 | 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.
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
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.
|
|
