variable voltage question

[chrisaphrenia]

this might be a dumb question...... could i impliment a potentiaometer in a usb passthru as a variable voltage regulator?

 

[LucentShadow]

No. A potentiometer is too simple to be regarded as a regulator.

You could make a simple resistive voltage divider using one of those and at least one power resistor, but it'd have to be carefully designed so as not to overload the voltage source, the power resistor, or the potentiometer. Most potentiometers cannot handle much power.

Better off using a step-down regulator.

 

[chrisaphrenia]

Thanks for the info.

 

[WarHawk-AVG]

LT1086 and something like this

Put on a pcb like this

http://www.eidusa.com/Electronics_Kits_Voltage_Reg.htm

Thinking of doing this on my little cheapy USB passthru..the 2.1Ω (2.0Ω - 2.2Ω standard CE4 clones from China) run kinda hot!!

Oh snap...they have a 3.6vdc at 1.5A TO-220 package

LT1086CT-3.6#PBF

3.6V L/Dropout Pos VR 1.5A

TO-220

Purchase LT1086 direct from Linear Technology

Looking at the power chart 3.6vdc
http://www.ecigadvanced.com/community/wp-content/uploads/2012/07/power.jpg
You still should get decent wattage for vaping out at 2.0Ωish coils!

Variable...hmmm

 

[State O' Flux]

Hey chrisaphrenia... ain't it great having such smart and helpful people on this forum? I was so impressed by their selflessness that I moved my mouse over to the lower right side of their posts and hit the "like" button. Yep... that's what I did alrighty. ;-)

 

[dr g]

No. A potentiometer is too simple to be regarded as a regulator.

You could make a simple resistive voltage divider using one of those and at least one power resistor, but it'd have to be carefully designed so as not to overload the voltage source, the power resistor, or the potentiometer. Most potentiometers cannot handle much power.

Better off using a step-down regulator.

Question -- wouldn't it be better to go with a 1-cell booster?

 

[LucentShadow]

Question -- wouldn't it be better to go with a 1-cell booster?

Not for me, as I've never needed to go above 4.6v for my vaping, and the usb source would be 5v. A buck circuit would be what I would choose, presuming the 5v source could handle the current. Should be a bunch of choices out there that can use 5v for input.

A buck-boost circuit would be more flexible, but I would assume that the current demand would go up with in the boosted range, and I'm not very confident in the availability of high-current-rated usb pass-throughs.

ETA- Not sure if you meant using a booster suitable for use with 1 li-ion cell with the usb pass-through mentioned in the OP, or simply using the booster with a single li-ion cell instead of the USB passthrough. I would, indeed, choose a boosted single-cell mod, in that case. Less problematic.

 

[dr g]

duh, i missed the USB source :/

 

[chrisaphrenia]

Been away for a while, thanks for all that info guys!!

 

[DrMA]

USB 3.0 can handle more current... Just FYI

 

[State O' Flux]

Been away for a while, thanks for all that info guys!!

Three weeks, ah... ya' think there Chris? ;-)

 

[kaddigart]

USB 3.0 can handle more current... Just FYI

Almost twice as much as a matter of fact. USB 2.0 delivers 500mA, while USB 3.0 = 900mA.

The voltage is still the same though at 5v. This is from Wikipedia:

In July 2012 the USB Promoters Group announced the finalization of the USB Power Delivery ("PD") specification, an extension that specifies using certified "PD aware" USB cables with standard USB type A/B connectors to deliver up to 100 W of power at 20 V. For PD-aware cables with USB-micro B/AB connectors the maximum power supported is up to 60 W at 20 V, 36 W at 12 V and 10 W at 5 V. In all cases, either host-to-device or device-to-host configurations are supported. The intent is to permit uniformly charging laptops, tablets, USB-powered disks and similarly higher power consumer electronics, as a natural extension of existing European and Chinese mobile telephone charging standards.

I've been thinking about this for a while; the potential for a high powered pass-through is there, I just don't know exactly how to implement it. Time to start poring through pages of whitepapers I guess...