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Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: What is needed to make this work?
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Author Topic: What is needed to make this work?  (Read 13131 times)

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Offline blkbd

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What is needed to make this work?
« on: November 12, 2014, 01:08:47 AM »
What is needed to make this work? I'm thinking dual 18650s

I found this and think a VV unregulated mod would be great for a micro build but have some questions.

Would like to put a meter on it to monitor the batts and voltage input to atty, But would it be possible also measure the load to the atty like a chipped regulated mod?  I'm thinking no for that option.





 
« Last Edit: November 12, 2014, 01:11:57 AM by blkbd »

Offline CraigHB

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Re: What is needed to make this work?
« Reply #1 on: November 12, 2014, 10:55:43 AM »
Not sure exactly what you want to do with that circuit, but it's running the MOSFET in the active region where it behaves like a resistor.  That's not a problem for the relatively low current draw of an LED, but if you're thinking of powering an atomizer in place of the LED in that drawing, the transistor will overheat.  Also it will waste a lot of power.

The amount of power the transistor has to dissipate is input minus output times current.  So, if you have a 7.4V input and you are running the atomizer say at 3.4V and 4A, the transistor has to dissipate 4V x 4A which is 16 Watts.  That's more than the atomizer consumes.  Transistors like the one shown max out 5 to 10W depending on how they are mounted.

Offline blkbd

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Re: What is needed to make this work?
« Reply #2 on: November 12, 2014, 05:20:52 PM »
Thank you I'll scrap that schematic, I'll find a new one.

Offline david4500

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Re: What is needed to make this work?
« Reply #3 on: November 12, 2014, 05:35:20 PM »

Offline Visus

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Re: What is needed to make this work?
« Reply #4 on: November 12, 2014, 09:23:10 PM »
Craig why did having a led to vi off the power button run my batts down much faster than without it.  Its a 2.1v 20ma smd led with 470 ohm smd resistor on 7.4v  700mah 7A 14500's.  I get about an hour more vape time without the led..  I was surprised by that..

On my boost mod it would whine very early with the same spec led and without it would not.  Its only 20mA lol I cannot figure this out other than adding a ldo to power the leds..
« Last Edit: November 12, 2014, 09:34:06 PM by Visus »

Offline CraigHB

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Re: What is needed to make this work?
« Reply #5 on: November 13, 2014, 07:36:28 AM »
Hmm, that does seem odd.  If an LED is powered full time at 20mA, it's using 20mAh battery capacity over an hour.  If on all day is would consume 320mAh.  A hit being about 4mAh would cause a loss of 80 hits, probably about an hour of run time over the course of a day.  Though the LED is not illuminated full time is it? 

If the LED is illuminated only when the atomizer is energized, that's 20mAh compared to something like 10A for the atomizer.  That's an insignificant difference and should not cause any noticeable loss in run time.

The only thing I can think of is the addition of your LED circuit is adding some kind of full time draw or some kind of intermittent heavy draw.  You'll have to analyse your circuit to see if that's the case.  If possible check current demand from the battery when idle and also when under load using an ammeter.

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #6 on: November 13, 2014, 09:42:42 AM »
Just want to ask how to figure this right.  With a 7.4 volt supply, an LED with a 2.1 volt forward bias and a 470 ohm limit resistor really only draws: A) ~11.3 milliamp, because only 5.3 volts are "usable", or B) ~15.7 milliamp, because  470 ohms is the impedance in the circuit?

Thanks,
Wayne

P.S. - I should know this, but my head ain't right this morning!

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #7 on: November 13, 2014, 02:33:14 PM »
Well, the morning cobwebs cleared enough for me to at least use google, and for anyone interested, the answer is A. the formula is Rs=Vs minus Vf divided by If.

