After some bad luck with cheap Chinese products, I'm looking to build myself a simple USB "pass-through" e-cigarette.
For anyone not familiar with e-cigarette, the idea is very simple : you put voltage across a thin wire acting as resistor, it heats up the liquid and that's it. Most e-cigarettes got some PCB inside to manage different voltages and more importantly hold a battery.
However what I want to build is much more simple as it doesn't include a battery : all I want is get the power from a usb connection (rated for 2A) and output a voltage around 4V.
As I got some basic knowledge about electricity I recalled the voltage divider circuit which is quite simple and easy to make :
But it seems that V2 will change depending on the load (cf : https://en.wikipedia.org/wiki/Voltage_divider).
Another thing is I use 1.8 Ohm resistance as the heating element and I calculated that I would need R1 = 0.45 Ohm which I don't think is easily achievable.
So to wrap it up here is what I need a circuit for :
- Input : 5v USB
- Output : 4v across a 1.8 Ohm load
- If possible the possibility to use a variable resistor to tweak the output voltage (about 3.5v to 5v)
Thanks a lot to anyone willing to help !
PS : CircuitLab is awesomely intuitive but why no MathJaX syntax ?