12 volt

[nagaya]

It's easy.. Want 2 resistors. 1 ohm and 3 ohm.. or any two resistance with resistance ratio between them should be 1:3 ..
Now connect those two resistors in series with battery. now you can get 9V buy connecting the bulb or what ever the thing parallel with 3 ohm resistor,
Better to use a variable resistor for 3 ohm resistor.
If you know the resistance of the item you use, then this can be done with a single resistor too.

dont use 1 & 3 Ohm resistor,current will be 12V/4Ohm=3A,so you need huge resistors,and also a wastage of energy,go for 10kOhm + 30kOhm or something like that,but this will be an unregulated power supply,so it's not recommend for circuits with sensitive parts

 

[crazybaby]

dont use 1 & 3 Ohm resistor,current will be 12V/4Ohm=3A,so you need huge resistors,and also a wastage of energy,go for 10kOhm + 30kOhm or something like that,but this will be an unregulated power supply,so it's not recommend for circuits with sensitive parts

He should decide the values of the resistors keeping that ratio.. i just gave simple values. for easy to understand and I have no idea about the current he need to supply. Use a variable resistor as the higher resistor. I think this setup can be used for your work.

 

[accessuser]

danne ne machn

 

[uditha.x86]

7809 kiyala regulator 1k thiyenawa eka daanna

http://www.fairchildsemi.com/ds/LM/LM7805.pdf