Power adapter polarity?

[Trackr]

So, it has come to my attention, by happenstance, that power adapters have certain polarities on the DC side (which makes sense now that I think about it because DC current only flows in one direction..) and I don't know which kind I need to power fans.

I'm also a little confused as to how this works.

With a PSU you have +12v and Ground.. is it the same here?

Need some advice

EDIT: Also, my charger has a little capacitor at the end like this:

Am I supposed to cut the wire before it or after it (leaving it on)?

 

[Deleted member 88227]

Why do you keep making multiple threads on the same subject?

 

[Trackr]

Why do you keep making multiple threads on the same subject?

Every thread corresponds to a question, not a subject.

First thread - General inquiry.
Second thread - Focusing on the idea of using a PSU externally which I've decided not to do.
Third thread - Asking how, instead, to use a 12v power adapter now that I've discovered they have differing polarities.

I suppose it would be easier to do via PM, if anyone's willing..

 

[Deleted member 88227]

Right and each question is on the same subject. The adapter that was shown to you earlier would handle the polarity issue. You'll simply use a multi meter on the two exposed clamps to see which one was positive and which one is negative. Then you'll connect the wires to that accordingly.

The only thing that matters is if you're plugging that plug into a device that accepts that size. Then you need to worry about the polarity because some of them the inside is the positive side while the outside is the negative and vise versa. It will be listed on the power brick which is which and on the device you're plugging in will tell what kind it needs. It looks like this.

The center part of both of those symbols represents the round plug. The inside being the the solid dot and the outside being the half circle.

Additionally, you're doing all this non sense work when a $15 solution already exists.

 

[Tsumi]

You asking these questions makes your earlier statements about knowing electricity highly suspicious. This is basic amateur knowledge, and figuring it out with a multimeter is even more basic. If you don't even know this, just get that $15 molex power adapter before you kill someone (namely yourself).

 

[Deleted member 88227]

I wonder if the OP even has a multimeter.

 

[Arcygenical]

Its not a cap, its a ferrite choke meant to decrease rf interference and therefore microvoltage fluctuations.

Cut the cable wherever you like. There will likely be a white and black, or red and black wire in the pvc jacket. Black will most likely be ground, the other wire will be V+.

And the average 17-21v laptop supply will likely harm a fan in the short term. 5a 12v supplies cost around 5$ on ebay...
2 fans will consume around .15a per 1000 rpm. Most 12v fans will be fine with a 500ma supply.

 

[stormy1]

Cut it after the choke.

Then check voltage and polarity.

http://pconthego.wordpress.com/2010/08/01/how-to-manually-check-electrical-wires-for-polarity/

 

[larrymoencurly]

Cut it about midway between the choke and plug. That way if you screw up, you can splice the wires back together again and use the charger for its original purpose again. If you cut it really close to the plug, you'll likely have to get a new plug.

 

[Trackr]

Then you'll connect the wires to that accordingly.

How, though?

The wires in a molex connector are +12v and Ground.

The wires in this power adapter are +12v and -12v (unless I'm getting it wrong).

The only thing that matters is if you're plugging that plug into a device that accepts that size

What plug? I thought I was supposed to cut the plug out and wire a molex connector instead of it. I'm supposed to keep it?

Additionally, you're doing all this non sense work when a $15 solution already exists.

Right.. or, it would be if I were not abroad for the holidays.

You asking these questions makes your earlier statements about knowing electricity highly suspicious. This is basic amateur knowledge, and figuring it out with a multimeter is even more basic. If you don't even know this, just get that $15 molex power adapter before you kill someone (namely yourself).

This is how I work. I learn from experience and nothing more.

It's very possible that I won't know the very basics but at the same time will know something most others would consider astute.

That comment about killing myself sounds glib. How would I accomplish that with a 1.5A 12v connector?

I wonder if the OP even has a multimeter.

No, sir.

If you explain to me all the functions of said device, you might just convince me to purchase one when I get back home.

Its not a cap, its a ferrite choke meant to decrease rf interference and therefore microvoltage fluctuations.

*whisper* To he honest with you.. I don't know what the difference between a capacitor and a choke is, but of course, I do know there's a difference.

Cut the cable wherever you like. There will likely be a white and black, or red and black wire in the pvc jacket. Black will most likely be ground, the other wire will be V+.

Ah, so you're saying saying that the -12v = Ground and +12v = +12v?

And that it won't kill me as Tsumi believes?

And the average 17-21v laptop supply will likely harm a fan in the short term. 5a 12v supplies cost around 5$ on ebay...
2 fans will consume around .15a per 1000 rpm. Most 12v fans will be fine with a 500ma supply.

