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Don't know my Amps from a hole in the Ground.

Discussion in 'Electronic Basics' started by [email protected], Jan 14, 2005.

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  1. Guest

    I am not an Electrical Engineer. All I know about the topic is:
    a) If a lamp socket says "60W Bulb Max", then a higher wattage bulb
    would risk overheating.
    b) Power(Watts)=Volts*Amps

    Why don't packagers of computer peripheral devices list their power
    requirements?? Isn't it in their interest to protect their customers
    from premature hardware failure from using their product improperly??

    I wanted to add USB2.0 capability to my (elderly) Dell notebook so I
    could use a portable disk drive for backup and overflow storage.
    I found two products from Apricorn that seemed to fill my capacity and
    form-factor needs:
    1) USB2.0 Cardbus adapter (EZUSB2CB) is self-powered by the TypeII card
    socket, and provides two powered USB ports: 5V,100mA and 5V,500mA.
    2) Disk Drive (EZBUS40) needs 5 Volts, but the only other power specs
    are: "Bus powered or auxiliary power if needed"; auxiliary power cables
    are provided for USB port or PS2 port power.

    Now I have six possible combinations for cabling the devices, and no
    guidance on what is right or wrong!! I was forced to experiment, and my
    results are shown below.

    Dell PS2-port power specs: 5V * 100mA = .05W
    Cardbus power specs: 5V * 100mA = .05W 5V * 500mA = .25W

    Cardbus Socket the Disk is connected to:
    100mA........500mA........Auxiliary Power source
    ===============================================
    nothing......nothing......None
    OK??.........OK...........100mA PS2 socket
    ..............Boot Failed..100mA Cardbus socket
    Boot Failed...............500mA Cardbus socket

    "nothing".....Drive did not power-up
    "Boot Failed".Drive power light was flashing, followed by "Blue Screen
    of Death" in a USB boot subroutine
    "OK"..........Drive booted normally and functioned normally.
    "OK??"........Drive booted normally and functioned normally, even
    though it probably shouldn't??

    WOULD SOMEONE PLEASE ADVISE ME ON THE CORRECTNESS OF THESE
    CONCLUSIONS??
    1. Power supply by USB2CB cardbus device is only .25W total, across
    BOTH ports - not .30W as I had assumed.
    2. Power draw by EZBUS40 disk drive is more than .25W, which caused the
    USB boot failure.
    3. I think I risk PS2 socket failure from a sustained "over-draw"
    situation, if I continue with PS2 auxiliary power and the disk drive
    connected to the 100mA USB port.
     
  2. You have a decimal point wrong on all those. 5V * 0.1A = 0.5W
     
  3. Ban

    Ban Guest

    Best is if you go to the hardware store where you bought the items and have
    them installed by the sales person. I suspect a driver problem or a problem
    adressing USB2. You will eventually need WindowsXP and maybe an external
    wall wart.
     
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