GB2520809A

GB2520809A - Fan controller

Info

Publication number: GB2520809A
Application number: GB1417075.7A
Authority: GB
Inventors: Henry Jamieson Riddoch; Philip David Try
Original assignee: Alifabs Cabinets and Ancillaries Ltd
Current assignee: Commscope Design and Integration UK Ltd
Priority date: 2013-09-27
Filing date: 2014-09-26
Publication date: 2015-06-03
Anticipated expiration: 2034-09-26
Also published as: GB2520809B; GB2518659A; GB201417075D0; GB201317189D0

Abstract

This is for a fan controller that has two temperature sensor inputs 116, 118 and four fan interfaces 106, 108, 110, 112. These are controlled by a microprocessor 102. The invention is designed to help maintain the temperature of electronic devices such as mobile telephone base stations, while also minimizing noise for the people living and working nearby. The settings for the four fans can be changed via separate plugs or sockets, and there are three alarms 122, 124 and 126 that indicated if the equipment is not functioning properly. There is also an auxiliary output 120. Normally, if the fans were running too fast all the time, an engineer would have to be sent out to fix it, but this can be repaired remotely and thus reduce noise for the people living and working nearby. The speed of the fans is controlled using a pulse width modulated (PWM) signal. The invention uses a first and second PWM signal, and there is a first and second duty cycle for their respective PWM signals.

Description

FAN CONTROLLER

Technical Fi&d

S

Embodiments of the invention described herein relate to fan controllers, for example controlling the speed of fans within a cabinet that contains electronic devices and systems implementing for example a mobile phone base station.

Background

Electronic devices such as those that are used in mobile telephone base stations are generally installed in enclosed cabinets at the site of the base station mast. These electronic devices when in operation generate significant amounts of heat, and so the enclosure in which they are installed must be cooled. Previously, air conditioning units have been provided to actively cool the air inside the cabinet but these are expensive to install and operate.

A more cost effective solution to control the temperature in the cabinet is to use fans to draw cool outside air into the cabinet and expel the warm air from inside the cabinet.

Significant amounts of heat can be extracted from the cabinet, such as 1-4 kW for smaller cabinets up to 12-15 kW for larger cabinets. Therefore, large or powerful fans can be required. Such fans are typically variable speed with the speed being monitored using a pulsed signal generated within the fan which is proportional to the speed of the fan, and are typically controlled using a pulse width modulated (PWM) signal provided to the fan from an external control. These fans can be noisy when operating at frill speed, and the cabinets (such as for example associated with mobile telephone base stations) can be installed in urban areas close to dwellings. To reduce noise, a cabinet may include a fan controller that measures the ambient temperature within the cabinet and controls the fan speed accordingly, such that the fans can operate at a lower, quieter speed when the temperature inside the cabinet is not high.

Sometimes problems develop with the equipment in the cabins or with the installation of the equipment, causing the controllers to operate the fans at higher speeds than had been anticipated, Typically this is noted by increased or sustained noise from the fans and is reported by those living or working near the cabinet. A subsequent visit by a specialist engineer is then required to investigate and/or monitor the problems. Typically this is a complex investigation requiring the set up of data monitoring and logging equipment to monitor and log the temperatures in the cabin and fan speeds over an extended period of time

Summary of embodiments of the invention

According to a first aspect of embodiments of the invention, there is provided a f an controller comprising a microprocessor, a first input adapted to receive a first temperature measurement signal from a first temperature sensor, a second input adapted to receive a second temperature measurement signal from a second temperature sensor, first and second fan control interfaces adapted to provide a first pulse width modulated (PWM) signal, the first and second fan control interfaces including first and second fan speed inputs respectively, third and fourth fan control interfaces adapted to provide a second pulse width modulated (PWM) signal, the third and fourth fan control interfaces including third and thurth fin speed inputs respectively, and a communication interfice adapted to connect directly to a data processing device to receive operating parameters and/or a fan control program for execution by the microprocessor and to send the operating parameters and/or the fan control program to the data processing device, wherein the fan controller includes inactive software and is adapted to, in response to receiving a request from the data processing device at the communication interface, activate and execute the inactive software to cause the fin controller to send a data structure to the data processing device, the data structure comprising a plurality of fields that indicate a first temperature indicated by the first temperature measurement signal, a second temperature indicated by the second temperature measurement signal, a first target fan speed, a second target fan speed, at least a first speed measurement of a first fan indicated by a first fan speed measurement signal provided to the first fan speed input, a second speed measurement of the second fan indicated by the second fan speed measurement signal, a third speed measurement of the third fan indicated by the third fan speed measurement signal, a fourth speed measurement of the fourth fin indicated by the fourth fan speed measurement signal, a first duty cycle of the first PWM signal, and a second duty cycle of the second PWM signal.