Why would I use a 17-21v adapter? I have a 12v 1.5A ready to be cut.

I figured that would be enough for 3 fans. Looks like I was right

Cut it after the choke.

Then check voltage and polarity.

http://pconthego.wordpress.com/2010/08/01/how-to-manually-check-electrical-wires-for-polarity/

And without a multimeter? Is that a stupid question?

Cut it about midway between the choke and plug. That way if you screw up, you can splice the wires back together again and use the charger for its original purpose again. If you cut it really close to the plug, you'll likely have to get a new plug.

Mhm. There doesn't seem to be very much space between the connector and the choke. I suppose I could give it a shot. I'd need something to hold the tiny cable ends while I solder it.

 

[Tsumi]

Umm... really? I'm sorely tempted to post the Star Trek facepalm picture I keep bookmarked...

You should not do anything without basic knowledge, especially with something potentially as hazardous as electrical stuff. Are you in your early teens or something?

Some things to know first:

Voltage is always measured as a difference between two points. In a 12v adapter, with only 2 wires, the voltage difference between the two is 12v. In order for there to be a +12 and -12, there would need to be a third 0v wire, otherwise, it will simply be a 24v adapter (difference between +12 and -12).

12v isn't going to kill you, it might give you a bit of a shock if you're stupid enough to have it plugged in while working on it. On computer power supplies though, those capacitors can store a good amount of charge, which can potentially be lethal. Additionally, it isn't just about shocking yourself, you can create an electrical fire with improper wiring.

A multimeter is a device that measures voltage, amperage, resistance, capacitance, and more, depending on how expensive of a device you get, hence the name multimeter. Basic ones will at least measure the four I mentioned. Harbor Freight routinely has cheap multimeters for under $10, and occasionally has them for free. After you get a multimeter, you probably should Google how to use a multimeter. It's a tool that is a must for working with anything electrical.

 

[Trackr]

Umm... really? I'm sorely tempted to post the Star Trek facepalm picture I keep bookmarked...

You should not do anything without basic knowledge, especially with something potentially as hazardous as electrical stuff. Are you in your early teens or something?

So, just because I work in a different way than you, I'm automatically half your age?

Look, I work on a "need to know" basis. If I don't need to know, I don't want it taking space in my brain. I just work that way.

Voltage is always measured as a difference between two points. In a 12v adapter, with only 2 wires, the voltage difference between the two is 12v. In order for there to be a +12 and -12, there would need to be a third 0v wire, otherwise, it will simply be a 24v adapter (difference between +12 and -12).

Okay, see? Case in point.

I didn't NEED to know this to get my fans off the ground (Hah. I suppose there's a pun in there somewhere).

It's interesting to know and it makes me go "Ohhh.. cool." But I'm just not going to remember me.

You want to judge? I don't want to listen.

12v isn't going to kill you, it might give you a bit of a shock if you're stupid enough to have it plugged in while working on it.

So, why did you say that it would?

On computer power supplies though, those capacitors can store a good amount of charge, which can potentially be lethal.

Getting shocked by a plugged PSU is part of the learning process

Seriously, though, while it wasn't dangerous it certainly wasn't fun. Invest in rubber gloves.

Additionally, it isn't just about shocking yourself, you can create an electrical fire with improper wiring.

Well, that wouldn't happen on the cable side, if you use proper electrical tape and heatshrink.

But that's why I'm here - to make sure it doesn't happen on the adapter side.

A multimeter is a device that measures voltage, amperage, resistance, capacitance, and more, depending on how expensive of a device you get, hence the name multimeter. Basic ones will at least measure the four I mentioned. Harbor Freight routinely has cheap multimeters for under $10, and occasionally has them for free. After you get a multimeter, you probably should Google how to use a multimeter. It's a tool that is a must for working with anything electrical.

Thank you. But, I just don't see what I would use it for, except for this one scenario where I need to know the polarity of a given device.

 

[primetime]

lol this thread has me curious as to what its really for

 

[Trackr]

Update:

I spliced the +12v and Ground wires of a fan to the + and - of the adapter, and..

Nothing.

Obviously, I'm missing something.

EDIT:

Damn. Every tutorial online says that this should work but the fan just sits there, nothing happens..

 

[larrymoencurly]

Cut it about midway between the choke and plug. That way if you screw up, you can splice the wires back together again and use the charger for its original purpose again. If you cut it really close to the plug, you'll likely have to get a new plug.

Update:

I spliced the +12v and Ground wires of a fan to the + and - of the adapter, and..

Nothing.

Obviously, I'm missing something.

