Great questions, and thanks again (seriously) for giving me the motivation to work on this. I'll answer the best I can, based on my available information, and will find out what I don't know.

1. He was very clear that the temperature was adjustable. The basic design is for a block heater used with semiconductor test equipment, and this device is capable of over 1000C, so I'm certain we can get whatever optimal temp we need from it.

I'm not certain whether he was referring to core temp or outer temp, but since it's a fully ceramic-enclosed design, I would assume it would be surface temp. I'll clarify that on Monday. I searched the forum to try to find out the optimal temp of the nichrome coil, but wasn't able to find any actual measurements that had been taken. If you or someone else could point me to a thread that covers this, I would appreciate it.

2. The entire device is encased in high-temperature, non-porous ceramic material. It is waterproof, non-corrosive, and acid resistant. I brought this up with him, and he assured me that even at much higher temperatures nothing would leach into surrounding liquid or atmosphere. The leads are sealed within the ceramic, and as they extrude from the ceramic are sheathed with whatever material we choose to protect them from heat.

3. 10mm is the shortest we can make it. I was considering a threaded design, where the battery connector threaded to the bottom of the atomizer. When removed, one could simply remove the heater to clean or replace it, but then realized that to retain compatibility with the other existing components, it needed to reach the exact same height as the existing atomizer bridges. There would be no bridge required, but I would think that we would need to wrap the entire unit in the stainless wicking material, as the airflow is still required from the bottom of the atty in order to bring the liquid into contact with the heating surface.

Typically, when an atty is overflowing, a couple of quick, hard pulls (with the battery off) will pull the liquid away from the bottom vents, and into the ceramic pot. This will keep the liquid from dripping out the bottom of the atomizer. Since there has to be a way for air to enter the atomizer when one draws on the mouthpiece, there is going to have to be a hole (or several holes) at or near the bottom of the housing. Imo, this is a basic design flaw. I think the air should enter the atty at some point above the bottom, and be channeled to the bottom of the atomizer, rather than entering at the bottom. This would allow the bottom of the atomizer to be sealed, and make the atty leak-proof.

As far as simplifying the design, we could certainly get rid of the pot, although the existing pot is a great way to stabilize the base. Obviously, there is no central wick, as there is no coil to wrap around it. We do however, still need to make sure the appropriate amount of liquid comes in contact with the heating surface. In a standard atty, the liquid is delivered into the center of the coil via a wick that wraps over the edge of the ceramic pot and makes contact with the stainless wick wrapping the outside of the pot. This outer wrap wicks from the bridge, which is a significant distance from the coil itself. Therefore, the amount of wicking material that actually comes in contact with the coil is pretty small. I'm not sure yet how to regulate the amount of liquid actually touching the rod. I suspect that my first idea of simply wrapping the rod in stainless wicking material and letting the wrapped tip touch the cartridge would result in too much fluid coming in contact with a much larger heating surface, and could cause an explosion of vapor inside the e-cig. This is something that will have to be tested and played with once we have the devices, but I'm sure we can figure out something, given proper motivation.

Overall, the design I'm playing with right now incorporates the screw-on battery connector and removable heater. There is a small (2mm?) band of stainless steel wick around the sweet spot of the rod, and a band of ss wicking traveling up the side of the atty (not contacting the heater) to a bridge, supported by a steel arch (like in the BE112), just above the tip of the heater. I think this heater might be able to be used as part of a kit to rebuild worn or broken attys, in addition to creating new, stronger attys.

4. These devices are designed to run dry or wet at extremely high temperatures for hours at a time. Based on that use, they have over 10,000 hours mtbf (mean time between failure) of use. I'm not sure I could inhale on an e-cig for 10,000 hours in my lifetime. We would be using them in a way other than how they were originally designed, but I don't see how we could be overtaxing them. They are designed to be switched on and off several times per minute to very precisely regulate temperature within a heating block, so I believe that one heater would probably outlast the rest of the e-cig. I need to verify the mtbf, as I pulled that figure from a different website that talked about someone else's ceramic rod heaters, but I suspect it will be similar.