Other aspects include an environment management system, comprising, a first temperature sensor, a second temperature sensor, first, second, third and fourth fans, and a fan controller similar or identical to that of the first aspect.

Further aspects include a cabinet containing electronic devices and an environment management system according to the above aspect, and also include a mobile telephone base station, comprising one or more antennas and such a cabinet.

Additionally, aspects include a system comprising a fan controller and a data processing device, for example connected to a communication interface of the fan controller.

Brief description of the drawings

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows an example of a fan controller according to embodiments of the invention; Figure 2 shows an example of a cabinet according to embodiments of the invention; and Figure 3 shows an example of a mobile telephone base station according to embodiments of the invention.

Detailed description of embodiments of the invention Embodiments of the invention include fan controllers that are programmable using a programming interface, or via a communication interface of the fan controller. The communication interface is adapted so that on a request from an externally connected data processing device, such as a laptop personal computer (PC) or the like, software that was previously inactive within the fan controller is activated and executed, which causes the instantaneous status of various aspects of the environmental monitoring system associated with the fan controller to be provided to the data processing device. For example, the temperature sensed by temperature sensors, fan speeds and the like can be provided. This may be in the form of a data structure. The data processing device may then perform certain ifinctions such as data logging, time stamping, analysis and other flinctions such that there is no requirement for the fan controller itself to perform these functions.

Figure 1 shows an example of a fan controller 100 according to embodiments of the invention. The fan controller 100 comprises a microprocessor 102 in communication with memory 104. The memory may be volatile or non-volatile or a mixture of the two. The memory stores operating parameters and/or an executable program that dictates the operation of the fan controller -for example, the speed of the fans at a particular ambient temperature.

The microprocessor 106 is also in communication with four fan control interfaces 106, t08, and 112. Each of the fan control interfaces has four pins. Two of the pins provide a power supply and ground connection to the respective fan when connected. The power supply and ground connections may simply be a passthrough of the power supply and ground provided to the fan controller 100 and described further below. A third pin provides a pulse width modulated (PWM) signal from the microprocessor to the fan, and can be used by the fan to adjust its speed. For example, the fan may control its speed to be a proportion of its maximum speed, the proportion being the duty cycle of the PWM signal. A fourth pin of each fan control interface receives an indication of the actual speed of the respective connected fan, In some embodiments, for example, this indication may be a "tacho" signal that provides a predetermined number of pulses (one or more) per revolution of the fan. The microprocessor in some embodiments may use the tacho signal to calculate the fan's actual speed. In use, each fan control interface may have a fan connected to it. Thus the fan controller may have one, two, three or four fans connected to it. In practice, a "fan" connected to a fan control interface may comprise a plurality of fans (i.e. multiple motors with associated fan blades) that are controlled using a single fan control interface, The fan controller 100 may be powered using a power supply connected to a direct current (DC) power supply input 114, The power supply may comprise, for example, power supply and ground connections. In some embodiments, the power supply may comprise a safety (or separated) extra low voltage (SELV) power supply operating in the range -36 to -60V, The fan controller 00 further includes a first temperature sensor input 116 and a second temperature sensor input 118. Temperature sensors such as thermistors can be attached to these inputs to obtain a signal indicating the ambient temperature measured by the thermistors. Additionafly, the fan controller 100 has an auxiliary output 120. The microprocessor controls the auxiliary output t20 to be either "oft" whereby one of the two terminals of the auxiliary output, for example, is an open circuit, or "on" whereby the two terminals are connected to the power supply terminals, i.e. the power supply and ground respectively.