EDIT:

Damn. Every tutorial online says that this should work but the fan just sits there, nothing happens..

Most likely you simply have the polarity reversed, but you could have verified that with a multimeter. Anybody who has a soldering iron for electronics has a multimeter because it would be crazy to go without one.

You connect the +12V of the power supply to the +12V of the fan and the ground of the power supply to the ground of the fan. Don't call the ground the "-" here because computer PSUs put out -5V or -12V.

Don't mix up the colors of the wires. The two black wires in the center of the IDE molex are ground, and normally the yellow outer wire is +12V while the red outer wire is +5V, but the +12V wire leading directly to the fan may be red.

From your photo, there's plenty of room between the choke on the cord and the plug for splicing and soldering, but the only reason I recommended splicing it there was to keep it koshor, FCC radio emissions-wise, but in reality that choke probably doesn't matter much.

How did you cover your solder splices? Heatshrink is best.

Getting shocked by a plugged PSU is part of the learning process

Seriously, though, while it wasn't dangerous it certainly wasn't fun. Invest in rubber gloves.

Don't make jokes about electric shock, and don't assume rubber gloves will protect you from it because they commonly develop pinhole leaks, and hands usually sweat, so gloves can actually make any shock hazard worse. The safest thing to do is disconnect the electricity, or at least avoid high voltage. Using an AC outlet that's protected by a ground fault circuit interrupter (GFCI) also helps.

 

[Trackr]

Most likely you simply have the polarity reversed, but you could have verified that with a multimeter. Anybody who has a soldering iron for electronics has a multimeter because it would be crazy to go without one.

Why would it be crazy to go without one?

If I have the polarity reversed then shouldn't it be spinning in the opposite direction?

It just sits there and does nothing..

You connect the +12V of the power supply to the +12V of the fan and the ground of the power supply to the ground of the fan. Don't call the ground the "-" here because computer PSUs put out -5V or -12V.

The PSU puts out -5v/-12v but the wires are always +5v/+12v and Ground, and we're not talking about a PSU here. If we were.. it'd be a lot easier

Don't mix up the colors of the wires. The two black wires in the center of the IDE molex are ground, and normally the yellow outer wire is +12V while the red outer wire is +5V, but the +12V wire leading directly to the fan may be red.

I'm starting to question whether the yellow wire or the red wire on my fan is the +12v.

Doesn't matter, I suppose, since neither one works.

From your photo, there's plenty of room between the choke on the cord and the plug for splicing and soldering, but the only reason I recommended splicing it there was to keep it koshor, FCC radio emissions-wise, but in reality that choke probably doesn't matter much.

You mean the stock photo? Well, the distance is even shorter on my adapter.

How did you cover your solder splices? Heatshrink is best.

Heatshrink is essential. Tape almost always peels off after a certain time period.

On tasks where I require the thickness of tape, I apply two layers of heatshrink, usually one millimeter larger than the other.

Don't make jokes about electric shock, and don't assume rubber gloves will protect you from it because they commonly develop pinhole leaks, and hands usually sweat, so gloves can actually make any shock hazard worse. The safest thing to do is disconnect the electricity, or at least avoid high voltage. Using an AC outlet that's protected by a ground fault circuit interrupter (GFCI) also helps.

I've never trusted rubber gloves personally. I was simply speaking of the mistakes I've made in my somewhat long experience with computer modding.


EDIT:

I'm really at a loss here..

I've tried different sockets, every wire combination I can think of and yet.. nothing!

I've even tried splicing the fan wires to the wires of a USB cable, and I get the same results.

I tried connecting the red and black wire and it created a spark, so we know the cable is live, but nothing is cooking..

This is really frustrating me now. Anyone have an idea? I'm looking at 12 year-olds on Youtube who have managed to perform this simple task on video..

 

[Deleted member 88227]

Well if you wouldn't start 11ty billionty threads on the same subject you wouldn't get confused. This adapter that was recommended to you in another thread would require no cutting of the wires.

You should really just spend the $15 on a fan PSU since you obviously have no idea what you are doing.

 

[Trackr]

Well if you wouldn't start 11ty billionty threads on the same subject you wouldn't get confused. This adapter that was recommended to you in another thread would require no cutting of the wires.

You should really just spend the $15 on a fan PSU since you obviously have no idea what you are doing.

I take it your name is supposed to be ironic.

 

[Tsumi]

I would say there's a high possibility that you burned out the fan.

 

[Skripka]

OP if you don't know that your charger does not "have a capacitor on the end", but rather it has an inductor....then it means you're in over your head, doubly so if you have to Google what an inductor is after I have now pointed it out.

