12v 300ma transformers to power pc case fans?

[[email protected]]

I have a few old transformers that output 12volts at 300milliamps.
I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps and another that states 0.45amps.
Would it matter much if I used this transformer for either of these
fans as it is now?
Or would it likely ruin either fan?

 

[Michael Black]

I have a few old transformers that output 12volts at 300milliamps.
I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps and another that states 0.45amps.
Would it matter much if I used this transformer for either of these
fans as it is now?
Or would it likely ruin either fan?

This is not a repair issue.

Current is something that's available, and something that's used, not
something that is forced. So if you have a power supply that supplies
more current than the load requires, the load merely takes what current
it needs, and leaves the rest.

It is voltage that is forced. Connect something to a voltage supply
that is higher than needed, and you may burn out that something. Connect
soemthing to a voltage supply that is lower than needed, and it likely
won't work because there's not enough voltage.

On the other hand, some of those AC adaptors are marginal. They expect
to work with a certain current load, and thus they can be made cheaper.
If they aren't loaded to the specs, the voltage may be higher than
it says in the specs. Those expect the load to bring the voltage down
to where it should be. WIth those ac adaptors, connecting a lower
current fan may mean the voltage is higher than desired, and that may
be bad for the fan. It depends on how much higher the voltage.

Michael

 

[[email protected]]

I have a few old transformers that output 12volts at 300milliamps.
I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps and another that states 0.45amps.
Would it matter much if I used this transformer for either of these
fans as it is now?
Or would it likely ruin either fan?

These adaptors run 12v fans fine, for fans of 0.1A to 0.3A. You cant
run the 0.45A fan on one, it'll burn it up. You dont need a resistor.


NT

 

[CJT]

I have a few old transformers that output 12volts at 300milliamps.
I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps and another that states 0.45amps.
Would it matter much if I used this transformer for either of these
fans as it is now?
Or would it likely ruin either fan?

I hope you don't intend to try to run a DC fan on AC?

 

[Ancient_Hacker]

I have a few old transformers that output 12volts at 300milliamps.
I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps and another that states 0.45amps.
Would it matter much if I used this transformer for either of these
fans as it is now?
Or would it likely ruin either fan?

Why not use the Pc's power supply? It's there, convenient, probably
able to handle quite a few more amps of load, and automatically
switche4d at the right times.

 

[Jim Yanik]

Why not use the Pc's power supply? It's there, convenient, probably
able to handle quite a few more amps of load, and automatically
switche4d at the right times.

because he has these xfmrs laying around waiting to be used!

;-)

 

[[email protected]]

because he has these xfmrs laying around waiting to be used!

;-)

Maybe its not being used on a pc, who knows.


NT

 

[Michael Black]

Why not use the Pc's power supply? It's there, convenient, probably
able to handle quite a few more amps of load, and automatically
switche4d at the right times.

I assumed the fan had nothing to do with the computer.

Every time I pass a computer on the sidewalk waiting for the garbage truck,
I look it over. If it's recent enough and has ram, at the very least I'll
extract that. Sometimes the hard drives, and usually (because they are
easy to extract, and the cases can be used for building other things in),
the power supplies. Hence I have a lot of fans from PC power supplies.
I've made a few fans for the warm weather out of them, and have used
AC adaptors to power them. They work fine, and often create enough of
a breeze without me feeling like I'm facing a major storm.

Michael

 

[James Sweet]

Why not use the Pc's power supply? It's there, convenient, probably
able to handle quite a few more amps of load, and automatically
switche4d at the right times.

He's probably not using the fans in a PC.

 

[Bennett Price]

I hope you don't intend to try to run a DC fan on AC?

Read the labels on the fans. If they came out of a computer, they are
probably DC, not AC. Make sure that your power supplies are the same.
If they are just transformers, they are AC. If they are 'wall-warts',
they could be either AC or DC.

 

[[email protected]]

This is not a repair issue.
Sorry, but I figured that I had better ask first before I tried this.
This way it wont become a repair issue!
They are AC to DC transformers that used to be for recharging a
portable spotlight and,.. I forget what the other was for, maybe that
old luminare glass that broke.
I am using them outside the PC, as fart fans and such.
I thought about using a power supply for it, but I thought a complete
PC power supply would be a little overkill for just fans.

Yes they are PC case fans I will use.

Thanks for the feedback.
I try to learn what I can, but my full attention is on world history at
the moment.
I got an A in physical science, but thats a Tennessee A lol.

 

[Jim Yanik]

[email protected] (Michael Black) wrote in

I assumed the fan had nothing to do with the computer.

Every time I pass a computer on the sidewalk waiting for the garbage
truck, I look it over. If it's recent enough and has ram, at the very
least I'll extract that. Sometimes the hard drives, and usually
(because they are easy to extract, and the cases can be used for
building other things in), the power supplies. Hence I have a lot of
fans from PC power supplies. I've made a few fans for the warm weather
out of them, and have used AC adaptors to power them. They work fine,
and often create enough of a breeze without me feeling like I'm facing
a major storm.

Michael

I used two salvaged PC fans after Hurricane Charlie,Aug.13,2004,to keep
cool(Florida in August!) when my line power was out for 7 days. I powered
them with a 12v/20ah gel cell.It also powered a small fluorescent lamp.

The fans really helped at night when trying to sleep.

 

[bz]

[email protected] (Michael Black) wrote in

Those fans usually run on DC. The transformer puts out AC. You are likely
to ruin the fans.

As for current, do NOT series a resistor to drop the current to the spec'd
current.

What they are saying is that the fan will DRAW .45 amps of current when run
from 12 volts. The other fan will require less current. It you have to run
off of a battery, use the lower current fan. It will run longer.

If the fans DID run on AC, your 12 volt at 300 mA transformer would be
overloaded by the .450 amp (450 mA) fan and would likely fail after a short
time during which it would overheat.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[Dave Plowman (News)]

I have a few old transformers that output 12volts at 300milliamps.

It only outputs 300 mA if the load demands it.

I was wondering if it was all that important to use resistors to get
the current within the stated specs for a pc case fan I wanted to try
to run on it.
I have a fan that states 0.2amps
200mA


and another that states 0.45amps.
450mA

Would it matter much if I used this transformer for either of these
fans as it is now?

If it is just a transformer, yes, as this outputs AC and most if not all
PC fans need DC.

Or would it likely ruin either fan?

If it is a DC mains adaptor it will be ok with the 200mA fan but
overloaded with the 450 mA one.