electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  EdisonRex Edison's Electronic Review
Please visit the chat
 Forum index » DIY Hardware and Software
how to get 5v, from +-9v??
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
Lorenzo



Joined: Nov 09, 2008
Posts: 354
Location: Trieste - Italyjstan

PostPosted: Fri Jul 27, 2012 4:18 am    Post subject: how to get 5v, from +-9v?? Reply with quote  Mark this post and the followings unread

Hi,
the circuit I'm trying to build need +-9v and 5v to work.

For +-9v I will use two 9v batteries, but for 5v... have I to use three 1.5v batteries? or could I use the two 9v batteries someway?
Is it possible?

I mean to use 5 batteries for a little PCB seems to be a waste! Wink

Suggestion?

Thanks!

_________________
Yes!
Oh Yeah!
Wow!
Back to top
View user's profile Send private message Visit poster's website
bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Fri Jul 27, 2012 4:55 am    Post subject: Reply with quote  Mark this post and the followings unread

the easiest and simplest option imo would be to use a 5v voltage reg and a capacitor on the input and output and supply it from the +9v connection.

the draw on the +9v will be greater than the -9v but would be better all round. Very Happy
Back to top
View user's profile Send private message
corex



Joined: Mar 02, 2010
Posts: 114
Location: Las Vegas

PostPosted: Fri Jul 27, 2012 9:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Agreed -- take a look at the datasheet for LM7805.
Back to top
View user's profile Send private message
Lorenzo



Joined: Nov 09, 2008
Posts: 354
Location: Trieste - Italyjstan

PostPosted: Fri Jul 27, 2012 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

bod wrote:
the easiest and simplest option imo would be to use a 5v voltage reg and a capacitor on the input and output and supply it from the +9v connection.


Hi,
do you mean something like this? :

Posted Image, might have been reduced in size. Click Image to view fullscreen.

googling I found this topic, that seems to be written by me:

Question:Hello I am quiet nooby at the whole art of circuitry [...] can someone please show me how to build a circuit where I connect a
9V battery to the breadboard and by using my voltage regulator I change it to 5V
Please help me


Answer:You can simply use a voltage divider shown below:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Now, you want a 5V output so we'll have that for Vout and Vin is 9V. We'll just pick a random resistor value for R2 because of the ratio (but we'll have it in the KΩ range)...so for R1 you'll need a 19KΩ and for R2 you'll need a 20KΩ resistor. This will give you 4.6V which is very close.



so can I use 2 resistor only ?? or is better to build 9V to 5V voltage regulator using LM7805? I mean actually I haven't LM7805 at home! Wink

Thank you very much for your kindly replies Wink

_________________
Yes!
Oh Yeah!
Wow!
Back to top
View user's profile Send private message Visit poster's website
richardc64



Joined: Jun 01, 2006
Posts: 623
Location: NYC
Audio files: 26

PostPosted: Fri Jul 27, 2012 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Lorenzo wrote:
So can I use 2 resistor only ?? or is better to build 9V to 5V voltage regulator using LM7805? I mean actually I haven't LM7805 at home! Wink

It depends on what the 5V will be powering.

That formula doesn't take into account how much current will be needed @ 5V. If it isn't much -- which it can't be, since you plan to use 9V batteries -- then yeah, a voltage divider should be good enough. Keep the total resistance of R1/R2 low -- 1K or so -- so that what's powered by it "sees" a low impedance. Include a cap in parallel with R2 to smooth any fluctuations caused by varying currents.

This won't be ideal and you should eventually get a 7805.

_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler
Back to top
View user's profile Send private message Visit poster's website
fonik



Joined: Jun 07, 2006
Posts: 3761
Location: Germany
Audio files: 23

PostPosted: Fri Jul 27, 2012 2:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

another option would be to utilze a Zener diode. schem like divider, but:
R1 = 1K to limit the current, R2 = 5.1V Zener...

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Lorenzo



Joined: Nov 09, 2008
Posts: 354
Location: Trieste - Italyjstan

PostPosted: Fri Jul 27, 2012 3:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you all very much! I will try a voltage divider on the breadboard... then, if the circuit works fine, I'll make things properly using 7805.
_________________
Yes!
Oh Yeah!
Wow!
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1258
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Sat Jul 28, 2012 12:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

The best way to get a steady stable 5 volts at varying currents is to use a regulator such as 7805 or 78L05. The datasheet for the 7805 shows a quiescent current curve that goes from about 5 mA to 6 mA. Quiescent current is the current the regulator draws just by being in the circuit.

9 volt batteries are not high current devices. They are composed of 6 small 1.5 volt cells and were designed for transistor radios years ago (often they were then called "transistor radio batteries"). If the current draw on the +5 rail is fairly significant, it will cause the 9v battery powering the 5v regulator to die faster than the other. In fact, most analog application circuits tend to exhibit a behavior of higher current on the + rail than on the - rail. That said, you might be wise to power the +5 regulator from it's own 9 volt battery.

Also - do not be fooled by the use of CMOS and think that it's going to be low power. CMOS circuits are low power only when they are used in a purely digital fashion, that is, where the outputs are always at one rail or the other. Some very popular CMOS circuits used for audio with parts like 4069, 4049, 4007 and others are used in a "linear amplifier" configuration. The device then operates in some ways like a poor opamp This causes the device to draw much more current than when used in a digital manner. They can draw enough current to get physically warm.

Bottom line: know how much current is needed at +5 as well as the current requirements for +9 and -9. Then you can design a proper system that will not fade out and die when you're trying to get something done with it. And remember that a +5 regulator needs a minimum of +7.5 volts at the regulator input to operate statisfactorily. If the 9 volt supply to the regulator sags below 7.5 volts, the system will not be reliable.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Lorenzo



Joined: Nov 09, 2008
Posts: 354
Location: Trieste - Italyjstan

PostPosted: Sun Jul 29, 2012 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
The best way to get a steady stable 5 volts at varying currents is to use a regulator such as 7805 or 78L05. [...]

the 9v battery powering the 5v regulator to die faster than the other. [...]
That said, you might be wise to power the +5 regulator from it's own 9 volt battery.

Also - [...] Bottom line: [...]



ohh... Surprised Thank you very much for your exhaustive reply!!

_________________
Yes!
Oh Yeah!
Wow!
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use