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Old 5th August 2011, 11:37 PM   #11
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I went back to find the pics of the unit operating, but they got deleted (it happens). But then I started re-reading the thread (for the nth time), HERE I hate it when I prove my own stupidity. I guess after having read up on some of the concepts and tried a couple circuits on the bread board myself, and then re-reading the thread, I picked up on some things that didn't make sense before.
Even though it's not super impressive, nor anything to do with diy audio, I'll post a clip when i get it done.

OH, btw, "dead" to a vaper (that is, one who uses and e-cig or "personal vaporizer"), is about 3.2v for "low resistance". after that, the vapor production is almost nothing, really "wet" and the flavor is off. Optimally you want around 7watts for "low resistance" (2ohm attomizer @ ~3.6v) to 12 watts for "high voltage" (3ohm @ ~6v), also depending on what juice you're using and personal preference.
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Old 6th August 2011, 04:40 AM   #12
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You're not alone. I don't get the designer's "voltage divider" stuff. It just isn't coming together in my head. I think what is happening is that the resistors are simply setting the current thru the LEDs (as they're supposed to). The 4V LED has the highest series resistance, therefore the least current, so its light is visible only when the battery voltage is at maximum. The 3V LED has the lowest series resistance and most current, so its light is visible until the battery reaches the recharge voltage (That looks to be what your schematic is attempting, though the voltages are in reverse order). A schematic could show an LED and series resistor times n in parallel. Each resistor value set so that ~2mA flows at the designated voltage. 2mA may be too much, or it may not be enough. You have to determine the values for your battery & LEDs. The designer's circuit may be a stroke of genius, or just plain dumb luck. I can't say either way.
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Old 6th August 2011, 05:32 AM   #13
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YES.
All it is is multiple voltage deviders set up to make a set voltage from varying inputs........yeah, that's it.
You(pl) have to figure out the individual voltage dviders for the different input voltages (4v, 3.8v, etc) that all make the necissary output voltage (in this case, 2.8v).And then, yes; when it's at 4v, they all light up, even though the rest are above their target voltages (the divider set up for 3.8Vin and 2.8Vo, will actually have a higher Vo, until Vin is 3.8v)
Also, they don't just cut on/off, they dim off, and if you throw a cap in there too, when you let off the button, it will dim down sequentially instead of just cutting off. It's as much cool factor as function.

Yeah, it's late, and that was wordy.
schema and vid coming, just as soon as I figure out what values to use in my dividers (I keep coming up with wierd values, like 1kΩ+429Ω, and don't want 40 resistors in there for 5 LEDs)(OH, waitress, can you get me the world in a hand basket, please?)

And I"m gonna go with genius: the OP in the thread on ECF is one of those old timers who probably built his first 8888 computer when they were still $4k. He has time to just sit around and think **** up.
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Old 8th August 2011, 05:01 AM   #14
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try IC 8211 or 8212. Don't know if they r still available.
They r specifically designed to indicate LOW BATTERY.

Gajanan Phadte
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Old 8th August 2011, 07:12 PM   #15
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Another flaw with your Voltage divider idea is the continuous current draw of the LEDs will run the batteries down faster. Remember batteries are rated in mA Hours for capacity. Wasting even 1 mA can cause a noticeable change in battery life. You really should use a chip designed for this purpose as those are designed for very low power consumption and can do things like blink an LED which draws your attention and only wastes power when lit.

G
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Old 8th August 2011, 08:40 PM   #16
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Stratus,
Thanks for the advice, however, the LEDs will only light up when I push the button to take a toke on my ecig, for 2-10 seconds.
The person from whom I got the idea, had 4 leds and it drew 9ma. when the atomizer draws 1.8amps, 9ma isn't anything.

I wanted to build this circuit because I wasn't able to understand it; but now I do. in light of the difficulty in getting the precise values necessary to do what I want, i'm considering using a chip. do you have a recommendation? low power, small form factor, and low cost (of course).

EDIT*
I just remembered, one of the requirements is also that the ic has to run off of the voltage it's measuring. I just started googling chips, came across a few and realized it could be an issue.

TIA!

Last edited by interestingfellow; 8th August 2011 at 08:51 PM.
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Old 8th August 2011, 09:15 PM   #17
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checking out LM339; seems to be right fer'me?
Also trying to see if the radiocrack has anything close, as shipping is a beach.
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Old 9th August 2011, 09:40 AM   #18
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Radio Shack probably has LM339 comparators. The problem with this voltage divider method is that it is difficult the predict the LED behavior (at least for me it is). That's why I suggested the series/parallel approach. Move the resistors in your schematic so each is in series with its own LED. Then you can calculate the current flow, using higher resistance values to display higher voltages. Don't use the LED on the far left without a resistor between it and the battery, or just leave it out altogether.
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Old 18th August 2011, 02:58 PM   #19
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BAM!
LED Voltmeter ranging from 2.8v-3.6v+
(I couldn't figure out how to just emebed the video...)
Video

Remember, it had to be functional, but only to a point. I'm not using this for precision, more for general indication, and coolness.
For the E-cig, I also rigged up a resistive touch switch, and wired in a usb lipo charge board with micro usb. you can look around that photo album to see the other parts. Gen 1 has some issues. Gen II will be wayyy better!
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