US5790430A — Variable speed fan failure detector

Claim 1

Independent Claim 189 words

A motor speed failure detector comprising: a temperature sensor providing a first output voltage proportional to temperature; a frequency to voltage converter having an input for receiving voltage pulses having a frequency proportional to the speed of a motor and converting said frequency to a second output voltage proportional to motor speed; a first circuit receiving said first output voltage as an input and developing a third output voltage representative of a desired motor speed profile which varies as a function of temperature; and a comparator having as inputs said second and third output voltages and providing an alarm output if said second output voltage drops below said third output voltage; wherein said temperature sensor comprises voltage divider including a first resistor and a thermistor coupled between a voltage source and a reference potential, said first output voltage developed at a junction between said first resistor and said thermistor; and wherein said first circuit comprises: an amplifier receiving said first output voltage as an input and providing an amplified output; and a limiting circuit said amplified output as an input and providing said third output voltage at its output.

Claim 2

Dependent Claim 189 words

A motor speed failure detector comprising: a temperature sensor providing a first output voltage proportional to temperature; a frequency to voltage converter having an input for receiving voltage pulses having a frequency proportional to the speed of a motor and converting said frequency to a second output voltage proportional to motor speed; a first circuit receiving said first output voltage as an input and developing a third output voltage representative of a desired motor speed profile which varies as a function of temperature; and a comparator having as inputs said second and third output voltages and providing an alarm output if said second output voltage drops below said third output voltage; wherein said temperature sensor comprises voltage divider including a first resistor and a thermistor coupled between a voltage source and a reference potential, said first output voltage developed at a junction between said first resistor and said thermistor; and wherein said first circuit comprises: an amplifier receiving said first output voltage as an input and providing an amplified output; and a limiting circuit said amplified output as an input and providing said third output voltage at its output.

Claim 3

Dependent Claim 17 words

The motor speed failure detector of claim 1 wherein said desired speed is a minimum speed profile.

Claim 4

Dependent Claim 95 words

The motor speed failure detector of claim 1 wherein said limiting circuit comprises: second, third and fourth resistors in series coupled between the voltage source and ground, said second resistor coupled to said voltage source and said fourth resistor coupled to ground: a first diode having its anode coupled to the output of said amplifier and its cathode coupled to the junction between said second and third resistors; and a second diode having its cathode coupled to said output of said amplifier and its anode coupled to the junction between said third and fourth resistors.

Claim 5

Dependent Claim 26 words

The motor speed failure detector of claim 1 and further including a second circuit developing an offset voltage, said offset voltage coupled to said first circuit.

Claim 6

Dependent Claim 21 words

The motor speed failure detector of claim 4 wherein said offset voltage is also coupled to said frequency to voltage converter.

Claim 7

Dependent Claim 55 words

The motor speed failure detector according to claim 5 wherein said second circuit comprises: a voltage divider including fifth and sixth resistors in series between a voltage source and a reference potential; a second amplifier having an input coupled to the junction between said fifth and sixth resistors and an output providing said offset voltage.

Claim 8

Dependent Claim 23 words

The motor speed failure detector of claim 1 wherein said frequency to voltage converter and comparator are contained within a single integrated circuit.

Claim 9

Dependent Claim 21 words

The motor speed failure detector according to claim 1 and further including a light emitting diode coupled to said comparator output.

Claim 10

Dependent Claim 40 words

The motor speed failure detector according to claim 1 and further including a transistor having a control input and an output, with its control input coupled to said comparator output, the output of said transistor providing the alarm output signal.

Claim 11

Dependent Claim 23 words

The motor speed failure detector according to claim 9 wherein said transistor comprises a MOSFET having its gate coupled to said comparator output.

Claim 12

Dependent Claim 24 words

The motor speed failure detector according to claim 9 wherein said transistor comprises a bipolar transistor having its base coupled to said comparator output.

Claim 13

Dependent Claim 203 words

The motor speed failure detector according to claim 1 wherein said frequency to voltage converter comprises: an inverter having an input receiving said voltage pulses and an output; a NOR gate having two inputs and an output one input coupled to said input of said inverter; a first D type flip-flop having a D input, a clock input and an output, the D input of said first D flip-flop coupled to the output of said inverter, the output of said first D type flip-flop coupled as the other NOR gate; a second D type flip-flop having a D input, a clock input and an output said D input coupled to the output of said NOR gate; a clock source providing a clock signal to the clock inputs of said first and second D type inputs; a transistor having a base, emitter and collector, the base of said transistor coupled to the output of said second D type flip-flop and the collector of said transistor coupled to a voltage source; and a parallel RC circuit comprising a seventh resistor and first capacitor coupled between the emitter of said transistor and ground, the voltage signal proportional to motor speed being provided at said emitter terminal.

