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Help! Using a switching power supply...

Discussion in 'Electronic Basics' started by PoiYui, Dec 23, 2004.

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  1. PoiYui

    PoiYui Guest


    First, let me get this out of the way... I'm an idiot when it comes to
    working inside electronics (but I do have most of the tools!)

    I am trying to use a 12VDC device in a small project. When in standby,
    the device will need a small amount of continuous power for memory
    (<100mA). When at max operation, it may need up to 5A. I realize I need
    a high-efficiency, compact AC-DC power supply, but I'm not sure what
    else is necessary. Can someone help me?

    So if I buy the following AC-DC switching power supply
    what else do I need to purchase? Connector pins? Crimps? AC power cord?
    Wire (what gauge)? Fan? Housing?

    Can I split the output -- one wire to the device (always on) and one to
    a toggle switch to turn the device on and off? If so, can I save money
    and use an automobile toggle switch (12V)?
    Any help would be much appreciated?
  2. JeB

    JeB Guest

    You can usually pick up a good used computer power supply for near free.
    You may need more than 100ma load for it to work propely, the 5V output
    needs to be loaded, some sort of indicator light can do the job.
  3. PoiYui

    PoiYui Guest

    I tried an ATX PSU, but I'm not drawing enough power. I tied together
    the PS_ON (green - pin 14) and a ground with hopes that it would keep
    the unit running, but it turns the fan about 1/2 turn and then nada.

    The reason I'm looking at the unit above is that it is very small (much
    smaller than an ATX PSU). Any thoughts about what components I need?
    Also, can I salvage some of the components from the ATX PSU (e.g., AC
    power cord)?

    Thanks for all your help...
  4. I would purchase the appropriate input and output connectors and crimp
    terminals, but you could also solder directly to the terminal pins
    (and probably cover them with heat shrink tubing to protect them, and
    prevent short circuits.) These supplies are intended to be mounted
    inside some equipment, so if you are using it alone, you will need a
    power cord and an enclosure. You shouldn't need a fan. I would
    probably use AWG 16 wire for all connections.

    Peter Bennett, VE7CEI
    peterbb4 (at)
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  5. PoiYui

    PoiYui Guest

    Thanks Peter.

    If I buy the terminal pins (I think they were like U$.70), can I simply
    crimp the AC power cord to the terminal pins? On the other side, can I
    crimp the AWG16 wire to the DC terminal pins and connect that directly
    to my device?
  6. You would need the crimp contacts and the connector housing. If you
    don't have the correct crimping tool, you can use pliers to crimp the
    contact onto the wire - but you should also solder the connection.
    You then insert the contacts into the connector housing, and plug the
    connector onto the power supply.
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