There are also three alarm outputs 122, 124 and 126 in the fan controller 100. Each of the alarm outputs is relay controlled by the microprocessor t02. The first alarm output 122 is energised in the non-alarm condition such that in the event of a power failure the relay associated with the first alarm output 122 is de-energised indicating an alarm condition, The first alarm output 122 is also de-energised by the microprocessor 102 in the event of a failure of a thermistor connected to either of the temperature sensor inputs 116 and 1t8. Failure of a thermistor is assumed if the measured temperature exceeds 85°C and the thermistor is considered to be an open circuit, or if the measured temperature falls below -40°C, whereby the thermistor is considered to be a closed circuit. In addition, the first alarm output is de-energised by the microprocessor 102 if the fan speed of any of the connected fans falls below a certain percentage of the expected or target speed, The second alarm output 124 is actuated by the microprocessor 102 to indicate an over-temperature alarm, when the temperature measured by either of the thermistors connected to the temperature sensor inputs 11 6 and 11 8 exceeds a predetermined temperature, The third alarm output 126 is actuated to indicate an under-temperature alarm, or dependent on the configuration if a blocked air filter is detected, The air filter may be present to filter air from outside the cabinet before it enters the interior of the cabinet, The fan controller 100 also includes a communication interface 128. The communication interface may be connected to an external data processing device such as, for example, a laptop PC or other suitable data processing device, When connected, the data processing device may be used to provide (e,g, upload) operating parameters and/or an executable program to the fan controller 100, whereby for example the parameters and/or program are stored in the memory 104, The data processing device 128 may also be used to retrieve (e.g, download) the operating parameters or executable program. The fan controller may communicate with the data processing device using any suitable protocol, for example IJSB orRS232.

In operation, the fan controller operates according to the set of parameters or the executable program when executed by the microprocessor 102. The parameters or program may specify the operating conditions of the fan controller. For example, such conditions may include the desired fan speed (i.e. target speed) of the connected fans at particular temperatures as indicated by a signal received at either of the temperature sensor inputs 116 and 118. Such conditions may also include the fan speed or percentage of target fan speed below which the first alarm output 122 is activated, the temperature over which an over-temperature alarm is indicated by the second alarm output 124, or the function of the third alarm output 126. The function may be to indicate one of an under-temperature alarm (in which case an additional condition indicates the temperature below which the alarm is activated) or a blocked filter alarm which is determined by comparing the difference in temperature between the air entering the cabinet and the air leaving the cabinet against predetermined values for different fan speeds.

In some embodiments, the fan controller operates using two "channels." The first temperature input 116, first fan interface 106 and second fan interface 108 are associated with a first channel, whereas the second temperature input 118, third fan interface 110 and fourth fan interface are associated with a second channel. This allows two temperature sensors (e.g. thermistors) to be placed at separate locations within the cabinet and a pair of fans to be controlled based on one of the temperature sensors and independently of the other pair of fans. For example, a pair of fans may be installed in close proximity to the associated temperature sensor. The pulse width modulation (PWM) signal used to control a pair of fans may be an identical signal for both fans, such that each channel has an associated PWM signal controlling the appropriate fans.

In some embodiments, the fan controller 100 does not include the capability to monitor and log any information, or does not use such capability. This may reduce the hardware and/or processing requirements of the fan controller 100, and thus reduce the cost and/or power consumption of the fan controller. In such embodiments, the fan controller may be responsive to a request from an external data processing device (not shown) connected to the communication interface 128 to provide a data structure including certain information to the data processing device. The data processing device may, for example, process, timestamp, store, display and/or analyse the data structure and information contained therein as appropriate.

In some embodiments, for example, a fan controller may be used that has minimal capability for communicating with external devices. A system that includes the fan controller may be provided with an external connector coupled to the fan controller to enable a direct, wired, point-to-point connection between the fan controller and an external device. For example, the connector may be an RS232 connector, and an RS232 cable could be used to connect the fan controller directly to an RS232 connector of an external device. Thus, the external device may request information from the fan controller while the two are directly connected using a cable. The data processing device may process, store and/or display the information as appropriate. In this example, the fan controller communicates directly with the external device, that is, the fan controller uses a communication protocol that is not translated into other protocols between the fan controller and external device. This ensures that unnecessary cost is not added to the system. In come embodiments, the fan controller is implemented as an integrated circuit or chip that includes the capability for communicating with the external device using the chosen protocol.

The fan controller may have embedded within it software that is inactive during normal operation of the fan controller. When an external device is connected to the fan controller, the fan controller may activate the previously inactive embedded software and execute this software, This software may in some embodiments enable the fan controller to communicate with the external device, such as by sending information to the external device for example.