Claim 14

Dependent Claim 24 words

A motor speed failure detector according to claim 1 in combination with a motor driving a fan, said motor and fan cooling electronic equipment.

Claim 15

Dependent Claim 16 words

A motor speed failure detector according to claim 13 wherein said electronic equipment comprises computer equipment.

Claim 16

Dependent Claim 137 words

A motor driven fan speed failure detector comprising: a frequency to voltage converter having an input for receiving voltage pulses having a frequency proportional to the speed of a motor and converting said frequency to a second output voltage proportional to motor speed; a voltage divider including a first resistor and thermistor coupled between a voltage source and reference potential, a first output voltage developed at the junction of said first resistor and said thermistor; an amplifier receiving said first output voltage as an input and providing an amplified output; a limiting circuit receiving said amplified output as an input and providing a third output voltage at its output; and a comparator having as inputs said second and third output voltages and providing an alarm output if said second output voltage drops below said third output voltage.

Claim 17

Dependent Claim 137 words

A motor driven fan speed failure detector comprising: a frequency to voltage converter having an input for receiving voltage pulses having a frequency proportional to the speed of a motor and converting said frequency to a second output voltage proportional to motor speed; a voltage divider including a first resistor and thermistor coupled between a voltage source and reference potential, a first output voltage developed at the junction of said first resistor and said thermistor; an amplifier receiving said first output voltage as an input and providing an amplified output; a limiting circuit receiving said amplified output as an input and providing a third output voltage at its output; and a comparator having as inputs said second and third output voltages and providing an alarm output if said second output voltage drops below said third output voltage.

Claim 18

Dependent Claim 18 words

A motor speed failure detector according to claim 15 wherein said fan is disposed to cool electronic equipment.

Claim 19

Dependent Claim 16 words

A motor speed failure detector according to claim 16 wherein said electronic equipment comprises computer equipment.

Claim 20

Independent Claim 164 words

A method of detecting a failure of a motor to maintain a commanded speed, said commanded speed varying as a function of temperature, such that at temperatures below a first predetermined temperature the motor runs at minimum speed and at temperatures above a second predetermined temperature it runs at maximum speed, with the speed varying substantially linearly between said first predetermined temperature and second predetermined temperature comprising: developing a first voltage proportional to motor speed; sensing a temperature; developing a second voltage proportional to a desired speed based on said sensed temperature, said voltage having a first value at sensed temperatures below said first predetermined temperatures a second value at sensed temperatures above said second predetermined temperature and a value which varies substantially linearly between said first and second values as sensed temperature varies between said first predetermined temperature and second predetermined temperature; and comparing said first and second voltages and providing an alarm output if said first voltage drops below said second voltage.

Claim 21

Independent Claim 164 words

A method of detecting a failure of a motor to maintain a commanded speed, said commanded speed varying as a function of temperature, such that at temperatures below a first predetermined temperature the motor runs at minimum speed and at temperatures above a second predetermined temperature it runs at maximum speed, with the speed varying substantially linearly between said first predetermined temperature and second predetermined temperature comprising: developing a first voltage proportional to motor speed; sensing a temperature; developing a second voltage proportional to a desired speed based on said sensed temperature, said voltage having a first value at sensed temperatures below said first predetermined temperatures a second value at sensed temperatures above said second predetermined temperature and a value which varies substantially linearly between said first and second values as sensed temperature varies between said first predetermined temperature and second predetermined temperature; and comparing said first and second voltages and providing an alarm output if said first voltage drops below said second voltage.

Claim 22

Dependent Claim 19 words

The method according to claim 18 for detecting the failure of a motor driving a fan cooling electronic equipment.

Claim 23

Dependent Claim 28 words

The method according to claim 19 wherein said electronic equipment is computer equipment including at least one processor and the temperature in the vicinity of processor is sensed.

Claim 24

Dependent Claim 13 words

The method according to claim 20 wherein said computer equipment is a server.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-08-03	2002-02-02	2002-08-04	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-08-03	2006-02-02	2006-08-04	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-08-03	2010-02-02	2010-08-04	$7700.00	Window Closed / Lapsed

Variable speed fan failure detector

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