I love this website already guys, This is great

Thread Starter

Jeremysilva

Joined Apr 29, 2016
5
Nice to meet you all, I am Jeremias
I feel like i just found gold, is this website , this is my first thread . I am not at all a electronic involved guy, but I like to modify stuff,I weld and build , but "did I said i suck in electronics?
here is my first question - you find two wire -same color - you know one is positive and other is negative . how can i check ?without ground myself and touch the wire?
lol , if is easy don't judge me , please.
 

MrChips

Joined Oct 2, 2009
21,635
Welcome to the club, Jeremy.
You will find a lot of useful helpers here. There are no stupid questions. We all have to start someplace.

You find two wires. Are they live, meaning are they connected to some power source?

Color codes can be important. Sometimes they're not. Every country uses different colors to mean different things. Sometimes the installer makes mistakes. Sometimes he doesn't give a darn.

So back to the problem.
Is it connected to a live power source?
Is the source DC (such as a battery)?
Is the source AC (such as mains power)?
Do you have a test meter, such as a DMM, Digital Multi-Meter?
Do you have one of those little neon test lights, sometimes built into a small screwdriver?

Testing DC is different from testing AC. You have to know your situation.
 

wayneh

Joined Sep 9, 2010
16,399
There are good and very inexpensive tools that can both answer the question and do it safely. My preference would be a 0-5$ multimeter such as the Cen-Tech one at Harbor Freight. But you can also get a little bulb with leads that indicates line voltage. It's less versatile but handy and rugged.

These tools have plenty of uses even if you're not into electronics. I wouldn't hesitate to get one. I would hesitate to touch wires I don't know anything about.
 

tcmtech

Joined Nov 4, 2013
2,867
I feel like i just found gold, is this website
Watch out a lot of what glitters here is not gold. :eek:


There are no stupid questions. We all have to start someplace.
Seriously? You have never seen a stupid question while here?o_O Don't give the guy false hopes man! :p

Ignorance is honourable and something we all have and should never feel ashamed of.;)

Stupid questions, Well that's a standard part of forum life and function just like Nitrogen makes up the majority fo the air we breathe yet serves us no gainful purpose in our breathing itself. :rolleyes::p
 
There's no real universal color. There are conventions, but it's not across all "disciplines".

Positive and negative is relative to a reference. Many times it's Earth. In the case of a battery: Some cars had a positive ground. Most cars are negative ground.

AC power has a reference too. We call that Neutral and Neutral is connected to Earth in one place per demarcation.

With red and black, a lot of times we think of red as positive. In the word of thermocouples, red just happens to be negative.

In the US we use white for Neutral, Green for Ground and Black for hot for a 120 VAC system. A power cord might actually have black, white and green, but it can also have blue, brown and green with a yellow stripe.

Air bag circuits in a car are orange. Fire alarm cable typically has a red PTFE jacket. Thermostat/door bell wire usually has a brown jacket.

Here https://wiki.xtronics.com/index.php/Thermostat_signals_and_wiring is another example.
 

Thread Starter

Jeremysilva

Joined Apr 29, 2016
5
thank you all so fare,
it was ac , and all wires were black ,but one positive the other negative, it powered a motor, I am sure there is some toll that can identify the polarity, i want to know how I can do on the job without tools?
 

MaxHeadRoom

Joined Jul 18, 2013
21,193
it was ac , and all wires were black ,but one positive the other negative, it powered a motor, I am sure there is some toll that can identify the polarity, i want to know how I can do on the job without tools?
There is no neg & pos with AC, that terminology is used for DC.
I assume you are in N.A. if you say you have 120vac, If so then unless you have a transformer in there somewhere then one side will be at earth ground potential, to discover which is which, measure AC from each conductor to ground, one will show 120vac the other almost zero, the latter is the neutral.
Max.
 

wayneh

Joined Sep 9, 2010
16,399
Hard to measure safely with no tool, unless you don't consider a light bulb a "tool". I'd determine the hot wire by wiring one terminal of a bulb to ground and then touch the other terminal alternately with the two unknown wires. The one that lights the bulb is the hot one.
 
thank you all so fare,
it was ac , and all wires were black ,but one positive the other negative, it powered a motor, I am sure there is some toll that can identify the polarity, i want to know how I can do on the job without tools?
It's actually common to have things like T1 T2 etc written on the wire insulation.