I posted the image that he sent me here, but it is only representative of what the final product will look like. The final product will not have contact pads on the side (the photo shows leads soldered to the pads), but rather have leads extending out of the bottom of the ceramic rod. He didn't have a product photo of that particular design. It will also be the dimensions I quoted above, this one is much longer (60mm).

Let me know if this clarifies things a bit. I know this is a long post, but there is a lot of information that needs to be considered when designing something like this, and I need all the expert input I can get. I know that these cannot be built and sold for the same price as conventional attys, but I'm hoping that I can get them done for 4-5 times the current price, and warranty them for several years.

Thanks,

Q4mK

[Quit4myKids]

Sounds very interesting. Could you find out the coefficient of resistance change with temperature? I'm working on a temperature regulator circuit at the moment measuring the atomizer resistance.

Pardon my ignorance, Ralph, but I'm not sure exactly what you mean. I would like to provide a useful answer, but I'm not exactly an engineer when it comes to this, and wouldn't be sure what I was asking the rep. Can you help me understand what you are asking, so I can get the correct information?

Q4mK

[Ralph Hilton]

The electrical resistance of different conductors changes with temperature - here's a table for common metals.
Temperature coefficient of resistance : PHYSICS OF CONDUCTORS AND INSULATORS
If I knew the coefficient of the metals in the heater then I could measure the temperature of the heater directly and control it.

[Quit4myKids]

Ok, my guy got back to me on a Saturday night (his time), and I found out what I could.

RoadKill:
200C isn't a problem. The temp is controlled by the circuit embedded in the ceramics. They measure temp at the surface of the ceramic.

The leads are not sealed, they are nickel plates, and copper wires soldered with silver/copper alloy solder. The ceramic product is sintered at 1700C in an oven. Will these have to be sealed before they are safe? I don't know, but I don't think the ambient temperature will cause the leads to leech anything into the air or fluid.

He was at home, and couldn't give me an mtbf for this particular product, but said he would get this info for me when he got back to the office.

Ralph:
Even though I have no idea what the question meant, the answer he gave me was "2900 ppm". He said, "when ceramic heater is heated, the temp will be grow up slow,maybe stop becsuse of the ohm rating grows up the power will be reach down." I hope that is meaningful. If you can educate me enough to understand the question and the answer, I would be grateful.

I'm going to bed now guys. I'll attack this again later, perhaps I may even let it be until I get some more responses (but probably not).

Q4mK

[Ralph Hilton]

2900ppm means a change of resistance of 2900 parts per million or 0.29% per degree of temperature change. So a 3 ohm heater raised 200 degrees would have a resistance of 3 + (200 * 0.0029 * 3) = 4.74 ohms. Given a constant voltage of 3.7 the heater would use
(3.7 * 3.7 / 3) = 4.56 watts With a temperature increase of 200C it would only draw (3.7 * 3.7 / 4.74) = 2.89 watts. Eventually, on further increasing the temperature, the power would decrease to a point where it matched the heat dissipated from the heater and the temperature would remain constant.

[jacko]

Very nice find. This really sounds like it may be the way to go. You could be on to a somewhat permanent atty (I say somewhat because MTBF is only the 'mean' time to failure,,,,, could be quite a bit shorter for a number of them) but it would probably be the last one that would need to be purchased... I would like to help out with this. PM on what you could use.

[jacko]

2900ppm means a change of resistance of 2900 parts per million or 0.29% per degree of temperature change. So a 3 ohm heater raised 200 degrees would have a resistance of 3 + (200 * 0.0029 * 3) = 4.74 ohms. Given a constant voltage of 3.7 the heater would use
(3.7 * 3.7 / 3) = 4.56 watts With a temperature increase of 200C it would only draw (3.7 * 3.7 / 4.74) = 2.89 watts. Eventually, on further increasing the temperature, the power would decrease to a point where it matched the heat dissipated from the heater and the temperature would remain constant.

And I liked the comment that these things monitor the temp. They may not need any external monitoring at all.