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Abstract - The paper develop a solution of integrating heating, cooling and ventilation equipments, which are monitored and commanded by a controller, for the telecommunications equipments and air conditioning equipments, that assure a significant decrease in electric energy consumption, as well as a decrease of management costs that are very high.

I. INTRODUCTION

Communications equipments that are installed outdoors, in special containers to which the literature refers as shelters, need certain conditions of temperature and humidity. These conditions must take into account the day / night, seasons, and the climate, the location on the seaside or at altitudes greater than 1500 m where environmental conditions, temperature and humidity are extreme.

Concerns related to achieving rooms intended for telecommunications equipments, are higher and easier to accomplish when the equipments are placed in residential buildings or offices within cities. The same can not be said about shelters located outside cities, usually on the outskirts of towns or edge of forests where thermal insulation is undersized or nonexistent, in winter condensation water posing trouble to equipments and in summer air conditioning installations very often fail due to uninterrupted operation for months and last but not least due to poor protection from vandalism.

These shelters are equipping the mobile networks Orange, Vodafone, Cosmote and they are also equipping the Ministry of Defense, Ministry of Interior, the National Meteorological Administration, some agencies dealing with the measurement of environmental parameters, etc.

To maintain constant temperature and humidity parameters, we aimed to develop a monitoring and control system which consists of: -microcontroller; - exterior / interior temperature sensors; - air fans; - heating system for the winter season; -cooling and dehumidification system for the summer;

The requirements imposed by communication equipments are to maintain a temperature between 15 º C and 30 º C and humidity less than 90%, which are tracked to be provided automatically by an intelligent monitoring and control system SIC -01.

The volume of a shelter necessary for housing communications equipments from the heat generated by them and from the heat transfer of the shelter with the external environment was considered in the paper in order to

Dicu Doru is PhD student at University of Craiova

size heating / cooling equipments. Also, in order to optimize the functioning of the heating / cooling system, we chose to divide the temperature range into seven main areas for which we have completed the operating flow charts, which will then be the basis for achieving the software program.

II. FUNCTIONAL STRUCTURE OF THE CONTROL SYSTEM

The controller for air conditioning and monitoring telecommunications containers SIC - 01, is a process system obtained with ColdFire V1 microcontroller, MCF51JM64 manufactured by Freescale (USA). The Intelligent Control System - 01 can achieve air conditioning and monitoring of telecommunications containers by continuous running of a software application pre-recorded in the flash memory of the microcontroller. This application is launched automatically at the application of voltage and does not require any operator intervention or initial settings. The intelligent monitoring and control system is programmed to provide an internal temperature between 15 º C and 30 º C within the container in which it is installed.

External environmental conditions in which the telecommunications shelters equipped with intelligent control system can be installed, are: environmental temperature between -33 º C and +50 º C; maximum relative humidity 100%; maximum air speed 50 m / s; maximum intensity of rain 6 mm / min.

In parallel with the air conditioning operation, SIC-01 also performs the monitoring of telecommunications shelter. For this purpose SCS-01 performs the following operations:

• it gathers data with regard to: status of AC power (presence or absence); status of DC power (battery voltage); internal and external temperature of the container at predetermined intervals;

• it generates temperature alarms if the admitted limits of the internal temperature are exceeded;

• it memorizes the data gathered and the alarms in folders on micro SD CARD, FAT32 format.

Every day SCS-01 makes a text file in which the abovementioned data are stored.

Viewing, archiving or printing of generated files can be done anytime generated using an independent card reader (CARD READER) independently. In its absence SIC-01 may be put in CARD READER mode and SD CARD memory can be explored by connecting to a PC using the USB interface.

From the constructive and functional points of view, SIC-01 consists of two modules:

Intelligent System for Monitoring and Controlling Environmental Parameters for Spaces Intended for Telecommunications Equipment

Gheorghe Doru Dicu Ionut Bogdan Dicu

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• DATA LOGGER Module;

• FAN CONTROLLER Module.

