Amperage of atomizer coil

[mogur]

Hope I haven't overlooked this, but I sure couldn't find any hard info on it, so I benchmarked the amps at several voltages to see what was going on. The test atomizer is a 901 measuring 3.5 ohms cold.

3.3 volts = .66 amps [could barely get any visible vapor]
4.2 volts = .85 amps [draws a moderate amount of vapor]
5.0 volts = 1.05 amps [choking quantity of vapor]

On a five second draw, the amps stayed well within 1 percent of the initial amps, actually increasing very slightly. I originally thought nichrome had a huge inrush current similar to a tungsten filament, but this shows that the calculated ohms at all these various voltages (using ohms law) is at or slightly under 5 ohms when heated.

3.3v / 0.66a = 5.00ohms
4.2v / 0.85a = 4.94ohms
5.0v / 1.05a = 4.76ohms

Weird that as the current increased (and therefore temperature), the resistance dropped somewhat. I will make these tests more accurately in the future with a calibrated power supply. This time I simply used diodes to drop my 5v supply in .8 volt increments.

 

[Sun Vaporer]

Hope I haven't overlooked this, but I sure couldn't find any hard info on it, so I benchmarked the amps at several voltages to see what was going on. The test atomizer is a 901 measuring 3.5 ohms cold.

3.3 volts = .66 amps [could barely get any visible vapor]
4.2 volts = .85 amps [draws a moderate amount of vapor]
5.0 volts = 1.05 amps [choking quantity of vapor]

On a five second draw, the amps stayed well within 1 percent of the initial amps, actually increasing very slightly. I originally thought nichrome had a huge inrush current similar to a tungsten filament, but this shows that the calculated ohms at all these various voltages (using ohms law) is at or slightly under 5 ohms when heated.

3.3v / 0.66a = 5.00ohms
4.2v / 0.85a = 4.94ohms
5.0v / 1.05a = 4.76ohms

Weird that as the current increased (and therefore temperature), the resistance dropped somewhat. I will make these tests more accurately in the future with a calibrated power supply. This time I simply used diodes to drop my 5v supply in .8 volt increments.

Mogur--Great work and great post. We will be interested to see any further findings you post. Are you going to do any testing on the 801's as well or just the 901's---Thanks--Sun

 

[kender]

Good find that the amps actually increase when it gets hot. I would have expected a decrease. Looking forward to your further tests.

 

[mogur]

Sun, I'm a noob, all I have is three 901's and a girl who would smoke me if I destroyed her pretty pink 901. But, I'll grab an 801 next order since I am curious about the differences. And an e-cigar.

Yeah, kender, doesn't make any sense to me. That's why I hope to improve accuracy down the road. Both nichrome 60 and 80 have a positive thermal coeffient of resistance, albeit only about 1.05 or so at 400C (750F). I haven't heard what actual temperatures are involved, but I suspect only 200-250 degrees celsius. The coils are so tiny, even infrared thermometers would be hard pressed to pin down the actual temps involved.

 

[kinabaloo]

It could be an effect of the diodes; the exact voltage drop depends slightly on the current. Did you measure the voltage across the atomizer?

 

[kender]

I took the temp under the bridge before and was only reading 205 degrees Fahrenheit.
I measured it with a small K-Type thermocouple with a fieldpiece meter. Its small enough to touch the coil and gives pretty accurate results. I was thinking about 400 degrees but 205 was as high as it went.

edit to add: I was vaping also so air flow was keeping it cool. I was checking "operating" temperature.

 

[Jim Davis]

The coils are so tiny, even infrared thermometers would be hard pressed to pin down the actual temps involved.

C'mon mogur! Infared Thermometer? Ya put yer tongue on it, and then measure the blister.

 

[mogur]

Kinabaloo, yep, I measured just across the coil, or more precisely, the two 1 inch leads soldered to an adapter that I screwed into the atomizer. My multimeter is a BK 2707A that I have had for years, and I trust its accuracy within a percent or two. The cold ohmmeter reading is 3.5, and I think I can safely assume the connector resistance plus the lead resistance is less than a tenth of an ohm, since I don't have enough atts to disassemble this one and measure that resistance directly. The dropping diodes are new 1N4004s.

