Power computer fans with a wall wart? (help)

[Supernova]

I built a home theater and have a rack system that's vented at the top. I found my amplifier is getting quite hot so I've decided to built a rack mount cooling system. I'm using a 3 U Rack Panel with 3 fans.


Rack Panel: https://www.pennelcomonline.com/en/P...F3/m-6565.aspx

Fans: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



The fans are rated 12VDC at 1.7W. Since I have 3 of them would I use a 12V walwart with .4A?

[Kevin P]

You'll need a 12V power supply that supplies at least enough current to power all the fans. 1.7W @ 12V is 0.15 amps (150 mA). 3 fans would take 450 mA, so get a power supply (wall wart) rated at 0.5A or more.

You can go higher with current on a power supply, but not less, but the voltage should match. So a 12V 1A supply would be fine as well.

[Supernova]

Thank you. I wasn't sure if I could go more and it would cause damage. I actually have 2 of these with 6 fans in total. Not sure why but after a 2 hour show my marantz receiver 6011 is super hot and I'm using an external amp.

Thanks again Kevin.

[Kevin P]

Glad to help. If you think about it, your car battery can deliver 200 amps to start your car's engine, but the dome light still only draws 1 amp.

In case you're curious, it all boils down to Ohm's Law. Current = Voltage / Resistance. Assuming the voltage is always 12V, the current drawn will be determined by the resistance of the load.

In reality, the load of your fans isn't constant. They will draw more when starting up than when running steady, and the 1.7W is probably peak, but for determining how much juice your wall wart needs to supply, the rated draw in the specs works fine in most cases.

It also doesn't hurt to have a little extra capacity, because if you run the wart at near its max current draw constantly, it will get hotter and fail sooner, plus if you add more fans down the road you'll want the capacity without having to replace the power supply again. i'd go with a 1A wart for 3 fans, and if you want to use all 6, 1.5A. 3 should be plenty for a home theater cabinet though.

Also make sure you get a regulated wall wart that puts out 12V DC. Unregulated won't have a steady voltage, and 12V AC will fry the fans. 8O Though, nowadays nearly all wall warts have switching supples that are regulated DC.

[Supernova]

Thank you for the education. Electronics is something I'm interested in but didn't realize it until later in life. Any book recommendations?

Here's the outcome. Again, thanks for the help. My wal-wart is a switched supply. I just happen to have a bunch of them that I saved over the years.

[Kevin P]

Cool, it woiks! Does it keep the cabinet cool?

Do the blue LEDs distract you while watching TV/movies? I find blue LEDs too bright and hard on the eyes. I prefer red, or no lighting at all. But then I'm an old phart. :fart:

As for learning electronics, I had a Radio Shack 150-in-1 project kit when I was a kid. Nowadays, there's Google.

[Supernova]

No you don't notice them at all since the rack is in a separate room. :wink: The rack has built in fans at the top and they're super loud so they may get replaced. You can't hear them in the theater anyway unless you open the door. I have a build thread on AVSForum. https://www.avsforum.com/forum/19-de...ter-build.html

It does seem to help with cooling. At least the bottom of my oppo 203 isn't nearly as hot. I'll be pulling the system out soon and cleaning up some wiring in the back and putting the Adcom 7707 on the bottom. Eventually I'll upgrade the processor but no immediate plans. The only reason for the upgrade is that I'd like DIRAC.