5v power supply - Electronic Circuits Projects Diagrams Free

samtheboxer · 9th September 2007, 05:01 AM

regarding a power supply for a pic 12f629. a LM7805 is too big, im looking for something smaller. Is there a surface mount 7805? or is there another way to build a smaller circuit (im trying to get it all about the size of a nickel, maybe)

Sceadwian · 9th September 2007, 05:11 AM

What's your input voltage, and how much current are you going to need? A zener diode and a resistor are good for basic situations as long as the voltage you're dropping isn't too large, less than the size of a dime.

samtheboxer · 9th September 2007, 05:15 AM

Quote:

Originally Posted by Sceadwian

What's your input voltage, and how much current are you going to need? A zener diode and a resistor are good for basic situations as long as the voltage you're dropping isn't too large, less than the size of a dime.

the voltage would be 12v with a 3 cell lipo battery. it will power a 12f629 flashing different light patters, it will then monitor the power supply and change flash patterns when it drops below 9.8 volts.

audioguru · 9th September 2007, 09:27 AM

A 78L05 comes in a TO-92 small transistor case and two surface-mount packages. It can supply up to 100ma.

Hero999 · 9th September 2007, 07:36 PM

What's your minimum and maximum input voltage?

If it's a 9V battery and you only want 50mA then go for the LM2936-5.0 as it has a lower output voltage and a lower quiescent current.

mvs sarma · 10th September 2007, 03:06 AM

Quote:

Originally Posted by Hero999

What's your minimum and maximum input voltage.

If it's a 9V battery and you only want 50mA then go for the LM2936-5.0 as it has a lower output voltage and a lower quiescent current.

You mean low dropout voltage?

Hero999 · 10th September 2007, 04:31 PM

Yes, I meant lower dropout voltage than the LM7805.

audioguru · 10th September 2007, 05:10 PM

The 7805 needs a minimum input voltage of about 7.5V.
But a 9V alkaline battery's voltage drops quickly to 7.2V which is too low, then drops more to 6V.

A rechargable "9V" battery is frequently actually 7.2V.

So a low-dropout regulator is needed.

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9th September 2007, 05:01 AM	(permalink)
samtheboxer	5v power supply regarding a power supply for a pic 12f629. a LM7805 is too big, im looking for something smaller. Is there a surface mount 7805? or is there another way to build a smaller circuit (im trying to get it all about the size of a nickel, maybe)

9th September 2007, 05:11 AM	(permalink)
Sceadwian	What's your input voltage, and how much current are you going to need? A zener diode and a resistor are good for basic situations as long as the voltage you're dropping isn't too large, less than the size of a dime. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

9th September 2007, 09:27 AM	(permalink)
audioguru	A 78L05 comes in a TO-92 small transistor case and two surface-mount packages. It can supply up to 100ma. __________________ Uncle $crooge

9th September 2007, 07:36 PM	(permalink)
Hero999	What's your minimum and maximum input voltage? If it's a 9V battery and you only want 50mA then go for the LM2936-5.0 as it has a lower output voltage and a lower quiescent current. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here. Last edited by Hero999; 10th September 2007 at 05:22 PM.

10th September 2007, 04:31 PM	(permalink)
Hero999	Yes, I meant lower dropout voltage than the LM7805. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

10th September 2007, 05:10 PM	(permalink)
audioguru	The 7805 needs a minimum input voltage of about 7.5V. But a 9V alkaline battery's voltage drops quickly to 7.2V which is too low, then drops more to 6V. A rechargable "9V" battery is frequently actually 7.2V. So a low-dropout regulator is needed. __________________ Uncle $crooge