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FanMagic – intelligent controller for fan diagnostics and monitoring depending upon temperature

 
     

FanMagic assures early diagnostics of fans, prolongs their service life period, diminishes power consumption and fan-made noise. The use of controller increases reliability of hardware work due to total monitoring of cooling system and signalling in case of failure. The use of controller combined with the system of redundant cooling allows to create fault-tolerant system with long-life performance. Controllers run for more than 2 years confirms the appropriateness of their use in constructing of reliable servers with effective cooling.
The principle of controller functioning consists in constant measurement and analysis of airflow temperature and of rotation speed of 2 fans as well as in generation of fan voltage according to preliminary charted matrix.

FanMagic assures:

 FanMagic

 
  • Digital filtering and accurate selection of impulses of signals from rotation sensor against ripple and bounce during decreased fan-feeding voltage.

  • Measurement of fan rotation sensor impulse frequency.

  • Measurement of temperature of passing airflow and smoothing of taken measure.

  • Slide control of fan rotation speed by means of fan voltage variation. Fan voltage variesfrom 5 -7V to 11,7V by changing on-off ratioof pulse wide modulation (PWM). PWM frequency is 62,5 kHz.

  • Storing of matrix of dependence of PWM on-off ratio values upon temperature in EEPROM.Matrix contains values for 12 temperature intervals from 20°Ñ to 55°Ñ. This allows for easy creation of controllers with individual adjustment to user's needs.

  • Storing of matrix of dependence of minimum valid rotation speed upon PWM on-off ratio.This allows to use 2 fans with different rotation speed paramenters with one controller.

  • Automatic determination of minimum valid rotation speed values of real attached fans (SETUP mode).

  • Chime and warning lights if temperature exceeds 55°Ñ (overheating) and if fan fails (rotation speed decreases below matrix values).

  • Generation of signal with frequency 30 – 100Hz (signal for emulation of rotation sensor when connected to motherboard). Frequency 30Hz corresponds to PWM value of 48,4%, frequency 100Hz corresponds to PWM value of 100%. Frequency of 16Hz corresponds to failure status (overheating or decrease of rotation speed).

  • Output of sequence of 100% fan voltage (11,7V) alternating with short-term pause to ease startup of fan that has stopped or which rotation speed has decreased below allowed value and creation of possibility for other fan to ensure necessary level of cooling.

  • Operation in SETUP mode if corresponding jumper is closed. In this mode controller performs diagnostics of fans and updates the matrix of minimum valid rotation speed values.If error occurs, the default matrix of values is restored.

Depending on number of funs that must be controlled, the FanMagic family has two versions: FanMagic-2 and FanMagic-4. Controllers have the same functions but they have different numbers of connectors and microCPUs. Next description illustrates the principles of work of the FanMagic-2 but can be applied for FanMagic-4 too.

  

 

FanMagic is a board (26x64mm) with single-chip microcomputer, miniature speaker, LED and heat sensor. Device can be connected to 2 fans with 12V supply. Fans should have rotation sensor signals. Controller is fed by +12V voltage and by +5V voltage through connector for 5,25" devices (CDD) that is enlarged for 10 cm by wires.

Default matrix of dependence of PWM values upon temperature is provided below:

T(oC)

less 20

20..21

22..24

25..26

27..29

30..32

33..35

36..39

40..43

44..48

49..53

More 54

PWM(%)

48,4

53,1

57,8

62,5

67,2

71,9

76,6

81,3

85,9

90,6

95,3

100

When standard 80 mm fans with four-lane rotor that consumes 0,14A at 12V and nominal 2300rpm connected , the PWM values will correspond the following voltage values:

PWM (%)

48,4

53,1

57,8

62,5

67,2

71,9

76,6

81,3

85,9

90,6

95,3

100

U(Â)

7

7,5

7,9

8,2

8,5

8,8

9,1

9,7

10,3

10,9

11,5

11,7

Matrix (default) of minimum valid rotation speed values of rotation speed (the same for 2 fans) depending upon PWM is given below:

PWM (%)

48,4

53,1

57,8

62,5

67,2

71,9

76,6

81,3

85,9

90,6

95,3

100

RPM

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

This matrix is recorded in controller EEPROM during manufacturing and can be easily changed in "SETUP" mode. In this mode controller yields PWM values from 48,4% to 100% in turns, with 2 sec time gaps, and measures fans rotation speed. The obtained 12 pairs of values (for each fan separately) are recorded in EEPROM and are used by algorithm of early diagnostics of fan condition. If turning speed of at least one fan is below tabular value, beeps and warning lights are yielded with simultaneous formation of 100% output PWM(voltage). If fans behaviour in "SETUP" mode is incorrect, the default values are recorded in EEPROM.

In order to switch controller to"SETUP" mode, one should close pins of 1st and 2nd connectors J2 and turn on the controller. In 4 sec controller will start generate sequence of 12 short beeps (0,5 sec) which are followed by 2 sec pause. At that time controller forms 12 values of PWM, applying voltage at fans and simultaneously measuring fan ratation speed and recording them into the matrix. The obtained resulting matrix of fan rotation speed values is used during normal controller work by the algorithm of early diagnostics. If error occurs, controller yields intermittent beeps and restores the default matrix of minimum valid rotation speed. To prevent invalid filling of matrix DO NOT attach defective fans in "SETUP" mode! To make forced restoration of default matrix of minimum valid rotation speed, disconnect of brake one of fans after

 

 

PWM-sequence of 12 values begins to form. At the end of filling the matrix controller yields short beeps with 1 sec period. The number of beeps fits with measured tempera-ture and is used at control-lers manufacturing. After removing of jumper and restarting, the controller is ready for work in normal mode.


FanMagic

 

 
FanMagic is used in HDD Noise killer device and in 19" rack-mount server chassis. In rack-mount chassis controller monitors fans of cooling of chassis (hard drives). FanMagic may be used in personal computers for controlling of additional fans that are mounted in the case. Also it may control the fans that are ususally present in standard case of trivial PC. In this situation one controlled fan can be located on CPU and second – in power supply. It is desirable to place controller with heat-sensing device on the way of airflow from CPU to power supply in such a way that heat-sensing device is placed between CPU cooler edges. Good results may be obtained if passive cooler (heatsink) places on CPU is used with additional 80mm or 92mm fan that is mounted in the case in immediate vicinity from CPU. The larger diameter fans have better productivity, smaller noise production and better "controllability".

The following diagram shows temperature depedent changes of PWM, fan voltage, matrix values of minimum rotation speed and real values of rotation speed. Mesurements are taken when two fans are connected. The fan is with four-lane rotor that consumes 1,7W at 12V and nominal 2300rpm. Diagram

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