 

[ballistic]

I strongly suggest going down to your local library and checking out a few books on the basics of electricity and electronics.

If this is something you have a real interest in perhaps you should invest in a copy of one of these books.
http://www.amazon.com/Electronics-For-Dummies-Cathleen-Shamieh/dp/0470286970/ http://www.amazon.com/Magic-School-Electric-Field-Trip/dp/0590446835/

 

[Trackr]

I would say there's a high possibility that you burned out the fan.

Definitely not. It never even started. There was not even the faintest odor and I've burned things before.

OP if you don't know that your charger does not "have a capacitor on the end", but rather it has an inductor....then it means you're in over your head,

Why? Why does it mean I'm over my head? Serious question.

doubly so if you have to Google what an inductor is after I have now pointed it out.

Oh, I see. So, I'm in over my head because you want to feel superior to me.

This is part of why I don't like to learn something that has no use to me; I don't want to think more of myself because I know something. Knowledge is easily obtained.

I strongly suggest going down to your local library and checking out a few books on the basics of electricity and electronics.

Why? Why do you strongly suggest this? I am not hard to convince.

 

[Skripka]

Definitely not. It never even started. There was not even the faintest odor and I've burned things before.



Why? Why does it mean I'm over my head? Serious question.



Oh, I see. So, I'm in over my head because you want to feel superior to me.

This is part of why I don't like to learn something that has no use to me; I don't want to think more of myself because I know something. Knowledge is easily obtained.



Why? Why do you strongly suggest this? I am not hard to convince.

It is really pretty simple...while you're wanting to do something, that although relatively simple in concept, you don't understand the basic theory behind. And the consequence of screwing up this little project will entail either damaging your equipment, electrocuting yourself, or starting an electrical fire, or some combination of all of the aforesaid.

As mentioned you can buy premade electronics that do the job that work and are safe and you don't have to worry about killing yourself, or needing to call your insurance company and explaining WTH you were doing....because if you have a short and you take the brunt of it powering some fans there's enough current to stop your heart beating. And if you start an electrical fire with your McGuyver mod job, do you know how to put an electrical fire out, for example what letter-rated fire extinguisher to use and which ones not to use?

I'm being blunt, not to be mistaken with trying to be a show off know-it-all, to get the message across that you're literally playing with a fire-hazard here. And having cowboy cock-sureness that you can "handle it" is how people get hurt. I've seen it come very close to happening at work way too often with people playing at being an electrician. We're coming down on you to keep you safe, hoss.

 

[stormy1]

wow just wow, some people are just beyond help.
I'm done.

 

[FearTheCow]

What is it with people fucking with things they know nothing about, then getting defensive when they are called out on their stupidity?

 

[Red Squirrel]

Hilarious.

This is completely basic electrical, as basic as it gets. I don't know how anyone can also go without owning even a basic multimeter. You can get one for under 100 bucks.

Also lol @ getting a shock on 12v. I don't care how many amps, it's just not enough voltage to feel anything. I suppose if you were to put the two ends in your mouth maybe you'd feel something.

Also DO NOT cut that capacitor out. Every time you plug one of those wall warts in, it creates an imbalance on the entire electrical grid. This capacitor is there to help stop it. Blackouts happen because of people who take these capacitors out.

 

[Deleted member 88227]

Hilarious.

This is completely basic electrical, as basic as it gets. I don't know how anyone can also go without owning even a basic multimeter. You can get one for under 100 bucks.

Also lol @ getting a shock on 12v. I don't care how many amps, it's just not enough voltage to feel anything. I suppose if you were to put the two ends in your mouth maybe you'd feel something.

Also DO NOT cut that capacitor out. Every time you plug one of those wall warts in, it creates an imbalance on the entire electrical grid. This capacitor is there to help stop it. Blackouts happen because of people who take these capacitors out.

Yeah your post was hilarious.

Volts don't kill you. Neither does the amperage. It's the current that kills you.

My jaw is still dropped at the last paragraph. Just wow.

 

[larrymoencurly]

A multimeter is a fundamental tool for electronics, just like a soldering iron and pliers, and a multimeter can test power supplies, fuses, switches, batteries, wiring, diodes, transistors, and diodes. In this case, we don't know if your AC power adapter is even putting out voltage, and you need to know that fact because it's futile to run a fan from a power adapter that doesn't work. Those multimeters sold by Harbor Freight, often just $3 with a coupon or even free with any purchase with an even better coupon, are perfectly good for this type of work, but try to avoid measuring high voltage with them. Also they're often bad for measuring low resistance because their test lead plugs or sockets are often dirty and need to be cleaned by inserting and removing them 10-20 times.