The two modules are connected to each other through two connectors, one of 36 pins for low voltage logical and analogical signals and one of 5 pins for -48V supply.

A. DATA LOGGER Module DATA LOGGER module is an embedded system,

meaning a microcomputer which runs a specific application. The basic component of an embedded system is the microcontroller. In the case of DATA LOGGER module, the microcontroller is MCF51JM64.

MCF51JM64 is a microcontroller which operates on 32 bits. The characteristics of MCF51JM64 microcontroller allowed the implementation of the following operational units in DATA LOGGER module:

- LCD Display with 2 lines with 16 characters ; -Interface of micro SD memory CARD; -Real time clock and calendar; - EEPROM-type memory, for constants, with I2C interface; -Serial port with RS232 interface, (COM Port) ; -USB Port; Key buttons for commands ; -Four analogical entries; -Four digital entries.

Figure 1. Shelter Control System Block Diagram

Except the functional units mentioned, DATA LOGGER module also contains a power unit, Figure 2, consisting of two dc-dc voltage converters.

Figure 2. Power block

● LCD display 2x16 characters

The LCD display, model DEM16216SYH-PY, is a liquid crystal display with two lines of 16 characters each.

The Intelligent Monitoring and Control System -01 can pass through the following states during the air conditioning process: heating - HM (heating mode) is shown on the display; natural air conditioning - VO is shown on the display; six-step ventilation - V1 , V2, V3, V4, V5 or V6 is shown on the display; cooling - CM (cooling mode) is shown on the display;

● Interface of micro SD memory CARD

DATA LOGGER module is provided with an interface for the micro SD memory card. From the electromechanical point of view, the interface is accomplished with a connector specific to micro SD memory that allows its insertion and extraction by double pressing (push-push).

The interface of micro SD memory CARD may operate in two ways: SD CARD mode; SPI mode.

● Real time clock and calendar

Real time clock and calendar provide SIC-01 system with information regarding local time and date as follows: date (day of the week, date, month, year); time (seconds, minutes, hours).

This information is displayed permanently on the LCD display of the system, but it is also used by FAT32 file system in order to create the temporary attributes of files and folders.

Real time clock and calendar are performed with the specialized DS1337 integrated circuit, manufactured by DALLAS-MAXIM.

The last two features enabled DS1337 real time clock to be powered directly from a lithium battery.

B. FAN CONTROLLER Module

● Digital outputs

● DC fan control outputs

To this effect, SCS-01 measures the interior temperature in various points and then it commands the air conditioning elements with which the cabinet is equipped: fans; convector; air conditioning equipment.

Depending on the power dissipated inside the cabinet and outside temperature, SIC-01 activates at most one of abovementioned air conditioning elements.

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Thus, the following operating modes result: ventilation, when fans are activated; cooling, when air conditioning is activated; heating, when the convector is activated, and natural air conditioning, when none of the air conditioning elements is commanded.

If the temperature inside the telecommunications cabinet exceeds the admitted limits, SIC-01 can signal the following two alarms:

-alarm for exceeding the upper temperature limit;

-alarm for exceeding the lower temperature limit;

To control the temperature inside the cabinet SIC-01 uses three temperature sensors. If one of the sensors is defective or not connected, the temperature control is done using the other sensors remained in the system.

The redundancy of sensors ensures increased system reliability and also optimizes the internal temperature of the cabinet.

III. TESTING PROCEDURE

The functional testing of Air Conditioning Controller can be carried out in laboratory. To this effect we need the following equipments:

● Controller for the air conditioning and monitoring of containers, which will be tested;

● DC Laboratory Source with output voltage of 48V and output current minimum of 2 A which connects to the POWER IN;

● One or two DC fans, model EBM PAPST 6248N, connected to VOLT OUT 1 and VOLT OUT 2;

● Temperature sensors type KTY81-110, equipped with bond wires connected to SENSOR 4;

● 2200 ohm multi-turn potentiometer to simulate temperature changes connected to SENSOR 1.

