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Multiple DC Power Supply

Discussion in 'Electronic Basics' started by Manchu, Feb 17, 2004.

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  1. Manchu

    Manchu Guest

    I have twelve 6-9VDC/200-250mA CMOS cameras and have been attempting
    to design a power supply for them. The Transformer I am using is
    24VAC/100A. Unfortunately, the cameras are extremely sensitive to
    power fluctuations above the 9VDC/250mA levels. Does anyone know of
    schematics or references I can use to develop this? Any help would be
    greatly appreciated.
  2. Guest

    Guest Guest

    24VAC @ 100A?
    That's just a little hot for your application I would think! I read your
    last post - how about starting with something like raw 12 to 15VDC (4 to
    5A) supply. Feed this to 12 seperate legs each feeding a 9v 3 terminal
    regulator (7809 rated 1 amp) which then feeds thru a diode to your camera.
    Except you could attach a 6V or maybe better yet a 7.2v nicad or lithium-
    Ion battery at the V+ input of your camera as well. I would think a
    charging limit resistor would be needed in series with the chargeable
    battery or you could do the same with regular batteries if you add another
    diode in series with the + battery lead.
    This way if your supply fails you have battery backup to take over. This
    would be the ideal I would design around if I was you. To get an idea of
    what I am talking about, refer to the "steering diode" posters link:

  3. Manchu

    Manchu Guest

    Todd Thanks!

    This looks like a promising solution. I'll be setting this up this
    weekend to see how she works out. I'll let you know.

  4. DarkMatter

    DarkMatter Guest

    Design for the nominal voltage of 7.5 Volts. At a 0.25 amps each at
    low line, and 0.20 amps each at high line, the power for twelve at 7.5
    volts should be at around 225mA each unit for a total of 2.7 amps at
    7.5 volts, or just over 20 Watts.

    You could likely take the 5 volt rail of a good stiff 50W switcher
    supply, and adjust it to get 7.5 volts out, and easily push into a 20
    watt load. Maybe a cap bank on the output to reduce ripple even
    further... Or a cap at each camera.

    See a military surplus store, or an industrial liquidator.

    Better yet, just get on e-bay and buy one. Hell, even a bench
    supply will do nicely.

    Definitely get a bigger supply than you think you appear to need, as
    the cameras like steady, quiet voltage. Headroom is a good thing.
  5. Manchu

    Manchu Guest

    Todd It worked out Great. Thanks for your help. Got another idea from Amnon.
  6. Guest

    Guest Guest

    So you are making progress? are you using the battery scheme - nicads?
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