Offline Visus

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Re: What is needed to make this work?
« Reply #8 on: November 13, 2014, 03:12:48 PM »
I knew the maths but the reality is not the same.  In a config off the power switch into a reg it's somehow drawing more than spec..  I will put an meter on it but into it a math problem in it, huge effect to the regulator, maybe a wormhole to the infinite space that the led is reversed traffic lol..
-----------------------------------------------------------

52 and 51mA
resistor 472ohm 7.4v and 335ohm on 3.7v
I knew it was a little more than the stated ~20mA supposed to be around 11mA @ my batts, their actual capacity is 550mah so ya when chain vaping which is how I vape, nets a significant loss..  Still wondering why ohms law is not applying here..


Definitely gonna add a 20mA 2.1v ldo for my led heavy mod use 0 resistors..
Then no ? of whats what   :beer-toast:





« Last Edit: November 13, 2014, 08:24:08 PM by Visus »

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #9 on: November 13, 2014, 10:00:17 PM »
Wow. That LED should be burning very bright if it's passing over 50 mA of current. Is that a carbon comp limit resistor?  Now that you know the draw "as is", why not try just upping the limit res?  Sounds like a 1K  would be worth a try. Metal oxide preferably.

Peace,
Wayne

Oh, and just want to ask, what color does that LED burn? I would assume yellow for 2.1v, but tech changes so fast......
« Last Edit: November 13, 2014, 10:09:29 PM by wa9w00d »

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #10 on: November 13, 2014, 10:16:43 PM »
Just realized we kind of jacked a thread,  wonder if you "had to" make a an "unregulated V V" mod, maybe a 555 circuit driving a fet would qualify? Anyone?

Offline Visus

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Re: What is needed to make this work?
« Reply #11 on: November 13, 2014, 11:34:00 PM »
Wow. That LED should be burning very bright if it's passing over 50 mA of current. Is that a carbon comp limit resistor?  Now that you know the draw "as is", why not try just upping the limit res?  Sounds like a 1K  would be worth a try. Metal oxide preferably.

Peace,
Wayne

Oh, and just want to ask, what color does that LED burn? I would assume yellow for 2.1v, but tech changes so fast......
yeah they are bright as heck
Its green
25ma 2.2v   max 160ma

http://www.lumex.com/specs/SSL-LXA228GC-TR11.pdf

The red one is 30ma 2.1v    160ma max
http://www.lumex.com/specs/SSL-LXA228SIC-TR11.pdf

Its under a water bottle homemade frosted lens



Looking at it maybe reading meter wrong is that 5ma or 51ma lol on a 20ma scale  lol
If it's 5ma I am really not sure whats going on then cause it definitely is having an effect on the regulator.

Offline Visus

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Re: What is needed to make this work?
« Reply #12 on: November 13, 2014, 11:36:10 PM »
Just realized we kind of jacked a thread,  wonder if you "had to" make a an "unregulated V V" mod, maybe a 555 circuit driving a fet would qualify? Anyone?

 :whistle:

Sorry OP  lol

Offline blkbd

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Re: What is needed to make this work?
« Reply #13 on: November 13, 2014, 11:54:08 PM »
No problem.  :beer-toast:

Offline blkbd

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Re: What is needed to make this work?
« Reply #14 on: November 14, 2014, 12:38:23 AM »
I played with this schematic and would it work with the pot and meter I added, Also is there a way to wire the meter to read the bat level and bat load using the 4 position switch schematic?

If I'm right the way it is now I should be able to control the volts to the atty via the pot.


Offline wa9w00d

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Re: What is needed to make this work?
« Reply #15 on: November 14, 2014, 06:44:42 AM »
I haven't tried to work the bias levels or anything blkbd, but I kinda don't need to.  Remember that a FET isn't just a switch. It's a variable resistor with an on and an off at each end.  If you don't want to waste energy heating up the FET, you stay out of that middle section as much as possible.  If current flows at all, then all of the battery's voltage has to go somewhere.  If it's not at the atty, then the FET has to "eat" it.  Hope this makes sense, haven't even finished my coffee yet.  :)

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #16 on: November 14, 2014, 06:54:39 AM »
Visus, the pic and/or my eyes are fuzzy, but that looks like 5ma to me.  Not sure what's going on with that power loss.