From a functional point of view Air Conditioning and Monitoring Controller for containers is an automaton whose inputs are:

● Temperature sensors: SENSOR1, SENSOR2 and SENSOR3 and

● Digital input INPUT3, and whose outputs are:

● Controlled voltage outputs for fan control: VOLT OUT1 and VOLT OUT2

● OUTPUT5 for cooling equipment command (air conditioning),

● OUTPUT6 heating equipment command (convector),

● OUTPUT3 for temperature alarm,

● OUTPUT4 for under-temperature alarm.

Temperature sensor from SENZOR4 input is used to measure the temperature outside the container. The external temperature of the container is not used in air conditioning algorithm.

The sensors from the inputs: SENZOR1, SENZOR2 and SENZOR3, measure the internal temperatures of the container. Air conditioning algorithm makes decisions based on the maximum temperature measured by these three sensors. If one or two sensors are disconnected air conditioning algorithm ignores it or them. Therefore you can use a single sensor to test the operation of Air Conditioning Controller. It has three internal sensors for safety reasons during functioning and for the leveling of internal temperature.

If all three temperature sensors: SENSOR1, SENSOR2 and SENSOR3 are disconnected, air conditioning algorithm can not work any more and in this situation both fans are commanded at full speed, and temperature alarms are activated to identify the situation.

KTY81-110 is a silicon temperature sensor with positive temperature coefficient. The range of temperatures in which it can be used is comprised between -55ºC and +150 ºC.

Within this range the resistance of the sensor modifies from 490 ohms to 2211 ohms.

INPUT3 jumper simulates the presence of voltage inside the network (electric-power-supply network of 220Vc.a.). By disconnecting the jumper the absence of network voltage is signaled. In this situation air conditioning controller can only ventilate, situation in which the equipments are powered from DC power supply, (-48V). Heating or cooling commands are inhibited even if the internal temperature would impose the activation of either.

After AC power supply is restored, the activation of cooling or heating commands (if need be) is made with a one minute delay.

IV. DESIGNING OF FUNCTIONING FLOW CHARTS

Seven internal temperature ranges are distinguished, but we will present the main heating, ventilation, cooling and over-temperature ranges.

15 min.

3 min.

5ºC 15ºC 18ºC 25ºC 30 31ºC 35ºC

OUTPUT 3

OUTPUT 4

OUTPUT 5

OUTPUT 6

Heating Mode

Cooling Mode

V 0V 1‐6V 6

OUTPUT 3 - for temperature alarm,OUTPUT 4 - for under-temperature alarmOUTPUT 5 - for cooling equipment command OUTPUT 6 - heating equipment command V 0-6 - ventilation mode

Histeresis heating

Histerezis cooling

Figure 3. Functioning chart of the Intelligent Control System -01

A. Heating regime Temperature higher than or equal to 15 ºC and strictly

lower than 18ºC (15ºC≤t<18ºC). This temperature range is the hysteresis area of heating mode. If air conditioning

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controller is in heating mode, HM (heating mode) is displayed in the bottom right corner of the display; this mode is then maintained until the internal temperature of the container becomes higher than or equal to 18 º C. If air conditioning controller is in natural cooling mode, V0 is displayed in the bottom right corner of the display; this mode is then kept until the temperature inside the container decreases below 15 º C. At this point it switches to heating mode, HM, and the led corresponding to OUTPUT6 is turned on.

Figure 4. Heating regime

If the temperature is lower than or equal to 5 º C (t ≤ 5 ° C), low temperature alarm is activated, the led corresponding to OUTPUT4 turns off. If power-supply voltage is present, the heating mode is activated and the led corresponding to OUTPUT6 is turned on.

If the temperature is strictly higher than 5 º C and strictly lower than 15 º C (5 º C <T <15 ° C), low temperature alarm is disabled, and the led corresponding to OUTPUT4 is turned on. If power-supply voltage is present, the heating mode is activated and the led corresponding to OUTPUT6 is turned on.