AC motors don't reverse direction just by swapping the power input. There is more to it and it depends on the type of motor.
 

shteii01

Joined Feb 19, 2010
4,644
It's actually common to have things like T1 T2 etc written on the wire insulation.

AC motors don't reverse direction just by swapping the power input. There is more to it and it depends on the type of motor.
It is common on motors. I just saw a 120VAC valve two weeks ago, two black wires, no markings on them.
 
AC usually doesn't care. Polarized plugs can be used for safety: e.g. A light socket. Make the female threads neutral/ground. The HOT wire is normally switched. On a solenoid valve, there really isn't any difference.
 

Tonyr1084

Joined Sep 24, 2015
4,894
Lots of good information here. But so far I haven't seen anyone address this one particular possibility I'm seeing. You said that both wires are black. Well, as is the case with many lamp cords, they're all one color, be they white, black, grey - or whatever - on an AC lamp cord (or extension cord or such) one wire is the polar HOT wire and the other is the NEUTRAL. The drawing below may help you identify which wire is the hot and the neutral.

Notice that one wire (cross sectional view) is round while the other has ribs on it. The ribbed wire means (and someone will correct me if I get this wrong) the NEUTRAL wire. Sometimes you get two wires that have no ribbing, usually you'll find a small white stripe (or some other color - depending on the manufacturer) that indicates the neutral wire.

In stereo speaker wiring (automotive) typically two wires of the same color will denote a particular speaker. One of the two will have a black stripe to indicate the negative phasing of the speaker. There's almost always some indication as to which wire is which - especially when they are the same color overall.

Look for ribbing or some other NON CIRCULAR feature of your wire and consider it to be the neutral part of your circuit. WARNING - DON'T ASSUME IT TO BE NEUTRAL, I SAID "CONSIDER" IT TO BE. But before you make any deadly assumptions - VERIFY exactly what each wire is. The information I'm providing is for reference only and should NOT be considered any sort of authority on the subject. The LAST thing I'd ever want is for someone to end up hurt because of something I said. So consider carefully what you're dealing with and make no assumptions. VERIFY VERIFY VERIFY. KNOW what you have and what you're dealing with.

Ribbed Wire.png
 
Last edited:

shortbus

Joined Sep 30, 2009
7,840
Notice that one wire (cross sectional view) is round while the other has ribs on it. The ribbed wire means (and someone will correct me if I get this wrong) the NEUTRAL wire.
Never heard there was a convention to the 'ribbed' conductor. It is just so the same blade of a plug is connected to the corresponding part of the lamp socket. This means the longer and wider or neutral blade is wired so it goes to the 'shell' of the lamp socket. Normally the plug is called a NEMA 1-15A ungrounded. But the socket for them is no longer up to code, but the plug works in the code grounded socket.
 

Tonyr1084

Joined Sep 24, 2015
4,894
Never heard there was a convention to the 'ribbed' conductor.
Check your lamp cords and extension cords. The ribbing is so that whomever is wiring the lamp socket knows which is the neutral.

Now, I said I'm not certain which is which - but I DO know that the ribbing is so that whomever is working with the wire can identify one from the other. I've also seen clear speaker wire where one internal wire is copper and the other is (and I'm guessing at this) the other is silver plated or something. But one is definitely identifiable from the other. That way if you have to wire something with a particular polarity - be it neutral or negative (or whatever you choose to call it) you know which wire is which.

Whether it's molded in ribbing or a stripe - something identifies one from the other. Unless you're using wire made in a third world country.

[edit]

Just grabbed an extension cord and a lamp cord. Both cords have the ribbing on the neutral side.
 
https://en.wikipedia.org/wiki/Power_cord

wikipedia said:
North American lamp cords have two single-insulated conductors designed for low-current applications. The insulator covering one of the conductors is ribbed (parallel to wire) for the entire length of the cord, while the other conductor's insulator is smooth. The smooth one is hot and the ribbed one is neutral.[2]
But any smuck can wire it. A molded plug and power cord should be wired correctly.
 
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