USB 5v to 3v

SavellM · 3 Jul 2012 at 22:46

Hi guys.

I have USB powered fans in the back of my TV unit.
But finding it a bit little loud.
So wondering if it is possible to have something maybe a usb adapter to downvolt from 5v to 3v?

I dont really want to cut wires or anything.
So wondering if there is something I can plug inbetween?

Tealc · 3 Jul 2012 at 22:50

I've never heard of or seen anything.

What do the fans look like?

SavellM · 3 Jul 2012 at 22:59

They are normal fans but run into usb instead of PWM or 3pin.
So it plugs right into a usb port, quite nice.

This: http://www.coolerguys.com/840556090588.html

areksnumbr1sxylady · 3 Jul 2012 at 23:02

What tv you have, that needs cooling !?

SavellM · 3 Jul 2012 at 23:03

Its not for my TV, its for my HTPC and AMP that are in my TV unit

It gets pretty warm in there, so its pulling out hot air.

Tealc · 4 Jul 2012 at 00:54

I think you'd need to cut the cable and add something in line with the +5v. You could use an extension rather than cut the USB proper.

A diode such as 1N4001 would drop 0.6-0.7v.

SavellM · 4 Jul 2012 at 01:00

Wonder if I can find a usb with pwm on the other side and can get to new fans.

SavellM · 4 Jul 2012 at 01:22

I've found this:
http://uk.thermaltake.com/products-model.aspx?id=C_00001625
http://uk.thermaltake.com/products-model.aspx?id=C_00001499

Dont like the fan but wonder if I can get the usb thinggy..
Dont much like the look of it but something like that would be AWESOME

MikeHunt79 · 4 Jul 2012 at 03:30

an l7803 will work.

EDIT: They don't exist, l7805 is the lowest linear reg ST make.

You can use resistors to slow fans, try 10ohms and work your way up.

Tealc · 4 Jul 2012 at 08:50

SavellM said:
I've found this:
http://uk.thermaltake.com/products-model.aspx?id=C_00001625
http://uk.thermaltake.com/products-model.aspx?id=C_00001499

Dont like the fan but wonder if I can get the usb thinggy..
Dont much like the look of it but something like that would be AWESOME

Yeah unfortunately that box is just a cable winder. The button just retracts the cable back into itself.

As Mike says you are probably looking at a resistor or diode or an LM317T to drop voltage to the fan. You'd have to be very careful though as the starting voltage won't be much lower than 5v.

Another solution would be to use 12v PC fans to your taste of speed and capability. You can power them with a 12v power brick, plug in charger, or Molex from the HTPC and even add a cheap fan controller, or even a temperature sensing and controlling fan controller of some kind.