batteries connected to voltage regulator

[bhan1992]

i wants to get 5v out of the 9v battery to power the mcu. im thinking of connecting the 9v battery to 7805 voltage regulator.
will this connection drain the battery faster?

 

[Mithun_K_Das]

Use a seriesed resistor (4.7Ohm/1W) between the battery and 7805.

 

[bhan1992]

can you tell me why we need a series resistor plz? thanks
is it ok that i use a voltage divider instead of 7805?

 

[Audioguru]

A 9V alkaline battery voltage quickly drops to 7V then drops slower as it is used. But an ordinary 7805 regulator stops regulating when its input is 7V and less.
Use a "low-dropout" 5V regulator instead that works perfectly when its input drops to 5.5V or less.

The datasheet shows the current that is used by the regulator. Some regulators use a very low current.

A resistor in series is not wanted.

A voltage divider has NO voltage regulation. The output voltage varies when the input voltage varies and the load current varies.