How do you reduce 9V DC to 3V DC?

Answer 1

by using the step down transformer we can easily reduce the voltage.if we step down means the current(amps) icrease its vry useful for us

Answer

As Transformers are a.c. machines, you cannot use a transformer for this purpose. You will need to create a voltage dividercircuit -essentially a pair of resistors, of appropriate value, connected in series across the supply.

Answer 2

Use either DC to Dc converter or voltage regulators for the required voltages.

AnswerA common method is to use a voltage dividercircuit. This comprises a number of resistors, connected in series, across the power supply. This creates a series of voltage drops across each resistor and, by choosing resistors of appropriate value, the desired load voltage can be achieved.

For example, if three identical resistors are connected in series across 9 V, then the voltage across each resistor will be 3 V, and the load can be connected across any one of these resistors.

In practise, selecting the appropriate values of resistance is more complicated than this simple example, because (1) the resistors themselves mustn't overload the power supply, and (2) the load itself, being connected in parallel with one of the voltage divider resistors, affects the overall resistance of the voltage divider circuit and must, therefore, be taken into account when designing the circuit. This is called the 'loading effect' and, to put it simply, its effect is minimised providing the resistance of the load is VERY much larger than that of the voltage divider resistor it is connected across.

Answer

This sounds like you're trying to run a 3-volt device off a 9-volt battery. I would do it in one of three ways.

First way is if there's nothing in the circuit that needs 9 volts. Your best bet here is to replace the 9-volt battery clip with either a holder for two AAA cells or two A-76 button cells. Trying to reduce the output of a 9-volt battery to 3 volts will produce lots of heat. You'll get a fairly short battery life, too. AAA cells are about the same size as a 9-volt; button cells are way smaller. There is a 3.3-volt regulator called the 7803SR - Murata makes it - but they cost $10 each.

Second way is if you need both 3v and 9v...in that case, I would install a pair of AAA cells alongside the 9v cell and wire the 3v supply to the circuit that needs it.

And third is if this is a flashlight. In that case it's even easier: replace the 3v bulb with a 9v bulb (yes, there are 9v flashlight bulbs) and be happy.

Answer 3

Use a voltage divider (see the related link).

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Answer 4

by using a step down transformer we can reduce voltage values to the desirable limilts.