Once the external device is disconnected, the software may return to an inactive state.

The manner of communication between the fan controller and external device is preferably a simple, low cost manner that does not add significant cost in particular to the fan controller.

In addition to the above example of RS232 communication, other communication types such as IJSB or other serial communication types could be used. In one example, communication is performed using simple, low speed three-wire logic level serial data with a TX (Transmit) line and RX (receive) line both referenced to ground (OV) at the fan controller.

Data processing, storing and/or displaying routines are implemented in an external device (such as for example software executing on the external device) and are able to activate, as and when required, embedded software in the fan controller to retrieve information from the fan controller.

In use, when information is required from the fan controller, in some embodiments an individual such as an engineer may attend the location of the fan controller (or a cabinet containing the fan controller and other components as appropriate). The individual may then connect an appropriate cable between the fan controller and a data processing device carried by the individual. The fan controller, fan controller housing or cabinet may include an external connector for this purpose. The individual may then execute software on the data processing device that causes the data processing device to communicate with the fan controller and to request information. The information may be processed by the data processing device, stored on the data processing device and/or displayed on the data processing device. Once the operation is complete (for example the individual may view the information displayed and note there are no anomalies) the cable can be disconnected.

Suitable devices that could be used for the fan controller include, for example, a Microchip® P1C18F2520, P1C18F25K22, or subsequent devices in the same family. In other embodiments, however, other devices can be used to implement the fan controller.

In some embodiments, the fan controller and the externally connected data processing device exchange information in the form of ASCII characters and values. For example, in some embodiments the data processing device may send a request to the fan controller in the following format: ascii 2 ascii character D ascii 3 Thus the data processing device sends three characters, with the values 2, 68 and 3. The fan controller responds by preparing a data structure containing information and sending the data structure to the data processing device, In some embodiments, the data structure includes fields that are separated by a colon: character, An example of such a data structure and the information it may contain is provided in the following table: Characters Purpose ascii 2 Data structure header xxxx Temperature measurement I Temperature measurement 2 Target fan RPM I xxxx Target fan RPM 2 xxxx Fan I measured RPM xxxx Fan 2 measured RPM xxxx Fan 3 measured RPM xxxx Fan 4 measured RPM xxx PWM signal 1 duty cycle % xxx PWM signal 2 duty cycle % xx. xx DC supply voltage ascii 3 Data structure terminator For example, the temperature measurement 1 field (which indicates the temperature measured by the temperature sensor connected to the first temperature sensor input 116) begins with a colon character and comprises four ASCII characters that indicate the measured temperature, Similarly, for example, the target fan RPM field (which indicates the target RPM of the first channel, and thus the first and second fans connected to fan control interfaces 106 and 108) comprises a colon character followed by four ASCII characters. The PWM signal 1 duty cycle indicates the duty cycle percentage of the PWTVI signal associated with the first channel and provided to the first and second fans. The DC supply voltage field comprises a colon character followed by five ASCII characters. The third of these characters is a period character and hence the DC voltage is expressed as a number having two decimal places.

The presence of the colon characters allows each field to vary in size (i.e. number of ASCII characters), if desired.

In other embodiments, more or less information can be provided. For example, in some embodiments, the data structure may also indicate the status of each of the alarm outputs and the auxiliary output (on or off).

In other embodiments, more alarm outputs (not shown) may be present. For example, two additional alarm outputs may be present. In such embodiments, additional functionality may be included in the fan controller. For example, the fan controller may provide alarm outputs that indicate a minor over temperature, a major over temperature, minor under temperature and major over temperature. These alarms may be provided by the fan controller using, for example, the second alarm output 124, the third alarm output 126 and the two additional alarm outputs. In such embodiments, appropriate response may be made to a minor or major over or under temperature alarm. For example, a minor alarm may require a routine engineer visit whereas a major alarm may require a high priority or emergency response.

In some embodiments not all fan control interfaces may have a fan connected, For example, only one fan may be connected to one of the fan control interfaces, whereby the other fan control interfaces do not have any connected device, In such cases, the data structure may reflect the fan control interfaces that do not have fans connected. For example, the associated fan speeds may be indicated as zero, or some other indication, value or characters may be specified in the data stmcture to indicate that a fan is not connected to a particular fan control interface.

