bipolar regulated supply question....

MIDIbox SID
1

I have some analog filters that need a bipolar supply. I was pondering how I can make one with the parts that I have.

I built a bipolar 9v supply using 2 batteries but it’s not enough for these filters.

So I have a question. this is a basic draft…

could this idea work, or is it just wishful thinking?  ::slight_smile:

thnx

2

won’t work. you will get nothing at -12 with this design.

you might even let the magic smoke out of that regulator.

3

There are many good schematics for bi-polar power supplies on the net.

The 7812 regulator is designed to deliver a positive 12V DC, but there’s also a 7912, which delivers a negative 12V DC. A combination of those should be able to give you the voltage you need. However, it’s not that simple. Besides this voltage regulation you may also need more capacitors in the circuit for decoupling.

Greetings,

Rutger

4

…

but there’s also a 7912, which delivers a negative 12V DC. A combination of those should be able to give you the voltage you need. However, it’s not that simple. Besides this voltage regulation you may also need more capacitors in the circuit for decoupling.

…

even with 7912, you will need -14v at the input instead of +14…

5

check this design, from Yves Yusson:

http://www.modularsynth.net/viewtopic.php?t=94&postdays=0&postorder=asc&start=1340

there is a link to download the ready to print pcb, and explanations for the transformers, I built it using two transformers to feed the +15v and -15v needed it works fine, just change the regulators for the 7812 and 7912.

6

A nice easy way to get bipolar from a single AC supply (i.e. a “walwart”, AC adapter):

http://www.paia.com/ProdArticles/dual-ribbon-howto.htm

I like it because I don’t need to mess about with mains voltages. I use bigger filter caps because if MBHP uses 2200uF to smooth out AC before a regulator, then I should do it also (since I know no better).

Note that you’re only going to get half (?) the max current… i.e. a 500mA 9V AC supply can probably only be turned into 250mA +9V DC and 250mA -9V DC.

Hope that helps.

7

Thanks, Wilba. That should work for what I’m trying to accomplish.  :slight_smile: