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fast and easy way to get 3.3v from 5v without a lm317? Answered

i got a dvd player but the power supply was missing. i can get the 5v and the 12v, but other than a lm317 (which i dont have) i cant get 3.3v. ive looked at all sorts of things to try and find a 3.3v regulator, but everything i have searched up lead to several misleading results.

so i was wondering, what value resistor could i use to get 3.3v from 5v
or
what devices could i look in to find a 3.3v regulator? i have several computer motherboards, a bunch of cd drives, a couple hard drives, etc.

please help!

thanks in advance,
          zack247.

Discussions

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AndyGadget
AndyGadget

Best Answer 9 years ago


Don't use a resistor - The voltage would vary depending on the load.
A dirty way of getting to 3.3V it is to drop the 5V rail with a couple of diodes.
A silicon diode (e.g. IN4001) gives a voltage drop of around 0.7V, but different types do vary slightly and by experiment (100R load without the MP3 connected) you should be able to get 3.3V within 0.1V which would be close enough.

0
zack247
zack247

Answer 9 years ago

thanks, i will check into that if i cant find any other method for getting the 3.3v, i really want to see if this dvd player works.

0
darrenwindmill
darrenwindmill

7 months ago

An atx computer power supply generates a 3.3v rail. You will need to check the power supply casing label to get the correct colour wire with reference to ground which is black if you didnt know

0
saidev
saidev

2 years ago

Use AM1117 with cap on both in and out

0
ArcAiN6
ArcAiN6

4 years ago

The small SMD SOT-223 package AMS1117-3.3's work a treat, as they are a
voltage regulator, and are pretty ubiquitous on motherboards, and sound
cards. If i remember correctly, 5v falls within the typical specs of
the device (5v - 7v) with the max range being around 12v - 15v.

Of coarse, you'll need a couple of capacitors, and resistors, but they should be available in small enough packages to suit your need...

Here's a typical circuit for using the device:

AMS1117.png
0
seandogue
seandogue

9 years ago

You could, as has been suggested, use series diodes, but imo it would be far simpler to purchase a step-down dc/dc converter IC and build a small board to supply your 3.3V needs.

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steveastrouk
steveastrouk

9 years ago

A PC power supply generates 3.3V directly.

You may well find a single regulator on a PC motherboard, but they are likely to be switchers, and hard to transplant. THey are often found near some coils on the board - take a look.

Otherwise: http://www.sparkfun.com/products/526
...or similar,. depening on the current requirements,

Steve

0
zack247
zack247

Answer 9 years ago

i would use a pc power supply but its a bit too big to fit into this dvd player, and i fear it might get too hot.

by switchers do you mean a regulator with multiple output capabilities?

0
steveastrouk
steveastrouk

Answer 9 years ago

No, I mean "Switch mode" - where you need a couple of extra parts as well as the "regulator" to make the power supply, and it works by chopping the DC input up, stuffing it through an inductor and smoothing it out again.

Try the PC supply first, if it works, an old Xbox would also yield a small-ish PSU
Steve