Modern DC brushless fans can't run backwards, unlike old-style fans that use brushes and run off DC. A brushless DC fan actually uses an AC motor driven by an oscillator powered by the incoming DC. Most are made so they simply won't run if the power is connected backwards, and fortunately they're usually designed to not be damaged by that, either. Most DC fans rated for 12V will spin with as little as 6V applied, some 5V, but because USB ports put out only 5V, don't assume the fan is bad simply because it doesn't spin when connected to a USB port.

If your fan has 3 wires connected directly to it, then the third wire is the RPM signal output and does not have to be connected to anything. With 3-wire fans, one wire is black (ground), another red (+12V -- notice this is different from the yellow used by the computer's +12V lines), and the RPM wire is yellow (do NOT connect this wire to +12V power or it could burn out the chip that drives the fan).

Contrary to what's shown in fiction movies and TV shows, when electronics burn out they usually don't create flames, smoke, or sparks because their internals can vaporize or melt too quickly to be noticeable on the outside.

You need to answer the following:

1. What happens when you plug the fan into its normal connector (I assume it's an IDE molex)?

2. What is the voltage coming out of the AC power adapter?

There's no sense trying to run the fan from your AC power adapter if that adapter doesn't work.

How about posting some sharp, well-lit photos of what you've done, showing all the important details clearly, especially the connections at the fan and at the AC power adapter?

 

[Deleted member 88227]

Are you saying the fan has more than 2 wires? If so, there's a good chance its 3rd wire is for the RPM signal and is the fan's yellow wire, while the fan's red wire is for +12V. The 3rd wire does not have to be used.


1. What happens when you plug the fan into its normal connector (I assume it's an IDE molex)?

2. What is the voltage coming out of the power adapter?

If you are assuming it's an "IDE Molex" connector on that fan than the yellow wire is the 12v, red is 5v and the two blacks are grounds.

If the fan plugs into a motherboard header, then it's not an "IDE Molex" connector.

 

[larrymoencurly]

If you are assuming it's an "IDE Molex" connector on that fan than the yellow wire is the 12v, red is 5v and the two blacks are grounds.

If the fan plugs into a motherboard header, then it's not an "IDE Molex" connector.

I don't know what kind of connector is on that fan, but the +12V wire can be red if that connector is wired straight to the fan, unlike the usual situation with IDE Molex connectors from an ATX PSU. I wish OP would post pics to show what he's actually working with.

 

[Red Squirrel]

Yeah your post was hilarious.

Volts don't kill you. Neither does the amperage. It's the current that kills you.

My jaw is still dropped at the last paragraph. Just wow.

LOL the last paragraph was a joke. You actually believed I was serious?

Amperage IS current. Just another way of saying it. Current = how many amps being drawn. But you need enough volts to "push" it to your heart. 12 volts aint enough. A car battery can deliver hundreds of amps, but you're not going to drop dead if you touch the two terminals. Heck, there are 4 strings of 24 2-volt 4000ah cells here in the basement, equaling 48v (well 54v actual due to the rectifiers' float voltage). I can touch that bus bar and nothing happens. Again, not enough volts, even though there is 1,600 amps being drawn from the rectifiers. It's capable of delivering much more if it has to, but when I touch the bus bar, my body's resistance is too high to draw much amps. Ohm's law..

 

[Trackr]

LOL the last paragraph was a joke. You actually believed I was serious?

I find this particularly hilarious.

Looks like the Red squirrel got caught Red handed.

 

[BinarySynapse]

Without knowing which wire was positive, and which was ground, then you had a 50% shot of hooking it up backwards which could have killed it.

Without knowing which fan wire is which (assuming it's a three wire fan), you had a 66% chance of hooking up the RPM sense wire to ANY of the adapter wire which, as Red said, would insta-zap the fan's electronics... killing it.

That's why there's so many warnings about static electricity when dealing with electronic components. There are thousands to billions of parts inside chips that are on the atomic scale these days, and a static spark of only a few hundred volts will drive enough current to melt something in there, and you'd never even feel, see, or smell any evidence to know it had happened.

I recently worked a laptop with a failed voltage regulator put 19.5V directly into the 1.5v VCC input of every chip on the motherboard. Three of them caught fire, two just smoked, the rest I knew were most likely dead just because of what happened, but they showed no signs of damage. Imagine if it was a AC-DC adapter that failed short instead a DC-DC converter. There'd have been 120v (or more) on the motherboard plain, and things would have been very nasty for me.