The fan controller 100 described above includes one communication interface 128. In other embodiments, the fan controller may include an additional communication interface. One communication interface may be used to write an executable program to the memory 104 for execution by the microprocessor 102, whereas the other communication interface may be used for upload and/or download of operating parameters of the fan controller, The communication interface used for the operating parameters may also be used by an external data processing device to request and receive a data structure as described above.

Figure 2 shows an example of a cabinet 200 according to embodiments of the invention, The cabinet 200 includes a substantially enclosed space or enclosure 202 in which electronic equipment and/or devices 204 are installed. The cabinet also includes a fan controller 206, which may comprise for example the fan controller 100 shown in Figure 1, A power supply unit (PSU) 208 provides a power supply to the equipment/devices 204 and the fan controller 206, A first fan 210 and a second fan 2 2 are connected to the fan controller 206 along with a first temperature sensor 214. The fans 210 and 212 and temperature sensor 214 may be associated with a first channel. A third fan 216, fourth fan 218 and second temperature sensor 220 are connected to the fan controller and may be associated with a second channel.

The fan controller 206 and the connected fans, temperature sensors or other peripherals may be referred to as an environment management system for managing the environment (such as, for example, the ambient temperature) within a cabinet. Although four fans are shown connected to the fan controller 206, fewer than four fans may be connected, and thus one or more of the fan control interfaces of the fan controller 206 may have no connected device.

Figure 3 shows an example of a mobile telephone base station 300 according to embodiments of the invention, The base station 300 includes a cabinet 302 that contains electronic equipment/devices implementing functions of a base station, and an environment management system. The base station 300 includes a mast 304 on which a number of antennas (one or more) may be mounted. Shown are two antennas 306 and 308 that are connected to the cabinet 302.

