Would you like a constant current MOD ?

[Thales2]

HI,

I am new to the ecig world and I love to play with electronics. So far I have only see mod that change the voltage, 3xAA 4.5V mod, 2 Li-on cell, boost-circuit MOD, LDO regulated, PWM mod ect

They all have one think in common they regulate the voltage, but what really matter is the current passing through the heater element. Obliviously if you raise the voltage you increase the current, but the current will be atty resistance dependent.

So my main question Is will be a adjustable constant current atty resistance independent mod be useful ?


My first idea what to take 2 Li-on in series mod and use a MOSFET to rapidly turn on and off the circuit (PWM) to get a AC waveform to get a constant RMS current passing thought the atty. With a sense resistor of 0.02 ohm in serie with the atty to sense the current and regulate the duty cycle on the PWM driver to get a constant (RMS) current output. So even if the battery voltage drop you get constant power output with great efficiency 95% +

My second idea is to make a general purpose mod capable on taking various battery arrangement from 2V to 12V input and output a constant current output (DC or AC). The ideal circuit for this task is a buck-boost converter. This will be least power efficient (75-90% average) because it use an inductor but capable of using a wider range of power source.

So my second question is what look more practical to you, the 2 cell high efficiency mod or the general purpose still good efficiency circuit (and more expensive ) ?

And last is there anyone ever tried to mod something like that or have any input, idea, cool feature, suggestion ,ect

Thx

Eric


PS : btw I have the skill to make PCB and solder SMT component so all option are open.

 

[alisab]

Hi, I admit I didn't follow your whole thread but I think you should look at the darwin - as I understand it, it is constant voltage that can be adjusted atty independently. Take a look.

 

[rannox]

I like the mosfet Idea. I might have to give it a try. But give me a little more detail on what the main benefit of that would be? I understand the function and how I would build one, but no idea why it would be better that way. (im learning )

People already use the TI ptn4050 for a buck booster. Which does seem quite efficient, I just build one with 2 cheap ... 18650s, still running about 3 days so far...

 

[duby]

2 cell high efficiency. I doubt most people have various voltage batteries lying around that they will want to swap out with. You'll also have to worry about size with variable input. I personally would only use the largest capacity battery that would fit the mod, and would see little reason to use something smailler.

 

[Thales2]

Hi guy,

@rannox
I assume run wired you 2 Li-on cell in parallels and use the boost converter to up and get a nice regulated voltage output that is constant no matter if the voltage start drooping from 3.7. So you got constant DC voltage and DC current in the atty. This is an pretty efficient power converter lets say 90%, we only lost about 10% of power meanly with the switching of the transistor and in the inductor.

With the PWN setting you put the 2 bat in serie so they no need to raise the voltage. Since the atty is only a resistor you dont need a constant current to drive you can use a equivalent AC voltage for the same effect. Like a light bulb plugged in the 120V outlets, in reality the waveform in a sine wave ~169V peak-to-peak, but is equivalent of a 120V DC voltage.

So you can eliminate the need for a inductor and use a low switching frequency(ex from 52k to 120Hz), so you can save a few % of efficiency with this method, bu eliminating the inductor flux/core lost amd my reducing switching lost.The main disadvantage is that there is no IC built exactely for that. If you want a unregulated output you can always use a simple 555 circuit like driver or PWM driver IC. But if you want a regulated current ouput you need first to measure the current, to do that you can use a sense resistor (ex 0.02) in series with the atty monitored by a current sense amplifier with a simple RC filter to get the average current in the atty.

Since there is no IC that can do that out of the box, you need to use something like a microcontroler to generate the PWM output and to monitor the current sense voltage thought an ADC. So basically the circuit is more complicated and need software to work for a few % power gain. For your mod you would gain like ~3 hours of bat.

ItI may be not worth the trouble but I like trouble and I have already this cheap micro tp play around EZ430-F2013

 

[rannox]

Well thats a little more complex than I though. I thought it would something as simple as a mosfet and a 555 timer. Haha.

Well if you like complicated, lets see something

 

[Thales2]

Yeah the 555 circuit will work nicely it just that as the voltage of the battery drop the output current will also drop, maybe you can add a simple analog feedback loop to.

You can also use the MPS430 micro to emulate a 555, by using the internal oscillatory and timer to generate the PWM to directly drive a N MOSFET transistor, if you like the flexibly software give.

I did a quick design View attachment PWNecig_2.pdf based on the MPS430F2012 (it may contain error), it use a simple open loop PWN driver with the flowing function.
- ADC sampled potentiometer control to adjust current output/PWN on the fly
- ADC sampled battery voltage monitor with 3 LED display, can also be used to adjust the PWM output as the voltage of the battery drop to get constant output.
- Standard ON led, can also be used for a maximum on time function (ex cut power after 10 sec and led blink)
- On push button and main power switch

It should not be over complicated to make a quick proto with the TI MPS430F2012 PCB, the MSP430 USB Stick Development Tool and a breadboard, now I just have to wait for the stuff

What do you thing of the design ? any suggestion ?

 

[Scottbee]

Since power correlates to heat.. and heat correlates to vapor production (given sufficient liquid delivery and a properly designed and manufactured atomizer/cartomizer). Therefore, "constant power" would be a better control parameter for vapor production and performance... especially in situations where the atomizer//cartomizer resistance may be varying, or you change units.