And the number one reason to own a multimeter if you're doing any kind of electrical work, is to know for sure that the wires you're about to mess with are doing exactly what you're expecting them to. I re-learned this (and almost the hard way) when I was doing the wiring in my wife's new laundry room. I THOUGHT I had killed the right breaker, but when I undid a wire nut on a temp wire that I had going so there'd be some electricity in the adjoining bedroom while I was gone, I heard my kid yell across the house "HEY, MY XBOX JUST DIED!". If he hadn't yelled that I'd have grabbed hold of a live wire without even knowing it because I slipped up one time.

That's why everyone here is warning you about messing with things you don't understand. With electricity and electronics, you don't learn as you go, you learn before you go.

 

[Trackr]

It is really pretty simple...while you're wanting to do something, that although relatively simple in concept, you don't understand the basic theory behind. And the consequence of screwing up this little project will entail either damaging your equipment, electrocuting yourself, or starting an electrical fire, or some combination of all of the aforesaid.

Your argument that you have to understand the basic theory behind something in order to use it or work with it is glib at best and downright pompous at worst.

.because if you have a short and you take the brunt of it powering some fans there's enough current to stop your heart beating,

If you really think I am in danger of hurting myself, you could explain exactly how and what to avoid.

do you know how to put an electrical fire out, for example what letter-rated fire extinguisher to use and which ones not to use?

Your suggestion that a milliamp phone charger is going to start an electrical fire has discredited you in my eyes.

not to be mistaken with trying to be a show off know-it-all,

We're coming down on you to keep you safe, hoss.

Yes, clearly you have only my best regard in mind.

I've basically wired my entire house, with proper guidance from my uncle who is an electrician. I know what I need to know.

And if you're right, then I'll just grab a Darwin Award and you can sit there all smug and say with your best Jack Nicholson impression "I warned hoss, but he wouldn't listen."

What is it with people fucking with things they know nothing about, then getting defensive when they are called out on their stupidity?

Not being one of those people, I couldn't tell you.

But if I may pose a question to you - what is with people trying to justify the amount of time they've wasted learning useless information by expecting everyone to do the same and otherwise seeing less in them?

This is completely basic electrical, as basic as it gets. I don't know how anyone can also go without owning even a basic multimeter. You can get one for under 100 bucks.

Under 100$?! Why didn't you say so! I'll get 12!

Also lol @ getting a shock on 12v. I don't care how many amps, it's just not enough voltage to feel anything. I suppose if you were to put the two ends in your mouth maybe you'd feel something.

Well, I learn best by example.

A multimeter is a fundamental tool for electronics, just like a soldering iron and pliers, and a multimeter can test power supplies, fuses, switches, batteries, wiring, diodes, transistors, and diodes. In this case, we don't know if your AC power adapter is even putting out voltage, and you need to know that fact because it's futile to run a fan from a power adapter that doesn't work. Those multimeters sold by Harbor Freight, often just $3 with a coupon or even free with any purchase with an even better coupon, are perfectly good for this type of work, but try to avoid measuring high voltage with them. Also they're often bad for measuring low resistance because their test lead plugs or sockets are often dirty and need to be cleaned by inserting and removing them 10-20 times.

So, you're saying that this multimeter can tell me why the fan isn't spinning by testing the adapter and seeing if it does, in fact, give off power?

And they're only 3$?

Well, alright then. I will purchase one as soon as I am stateside.

Modern DC brushless fans can't run backwards, unlike old-style fans that use brushes and run off DC. A brushless DC fan actually uses an AC motor driven by an oscillator powered by the incoming DC. Most are made so they simply won't run if the power is connected backwards, and fortunately they're usually designed to not be damaged by that, either. Most DC fans rated for 12V will spin with as little as 6V applied, some 5V, but because USB ports put out only 5V, don't assume the fan is bad simply because it doesn't spin when connected to a USB port.

Thank you. This is what I figured.

But then, if the fan doesn't get damaged, why doesn't it work with either wire in connected to either wire?

If your fan has 3 wires connected directly to it, then the third wire is the RPM signal output and does not have to be connected to anything. With 3-wire fans, one wire is black (ground), another red (+12V -- notice this is different from the yellow used by the computer's +12V lines), and the RPM wire is yellow (do NOT connect this wire to +12V power or it could burn out the chip that drives the fan).

Fuck.

Okay, I admit it. I haven't modded fans in a while. I connected the yellow cable to the +12v on the charger.

Contrary to what's shown in fiction movies and TV shows, when electronics burn out they usually don't create flames, smoke, or sparks because their internals can vaporize or melt too quickly to be noticeable on the outside.