Crap, I just discovered the answer to the mystery... my damn alligator jumpers are measuring 1.2 ohms and 3.4 ohms. Unbelieveable, I've designed several microprocessor circuits with them and my breadboard without a hitch. This just blows me away. Okay, back to the drawing board, I'll solder some real jumpers and retest.... back in an hour. Thanks for pointing me to the problem, kinabaloo.

Jim, hehe, I would but my dog ate my digital calipers.

 

[kinabaloo]

I know exactly what you mean - it takes very firm contact pressure to eliminate the last 5 ohms or so of contact resistance.

Kinabaloo, yep, I measured just across the coil, or more precisely, the two 1 inch leads soldered to an adapter that I screwed into the atomizer. My multimeter is a BK 2707A that I have had for years, and I trust its accuracy within a percent or two. The cold ohmmeter reading is 3.5, and I think I can safely assume the connector resistance plus the lead resistance is less than a tenth of an ohm, since I don't have enough atts to disassemble this one and measure that resistance directly. The dropping diodes are new 1N4004s.

Crap, I just discovered the answer to the mystery... my damn alligator jumpers are measuring 1.2 ohms and 3.4 ohms. Unbelieveable, I've designed several microprocessor circuits with them and my breadboard without a hitch. This just blows me away. Okay, back to the drawing board, I'll solder some real jumpers and retest.... back in an hour. Thanks for pointing me to the problem, kinabaloo.

Jim, hehe, I would but my dog ate my digital calipers.

 

[kinabaloo]

That's 96C for those of us in the modern world

Very unlikely. I think it's just not possible to measure the temperature of the coil accurately simply touching it.

The actual temp will vary depending on how much liquid is on the coil.

When dry and glows red it must be at least 500C (http://hypertextbook.com/facts/2000/StephanieLum.shtml)

I took the temp under the bridge before and was only reading 205 degrees Fahrenheit.
I measured it with a small K-Type thermocouple with a fieldpiece meter. Its small enough to touch the coil and gives pretty accurate results. I was thinking about 400 degrees but 205 was as high as it went.

edit to add: I was vaping also so air flow was keeping it cool. I was checking "operating" temperature.

 

[mogur]

Pure monopropylene glycol vaporizes at 188C (370F for us doodle dandies). So a water/glycol solution will vape somewhere between 100C and 188C. Glycerine has a pure vape temp of 290C, but a 5% water solution drops the vape temp down to 164C.

No wonder my jumpers were screwed, they weren't even soldered to the clips, and over the years, the copper strands oxidized. Anyway, back to the experiment, here is what I found with proper execution-

3.09v @ .66a gave fair vapes
3.90v @ .85a gave good vapes
~4.80v @ 1.05a gave great vapes for about a sec and a half, then fried the atomizer, with the voltage instantly flipping to the 5.07 nominal volts of my breadboard supply. Acrid, burned taste at that instant. Obviously, the juice breaks down into something nasty at those temperatures. Lucky I started at the lower voltages, and grabbed a couple measurements, because I'm going to have to wait on my next order to continue.

Calculated resistance is still a mystery. How can a 3.5 ohm NiChrome coil jump up to almost 5 ohms when heated?

3.09v / .66a = 4.68 ohms
3.90v / .85a = 4.59 ohms
~4.80v / 1.05a = ~4.57 ohms

 

[surbitonPete]

Strange ....I am getting great vapes and not frying the atomizer with four rechargeable 1.2 volt batteries that give a total of about 5.2 volts fully charged. ....perhaps it's something to do with voltage drop when the current flows?......I don't know enough about electricity.

 

[kinabaloo]

Pete - probably, yes. Internal resistance. usb or mains power pack more dangerous as voltage keeps up under load.

 

[surbitonPete]

Pete - probably, yes. Internal resistance. usb or mains power pack more dangerous as voltage keeps up under load.

