Hi all,
I have four SUNON cooling fans with the rating DC 12V 1.8W. I am going to power all four fans with DC 12V 60W power supply. All four fans and power-supply will be in parallel circuit. Since the source power is higher than fan's power rating, should I have to add any current limiting resistors to the fans? If so, how much be the resistor value?

Thanks in advance.

-Ajay

 

http://www.electro-tech-online.com/content/222-amp-hour-fallacy-ohm-s-law-noobies.html

Read this.

 

You should not need to place any resistors in the wiring setup. I just recently built a wire harness for three 12v fans from a 12v source (not in parallel) and did not need any resistors. 60w is definitely sufficient for your application. You are just providing the 12v source to multiple fans by piggybacking off the positive 12v source line and the ground. Since you have a sufficient amount of power (60w) there should not be any significant drop seen at the load.

 

^- I second that opinion. Your fans will draw whatever power they need and not more. I run multiple 12Vfans on my boat from a single 250AH battery, wired in parallel. I have a single 25amp inline fuse and 5A fuse in each fan connection just in case I get a short.

 

You should not need to place any resistors in the wiring setup. I just recently built a wire harness for three 12v fans from a 12v source (not in parallel) and did not need any resistors. 60w is definitely sufficient for your application. You are just providing the 12v source to multiple fans by piggybacking off the positive 12v source line and the ground. Since you have a sufficient amount of power (60w) there should not be any significant drop seen at the load.

Thanks for your reply.

But, I am not worried about the insufficient power. I am worried about the extra power my power supply delivers. 60W is very larger than 1.8W need of fans.

If fan consumes 1.8W, what happens to the remaining power of 58.2W? Won't the power supply try to deliver the whole power? Will it deliver the power, only based on the need of application?

Thanks
Ajay

 

Power is used only when needed.

Do ur homework before asking the basics of electronics.

 

We need a sticky for Ohm's Law

 

As a side note, something ohms law doesn't come out and tell you, the data on the fan tells you that at the given voltage what the power draw will be. It don't matter if your power supply is capable of delivering fifty amps your fan will only take what it needs.

 

Returning to my example, my battery is theoretically capable of delivering 250Amps, but when I plug in each fan, the battery delievers only the 2-3 Amps that makes the fan work.

 

As a side note, something ohms law doesn't come out and tell you, the data on the fan tells you that at the given voltage what the power draw will be. It don't matter if your power supply is capable of delivering fifty amps your fan will only take what it needs.

Ohm's Law states I = V/R

You determine I based on V and R.

 

Thanks for your reply.

But, I am not worried about the insufficient power. I am worried about the extra power my power supply delivers. 60W is very larger than 1.8W need of fans.

If fan consumes 1.8W, what happens to the remaining power of 58.2W? Won't the power supply try to deliver the whole power? Will it deliver the power, only based on the need of application?

Thanks
Ajay

/start rant
The first reply to your question provided a link that has the answer. Perhaps you should be polite enough to bother reading it.

Sorry if this sounds a bit grumpy, but it is: People here go to the trouble of helping you out, yet you don't appear to be able to help yourself...
/end rant.

 

Ohms law, volts, Amps, Watts.

Simple LED/resistor circuits,
simple 7805 circuits,
simple transistor circuits (for instance drive a bulb).

Aren't there tutorials about that?

On the one hand it's OK we have a good forum here where people
even can ask the simplest question (beyond logic).

On the other hand, this is teached at school/college, can be found
in most electronics books,
and some people have done these basic circuits when they were young.

I would not mind to make myself familiar with the basic matter, before I begin a new hobby, or before I start tinkering with applicances.

But it's also true, myself I am not the brightest for computer tech,
I had 2 hard drives, 1x40GB slow IDE, one 250GB SATA.
Only recently I figured out, I could use the SATA drive for Windows,
much much faster startup...

This can be confusing for noobs, and so can electronics basic topics be confusing as well.