Well, if in this case the fan did, in fact, burn internally then that would be the only time I've had something burn without it being noticeable.

1. What happens when you plug the fan into its normal connector (I assume it's an IDE molex)?

No, it's a 3-pin motherboard connector. It works.

2. What is the voltage coming out of the AC power adapter?

12v, of course. 1.2A.

How about posting some sharp, well-lit photos of what you've done, showing all the important details clearly, especially the connections at the fan and at the AC power adapter?

Well, as a photographer, I think I might be able to oblige.

However, since you claim the fan is dead after wiring the yellow wire to the 12v wire, I suppose there's no point.

If you are assuming it's an "IDE Molex" connector on that fan than the yellow wire is the 12v, red is 5v and the two blacks are grounds.

If the fan plugs into a motherboard header, then it's not an "IDE Molex" connector.

This is correct. I was going to use a different fan at first but chose the S-FLEX instead. Poor, poor S-FLEX.

I don't know what kind of connector is on that fan, but the +12V wire can be red if that connector is wired straight to the fan, unlike the usual situation with IDE Molex connectors from an ATX PSU. I wish OP would post pics to show what he's actually working with.

No, it's exactly what he said. A 3-pin motherboard header with three colors - black, red and yellow.

I connected the yellow to the +12v on the adapter, and thus must have burned it.

We best not tell Scythe about this..

 

[Trackr]

Without knowing which wire was positive, and which was ground, then you had a 50% shot of hooking it up backwards which could have killed it.

Without knowing which fan wire is which (assuming it's a three wire fan), you had a 66% chance of hooking up the RPM sense wire to ANY of the adapter wire which, as Red said, would insta-zap the fan's electronics... killing it.

Looks like your 66% figure was spot on. I can't lie - I made a mistake.

I recently worked a laptop with a failed voltage regulator put 19.5V directly into the 1.5v VCC input of every chip on the motherboard. Three of them caught fire, two just smoked, the rest I knew were most likely dead just because of what happened, but they showed no signs of damage. Imagine if it was a AC-DC adapter that failed short instead a DC-DC converter. There'd have been 120v (or more) on the motherboard plain, and things would have been very nasty for me.

Actually, it would be 240v for me here in Israel. That's why electricians here are such champs.

But wow, 19.5v to 1.5v.. I once placed a battery charger designed for 110v into a 230v socket and it started to smoke in about 5 seconds flat. That was a shitty day because I really need that battery..

And the number one reason to own a multimeter if you're doing any kind of electrical work, is to know for sure that the wires you're about to mess with are doing exactly what you're expecting them to. I re-learned this (and almost the hard way) when I was doing the wiring in my wife's new laundry room. I THOUGHT I had killed the right breaker, but when I undid a wire nut on a temp wire that I had going so there'd be some electricity in the adjoining bedroom while I was gone, I heard my kid yell across the house "HEY, MY XBOX JUST DIED!". If he hadn't yelled that I'd have grabbed hold of a live wire without even knowing it because I slipped up one time.

My god, man.. are you saying you were almost killed in front of your own children? I'm just going to assume I didn't read that..

That's why everyone here is warning you about messing with things you don't understand. With electricity and electronics, you don't learn as you go, you learn before you go.

No, I completely agree. With AC current, I phone it in before I even begin. I did something slightly stupid with AC once before and I could never forget it.

Also, if you're saying that a multimeter could have spared the fan by being able to tell me which wire (red or yellow) was the +12v, I will certainly be buying one.

 

[BinarySynapse]

Looks like your 66% figure was spot on. I can't lie - I made a mistake.



Actually, it would be 240v for me here in Israel. That's why electricians here are such champs.

120v or 240v, no difference since they'll both kill you quick.

But wow, 19.5v to 1.5v.. I once placed a battery charger designed for 110v into a 230v socket and it started to smoke in about 5 seconds flat. That was a shitty day because I really need that battery..

How in the hell did you manage that? The sockets are different for that exact reason.

My god, man.. are you saying you were almost killed in front of your own children? I'm just going to assume I didn't read that..

Not in front of, but they very likely could have seen me dead at some point in the day.

No, I completely agree. With AC current, I phone it in before I even begin. I did something slightly stupid with AC once before and I could never forget it.

AC or DC doesn't matter, both are electrons moving through a wire, current is current, and it going somewhere it should has disastrous effects.

Also, if you're saying that a multimeter could have spared the fan by being able to tell me which wire (red or yellow) was the +12v, I will certainly be buying one.

