how do i reduce 12volts dc to 3 volts dc?

Question

i want to wire an airerator up in my boat but it runs off 3 volts dc. i thought i could just hook it up to the battery but that didnot go over too well. i need to fine a 3 volt dc source but do not know how. all suggestions will be taken seriously and thanks in advance. jeff

Answer 1

Although I'm sure the intention is right, a lot of things written here are clearly based on some vague electrical knowledge, and don't make much sense.

-Using a step-down transformer isn't the way to go. Since transformers need either AC or pulsed DC in order to work, you'll need to build an oscillator circuit to drive the transformer from the 12v battery, and then rectify/flatten out the transformer output to get a constant 3VDC output to feed your application.

-I've never heard of an airerator, but if you know its current draw 'i' (i=P/U) you can use ohms law. You add a resistor in series with the airerator, and you need 9v to be over this resistor(gives 3v over the airerator), so; R=9/i is its value.

Its true that you will waste quite some power 'P' that is dissipated in the resistor though;
P=(I^2) . R
More energy will be dissipated in the resistor than there there is consumed in the airerator (I is equal for resistor and airerator, R of resistor is higher then R of airerator)

I hope this helps, correct me if I'm wrong..

Answer 2

As somebody else said, a transformer would only work for an AC voltage, and you have a DC circuit. So you can't use a transformer.

A series resistor would only work IF the load (your airerator) draws a steady, constant current. The voltage would change if the current changes. If you don't understand very well the electrical characteristics of the airerator, then __do__not__ use a series resistor to drop the voltage.

Then there is the voltage regulator. Actually, there are two basic types of regulator.

There are linear regulators, which consume extra power but are simple to wire up, and switching regulators, which consume little power but are not as straightforward to hook up. Try to use a linear regulator if you can, but since you didn't tell us how much current the airerator uses I can't tell you if a linear regulator is the way to go in your case.

Also, you might need a heat sink (again, depending on how much current the airerator uses) for the linear regulator.

Hope this helps.

Answer 3

Although you could use a resister to drop the voltage to 3 volts, 9 volts would be dissipated by the resistor, giving off quite a bit of heat. If the aerator is a low current draw you might try a couple of flashlight batteries in series to make 3 volts, or one of the universal battery units for various cell phones that have a switch to set various voltages.

Answer 4

3 Volt Power Supply

Answer 5

Simple. Apply Ohms law.attach a 4 volt resistance in parallel with the circuit

Answer 6

How about Using ohms law?

I'd get a variable resistor, put it in the circuit... adjust it until the voltage reads just over 3 volts...

Then Read the resistance of the POT, and buy a fixed resistor of that value.

Answer 7

Radio shack most likely still sells a 3 volt cigarette adapter that is fused. If you have little knowledge of resistors I would just spend about 10 dollars or less and get this.

Answer 8

you cant reduse those volts like that!!you can only use a 220/3v corrector that is offten used in phones at home!!

Answer 9

Use a transfomer. Transformers are used to step up of step down voltage. you might find what you need here www.mcmaster.com

Answer 10

Transformer, stepdown of course..