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reducing voltage

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JDW89

New Member
im trying to reduce 5v to anywhere in between 3.3v to 4.2v preferably about 4v. how do i do this with resistors? any help will be appreciated, thanks
 

MikeMl

Well-Known Member
Most Helpful Member
Need more info: What is the nature of the load? What sort of voltage tolerance does it require? How much current does the load draw @ 4V?
 

JDW89

New Member
It is for an electrinic cigarette, the battery works at 3.3v - 4.2v. Im trying to work it without the battery, through a usb. I cant get my probes in to measure the current from the battery when its used but when its on 5v it draws 0.85A, which is weird because i thought you could only get 0.5A from a usb, is this info any good?
 

Hero999

Banned
5V probably won't do any harm, just add a diode (1N4001) if you're worried.
 

JDW89

New Member
I think it will reduce the life of the atomizer if the voltage is too high. What will a diode do?
 

MikeMl

Well-Known Member
Most Helpful Member
A single Silicon rectifier will have a forward voltage drop of about 0.8V at 0.8A. A 1N5817 Schottky rectifier will have a forward drop of about 0.4V. Add one of each in series and you will drop the 5V to about 3.8V
 

Hero999

Banned
The maximum voltage rating is 4.2V so add the silicon diode, mission completed.:D
 
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