Computer fan alarm circuit

1. Technical Field

The present disclosure relates to alarm circuits, and particularly, to an alarm circuit capable of alerting users to an abnormal state of a computer fan.

2. Description of Related Art

Generally, a computer includes a motherboard with various electronic elements mounted thereon. Many of these electronic elements generate heat when the computer is operating. Normally, the computer uses one or more fans to dissipate the heat from the electronic elements.

However, the fan may malfunction and stop working For example, a blade of the fan may be jammed by some obstruction, a poor electrical connection between the fan and its power source, or a motor of the fan may be damaged. In the event of any of the above situations, the heat in the computer cannot be dissipated timely and the performance of the computer will be compromised.

Therefore, it is desirable to provide an alarm circuit which can warn a user about an abnormal state of a computer fan.

Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a diagram of an alarm circuit for a computer fan in accordance with an exemplary embodiment.

FIG. 2 is a function block diagram of one embodiment of a controller in FIG. 1 .

Embodiments of the disclosure are now described in detail with reference to the drawings.

Referring to FIG. 1 , an alarm circuit 1 for warning an abnormal state of a computer fan 14 , according to an exemplary embodiment, is illustrated. The computer fan 14 is connected to a motherboard socket 10 . The motherboard socket 10 provides a power source and a speed control signal to drive the computer fan 14 and the computer fan 14 feeds back a speed signal to the motherboard socket 10 .

The alarm circuit 1 includes a controller 12 , a detection circuit 15 , a relay 17 , and an alarm unit 18 .

The computer fan 14 includes a control pin 14 a , a detecting pin 14 b , a power pin 14 c , and a grounded pin 14 d . The control pin 14 a is configured to receive the speed control signal from the motherboard socket 10 . The power pin 14 c is configured to receive a power source from the motherboard socket 10 . The computer fan 14 feeds back the speed signal to the motherboard socket 10 through the detecting pin 14 b . The speed signal corresponds to an actual rotation speed of the computer fan 14 .

The motherboard socket 10 includes a control terminal 10 a , a detecting terminal 10 b , and a power terminal 10 c . The power terminal 10 c connects to the power pin 14 c through the relay 17 to transmit the power source from a motherboard to the computer fan 14 . The control terminal 10 a connects to the control pin 14 a to transmit the speed control signal from the motherboard to the computer fan 14 . The speed control signal is a pulse width modulation (PWM) signal. The computer fan 14 increases or decreases the rotation speed according to a duty cycle of the speed control signal. The detecting terminal 10 b connects to the detecting pin 14 b to receive the speed signal.

The detection circuit 15 is configured to detect the power source received by the computer fan 14 . The detection circuit 15 includes a sampling resistor R 1 and a differential amplifier circuit 16 . The sampling resistor R 1 is coupled in series between the power terminal 10 c and the power pin 14 c.

The differential amplifying circuit 16 is configured to amplify the power source across the sampling resistor. The differential amplifying circuit 16 includes a first operational amplifier 16 a , a second operational amplifier 16 b , and a third operational amplifier 16 c . An inverting input terminal (−) of the first operational amplifier 16 a is coupled to an inverting input terminal (−) of the second operational amplifier 16 b . A non-inverting input terminal (+) of the first operational amplifier 16 a and a non-inverting input terminal (+) of the second operational amplifier 16 b are correspondingly coupled to opposite ends of the sampling resistor R 1 . An output terminal of the first operational amplifier 16 a and an output terminal of the second operational amplifier 16 b are correspondingly coupled to a non-inverting input terminal (+) and an inverting input terminal (−) of the third operational amplifier 16 c . An output terminal of the third operational amplifier 16 c is coupled to the controller 12 . The power source across the sampling resistor R 1 is amplified by the differential amplifying circuit 16 and outputted to the controller 12 through the output terminal of the third operational amplifier 16 c.

Also referring to FIG. 2 , the controller 12 includes a first detecting terminal 120 , a second detecting terminal 121 , a third detecting terminal 122 , a first output terminal 123 , a second output terminal 124 , a third output terminal 125 , and a fourth output terminal 126 . The first detecting terminal 120 is coupled to the output terminal of the third operational amplifier 16 c and configured to detect the amplified power source. The second detecting terminal 121 is coupled to the control terminal 10 a and configured to detect the speed control signal. The third detecting terminal 122 is coupled to the detecting pin 14 b and configured to detect the speed signal feed backed from the computer fan 14 which represents an actual rotation speed of the computer fan 14 . The first output terminal 123 is coupled to the relay 17 .

The controller 12 further includes a memory module 127 , an analyzing module 128 , and a comparing module 129 . The memory module 127 is configured to store relationship data about the power source, the speed control signal, and a corresponding normal speed range. The analyzing module 128 connects to the memory module 127 , the first detecting terminal 120 , and the second detecting terminal 121 . The analyzing module 128 is configured to calculate the normal speed range of the computer fan 14 according to the relationship data stored in the memory module 127 . The comparing module 129 connects to the analyzing module 128 , the third detecting terminal 122 , the first output terminal 123 , the second output terminal 124 , the third output terminal 125 , and the fourth output terminal 126 . The comparing module 129 is configured to receive the normal speed range from the analyzing module 128 and the speed signal from the computer fan 14 and compare the normal speed range with the speed signal to generate a control signal according to the comparison.

It is to be understood that the relationship data stored in the memory module 127 can be a predetermined formula used to calculate the normal speed range of the computer fan 14 according to the power source and the speed control signal. Alternatively, the relationship data may be a look up table (LUT) consisting of the power source, the speed control signal, and the corresponding normal speed range. Therefore, the analyzing module 128 can calculate the normal speed range using the formula or look up the normal speed range in the LUT according to the power source and the speed control signal.

The alarm unit 18 includes a buzzer 18 a , a first illuminating device 18 b , and a second illuminating device 18 c . The buzzer 18 a is coupled to the second output terminal 124 . The first illuminating device 18 b is coupled to the third output terminal 125 . The second illuminating device 18 c is coupled to the fourth output terminal 126 .

In one embodiment, the analyzing module 128 calculates the normal speed range according to the power source and the speed control signal. The comparing module 129 compares the speed signal of the computer fan 14 with the normal speed range. If an actual rotation speed represented by the speed signal of the computer fan 14 is located in the normal speed range, the comparing module 129 generates a normal working signal to turn on the first illuminating device 18 b through the third output terminal 125 . Therefore, the first illuminating device 18 b illuminates to indicate the computer fan 14 is operating normally.

If the actual rotation speed falls below the normal speed range, the comparing module 129 generates an abnormal working signal to turn on the second illuminating device 18 c through the fourth output terminal 126 . The second illuminating device 18 c to indicate the computer fan 14 is not operating normally. At the same time, the comparing module 129 transmits a cut off signal to the relay 17 through the first output terminal 123 . The relay 17 cut off the electrical connection between the power terminal 10 c and the power pin 14 c to prevent the computer fan 14 from damage. The comparing module 129 also generates and transmits an alarming signal to the buzzer 18 a through the second output terminal 124 . The buzzer 18 a sounds an alarm when it receives the alarm signal.

While various exemplary and preferred embodiments have been described, it is to be understood that the invention is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art) are intended to also be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.