Claims

Claims 1. A fan controller comprising: a microprocessor; a first input adapted to receive a first temperature measurement signal from a first temperature sensor; a second input adapted to receive a second temperature measurement signal from a second temperature sensor; first and second fan control interfaces adapted to provide a first pulse width modulated (PWM) signal, the first and second fan control interfaces including first and second fan speed inputs respectively; third and fourth fan control interfaces adapted to provide a second pulse width modulated (PWM) signal, the third and fourth fan control interfaces including third and fourth fan speed inputs respectively; and a communication interface adapted to connect directly to a data processing device to receive operating parameters and/or a fan control program for execution by the microprocessor and to send the operating parameters and/or the fan control program to the data processing device, wherein the fan controller includes inactive sofiware and is adapted to, in response to receiving a request from the data processing device at the communication interface, activate and execute the inactive software to cause the fan controller to send a data structure to the data processing device, the data structure comprising a plurality of fields that indicate: a first temperature indicated by the first temperature measurement signal; a second temperature indicated by the second temperature measurement signal; a first target fan speed; a second target fan speed; at least a first speed measurement of a first fan connected to one of the first, second, third and fourth fan control interfaces indicated by a first fan speed measurement signal provided to the first, second, third or fourth fan speed input; a first duty cycle of the first PWM signal; and a second duty cycle of the second PWM signal. In IL)
2. The fan controller of claim I, wherein the first target fan speed is the target speed of the first and second fans, and the second target fan speed is the target speed of the third and fourth fans.
3 The fan controller of claim t or 2, wherein the fan controller further includes an auxiliary output that may be turned on and off by the microprocessor, and the data structure includes further fields that indicate the status of the auxiliary output.
4, The fan controller of any of the preceding claims, wherein the fan controller further includes one or more alarm outputs and the data structure includes fields that indicate the status of the one or more alarm outputs.
5. The fan controller of any of the preceding claims, further comprising a power supply input adapted to receive a direct current (DC) supply voltage, and the data structure further indicates the DC supply voltage.
6. The fan controller of any of the preceding claims, wherein the first fan is connected to the first fan control interface and the first fan speed measurement signal is received by the first fan speed input, and the data structure further indicates at least one of a second speed measurement of a second fan connected to the second fan control interface indicated by a second fan speed measurement signal provided to the second fan speed input; a third speed measurement of a third fan connected to the third fan control interface indicated by a third fan speed measurement signal provided to the third fan speed input; and a fourth speed measurement of a fourth fan connected to the fourth fan control interface indicated by a fourth fan speed measurement signal provided to the fourth fan speed input.
7. The fan controller of any of the preceding claims, wherein the fan controller is adapted to communicate with the data processing device using USB, RS232 or other serial protocol.
8. The fan controller of any of the preceding claims, wherein the fan controller is implemented as an integrated circuit or chip.
9. An environment management system, comprising: a first temperature sensor; a second temperature sensor; at least a first fan; and afan controller; the fan controller comprising: a microprocessor; a first input adapted to receive a first temperature measurement signal from the first temperature sensor; a second input adapted to receive a second temperature measurement signal from the second temperature sensor; first and second fan control interfaces adapted to provide a first pulse width modulated (PWM) signal, the first and second fan control interfaces including first and second fan speed inputs respectively; third and fourth fan control interfaces adapted to provide a second pulse width modulated (PWJvI) signal, the third and fourth fan control interfaces including third and fourth fan speed inputs respectively adapted to receive third and fourth fan speed measurement signals respectively; and a communication interface adapted to connect directly to a data processing device to receive operating parameters and/or a fan control program for execution by the microprocessor and to send the operating parameters and/or the fan control program to the data processing device, wherein the first fan is connected to one of the first, second, third and fourth fan control interfaces; and the fan controller includes inactive software and is adapted to, in response to receiving a request from the data processing device at the communication interface, activate and execute the inactive software to cause the fan controller to send a data structure to the data processing device, the data stmcture comprising a plurality of fields that indicate: a first temperature indicated by the first temperature measurement signal; a second temperature indicated by the second temperature measurement signal; a first target fan speed; a second target fan speed; at least a first speed measurement of the first fan indicated by the first fan speed measurement signal provided to the fan speed input of the fan control interface to which the first fan is connected; a first duty cycle of the first PWM signal; and a second duty cycle of the second PWM signal.
10. The environment management system of claim 9, wherein the first target fan speed is the target speed of the first and second fans, and the second target thn speed is the target speed of the third and fourth fans.
11. The environment management system of claim 9 or 10, wherein the fan controller further includes an auxiliary output that may be turned on and off by the microprocessor, and the data structure includes further fields that indicate the status of the auxiliary output.
12. The environment management system of claim 9, 10 or 11, wherein the fan controller further includes one or more alarm outputs and the data structure includes fields that indicate the status of the one or more alarm outputs.
13. The environment management system of any of claims 9 to 12, further comprising a power supply input adapted to receive a direct cunent (DC) supply voltage, and the data structure further indicates the DC supply voltage.
14. The environment management system of any of claims 9 to 13, further comprising second, third and fourth fans, wherein the first fan is connected to the first fan control interthce and the first fan speed measurement signal is received by the first fan speed input, and the data structure further indicates at least one of: a second speed measurement of the second fan connected to the second fan control interface indicated by a second fan speed measurement signal provided to the second fan speed input; a third speed measurement of the third fan connected to the third fan control interface indicated by a third fan speed measurement signal provided to the third fan speed input, and a fourth speed measurement of the fourth fan connected to the fourth fan control interface indicated by a fourth fan speed measurement signal provided to the fourth fan speed input.
15. The environment management system of any of claims 9 to 14, wherein the fan controller is adapted to communicate with the data processing device using TJSB, RS232 or other serial protocol.
16. The environment management system of any of claims 9 to 5, wherein the fan controller is implemented as an integrated circuit or chip.
17. A cabinet containing: electronic devices; and an environment management system as claimed in any of claims 9 to 16 for controlling an ambient temperature within the enclosure.
18. A mobile telephone base station, comprising: one or more antennas; a cabinet containing electronic devices connected to the one or more antennas, the electronic devices adapted to implement functions of the mobile telephone base station, the cabinet further containing an environment management system as claimed in any of claims 9 to 16 for controlling an ambient temperature within the enclosure.
19. A system, comprising a fan controller as claimed in any of claims to 8 and a data processing device connected directly to the communication interface of the fan controller.
20. The system of claim 19, wherein the fan controller is connected directly to the data processing device using a direct, point-to-point wired connection.
21. The system of claim 19 or 20, wherein the data processing device is adapted to provide the request to the fan controller and to receive the data structure from the fan controller. n j

22, The system of claim 19, 20 or 21, wherein the data processing device is adapted to timestamp, store, process, display andlor analyse the data structure and/or information contained in the data structure.