Passthroughs - The under-rated, underdeveloped APV?

[Chriskarr]

Hello everyone,

I've been looking around through all sorts of forums and observing all sorts of designs. It seems that - much like most other commercial APVs - almost all commercial passthroughs are based on a single architecture, and all VVs based on a single architecture.

My proposal is a discussion of passthrough box mods.

Being someone who is constantly working on computers or near-enough a USB port to use a passthrough, I'd much rather use one than potentially take hours away from an expensive battery-powered APV. Besides, while it may be comfortable to have a nice, heavy chunk of steel in your hand, it's not always convenient to have one at your computer desk or in your living room on the couch, or where ever.

So, my biggest qualm with passthroughs is their lack of variance in architecture. No, we don't care much about flashy OLED screens on a passthrough - it's effectively a disposable item. And no, we don't need a button-based VV device everywhere we go. Some of us like a set-it-and-forget-it piece which is always convenient. Perhaps something to come home to with a dead device and no charged spare batteries. But what your reason for wanting a passthrough is is negligible. Here is my list of pros and cons of passthroughs currently on the market -

PROS:

1. You don't need a battery.
2. They're easily portable.
3. You can use one anywhere there's a USB port available
4. You can attach any atomizer which fits the connector or for which you have an adaptor.
5. They are inexpensive and reasonably reliable.

Cons:

1. VV functionality is typically lacking or stepped.
2. VW is unheard of.
3. Your computer has you chained to it.
4. Amperage is limited to a point that a good vape is impossible.

In my search for a solution to these cons I've come up with a couple of possibilities for fixing the main issue. The most reliable and lightweight and inexpensive being devices known as 'Super Capacitors'.

Super Capacitor - 1F/5.5V

This unit is rated at 1F at 5.5V. The formula for finding a capacitor's storage energy in Joules is (V^2*C/2). This capacitor's energy would then be - 5.5^2 = 30.25; 30.25*1 = 30.25; 30.25/2 = 15.125J.

What does this mean in the world of ecigs? Well, it means you could run an atty at 2 Ohms for two seconds at its peak current handling. Then one could put these devices in parallel and, since their energy storage adds each time a new capacitor is added, you could have enough capacitors to serve any vaping habit in quite a small package. Add a variable resistor and welcome to variable vaping town.

These capacitors could build a charge from the USB port while you're not draining them, and then they could be discharged at your mercy at how ever many amps you choose.

You may be asking yourself, "What is the advantage of super caps over high-discharge batteries?" Well, for one, they don't blow up as often, regardless of manufacturer. Then there's the drain/charge characteristics. You don't have to keep these above 2V for them to be happy, nor do you need to store them charged. They never form a 'memory' and can be charged at almost any current (barring, say, a zap from a DC welder).

I don't currently have any atomizers on-hand, but you can bet I'm going to be building a device which fits these characteristics until I do. (Dang Postal service...)

Please let me know what you think. I've been considering building them to sell, yes, but I'd rather share my knowledge with the forum.

 

[meatsneakers]

There was a thread on this a while back. If I remember correctly, the issue was charging the caps from a USB port took too long for it to be viable.

 

[Chriskarr]

Well, if a passthrough is a viable method of getting *any* vapor, you could certainly get a much larger volume of vapor and a higher current with a capacitor. If I had to make a guess, I'd say the limiting factor in the other thread's mod was the lack of capacitance. A capacitor LITERALLY IS a battery; the differentiating factor is the method of storage - chemical or plate.

I'll explore the avenue further. Unfortunately, my current funds are lacking and I've not enough capacitors on-hand.

I'll do some research and put together a proof of concept.

 

[Chriskarr]

Universal Serial Bus - Wikipedia, the free encyclopedia (Paragraph 2)

"A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0"

There is something known as an 'RC Time Constant' in the world of electronics. It is used to define how long it takes a capacitor to charge to a given voltage if it has a given capacitance and resistance.

Let's figure out the number of capacitors it would take for one to vape a constant minute. That's six ten-second draws.

One capacitor is ~16J. That allows for a 2 second draw on 2 Ohms. Multiply that by 30 and you get 60 seconds and 480J.

Now let's find out how long it takes to charge that from a 5.5V 0.5A source.

5.5V @ 0.5A for two seconds is equal to 5.5 Joules. 480J (our capacitor's storage energy) divided by our charging power 5.5 [J(T)] = 174 seconds.

So it takes three minutes to charge such a device to allow for one minute of smooth vaping at 2 Ohms, without any breaks between vapes. That is more than acceptable, in my mind.

 

[meatsneakers]

USB is 5v but can dip as low as 4.75v and be in spec, so the math is a bit off.

Also, the cap will drop voltage linearly so halfway through it's discharge you have a 2.5v power source which isn't very viable in our application. A large bank of super caps plus a buck/boost converter would work but at that point you can just use a battery + USB charger and it'd be the same size.

edit-

There have been a few threads dating back to 2009 but here is the relevant post about charging: http://www.e-cigarette-forum.com/fo...-super-capacitor-booster-box.html#post4411213

 

[dlmarti]

Issues with the idea:
1. A TRULY compliant USB connection will only deliver 100ma, unless the end point negotiates (through a nasty protocol) for a higher supply current. Granted a lot of USB connections are not truly compliant, and just give the max they can give, but its a problem to deal with regardless. There are chips that do this request for you, in fact they can even request much higher currents if the connection allows.

2. Most "super caps" have a high internal resistance, so are unsuitable for driving high current loads. The ones that can drive high current loads are typically pretty large, and expensive.

 

[Gabe1291]

There is a way to make a viable high power PT, though you kinda hafta ditch the USB. I tried the cap route myself. I had a ton leftover from playing with my tesla coils, and building the cap banks for them using hundreds of them in parallel circuits sunk in oil. The USB just lacks the amps needed to run a VV PT without a battery, though a word of warning though on using USB, if you push the USB circuit too hard, you can potentially do some serious damage to your computer's motherboard. Saw that happen before, though it wasn't using a PT, they had hubs jacked into every available port they could find, and more crap jacked into the hubs, fans, lights, drives, ect....smh the crap you see working in IT >.>

There is an alternative source of power you can tap on most desktop PC's that can. You can tap straight into the PSU's 5v rail with a simple 4=pin Molex connector. The PSU on my compy has an 18 amp limit on it, so that's more than enough to even power my 0.8 ohm Genesis Atty at 5v. There are a few other things to take in mind though. Standard USB wire won't cut it, the gauge is just too small to carry enough current, on mine I ended up using standard stranded auto speaker wire to go from the connector to the box.

You may also want to throw a fuse inline as well. Since the internal breaker trip point on the 5v rail for my PSU is 18 amp, I dropped a 15 amp blade fuse in a holder coming out of the molex connector. The other thing to take into consideration is the amp limitation on the switch and circuitry you use as well. I took an old custom evercool VV box I had. The circuit I had was good for it, but the switch had a 5 amp limit, so I swapped it out for a 10 amp horn switch, and ran the speaker wire to the old battery contacts inside of it.

So far it's been vaping like a champ for about a year with no problems, and has handled everything I threw at it....and even throwing IT a few times for various reasons. I can push the circuit up to around 8v, though I generally vape around the stock 5v. The genesis can handle the 8...but I cant, I swear there was vape coming out of my ears after THAT hit O_O

So far this is the only way I've found to get a decent high power PT for the compy. I use it at work as well, though since I cant crack the case to access the PSU on my work computer I had to use an AC adapter I had laying around that had the 4-pin molex connector on it. I has a 10 amp rating on it, so it works pretty well. Hope this helps you pursuit of an upgraded PT.