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Which wire is which? Answered

Ok, I have this solar panel I was given, and a knex motor without a battery box, and In need to test which wire is positive and which is negative on the solar panel. I am no good at electronics, though I have done soldering before. I was wondering, how do I test to see which is positive an which is negative on the panel? I hope to join it to the motor to have a very powerful, eco-friendly solar model.


Heck, I'd just touch the ends to the leads of an LED to test it. Cheaper and probably easier to do. Though the motors in those boxes don't particularly care what way the current is going.

It's for the solar panel. Once I remove the plug, I will not know which one is positive/negative, because the plug has a red tip to show which part is positive. I might need this solar panel to use on something else, not just a motor. I can then mark the two wires accordingly.

You could, in fact, go to Radio Shack and buy a jack that fits your plug; then you wouldn't have to remove the plug. You could also carefully see which wire goes to the innermost piece of metal in the plug while removing it to check.

Look very closely at the wire insulation. Is one of them smooth/a single color while the other has ridges/is striped or has other identifying marks? The one that is not smooth (i.e., the one that has the ridge/stripe or other identifying marks) is usually the positive wire. I'd still check it with a multimeter as a precaution. You never know how things were made/messed with.


You need a multimeter to measure electricity. You can get one for less than $20 at various shops if you just look around a little. Shopping for a multimeter can be a little intimidating if you don't know what you need, but there are plenty of guides online for finding the one that's right for you. Don't worry about getting the right one the first time, because you will end up getting more than one if you stick with electronics as a hobby. I have an Extech meter - the one recommended on ladyada.net - and it works fine for me, but it's not the first one I got. I have an analog meter that I got from Radio Shack that worked fine for me when I was getting started. I also have two pocket meters that I've gotten at various times over the years, and an old Tandy benchtop meter I found at a yard sale.

So, that said, the logic of getting the best tool you can afford holds true. Get the best meter that you can afford; in my opinion the multimeter is one of those must-have household tools, like a hammer or a power drill.

As far as using it, there are tutorials all over the internet showing you how to do that. A little but of research will go a long way for you here.

if youre looking for really cheap one check to see if you have a harbor fright in your area. they usually sell multimeters for $10 but almost always have them on sale for around $5 or less

Do you have an LED? (like mettaurlover  says)
That should tell you pretty easily.



7 years ago

You need to use a multimeter. that will tell you what wire is what and also test for the integrity of the wires and components.