Will the thermo controlled fans still operate properly at 5V

GLO · Post by **GLO** » Sat Sep 23, 2006 2:34 am

I know standard fans will run a 5V but im not sure if the temp probe will still work properly at 5V?

What im looking at doing is mod one of these 80 or 120mm fans so that it gets its power from a usb port. It will be used to cool a PVR (non PC).

If you have any suggestions for which model/brand please let me know, as im looking for one with a probe that i can push down into one of the vents that the fan will be blowing into.

Its a little un-orthodox but if should work.

Thanks in advance.

Bluefront · Post by **Bluefront** » Sat Sep 23, 2006 4:15 am

Probably won't work like that. The thermo-control is reducing voltage to the fan motor.....it expects to get 12v to start with, and reduces the voltage from there. If you start with 5V, and the thermo-control reduces that further, the fan might be getting 3v, maybe less, to start up.

Most fans won't start at an analog 3v....that mod is very likely not to work at all.

GLO · Post by **GLO** » Sat Sep 23, 2006 4:57 am

So do you think that just a standard fan on 5V will be my only choice?

Bluefront · Post by **Bluefront** » Sat Sep 23, 2006 5:27 am

There are many options. A pwm controller can start fans at very low voltage. There are analog controllers that give a 12v burst to start spinning....but a straight 5v is the easiest.

hulubei · Post by **hulubei** » Sat Sep 23, 2006 7:20 am

It depends on the controller and how it works. There ar two major types:
- starts at full speed (12v or the maximum voltage on the line, ie 5v) and then decrease the voltage until it reaches a balance between voltage and temperature. When temps ar going high, it pumps more voltage until the maximum.
- reads the temperature and pumps the voltage written in it's registers that correlates for those temps.

You can first try how it work, on wich principle.