9v to 6v DC/DC Converter

[xoy]

hi!!!!
can anyone help me please how can i convert a 9v from battery to 6 volts supply.... please post a circuit.. thanks.....

 

[audioguru2]

can anyone help me please how can i convert a 9v from battery to 6 volts supply.... please post a circuit.

You can't use a 7806 regulator nor an LM317, because they need more than 8V or 9V at their input to regulate properly.
You can't use a 6V zener diode because it wastes power and its regulation fails as the battery runs down.

The problem is that the voltage of a 9V alkaline battery quickly drops to 7.2V, then slowly continues to drop to 6V over its life.
You need to find an adjustable low-dropout regulator IC, all Semiconductor manufacturers make them, then replace the battery when its voltage drops to about 6.3V.

If your circuit will operate at 5V, then there are many low-dropout 5V regulators available. I use the LM2931AP-5.0 100mA regulator for all my 9V battery-powered projects. It looks like a little 2N3904 transistor.

 

[xoy]

hi audiouru!!!


i will going to use that on a digital sphygmomanometer which has a 6v input... it will be acompanied with another circuit which has a 9v input...

is there still any way for this??

--thanks!!!


----xoy---

 

[ante1]

Hi xoy,

If your 9V is stable you could try with 5 diodes in series with the positive supply line! 8)

 

[xoy]

hi!!

what kind of diode?? is it s silicon diode?

 

[audioguru2]

The Stethoscope project will work fine with positive and negative 5V or 6V supplies.
A 9V battery's voltage will drop to 6V over its life. It drops to about 7.2V fairly quickly, then slowly drops to 6V when it is considered to be dead.

 

[ante1]

Hi xoy,

Just standard diodes but with the correct ratings.

 

[xoy]

hi audioguru,

does it mean, i can supply the electronic stethoscope2 with a positive and negative 6volts supply? whewwwwwww!!!!! so there is no need for me to have a converter??? maybe it is better for me to use 6vacdc adapter... i will only add what Alun advice me to have a -6v supply.. (at the #18 at the electronic stethoscope forum reply#245)

thanks again audioguru!!!!

-----XOY-----

 

[audioguru2]

does it mean i can supply the electronic stethoscope2 with a positive and negative 6volts supply?

Yes from a power supply. A 6V battery drops to 4V during its life, which is too low.

so there is no need for me to have a converter???

No, it isn't needed with a power supply.

maybe it is better for me to use 6vacdc adapter...

A tiny AC to DC adapter will probably cause mains hum. Try a 6V/500mA adapter that will have an output voltage of about 8V at the low current of the circuit, and will have low mains hum with such a low current.
Will your sphyg circuit be damaged with an 8V supply? A 4.5V/500mA AC to DC adapter might have an output of 6V at low current.