no idea if anyone is interested (apart from you and me Mildew ) I have noticed that my type A atty works a lot better on an eGo battery than on the indulgence at 3.7V, not sure why but it got me curious which is a dangerous thing. now I have a really big variable power resistor .. set it to 3ohm and ego would not drive it, in fact had to go to about 70ohm before the eGo would turn on, seems to be an inductive load, saw some spikes when I got it working. So ripped an old carto to bits and made a quick test rig .. (edit: lost photo) not very visible but the carto element is soldered to the wires just above the terminal. still measures 2.2 ohm or something, eGo drives it quite happily. stuck some batterys in the scope meter and took some waveforms .. first pulses at turn on .. as you can see .. about 4v p-p and starts off at a duty cycle of around 15% estimated, within a few hundred mS its up to about 85%, I assume this will change as the battery goes flat, that one was maybe at 50% capacity. I am wondering if this PWM helps pump liquid to the coil or whether its simply there to give a regulated voltage and provide an even vape from a flat battery or a full one.
Thats very interesting mate, thanks for taking the time to show us. My electronics knowledge is pretty basic however it would seem to me that a PWM driver would help with reduced current draw and a more stable temperature if the button is held down for a long drag. You should post these results at ECF, much bigger.comdience there and some technical folks too.
Hey stoney PWM is basically how switch mode power supplies work. The aim is to have a constant voltage at load (atomizer). As constant voltage means even vape. The pulse or on time increases or decreses depending on the voltage measured at the load. when the battery is a bit dead (lower voltage) the on time has to increase as it is being fed with a lower voltage. Most switch mode power suplies contain some sort of intelligent control based on feedback measurements. That is why it is an electronic cigarette as opposed to an electric cigarette. If your really curious http://en.wikipedia.org/wiki/Switched-mode_power_supply Regards Andrew
thanks andrew .. I know what PWM is .. I have designed and manufactured switch modes and use PWM quite a bit. They are not one and the same thing however, a switch mode requires an inductor to store the output energy, PWM .. well, it doesn't. I was looking at digikey recently and pricing mosfets for a mod, looking through datasheets and studying safe operating area graphs I have another possibility for the 85% maximum, there is a major difference in current for the SOA of a SOT23 mosfet at DC and at 80/90% duty cycle. This gives another advantage in being able to use a cheaper mosfet and still handle lower resistance heaters. To get DC currents suitable for a LR atty and with a safety factor you really need to go to packages with more pins and price.
thought I'd bump this thread as its also relevant to the 510N from bozecigs. for those who do not understand the CRO pictures .. a quick description. the CRO trace moves all the time from the left to the right of the screen, it moves up and down depending on the voltage. the pictures above show the ecig putting out no voltage or current when the trace (line) is a the bottom of the screen, then after a time the ecig turns on and the trace shoots up to the top of the screen. The writing on the top (first picture zoomed in) says 1V and 20mS .. these are the settings for the vertical and the horizontal, this means 1V will move the trace up one square and the trace moves from left to right at 20mS per square (division the are called). With that info you can see the rhs turn on is half a division or 10mS (0.01seconds) .. so the ego turns on for 100th of a second every 100th of a second or so. The voltage is about 3.7V peak to peak. The first picture is as the ego is first firing so its not up to voltage yet.
Interesting. On ECF Scottbee was one of the first to dissect the original Janty/Joye eGo. The apparent loaded volts were lower than the current crop. Here is his first test @ 2.5Ω of the 650mAh batt. He also tested the original Joye 180mAh and mega, the readings were quite similar. At that time many had said the KR808D-1 batts seemed to have more ooph. Here's that test. He also commented (overtime) the electronics in the eGo changed. He has various scope pics to show the differences. Some here. http://www.e-cigarette-forum.com/forum/joye-510/65055-battery-voltages-surprise-16.html#post1044798 I guess you could start at the top and read the whole rambling thread. All that said it seems the Joye circuit was just a way to cheaply regulate the output, but there have been a number of folks who have built PWM devices claiming they do in fact vape differently at the same apparent volts.
