Hi. I have a pretty old card reader made by "SWEEX" model NB000061. I'm having difficulty discovering the input voltage, the barrel connector size, and the polarity of the inner pin of the connector. I only know that the barrel connector appears to be 5.5mm in diameter. Just wondering if anyone bought this model and has the details I require. Thank you. Rich

EDIT:Just wondering if it safe to assume voltage is 5V and inner pin positive.

 

5 volts is reasonable but NEVER assume that the center is positive. I have a very nice high-resolution video camera that is burned up because the center was the negative power connection. There really should be a serious law that the center is always positive.
You will need to open the device and trace continuity from the power connector to a filter capacitorand see which polarity the center connection goes to. Do not ever presume that the makers did not do something stupid on purpose.

 

Hi. OK, upon examination, the capacitor marking tells me the centre pin is positive. I'll apply 5v and see what gives.

 

Positive is indeed more common, but some rather despicable organizations do it backwards. Label maker machines all seem to be 9 volts and center negative.

 

Hi. I plugged it into a USB power supply and it works - sort of. The thing is, this card reader is past it's sell by date and Windows 10 cannot recognise it. Basically, it's too aged for Windows to automatically find device drivers. Latest drivers are for Windows 2000. Best thing is to throw this legacy product into the bin. Thans for comments. Rich

 

Positive is indeed more common, but some rather despicable organizations do it backwards. Label maker machines all seem to be 9 volts and center negative.

Center negative allows the barrel to switch the positive when inserted.

 

Center negative allows the barrel to switch the positive when inserted.

When would switching the positive instead of the negative be an advantage in a device powered by an internal battery pack??? And what possible benefit when a video camera would not ever be powered from any source other than the external power connector??? And why would having the outer conductor of the power connector be at the supply positive, when the negative is grounded to the frames of all surrounding equipment, ever be an advantage??
It seems far more likely that it is done to assure failure of the equipment when any other power source is used.

 

When would switching the negative instead of the positive be an advantage in a device powered by an internal battery pack???

You tell me. I simply said having the barrel positive allowed one to switch the positive.

And what possible benefit when a video camera would not ever be powered from any source other than the external power connector??? And why would having the outer conductor of the power connector be at the supply positive, when the negative is grounded to the frames of all surrounding equipment, ever be an advantage??
It seems far more likely that it is done to assure failure of the equipment when any other power source is used.

Your projection of motive is baseless.

 

It may be that other means to use the data output from the device can be found. Years ago I had a bit od code provided by an associate called "DTE", "Dumb Terminal Emulator". It ran on versions of DOS3, and it was very handy because it simply displayed whatever was fed into the serial data (RS232) port. I found that nany devices sent a lot of non-ASCII characters. That was quite an education.
A current version might display whatever was fed into a USB or an ethernet port. THAT function would be very vauable, especially if it could monitor port activity without interfering.

 

You tell me. I simply said having the barrel positive allowed one to switch the positive.

Your projection of motive is baseless.

What other motivation can be given for the huge proliferation of power connectors in the past? Prior to the adoption of the USB connector for power? And the wide range of specified supply voltages?? Really, even in some of the technical journals it was mentioned. And is there a GOOD explanation of why this HP computer of mine will only function with an expensive HP supply??? I know there are tales of problems but really.