t_xen Posted November 27, 2007 Report Share Posted November 27, 2007 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? ::)thnx Quote Link to comment Share on other sites More sharing options...
bugfight Posted November 27, 2007 Report Share Posted November 27, 2007 won't work. you will get nothing at -12 with this design.you might even let the magic smoke out of that regulator. Quote Link to comment Share on other sites More sharing options...
rutgerv Posted November 27, 2007 Report Share Posted November 27, 2007 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 Quote Link to comment Share on other sites More sharing options...
bugfight Posted November 27, 2007 Report Share Posted November 27, 2007 ...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... Quote Link to comment Share on other sites More sharing options...
sineSurfer Posted November 27, 2007 Report Share Posted November 27, 2007 check this design, from Yves Yusson:http://www.modularsynth.net/viewtopic.php?t=94&postdays=0&postorder=asc&start=1340there 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. Quote Link to comment Share on other sites More sharing options...
Wilba Posted November 28, 2007 Report Share Posted November 28, 2007 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.htmI 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. Quote Link to comment Share on other sites More sharing options...
t_xen Posted November 28, 2007 Author Report Share Posted November 28, 2007 Thanks, Wilba. That should work for what I'm trying to accomplish. :) Quote Link to comment Share on other sites More sharing options...
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