B. Ventilation regime

Figure 5. Ventilation regime

Temperature higher than or equal to 18 ºC and strictly lower than 25ºC (18 ºC ≤ t < 25 ºC). In this temperature range, the controller for air conditioning is in natural cooling

mode, and V0 is displayed in the bottom right corner of the display.

C. Cooling regime Temperature higher than or equal to 25 ºC and lower than

or equal to 30ºC (25 ºC ≤ t ≤ 30 ºC). This temperature range is the hysteresis area of cooling mode. If air conditioning controller is in cooling mode, CM (cooling mode) is displayed in the bottom right corner of the display, and then this mode is maintained until the internal temperature of the container becomes lower than or equal to 24 º C. If air conditioning controller is in ventilation mode, Vi, i = 1,2,3,4,5 or 6 is displayed in the bottom right corner of the display, and then this mode is maintained until the internal temperature of the container rises above 30 º C . In ventilation mode, air conditioning controller has 6 ventilation stages: at 25 ° C level V1, at 26 º C level V2, at 27 º C level V3, at 28 º C level V4, at 29 º C level V5 and at 30 º C level V6 .

Figure 6. Cooling regime

When the temperature in the shelter reaches 31 º C, the transition to cooling mode is initiated and the led corresponding to OUTPUT5 turns on. At this moment the indoor unit of the air conditioning equipment is power-supplied, but the outdoor unit starts with a delay of no more than three minutes. In this 3-minute interval, Air Conditioning Controller remains in ventilation mode level V6. After these 3 minutes, the ventilation stops and Air Conditioning Controller switches actually to cooling mode and CM (cooling mode) is displayed in the lower right corner of the display. The switch to cooling mode is of course subject to the presence of power-supply voltage, otherwise it remains in ventilation mode level V6.

If the temperature is strictly higher than 25 º C and lower than or equal to 35 º C (30 º C <T ≤ 35 ° C), air conditioning controller remains in cooling mode, CM (cooling mode) is displayed in the bottom right corner of the

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display if power-supply voltage is present, otherwise it switches to ventilation mode level V6.

D. Over-temperature regime If the temperature is strictly higher than 35 º C, air

conditioning controller is initially in cooling mode CM, over-temperature alarm is activated and the led corresponding to OUTPUT3 turns off, and also the ventilation at level V3 is activated. If over-temperature alarm does not disappear in the next 15 minutes, this means if the temperature does not decrease below 36 º C, while cooling and ventilation at V3 are operating, cooling is stopped, the led corresponding to OUTPUT5 turns off, ventilation increases at V6 and Air Conditioning Controller is switched to ventilation mode, V6 is displayed in the bottom right corner of the display.

Figure 7. Over-temperature regime

In the absence of power-supply voltage and internal temperature is strictly higher than 35 º C, over-temperature alarm is activated and the air conditioning controller is switched to ventilation mode, maximum level. V6 is displayed in the bottom right corner of the display.

V. CONCLUSION The idea of this approach is the safe operation of

telecommunications equipments, the maintenance of certain environmental parameters inside the shelters.

The solution of integrating heating, cooling and ventilation equipments, which are monitored and commanded by a controller, constitutes the advantages for extending the life of both the telecommunications equipments and air conditioning equipments, a significant decrease in electric energy consumption, as well as a decrease of management costs that are very high. Currently at the beginning of winter / summer season, a body of men must go to shelters to check the operating condition of the heating / cooling equipments.

The safe operation of the equipment reduces the number of alarms and accidental stops, leading to the increase of data, voice communications efficiency, and implicitly of gains for mobile telephony operators.

Intelligent energy management provides the greatest opportunity today for energy efficiency. From the point of use, intelligent systems will be a significant factor, enabling the intelligent network to save energy and also optimum operating conditions of communications equipments.

There are companies which created solutions from energy producer to the user which enable customers to quickly realize significant improvements in energy efficiency in terms of use, costs, safety and environmental impact.

Next stage in further research is to achieve an intelligent control system, a software program, and also its experimentation.

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