# What is right size resistor

#### mrel

Jul 2, 2008
115
Hello

Have 6 volt battery , device call for 3 volts at 350MA .

Could it be a 10 ohms resistor at 25 watt or am I wrong.?

mrel

#### Resqueline

Jul 31, 2009
2,848
That could work only if the device always draws exactly 350mA (not MegaAmps). I would not dare go for that solution.

#### mrel

Jul 2, 2008
115
DC to DC conventer

I am using 6 volts battery on a dc to dc conventer that need 3 volts at 350 MA so am I doing right thing using resister to drop the voltage from 6 volt to 3 volts and 350 MA
Is there better way to drop voltage from 6 volts dc to 3 dc volts at 350 MA?
mrel

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#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
No.

One option is to use a DC to DC converter. Another is to use a regulator.

A DC-DC converter is a special case of a switchmode regulator.

What voltage does the DC-DC converter you're powering produce. I hope it's not 6V!

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Oh, and 350 mA

Not MA

edit 1 MA = 1,000,000,000 mA and is a current I can't imagine seeing in anything powered by less than a dedicated power station (kinda)

Last edited:

#### heri.aza

Dec 31, 2009
3
try using potensiometer, connect pin 1 to battery and connect pin 2 to voltmeter/multimeter then adjust the potensiometer to get the right voltage..

Last edited by a moderator:

#### Resqueline

Jul 31, 2009
2,848
Don't use resistors of any kind for voltage reduction unless you know that the converter either: draws a constant current, or: tolerates 6 Volts.
I know converters/inverters doesn't draw anywhere near constant currents. On the contrary they tend to draw a constant power.
If the converter can't stand 6V directly then the only low-tech solution is to use a 3V 1W zener in series with the battery.

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