Offline CraigHB

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Re: What is needed to make this work?
« Reply #17 on: November 14, 2014, 06:54:46 PM »
Just realized we kind of jacked a thread,  wonder if you "had to" make a an "unregulated V V" mod, maybe a 555 circuit driving a fet would qualify?

Yes, that would be a really easy and efficient way to to adjust an output to some extent.  555 timers are a good way to simply generate a PWM signal and they are 12V tolerant standard.  Though it would not be regulated to a specific power level since duty cycle is purely dependent on input voltage and component values.  Then voltages vary with battery charge. 

One note about biasing LEDs, you can't assume a 2V drop.  Common indicator LEDs vary from 1.8 to 2.2V depending on current flow.  So you really have to verify your bias with a meter.  Also 20mA is the limit for most surface mount indicator LEDs.  You would typically not want to load one more than 10mA and most are plenty bright at 5mA.

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #18 on: November 14, 2014, 07:40:59 PM »
you can't assume a 2V drop.

Heh, yeah. I'm old enough that while led's weren't "new" when I was starting out, they were new enough that us kids in the Navy loved playing with them.  I think I still have retina burns watching  a simple red led die as I cranked the current limit up on a very expensive, calibrated, government owned bench power supply.  :)
Your tax dollars at work.  And thanks for the diodes, too.  :thankyou: 

Offline wa9w00d

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Re: What is needed to make this work?
« Reply #19 on: November 14, 2014, 08:28:06 PM »
Just re-read that post, and realized it could be taken for cocky.  That's the last thing I would want to be to anyone, much less Craig. The man has the patience of Job. Just reminiscing.

Peace, y'all.
Wayne

Offline Visus

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Re: What is needed to make this work?
« Reply #20 on: November 14, 2014, 09:04:59 PM »
Yes, that would be a really easy and efficient way to to adjust an output to some extent.  555 timers are a good way to simply generate a PWM signal and they are 12V tolerant standard.  Though it would not be regulated to a specific power level since duty cycle is purely dependent on input voltage and component values.  Then voltages vary with battery charge. 

One note about biasing LEDs, you can't assume a 2V drop.  Common indicator LEDs vary from 1.8 to 2.2V depending on current flow.  So you really have to verify your bias with a meter.  Also 20mA is the limit for most surface mount indicator LEDs.  You would typically not want to load one more than 10mA and most are plenty bright at 5mA.

It's weird Craig I leave it in and reg whine very early in and shorter vape times when I knew it shouldn't have that much effectives.  I cannot believe it has this much effect but somehow it does.  Like I said ohms law somehow is not effective on my regs led circuits here.  Maybe the reg wants all the battery power and is not liking the led in its circuit IDK lol..  It's 100uf tan capped and 18ga wired very well with great solder joins, its so weird it is occurring in both the buck and the booster.  biasing is way over my head,  cathode anode;  its wired correctly to polarities all I know if thats what ya mean ya wired properly lol..  I have experimented with it numerous times adding thicker 27 gauge from original 32ga now and same shorter vape and reg whine outcome..  I even did a mech build with a led and same outcome much shorter vape times...  Yep aliens I guess sucking power thru the led in the vast beyond undetectable on the reverse backend of the led lol.

Offline CraigHB

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Re: What is needed to make this work?
« Reply #21 on: November 14, 2014, 09:38:04 PM »
Well I can't count how many weird things I've encountered in building circuits.  Sometimes you beat your head against the wall until you discover some strange current path that was not anticipated.

Oh, hehe, the patience of Job, thanks for that, I do try not to be an ass simply because I may know more than others that ask for help here.  Often people are dicks in forums because they expect others to know as much as they do.  I've had that happen to me in other forums discussing topics where I'm not as well versed.  That's just so lame, the internet can be a very unfriendly place.

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