istel Posted February 9, 2014 Report Share Posted February 9, 2014 (edited) Hi I was looking for a straight up BOM for the +/- 12v PSU for the AOUT board, but i can't seem to find any, so i am trying to gather the components for myself based on the center-tap transformer mode http://www.midibox.org/dokuwiki/doku.php?id=bipolar_12v_psu#center_tap_transformer I was thinking this setup: Transformer: http://www.reichelt.de/Transformers-PCB-5-0-8-0-VA/EI-42-14-8-215/3/index.html?&ACTION=3&LA=5&ARTICLE=27411&GROUPID=3316&artnr=EI+42%2F14%2C8+215 Rectifier: http://www.reichelt.de/Rectifiers/B40C800DIP/3/index.html?&ACTION=3&LA=5&ARTICLE=4639&GROUPID=2998&artnr=B40C800DIP 7812 and 7912 (pos/neg 12v) But the caps i am a little confused about - in the guide it says a general rule is 470 uF per 0.1 ampere - the transformer will provide 2x167mA - Meaning something lik 2x470uF on both sides, so around 1000 uF caps - and here i need 1 electrolytic and 1 cheramic for pos and neg side before and after the 7812/7912 - correct? To sum it up: 4 x http://www.reichelt.de/Electrolyte-Capacitors-105-C-1000-5000h/RAD-FC-1-200-16/3/index.html?&ACTION=3&LA=2&ARTICLE=84701&GROUPID=4000&artnr=RAD+FC+1.200%2F16 and then 4 x cheramic/film non-polarity? I can't find any on reichelt with the right specs, they are all in pF which seems like to little (http://www.reichelt.de/Ceramic-Capacitors/2/index.html?&ACTION=2&LA=2&PROFID=256&GROUPID=3159&SHOW=1).. Hope it makes sense - i am just a little confused with the cap values actually? Thanks! :smile: Edited February 9, 2014 by istel Quote Link to comment Share on other sites More sharing options...
Shuriken Posted February 9, 2014 Report Share Posted February 9, 2014 (edited) The caps need to be able to withstand the rectified voltage, no need for low esr ones. So use a 25V one: RAD 105 1.000/25 but i would personally take a 2200u one . For the non polarity ones use X7R-5 100N or Z5U-2,5 100N Edited February 9, 2014 by Shuriken Quote Link to comment Share on other sites More sharing options...
istel Posted February 9, 2014 Author Report Share Posted February 9, 2014 The caps need to be able to withstand the rectified voltage, no need for low esr ones. So use a 25V one: RAD 105 1.000/25 but i would personally take a 2200u one . For the non polarity ones use X7R-5 100N or Z5U-2,5 100N Thank you Shuriken Trying to get my head around these electronics one step at a time :) Isak Quote Link to comment Share on other sites More sharing options...
cosmosuave Posted February 10, 2014 Report Share Posted February 10, 2014 This is the one I plan on building... http://www.musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php Quote Link to comment Share on other sites More sharing options...
istel Posted February 10, 2014 Author Report Share Posted February 10, 2014 (edited) This is the one I plan on building... http://www.musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php Hmm, i'll just check this out.. Thinking i will make the other one, but i'll see. :) Edited February 10, 2014 by istel Quote Link to comment Share on other sites More sharing options...
Highcooley Posted February 10, 2014 Report Share Posted February 10, 2014 It definitely depends on what you are planning to drive with this PSU. MFOS' design is not a bad choice, especially if you want to go for a small footprint and don't need a lot of power. However, it's a bit like sucking every last mV out of the wall wart to produce +/-12V, hence the huge cap bank and the feedback diods. Also make sure you have an old school transformer in your wall wart and not a switched PSU, or directly go for a transformer. This design is suitable for basic functionalities without critical VCOs or circuits which need an absolute rock solid voltage source or a lot of power. If you can afford the cost, space and weight, I would go for a +/-15V center tapped transformer, as this will leave you with enough head room for mains noise, drops and ripple. You can also go more for the 2200uF-3300uF range than the 9900uF tank bank, which cuts cost on the other side. However, that's the opinion of an analog synth builder who needs a stable +/-12V source with about 1.2A. You're talking about 167mA transformers. One thing to consider is, that the AOUT_NG alone sucks about 40mA without the core, any other module, display or subsequent circuits attached. So keep power consumption in mind. Quote Link to comment Share on other sites More sharing options...
Altitude Posted February 12, 2014 Report Share Posted February 12, 2014 ^ Disagree 100%, an "old school" linear supply will be 10x bigger, 5x more expensive, and will get much hotter than a modern decent switching one which will also be 5x more efficient, just search the forums and see how many people here are using Meanwell PSUs without any issues. There is a reason that no one uses big linear supplies any more. For a $40 Meanwell you get a 5A 5V rail with +/-12V. How much would just a linear transformer cost to do 5A? Buchla Music Easels use SMPS for a reason. Quote Link to comment Share on other sites More sharing options...
Highcooley Posted February 12, 2014 Report Share Posted February 12, 2014 ^ Disagree 100%, an "old school" linear supply will be 10x bigger, 5x more expensive, and will get much hotter than a modern decent switching one which will also be 5x more efficient, just search the forums and see how many people here are using Meanwell PSUs without any issues. There is a reason that no one uses big linear supplies any more. For a $40 Meanwell you get a 5A 5V rail with +/-12V. How much would just a linear transformer cost to do 5A? Buchla Music Easels use SMPS for a reason. Sorry, I think this is a misunderstanding. I didn't want to say that a switching supply won't be a good choice at all. What I mean is, that a switching wall wart will likely cause troubles with the MFOS design, as the caps as well as the backward diodes are specifically designed for old school transformers with a 50Hz cycle. I just mentioned this, as nowadays it is not always clear what you get if you have a wall wart. However, it is very unlikely that there are many switching wall warts on the market which produce AC. But I think this input about using a switching PSU instead of a conventional one has definitely to be considered in the first hand. Quote Link to comment Share on other sites More sharing options...
cosmosuave Posted February 12, 2014 Report Share Posted February 12, 2014 Thanks for the tip on the Meanwell... Just ordered one from Jameco and will install into my SEQV4... Quote Link to comment Share on other sites More sharing options...
istel Posted February 20, 2014 Author Report Share Posted February 20, 2014 Didn't see all the replys on this topic - i was planning to build this just for the AOUT, but maybe i could switch out the transformer to get more current and tap out 5v DC for the core also? Only having one power supply would be nice :) I ordered all the stuff, so now i am just going for this, but next time i'll check out the Meanwell. Thanks! Isak Quote Link to comment Share on other sites More sharing options...
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