Ahh thanks kinaba...I can understand that.

 

[kinabaloo]

Pure monopropylene glygol vaporizes at 188C (370F for us doodle dandies). So a water/glygol solution will vape somewhere between 100 and 188 C.

No wonder my jumpers were screwed, they weren't even soldered to the clips, and over the years, the copper strands oxidized. Anyway, back to the experiment, here is what I found with proper execution-

3.09v @ .66a gave fair vapes
3.90v @ .85a gave good vapes
~4.80v @ 1.05a gave great vapes for about a sec and a half, then fried the atomizer, with the voltage instantly flipping to the 5.07 nominal volts of my breadboard supply. Acrid, burned taste at that instant. Obviously, the juice breaks down into something nasty at those temperatures. Lucky I started at the lower voltages, and grabbed a couple measurements, because I'm going to have to wait on my next order to continue.

Calculated resistance is still a mystery. How can a 3.5 ohm NiChrome coil jump up to almost 5 ohms when heated?

3.09v / .66a = 4.68 ohms
3.90v / .85a = 4.59 ohms
~4.80v / 1.05a = ~4.57 ohms

I have a possible solution - the solution

That is, extra current flows through the juice and some electrolysis takes place - eek, if true! We'd be talking circa 0.3A and that's a lot! (too high a value to be feasible almost, but the theory would explain the facts)

This might be a very interesting discovery with major implications.

Some might say that the nichrome is electrically insulated by an oxide film; perhaps. But the electrolytic current could be flowing from solder joint to solder joint, if the atty is semi/slightly-flooded; it would explain why so much tin is leeched and gets into the coil deposit(?)

 

[kinabaloo]

Ahh thanks kinaba...I can understand that.

I had noticed before more fails noted when running on usb - even over a nominally higher voltage supplied by batteries.

Mogur's testing shows that the load voltage should not exceed about 4.5v.

 

[kinabaloo]

Pure monopropylene glycol vaporizes at 188C (370F for us doodle dandies). So a water/glycol solution will vape somewhere between 100C and 188C. Glycerine has a pure vape temp of 290C, but a 5% water solution drops the vape temp down to 164C.

Hi Mogur - did you use VG or PG ?

Seems was VG but not sure as you mention both.

ps: if the atty was quite new, it shows that not only deposit buildup can kill the atty coil, as Sun found, told in another thread post today.

pps: could you check mogur how much current can pass through your juice by placing the crocs into a puddle of it about 1cm apart?

 

[chief druid]

ok i've done alil bit of searching the forum but i'm extra lazy so this seems like a fantastic place ask my question ... .. i'm working on a mod (but i'mlazy ..sis imention that ?? so it could take a while) what if i was to put lets just say 7.2 volts to an atomiser what would happen????

 

[kinabaloo]

ok i've done alil bit of searching the forum but i'm extra lazy so this seems like a fantastic place ask my question ... .. i'm working on a mod (but i'mlazy ..sis imention that ?? so it could take a while) what if i was to put lets just say 7.2 volts to an atomiser what would happen????

Depends on the atomizer type and a bit of luck Mostly it will depend on what the voltage actually is across the coil; this will go down considerably if the supply is batteries but might well stay high if from a desktop power-supply or usb.

edit (add): oh, not as high as i thought.

"The internal resistance of a typical lithium-ion cell is around 320 mOhm when new, compared to less than 100 mOhm for a NiCd cell, and it increases with both cycling and chronological age" (wikipedia)

So at 1A the voltage lost would only be perhaps 0.5V

 

[mogur]

Grin, I'm such a noob, I don't even know the terms VG or PG. I assume PG is propyleneglycol, is VG glycerine? Aren't most juices propylene glycol, glycerine, and a little water? If so, and if my memory reaches back to college chem, the boiling point of a tertiary volatile solution approaches the boiling point of the solution with the lowest boiling point, in this case, water. But this is all conjecture, do you have a blister size to temperature conversion chart or formula?