Spitting fan speed signal

[CaseyRedDragon]

Can I split the speed signal wire from a fan that goes to the motherboard and have it go to a fan speed display on the front of the case so I can see the fan speed both on the display and on windows? or do you guys know of a fan speed display that connects to the computer by USB getting the speeds from the motherboard itself?

 

[jay32267]

You should be able to do this.

The only reason you would have a problem is if the speed display drew enough current to drop the voltage on the speed signal wire.....and I don't think that is likely.

 

[Paperdoc]

I agree.
There may also be another alternative. Many mobos come with a display / configuration utility application on the CD that came with the board. This can be installed on your machine and run as an application under Windows to place a small display on your screen that shows fan speeds, temperatures, etc. Check that CD. In fact, it MIGHT already have been installed on your HDD when you did the intital installation and installed device drivers from the CD, so you just need to find it in All Programs.

 

[ron2456]

Download AIDA64 Extreme, there you can monitor the fan speed in rpm

 

[CaseyRedDragon]

I know that I can use a display software but I was seeing if I could use both so basically connecting the fan to the motherboard and having the speed wire from the fan split and also going to a fan speed display. Also do you guys know where I could fine this wire to do this?

 

[ron2456]

Yes you can but you need to make sure that you are not pulling more than 1A from the header or else you risk damagimg the motherboard.

 

[Paperdoc]

The signal is very small electrically (5 VDC pulses of small current), so any smallish wire gauge would do the job. You only need one lead, of course, not two. We are assuming that this "fan speed display on the front of the case" is a module that HAS standard 3- or 4-pin fan headers on it and that this module already is grounded to the rest of the chassis.

Now, maybe your query was more like "which wire do I splice into?" On the fan's female connector, IF it is for a 3-pin fans, the color codes and functions are:

Pin #1 - Black - Ground
Pin #2 - Red + DC Volts, varies from 12 down to 5
Pin #3 - Yellow - speed pulse signal

On a 4-pin fan female connector the color codes are different but most signals are similar:
Pin #1 - Ground
Pin #2 - 12 VDC always
Pin #3 - Speed pulse signal
Pin #4 - PWM signal

On BOTH types, there are ridges along the side of the connector nearly lined up with Pins 1 and 3. Pin 4 is beyond the ridges.

So, on BOTH types you are looking to tap into the signal on Pin #3. At the fan display device, that wire will connect to Pin #3 of its male header for a port.

 

[CaseyRedDragon]

Anyone know where i can get a cable like this already made?

 

[Paperdoc]

I really doubt you could find that - your idea is not a common thing to do. You will have to do a little custom splicing and soldering to accomplish this.

FIRST point is, what kind of connector do you have on that front panel device? IF is is really a common third-party "fan controller" that can display the speed of each of its fans, it probably has standard 3-pin male (with pins) fan headers on it to plug in fans. Or, they MAY be 4-pin. Either way, you will find that each such header has a plastic tongue sticking up beside Pins 1-3. Look now at the connector on the fan you have plugged into the mobo. It's female (with holes) and has two ridges on one side that fit around that protruding tongue. IF it is 3-pin, the colors of the wires will be as my June 28 posting above, so you can identify them. NOTE that, if you position the connector so you are looking at the side with the ridges facing you and the holes facing up, the Black (Ground) Pin #1 is to the right, and the Yellow (Speed signal) on #3 is to the left. IF it's a 4-pin connector the colors of the wires will be different. But still, orient it so ridges face you and holes face up, and Pin #1 (Ground) will be to the right, with Pin #4 to the left. In this case you can note that the ridges are alongside Pins 1 and 3, and Pin 4 is outside the ridges' space. Now, you want to connect from that fan connector to your front panel unit ONLY the speed signal from Pin #3.

Next you need a wire and a female connector that goes to the front panel unit. If you can scavenge and old fan that does not work you can snip off its wire set at the motor. Other wise you can buy a simple fan extension cable intended for use to place a fan a long distance from a mobo header. Whichever wiring source you get, disconnect and tie up the power wires from Pins 1 and 2, leaving only the Pin #3 (Yellow, maybe) wire connected. Bare the end of it, and bare a small length of the Pin #3 wire coming out of the fan, probably near its connector. Splice then solder the extension wire to the fan wire, wrap with tape to insulate. Plug the extension lead (Yellow(?) wire only) into the connector on your front panel unit, and that will feed the speed signal there for it to display, as well as to your mobo header.