LT1083 Linear PSU

Discussion in 'DIY' started by Poleepkwa, Sep 20, 2016.

  1. Poleepkwa

    Poleepkwa Friend

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    I need some assistance.
    I would like to build a linear PSU using the following components from audiophonics:
    Transformer R-CORE 30VA 2x9V and this supply board.
    http://www.audiophonics.fr/en/linea...ly-board-dc-lt1083-25v-to-35v-75a-p-8425.html

    I am planning to build this PSU to supply power to 2 raspeberry pi's at the same time, so that why I have 2 x LT1083 psu units providing 5 volts.
    I am however at a loss how this should be wired. I would rather rather be very safe than guess!

    I need advice how to wire this correctly as I have never wired a R-Core before.

    I am planning to use first one PSU like I have in 1x5V
    picture.
    1. Are the green and yellow cables correct?
    2. Does the yellow/green cable from the transformer go directly to the plug - (not through the switch)?
    3. Which cable goes to the white paintline? (red, white, orange, blue)
    4. Which cable goes to the black paintline? (red, white, orange, blue)


    Then later on use 2 x 5V as you can see from attached picture.

    5.Is this wired correctly?

    6. Anything else I have to keep in mind?

    https://drive.google.com/file/d/0B9Z9jjuNxJbOVTJ6Smp0Q2RKbDg/view?usp=sharing
    https://drive.google.com/file/d/0B9Z9jjuNxJbOZDE1d2NWRk54WVk/view?usp=sharing



    [​IMG]
     
  2. Clemmaster

    Clemmaster Friend

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    From the sticker it seems you need to wire the green-green together on one side and yellow-yellow on the other.

    There's 9VAC between the green pair and 9VAC between the yellow pair.
    A dot on one green and one yellow cable should indicate the start of the winding.
     
    Last edited: Sep 20, 2016
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  3. Poleepkwa

    Poleepkwa Friend

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    Thank you. Unfortunately there does not seem to be any dots anywhere to indicate the start of the winding.
    To use one PSU board do I green-green and use yellow-yellow for the other PSU board?
    If I decide to only use one PSU board with green-gree, what do I do with the yellow-yellow cable?
    You have any ideas about the primary wiring?
     
  4. Scott Kramer

    Scott Kramer Friend

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    Have a multimeter? I know these are much different, but your's are also dual primary, dual secondary -- maybe you can get something from my vid.

    (115V) Red/White... then see if it's the 2 greens (or 2 yellows) -- then go from there.

    (115V) Orange/Blue... wire this in parallel to the Red/White
     
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  5. Poleepkwa

    Poleepkwa Friend

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    Scott, I am in the EU, so I have to use 230V. How would the cabling go then?
    I have a multimeter.
    PS. Big fan of your work with the Pi.
     
  6. Scott Kramer

    Scott Kramer Friend

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    I see re: 230V It'll work, it involves hooking the 2 primaries in series, something like... hook white/orange together, hook 230V on red/blue... of course don't do this until you know for sure, don't want to short it out, might be ugly! (I don't quite understand the lingo on the sticker)

    Hopefully someone familiar with those r-cores will chime in!

    Thanks re: the pi :D
     
    Last edited: Sep 20, 2016
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  7. Clemmaster

    Clemmaster Friend

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    Right, you can also check the secondaries with a continuity test on your multimeter.

    Pairs are a straight wire in DC term, which means the DMM will beep between the 2 wires of a pair.
    In other words, if green-green beeps, then it's a 9VAC pair and Yellow-yellow is the other pair.
     
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  8. Cspirou

    Cspirou They call me Sparky

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    From the text you need to wire white and orange together. Then you have red as the 'live' side and 'blue' as the 'neutral'. I know it says that red is 0v but it's a transformer and shouldn't matter so it's just better to stick known color conventions.

    I read the specs for the PSU and it has a huge range, up to 26 VAC input. If you wire the green and yellow wires in series then you will get 18 VAC at most. This indicates a way of determining phase. Take any green wire and yellow wire and twist them together. Then put the unpaired wires in your PSU and measure the output. If it isn't turning on then that means you have 0VAC. This is good because it means that you paired the yellow and green correctly. Remove the wires from the PSU and pair those together. If the PSU is outputting a voltage then you should have 18 VAC as an input. This means you need to untwist your wire and then switch the green wire for the other green wire (or yellow for yellow). After which you should have correctly paired wires outputing 9 VAC.

    I'll upload a pic later with wiring scheme.
     
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  9. Poleepkwa

    Poleepkwa Friend

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    A picture would be of great assistance, not just too me, but too anybody who buys on of these. Noticed that my IEC plug does not have a fuse, so I should get one of those too.
     
  10. Cspirou

    Cspirou They call me Sparky

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    Here is the image for the double PSU. Since you have a DPST switch it is recommended that you wire both the red and blue wire to the switch. Part of the reason is in case you plug the system in backwards and reverse the live and neutral wires. You can also just skip the switch for the blue wire and just connect it to the IEC part on the left side. Crimp the orange and white wire together.

    If you are using two PSUs then you just put both green wires into one PSU and both yellow wires into the other, no need to worry about which order they go in. For a single PSU they need to be in parallel and you can use the scheme I already mentioned before to find out if you wired it correctly.

    Edit:

    uploading pics seems to be acting up a bit so here is a link instead

    https://drive.google.com/open?id=0B4Ja8JQUxJLzaU5zUElhdkZZU1U
     

    Attached Files:

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  11. Poleepkwa

    Poleepkwa Friend

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    Thank you too all who contributed to this "brainstorm". @Cspirou guide was spot on and I finished my trail setup without blowing up anything last night.
    For now I have just gone with feeding my Digi+ directly and it is not separated from the Pi as yet and its sound pretty darn good for the small financial outlay.

    Much more impressive than the SMPS that I was using and very little digital sheen left.
    Still have to work out some sort of case for it. All with good time though.
     
  12. Cspirou

    Cspirou They call me Sparky

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    Thinking about it now since you have two LT1083s already, you should just wire them both even if you only use one RPi to avoid the headache of making sure you have the right wires in parallel. Glad everything worked out.
     

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