Computer Fans from wall outlet- the most basic question ever

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
Hi,
I'm working on a project in which I need to power computer fans from a wall outlet.
my adapter is adjustable 12v at 1A max My fans are 12v at .16A I wired it correctly, touched the fan cable to adapter cable and it made a quiet "zzz" noise and turned like 1 degree, stinks a bit. Obviously something shorted but I'm not sure why. What did I do?

Thought I'd ask before I fry the other fans.
 

mvas

Joined Jun 19, 2017
538
Model # of the P/S ?
Model # of the fans and pin-out?

Did you measure the voltage of the P/S ?
Is it actually 12 Volts DC ?

"stinks a bit" is usually very bad news.
 

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
Model # of the P/S ?
Model # of the fans and pin-out?

Did you measure the voltage of the P/S ?
Is it actually 12 Volts DC ?

"stinks a bit" is usually very bad news.
I can't measure voltage because I have no multimeter at the moment; I assumed this would be somewhat straightforward.
Both are definitely 12v DC.
What is P/S? They're typical 3 pin connectors, I'm not sure of the exact model number but they're run of the mill 120mm fans from a no-name company (I figured I'd blow up at least one of them)
 

djsfantasi

Joined Apr 11, 2010
5,845
You need a multimeter.

Hopefully some moment soon, you’ll have to have one to do this properly.

P/S is a power supply. What you’re using to convert power from the wall outlet (120VAC?, 230VAC?) to 12 volts DC.

Do you have a diode, an LED and a 1k resistor? You can use those to make a simple polarity tester.

And do you have a diagram showing the purpose of each of the three pins in the connector? Since there are 3 pins and power only needs 2 pins, what does the third pin do? And to which 2 pins did you connect 12VDC? How do you know they’re the correct pins? And you are “pretty sure” polarity was connected correctly, I’m curious why you are “pretty sure”.

I know I’ve asked a lot of questions, but in order to help, we need that information.
 

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
You need a multimeter.

P/S is a power supply. What you’re using to convert power from the wall outlet (120VAC?, 230VAC?) to 12 volts DC.

Do you have a diode, an LED and a 1k resistor? You can use those to make a simple polarity tester.

And do you have a diagram showing the purpose of each of the three pins in the connector? Since there are 3 pins and power only needs 2 pins, what does the third pin do? And to which 2 pins did you connect 12VDC? How do you know they’re the correct pins? And you are “pretty sure” polarity was connected correctly, I’m curious why you are “pretty sure”.
I don't have the items, but I'll try to borrow a multimeter.
The converter is a universal power supply with voltage selector switch, output between 3 and 12V DC. Input is 230V.
Being super cheap fans there is no diagram. But the positive wire is indicated, the other two aren't. The third wire on PC fans is used to send information on RPM to the motherboard, on these fans it would appear to be the third (I'm assuming the fan wouldn't budge if I had attached the negative wire from the power supply to it).
 

djsfantasi

Joined Apr 11, 2010
5,845
That's almost as helpful as the message "Keyboard missing - press F1 to continue".
:rolleyes::D:confused:

Which one is for 12V? And where is the one with the hash mark? Can you identify
A specific order?

Without a multimeter and with this information... it’s almost impossible to help.
 

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
Ok problem solved

the positive wire was just marked incorrectly. I swapped them and the second fan worked fine. Pretty stupid, but thanks everyone for taking the time trying to help the electrically- handicapped. :D
 

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
:rolleyes::D:confused:

Which one is for 12V? And where is the one with the hash mark? Can you identify
A specific order?

Without a multimeter and with this information... it’s almost impossible to help.
It turns out the centre wire was 12v.

Problem solved but I have a quick question- if I wanted to be able to switch between 6 and 12V (since computer fans can run at varying speeds based on voltage), what would I use? Is there a simple in-line switch?
 

djsfantasi

Joined Apr 11, 2010
5,845
- if I wanted to be able to switch between 6 and 12V (since computer fans can run at varying speeds based on voltage), what would I use? Is there a simple in-line switch?
First, where are you going to get the 6VDC from? :rolleyes:

If you have both voltages available, you can use a SPDT switch. Such a switch has a common terminal and two switched terminals. Often, the common is the center terminal but other layouts exist.

Second, you have to identify the common terminal. Connect the fan’s positive wire to this terminal.

Thirdly, connect the two positive supplies (6VDC & 12VDC) to the remaining two terminals.

Toggling to switch one way will select 6VDV. Toggling the other way supplies 12VDC.
 

Thread Starter

ralroost einsnulldrei

Joined Jun 12, 2019
13
First, where are you going to get the 6VDC from? :rolleyes:
I guess I assumed there would be some sort of switch that could reduce the voltage, if it was already set to 12VDC maximum- for example I have a laptop stand with a cooling fan built it, it has a dial where you can manually change the speed. Or would that work differently than reducing the voltage?
 

djsfantasi

Joined Apr 11, 2010
5,845
I guess I assumed there would be some sort of switch that could reduce the voltage, if it was already set to 12VDC maximum- for example I have a laptop stand with a cooling fan built it, it has a dial where you can manually change the speed. Or would that work differently than reducing the voltage?
We have no idea about how the dial on the laptop stand is controlling the speed.

I’m not aware of a switch that would cut DC voltage in half by itself. It would need additional circuitry. Said circuit would likely take the higher voltage as input and output a voltage that’s half of the input voltage.

That having been said, to do what you want, you need a 6VDC supply (the aforementioned circuit)
 

atferrari

Joined Jan 6, 2004
3,581
I posted twice about fans which seem pretty much standard. They have a tacho output and two options depending of the pins number of the connector.
 
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