Determining Plug Polarity of a Wall Wart

[Tchail]

I just bought a 9V Wall-Wart for use with my lighted Enterprise-D model.

How do I determine the polarity of the plug?

I know that I need a multi-meter, but other than that...

Any help would be appreciated,

-Tchail

[One AM]

A really easy way would be to hook up 3 white 3.6v LEDs in series, then hook it up. If they light up, that's the way, and positive is positive, negative is negative. If they don't, reverse it. If they still don't, then you've got either bad LEDs or a bad power supply. You can do it without soldering using a breadboard and pressing the wires to the different parts of the plugs manually.

[tetsujin]

I just bought a 9V Wall-Wart for use with my lighted Enterprise-D model.

How do I determine the polarity of the plug?

Put the meter in DC voltage mode (it is a DC 9V wall-wart, right?), plug in the adaptor and hook it up. If you get a negative reading, switch the terminals around.

[Tchail]

A really easy way would be to hook up 3 white 3.6v LEDs in series, then hook it up. If they light up, that's the way, and positive is positive, negative is negative. If they don't, reverse it. If they still don't, then you've got either bad LEDs or a bad power supply. You can do it without soldering using a breadboard and pressing the wires to the different parts of the plugs manually.

This worked perfectly.

Thanks for the tip!

Although I'm sure that I'll eventually buy a multimeter, this helps me to put off the purchase.

-Tchail