No, knowing what you're doing would have saved the fan. Actually there is a diode feature on most multimeters that probably could have been used to test the wires to safely see which ones allowed current to pass and which ones didn't that probably could have told you that the yellow wire was a no go. Also, if you had a motherboard handy (which sounds like you do), then checking the pins on the board would have told you which one was +12v, which one was GND, and which one showed no connection as it drives the base or gate of a transistor.

 

[Trackr]

120v or 240v, no difference since they'll both kill you quick.

Yes, but I find that 120v doesn't give your body that topical aroma that 240v does.

How in the hell did you manage that? The sockets are different for that exact reason.

The sockets are different? I'm not sure what you mean by that.

Not in front of, but they very likely could have seen me dead at some point in the day.

I don't ever want you touching a power cord again. Okay, now I'm acting like a pompous douche.

AC or DC doesn't matter, both are electrons moving through a wire, current is current, and it going somewhere it should has disastrous effects.

But DC can't kill you.. at least not in voltages that computer components function in.

No, knowing what you're doing would have saved the fan.

Oh, you smug little bastard!

Actually there is a diode feature on most multimeters that probably could have been used to test the wires to safely see which ones allowed current to pass and which ones didn't that probably could have told you that the yellow wire was a no go. Also, if you had a motherboard handy (which sounds like you do), then checking the pins on the board would have told you which one was +12v, which one was GND, and which one showed no connection as it drives the base or gate of a transistor.

It really doesn't take a motherboard. You just have to remember that fans with motherboard headers have reversed 5v and 12v wires. I will remember from now on.

 

[Trackr]

Update:

Okay, I'm back and I've got 4 fans and a PSU just in case.

Just to make sure - a PSU only draws as much power as the devices it is powering, correct?

It's a 650w PSU, so I don't want my power bill to skyrocket.

 

[BinarySynapse]

Yes, but I find that 120v doesn't give your body that topical aroma that 240v does.

I presume the sense of smell matters the least if you're dead. I could be wrong I suppose.

The sockets are different? I'm not sure what you mean by that.

A 100-120V outlet is physically different from a 230-250v outlet in just about every country I know of (except for Brazil... they don't seem to have any concept of safety standards) there). Even a 120v 15a outlet is slightly different than a 120v 20a outlet (but a 15a device will plug into a 20a outlet).
So to have plugged a 120v cord into a 240v outlet would have had to take quite a bit of rigging up.

I don't ever want you touching a power cord again. Okay, now I'm acting like a pompous douche.

Feal not, I manage to finish that wiring job, and relocated three more circuits, including a 240v-30amp dryer line. afterwards. I just made to to test everything before I touched it.

But DC can't kill you.. at least not in voltages that computer components function in.

Oh DC certainly can kill you. But like you said, not at the voltages inside a computer.

Oh, you smug little bastard!



It really doesn't take a motherboard. You just have to remember that fans with motherboard headers have reversed 5v and 12v wires. I will remember from now on.

There is no 5v wire on a fan. There's not even a color standard per se. I've seen red, yellow, and black; green, blue, and purple; all black; etc etc.

Update:

Okay, I'm back and I've got 4 fans and a PSU just in case.

Just to make sure - a PSU only draws as much power as the devices it is powering, correct?

It's a 650w PSU, so I don't want my power bill to skyrocket.

It draws as much as the devices it's power plus some small amount for conversion losses (it takes energy to create the heat put off by a PSU afterall). Keep in mind some power supplies will fall off the efficiency curve when they're powering a light load. But that just means that instead of 80%+ it's like 65% efficient, so a 6watt load will draw 9watts from the wall instead of 7.5w.

 

[Skripka]

Your argument that you have to understand the basic theory behind something in order to use it or work with it is glib at best and downright pompous at worst.



If you really think I am in danger of hurting myself, you could explain exactly how and what to avoid.



Your suggestion that a milliamp phone charger is going to start an electrical fire has discredited you in my eyes.



Yes, clearly you have only my best regard in mind.

I've basically wired my entire house, with proper guidance from my uncle who is an electrician. I know what I need to know.

And if you're right, then I'll just grab a Darwin Award and you can sit there all smug and say with your best Jack Nicholson impression "I warned hoss, but he wouldn't listen."

Please tell me exactly where in this thread before now you said ANYTHING specific about what you're doing in terms of equipment you were using? All you did was post a stock photo of what appears to be a laptop charger and asking what wires to cut...using a bunch of words strung together that you don't know the meaning of, mistaking a ferrite inductor for a capacitor.

You want me to be pompous? Fine I'll be pompous. Retake high school physics, that curriculum usually includes basic circuits. That is me being fucking pompous. I could say more, but you are clearly not worth getting infracted over.