How to monitor fan speed of 8-9 fans ?

[Dorne]

Fan speed monitoring

my goal is to monitor the rpm of around 8 or 9 fans in my computer case and as everyone knows mobos only have around 3 or so monitoring jacks, so does anyone know how i can achieve this? some sort of circuit and software, etc...PLEASE HELP

 

[IanP]

Re: Fan speed monitoring

You will need multi-channel high speed DIO card ( example from National Instruments: **broken link removed** ).
This particular card has drivers for LabVIEW so reasonable easy will be to write application in this language.
So this is PC harware and software.

External hardware may consist of rotary encoders fitted on the fans' shafts. These rotary encoders (you need only 1 square wave to measure RPM) will feed square waves directly to the high-speed digital inputs.. and that is all..

Need more details?

 

[Dorne]

Re: Fan speed monitoring

well thats too bad cause it costs $995, but thanks for the help

 

[IanP]

Re: Fan speed monitoring

...and this is not the end..each rotary encoder will cost you another $100+.

There is different approach: external black box connected to PC serial port.
Inside this bbox you will have 8,9 .. (or as many as you need) small cards with microcontrollers such as 8051, PIC, AVR ....
Each card will have unique address and will be interogated by PC through multi-drop RS-232 port.
This way will give you more fun but I doubt it is much cheaper than of-the-shelf card..

 

[Mr_Programmer]

Re: Fan speed monitoring

buy fans with a output signal
take a fast microcontroller, and feed the speed signals from the fans to the micro
connect the micro via USB or RS232 to the PC,
write a program to display the values on the computer

This will be a lot of work.

 

[squiggy]

Re: Fan speed monitoring

It boils down to the tradeoff between how much money you are willing to spend / how much effort you are willing to put into it / and what ‘quality’ you expect or need of the final product.
If you are lucky, someone else has already done the work and is selling what you need at a ‘reasonable’ price.

If you have the electronics / programming background, Mr_Programmer’s approach is the way to go.

If you are willing to learn and do some work this is a straight forward and inexpensive project. I am sure you could find several examples on the net that you could modify to suite your needs, but doing it from scratch would not be unreasonable, and after you learn a little about embedded controllers you should be able to handle it. Sounds like a good beginners project.

I like Atmel’s AVR series, and recommend using one of them, i.e. mega8 is suitable and under $4.
You could do the electronics part (not including the fans) for under 30 dollars.

 

[albert22]

Re: Fan speed monitoring

Hi,
You may find this page, interesting. As it mentions some fan sensors. And a soft. to control and monitor.
https://www.almico.com/speedfan.php

If you just want to raise an alarm in case of failure of one or more of the fans. I mean not reading the exact speed. May be you can conect several of the fans to a same motherboard input. Probably by means of an analog circuit that combines the signals. I should be just a matter of investigating what type of signals do the fan gives and(or how the motherboard is detecting the speed/failure of the fan.
Just an idea, hope that helps
K

 

[Dorne]

Re: Fan speed monitoring

thank you, that website looks like its my answer

 

[nicleo]

Re: Fan speed monitoring

...I should be just a matter of investigating what type of signals do the fan gives ...

... A 3-wire fan has a tach output, which usually outputs 1, 2, or 4 tach pulses per revolution, depending on the fan model...

https://www.analog.com/library/analogDialogue/archives/34-04/fan/
https://www.analog.com/library/analogDialogue/archives/34-04/fan/fan_speed.pdf

... Modern fans are available with tachometer outputs (usually two pulses per revolution), to facilitate speed monitoring. Rotational speed is ascertained by simply counting the number of pulses over a fixed period of time...

https://www.analog.com/library/analogDialogue/archives/33-01/chip/
https://www.analog.com/library/analogDialogue/archives/33-01/chip/adm9240.pdf

You may consider the following approach:
8 fans (tacho signals) -> (digital) Multiplexer -> Counter/Microcontroller -> RS232/USB -> VB program

 

[puviarasu]

Re: Fan speed monitoring

Hi
The best and cheep way is use fans with built in sensors and feed the signals from the fans to pic or 8051 mcu i/o lines (pic will be best as it dosnt needs interfacing circuits, 8051 i/o lines are mostl TTL compactable) if the fans o/p pulses are in different voltage level use zenerdiode or potential divider . then you can scan I/O lines one by one estimate the speed and send it to pc via serial port or parallel port of the PC.

 

[metal]

Re: Fan speed monitoring

Hello

If I were you, I would not try to measure the speed of the fans.

What the fan is intended to do is just coolin the space, if you consider the idea of just watching how cool the case is, I recommend you using TC646B from microchip.

The features of this IC are really great :

• Temperature Proportional Fan Speed for Acoustic
Control and Longer Fan Life
• Efficient PWM Fan Drive
• 3.0V to 5.5V Supply Range:
Fan Voltage Independent of TC646 Supply Voltage - Supports any Fan Voltage
• FanSense™ Fault Detection Circuits Protect
Against Fan Failure and Aid System Testing
• Shutdown Mode for "Green" Systems
• Supports Low Cost NTC/PTC Thermistors
• Over-temperature Indication

At last, it is still up to you.

Regards

 

[puviarasu]

Fan speed monitoring

Hi metal
what you said was ok, but suppose if the temperature inside increased drastically even though your chip has sensed the temperature increase and increased the fan speed to full. and still if the temperature increases your chips good features becomes useless. until you have the control of shuting down the pc this can be only attained if you r chip has the control to shut down the pc (or) monitering the status of temperature and fan speed at various places and controlling the fan speed, processor speed etc.

 

[metal]

Re: Fan speed monitoring

Hello

The over temperature alert can be used to shut down the PC. I presume. Anyway, what did you mean by processor speed??

Regards

 

[puviarasu]

Re: Fan speed monitoring

hi metal

nowadas processors you can alter the processor's clk frequency at runtime according to the software load to reduce power consumption of the system : ).

puvi