Dynex DX-UC202 USB 2.0 PCMCIA CardBus Adapter External 5VDC Polarity

[jaugustine]

Hi,
I recently bought this Dynex DX-UC202 USB 2.0 PC card adapter for my
old laptop (WinXP) with USB1.1 ports, but I have no information regarding the
external 5VDC polarity (POSITIVE or NEGATIVE CENTER?). Note: I have a 5VDC
adapter with switchable polarity and a connector that fits, but I can't use it
since I don't know the polarity. I searched the web for this information but
I did not find it. Note: Not in the instruction manual.

Does anyone know the polarity?

Thank You in advance, John

 

[Paul]

Hi,
I recently bought this Dynex DX-UC202 USB 2.0 PC card adapter for my
old laptop (WinXP) with USB1.1 ports, but I have no information regarding the
external 5VDC polarity (POSITIVE or NEGATIVE CENTER?). Note: I have a 5VDC
adapter with switchable polarity and a connector that fits, but I can't use it
since I don't know the polarity. I searched the web for this information but
I did not find it. Note: Not in the instruction manual.

Does anyone know the polarity?

Thank You in advance, John

All I could find, by analogy, is the manual for a Belkin card.

http://cache-www.belkin.com/support/dl/f5u222ea.pdf

"Note: The included power supply is not needed for
bus-powered USB devices such as keyboards and mice,
or self-powered USB devices such as hard drives, printers,
etc. Bus-powered devices that draw large amounts of
power directly from the USB bus, such as webcams and
certain scanners, will require the use of the power supply."

On the specification page, theirs shows "Center Plus" via an icon
in the spec table.

You can probably verify that, using an ohmmeter. The USB port
has +5V and GND pins, and you should find continuity from
GND to GND.

There is little chance of that connector, being "polarity
protected". So be absolutely sure of your choice, before
connecting. If they added a polarity protection diode, it
could put the bus power too far out of spec (too much drop).

Based on the dimensions shown in the Startech manual for
their PCMCIA adapter, the barrel connector is an Adaptaplug "H".
3.4mm OD, 1.3mm ID according to the Startech manual. But there's
no reason they all have to be the same. So that's just a hint,
rather than a sure thing. If you were going to power via
the Adaptaplug route, you'd go to Radioshack and use their
wall display "Adaptaplug octopus" to test the PCMCIA card
connector before buying a plug.

http://en.wikipedia.org/wiki/Adaptaplug#RadioShack_Adaptaplug_conversion_matrix

I was really surprised the Startech manual didn't mention
polarity on theirs, as usually Startech is pretty good
about details. There aren't many companies that give good
tech specs.

Paul

 

[Paul in Houston TX]

Hi,
I recently bought this Dynex DX-UC202 USB 2.0 PC card adapter for my
old laptop (WinXP) with USB1.1 ports, but I have no information regarding the
external 5VDC polarity (POSITIVE or NEGATIVE CENTER?). Note: I have a 5VDC
adapter with switchable polarity and a connector that fits, but I can't use it
since I don't know the polarity. I searched the web for this information but
I did not find it. Note: Not in the instruction manual.

Does anyone know the polarity?

Thank You in advance, John

Center is positive.
Instruction manual is here:
http://www.google.com/url?sa=t&rct=...sg=AFQjCNF8c2i03NqD8A5ZupAdZeKIdxwFzQ&cad=rja

 

[Paul in Houston TX]

Hi,
I recently bought this Dynex DX-UC202 USB 2.0 PC card adapter for my
old laptop (WinXP) with USB1.1 ports, but I have no information regarding the
external 5VDC polarity (POSITIVE or NEGATIVE CENTER?). Note: I have a 5VDC
adapter with switchable polarity and a connector that fits, but I can't use it
since I don't know the polarity. I searched the web for this information but
I did not find it. Note: Not in the instruction manual.

Does anyone know the polarity?

Thank You in advance, John

and here:
www.dynexproducts.com/cms/documents/DX-UC202_Manual.pdf

 

[Paul]

As I thought, but didn't post...

Negative on the outside of a coaxial power connecter.

Not always. Devices exist with both center plus and center
minus. A number of the adaptaplug power supplies I've got,
support reversal by rotating the plug 180 degrees. You have
to be ready for anything.

http://en.wikipedia.org/wiki/Coaxial_power_connector

"Over time, there has been a trend to de facto standardize
with negative DC voltage on the barrel...

But barrel positive polarity is still occasionally seen,
along with the continued usage of coaxial power connectors
for low voltage AC power as well."

Somewhere, I read there was some standard, which suggests a label
be affixed to each barrel power hole. Usually, they mold the
polarity info, into the plastic, so you see "black on black"
and it's easy to miss. None of the PCMCIA USBs I just looked at,
had the molding.

To further complicate matters, barrel powered devices exist,
which can accept AC, unregulated DC, or regulated DC. The
unregulated one can be a bit deceptive. It consists of a
transformer, bridge rectifier, and filter capacitor, for its
power supply. This gives a DC level that varies with loading.
On my label maker, it says "7 VDC" next to the barrel connector,
but in fact, the power supply varies from around 7V (full load)
to 10V (no load). If you plug in a 7VDC regulated adapter
(which I tried), the device won't print. So in fact, the
label maker wants 7V unregulated DC (varying from 7V on upwards,
as a function of load). When the motor advances the label tape,
the voltage drops.

So really, you want documentation, before shopping for, or
connecting a barrel connector, just to be sure you've covered
the bases. And "Paul in Houston" found the real manual.

Paul

 

[Paul]

Which is why I didn't post my supposition.

What I don't understand, is why they don't mold the
polarity info into the plastic more often. It doesn't
cost anything to do that. Then it's one less thing
to have to put in the manual.

Paul