"Constant current" doesn't really offer any significant advantage over "Constant voltage". Variable current is really no better than variable voltage. Different, but not better.

 

[Jensb]

Check this out

This is a PWM with a programmed microchip. I can adjust the voltage on the atty by turning on the potentiometer.
We just updated the box with some new features:
-turn on and off the system by pressing 3times within 1 1/2seconds
-added Status a LED. this blinks every 6seconds if the system is on(can adjusted)
-the LED even blink in the speed you have adjusted on the atty. (low power=slow blinking)

This thing can made at home. I already build 2 of these and even the better one where i can adjust the voltage with a push on a Force Sensing Resistor....

 

[Thales2]

@Scottbee your right about the power thing, I was mistaken , so for the same power the current will not be the same with different load. But by sensing the current I think we still can achieve a constant power output, if we assume the voltage is constant no ?

@Jensb That really cool, what PIC did you use, I have a old PICSTART plus somewhere, maybe I will go the pic route.
So you use 1 cell with low res atty ? or you boost the voltage ?

I love those option, the Force sensing resistor look cool I never used one. What about dimming the LED (by PWM) so that brigthess is proportional to voltage ?

Are you willing to share you schematic and source ?

Eric

 

[Jensb]

No i dont use a Pic
I use a Attiny25
Here the schematics for the easy mod. But it is without LED. The LED need to be at PB2 and another software
Elektronisches Rauchen Forum

 

[sgtdisturbed47]

Awesome, but it's in German.

 

[tlocke]

The reality of the matter is that with the same atty resistance, constant voltage will give you constant current and constant power. It is basic Ohms law. Current = Voltage divided by resistance. Power = voltage (squared) divided by resistance. The only time the power would change in a constant voltage regulated circuit would be if you changed attys. The evercool thread is an example of a very high efficiency voltage regulator PV.

Just my 2 cents.

 

[AttyPops]

Scottbee is correct, tlocke too.

"If we assume voltage is constant, no?.... " It isn't. Not without a regulator. With a regulator, you already have a constant voltage mod (vv or not), up to the point that the batteries are depleted. You have 2 fixed variables in the ohm's law calculation .... voltage, and resistance. The current is a factor of that. Provide any 2 of the 4 variables and the rest calculate... up to the battery's ability.

In other words, the current regulator is basically doing the same thing as a voltage regulator would. IDK how the end result would differ.

Ohm's Law Calculator

If the battery is too depleted to give you the current, you can't "make it appear". So, it doesn't matter if you have constant voltage, or constant current, as far as I know. The resistance is fixed, the other factors "work out" until the batt dies.

EDIT: duh, tlocke basically said this.... sry for the dupe.

Is there any advantage to using some form of current regulator? Less expensive parts? Easier? You hint at efficiency, but don't explain. There are switching power supplies that are efficient, low cost, and turn-key solutions. Is your idea better in this regard?

I've seriously considered an MCU e-cig project. But then I remind myself of the KISS principal, and drop it. The only cool things about MCU's and e-cigs are 1) button control 2) a readout of some form; blinks, LCDs, etc. 3) logging of usage stats 4) Possible "quit plan" programming/usage monitoring 5) PWM adjustment of output 6) possible sensing of atty ohm resistance, and automatic adjustment of wattage.

(E-cig features copyright Attypops...lol)

All strikes me as "lipstick on a pig", so I keep em simple.

You can do button control and vv without an mcu. Bet you could design a discrete circuit to do auto wattage too.
If you go with an MCU, you should probably go with slightly higher pin-count. Then you could add one of those mini-speakers, and have it talk to you ..... "You're vaping too much!" "VAPE BREAK TIME!" "Happy Birthday to you...<with music>" "Ugh! same juice again?" "Get a new atty yet?" .... and have a few pins left over for a USB data connection.

 

[Java_Az]

I would like to see a constant Tap mod. Basically on one end of the pv you would have variable voltage juice feeder atomizer. Then on the other end you would have a tap. You would have to invent a atom changer first though . The idea is to push a button have electricity flow into the atom changer on one end. Inside the atom changer it would convert the electric atoms to Beer atoms. On the output end of the atom changer would be the tap. So you would always have a nice supply of beer as long as your PV was charged. If at all possiable i believe the output Beer temp should be 38f. Or maybe even have a variable temp tap so no matter who is getting a glass of beer they can choose their own prefect temp they like to consume beer at.

 

[Java_Az]

OH yeah Almost forgot. I think every one of these TAP mods should come with this Woman to show users how to operate it

 

[rannox]

^ lol, +1 Internets for you

 

[AttyPops]

ROFL... even better than the speaker idea.

Oh, yeah... Java, not that I want to minimize beer by any stretch of your excellent imagination, but if you get that whole energy-matter conversion thing (Star Trek?) worked out with the beer, you can probably mass-produce an army of those e-cig tutors. Better stock up on the "supplements".... Let us know how that one works out before this thread get banned. And when you start producing diamonds and gold, don't forget your friends here on ECF!

 

[addisdaddy07]

nope, stick with the beer, I love wine, women, song and wealth as much as the next guy, but give me that beautiful nectar of the gods any day!

 

[Java_Az]

Who needs gold and diamonds when you have the 3 B's , Boo koo vapor , Beer and a Beautiful woman. I don't see any reason this thread would be banned I don't believe any rules have been broken. In fact i see a lot worse all the time in the forums.