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How to connect a linear power supply

Discussion in 'Electronic Basics' started by Ant_Magma, Mar 10, 2006.

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  1. Ant_Magma

    Ant_Magma Guest

    I know this may sound like a dumb question but i have a Tracopower TML
    5 Watt AC/DC power module and i don't know how to connect them to my

    The datasheet is available here

    For the TML 5 Watt there are pins 1 2 3 at the input and 4 5 6 at the
    output side.
    1) What is FG? Where do i connect this?
    2) Pin 2 and 3 are both AC inputs which do i connect to line, which do
    i connect to neutral (from wall outlet)?
    3) What is pin 5 (NC)? If i only want +5V do i connect to pin 6 and 5
    and if i want +5V & -5V i connect pin 4 and 6?
  2. Deefoo

    Deefoo Guest

    Which TML do you have? Single 5V (05105) or double +/-5V (05205)?

    1. FG means Frame Ground and should be connected to the earth.
    2. The datasheet says pin 2 is AC N(eutral) and pin 3 is AC L(ine).
    3. NC here means Not Connected. This is for the single supply version only
    and you simply do not use this pin. In this case you will have +5V between
    pin 6 and pin 4. Pin 4 will connect to your circuit's 0V. For the dual
    supply version you will need pin 5 to have +5V between pin 6 and pin 5
    and -5V between pin 4 and pin 5. Pin 5 will connect to your circuit's 0V.

  3. Chris

    Chris Guest

    Hi, Ant. I'm not sure if you actually found the data sheet:

    If you look on page 4 of the datasheet, you see the pinout. On the
    input side (pins 1, 2, 3),

    1 = FG
    2 = AC(N)
    3 = AC (L)

    On the wall outlet, you have Line (pin 3), Neutral (pin 2), and Ground
    or Chassis/Frame Ground (Pin 1).

    On the output side, it depends on the model you purchased. By looking
    on page 1 of the data sheet, you can see that there are seven 5 watt
    models. If you've got a TML05105, there's a single 5V output. Pin 5
    is common, pin 6 is the +5V. Pin 4 is NC (No Connect). If you've got
    a TML05205, it has both a +5V and -5V available. For the dual +/-5V
    model, pin 5 is still common and pin 6 is still +5V. However, on that
    model, pin 4 is -5V.

    Good luck
  4. Chris

    Chris Guest

  5. Ant_Magma

    Ant_Magma Guest

    Mine is a single TML05105.

    I think i got the old datasheet coz mine did not have the (L) and (N).
    So for my case i just connect the pin4 and pin6 to get 5V.

    Now another problem. I'm using this PSU for this circuit:

    It's Belfuse's powerline signal coupler. On page 3 (Ethernet product),
    the PSU is connected parallely after the MOV to the L and N. Here, the
    Earth of the wall outlet is not used.

    So how do i connect FG?

    Connect FG and pin2 together and connect them to N?
  6. Chris

    Chris Guest

    Hi, Ant. I would assume there's internal shielding and circuitry in
    the switch-mode power supply connected to FG that helps reduce EMI/RFI
    emissions. If this were an actual engineering project, you would have
    to be very concerned with FCC emissions testing, and this seemingly
    trivial question would take on a lot of significance. In the real
    world, this can easily be a project killer, and is one major reason why
    many engineers use canned switchers instead of just rolling their own
    for low volume applications.

    In a college lab, you won't have the equipment available to measure
    emissions, and I guess you don't have the time to go down this rabbit
    trail anyway, so just gloss it. For now, just use a 3-conductor line
    cord, and connect GND on the line cord to FG.

    Remember that, unless you've got a handful of these, you may want to
    use another method of powering your prototype through the initial
    stages. Although this switcher data sheet says it's got overload and
    short circuit protection, a mistake is pretty expensive, particularly
    if you've only got one of them (another lesson -- in a development
    project, always get a couple of everything).

    Good luck
  7. Ant_Magma

    Ant_Magma Guest

    But in the Belfuse coupler schematics they only use the L and N lines.
    And the N line in this case is used as the reference potential or

    I just want to be sure. Are you suggesting that i use the G line as
    well just to connect it straight to FG?
  8. Chris

    Chris Guest


  9. Ant_Magma

    Ant_Magma Guest

    Thanks Chris.

    Now another thing, in theory the electronics that i learn on paper,
    there's always ground for the current to return.

    Based on Bel's coupler diagram, i would assume the -Vout of the PSU
    would be the current's return path where i connect all my grounds to,

    If so, now with the extra G line connected to the FG of the power
    supply, which would be my ground now?
  10. Chris

    Chris Guest

    Pin 1 is FG. That is added on the primary side of the switcher for
    reasons stated above.

    The switch-mode power supply has transformer isolation between the
    primary and the secondary. For the 5V power supply on the secondary,
    pin 5 is common or the current return path. There is no connection
    between the primary side and the secondary side.

    Ground means many things in electronics, including the return path for
    the current from the power supply. FG means frame ground.

    There have been many group discussions on s.e.b. about this question.
    Since you're using Google groups, search the word "ground" in this
    newsgroup for numerous discussions on this subject.


  11. Ant_Magma

    Ant_Magma Guest

    Thanks Chris, but since i'm using the SINGLE version and NC is not
    connected i should use pin 4 correct?
  12. Chris

    Chris Guest

    Ant, it's all in the datasheet. Here's a sketch (view in fixed font or
    M$ Notepad):

    | Ground .---------.
    | (Green) FG| |
    | >---------o 1 | +5V
    | | 6 o--------> Your
    |Neutral AC(N)| | Circuit
    | >---------o 2 5 o-------->
    |(White) | | COM
    | AC(L)| 4 o No Connect (that means leave it open, don't
    connect anything)
    | >---------o 3 |
    | Line | |
    |(Black) '---------'
    (created by AACircuit v1.28.6 beta 04/19/05

    NC means No Connect. If you're making a perfboard, don't solder
    anything to pin 4. If you're making a PC board, make a pad to allow
    the pin to be soldered to the board, but don't connect anything to that

    Frequently, NC pins will be used by the manufacturer as test points for
    QC to check something inside the black box post-production. Sometimes
    there's actually nothing connected to NC pins. But there's no law that
    says they can't make another version that uses that NC pin for
    something else, so always leave it alone. NC means No Connect.

    Ant, read the data sheet. If you don't understand it, reread it until
    you understand it.

    Just do the work. There really isn't a substitute, unless you want to
    subcontract the job to someone else.

  13. Ant_Magma

    Ant_Magma Guest

    Are we having the same datasheet? Mine only have the specifications and
    the dimensions.

    Sorry Chris, i did not intent look lazy or annoy anyone.

    It's just that it's my first time doing such a project and i'm just
    trying to get everything right before i start soldering and putting it
  14. Chris

    Chris Guest

    Hi, Ant. Three days ago I gave you the link to the data sheet:

    which requires two more mouse clicks from the page you referenced.
    Just look at the posts above this one. Since it's a .pdf file, it also
    requires the free Adobe Reader, which you can get from If
    you're using M$ Windows, right-click on the link, and click "Save
    Target As..." instead of just clicking on it.

    This fairly complete data sheet goes into more detail than typical on
    the power supply. There should be enough there to use the AC-to-DC

    No offense, Ant. Prototyping is a bit of a chicken-egg thing when
    you're dealing with SMT components, I know. But you're also under
    deadline. If you don't read the datasheet, you're toast.

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