09-05-2013, 12:54 PM
Design of Data Acquisition System Implemented with a Free Cooling Unit (FCU) Controller For a BTS Room
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Abstract
The scarcity of electricity causing serious dislocation in all spheres of life, including production in agricultue and industries as well as in the section of cellular communication. To reduce the wastage of electricity in BTS room now-a-days celluler operators are using different ventilation systems instead of Air Conditioner (AC). Recently many operators like Banglalink, a leading telecom operator in Bangladesh are interested to interface a data acquisition system with these ventilation systems in BTS rooms.So in this paper a modern ventilation system FCU is designed interfacing with a Micro SD card for data acquisition especially for Banglalink BTS. FCU is an electronic instrument that records the temperature data and takes decision according to that data. This research work deals with the PIC18F4520 which includes 10 bit ADC for data conditioning and 32K bytes of program memory which provides the advantage of interfacing a FAT-16 system with microprocessor. In display section 4X20 LCD display is used for user interaction.
INTRODUCTION
Free Cooling Unit is a ventilation system dedicated to the tele-com BTS [1]. The main objective of free cooling is to reduce AC run time and save electricity cost at the BTS sites [2]. It also can reduce the carbon emission as like as the IVS (Intelligent Ventilation System) used in Robi, another leading telecom operator in Bangladesh which is really an environment friend-ly feature [3].
A special feature is now added with this ventilation system which is data acquisition. Data acquisition systems, as the-name implies, are products and/or processes used to collect information to document or analyze some phenomenon [4]. So by using this data logger system we can store millions of data of BTS room temperature as well as outside temperature in-cluding the relevant date and time and also can collect those data for further analysis and improvement.
So Free Cooling Unit (FCU) controller is a microcontroller based electronic system that maintains the overall environ-ment of a BTS room by controlling a Fan Unit, a Filter Unit and an AC by observing the room temperature and battery voltage level of a BTS room. It also contains a data acquisition unit using SD card [5].
HARDWARE DESIGN
Power Supply Section
Most of the BTS rooms contain battery of 48 volt or 24 volt DC to give suppot when the PDB is unavailable. So it is necessary to convert this 48 volt or 24 volt DC to a 12 volt DC to run the controller circuit. This power supply is used to run the motor of the louver as well as it give support to the 5 volt DC section of the controller. We can easily convert the 12 volt DC to 5 volt DC by using LM7805 IC. Fig. 2 shows a power supply section.
Sensor Section
For measuring the temperature, FCU controller required two LM35DZ sensors shown in fig. 3. One is for the room tempera-ture and another is used to measure the outdoor temperature. The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature [8]. Temperature is directly measured by the AN0 and AN1 pin of microcontroller IC.
Battery Voltage Monitor Section
Battery voltage level monitoring section shown in fig. 4 is one of the important part of this device. In this section we have used a 5kohm multiturn which provides fine resistance ad-justment [9]. So we can monitor the battery voltage level of a BTS room precisely.
Data Acquisition Section
To store the room temperature and outdoor temperature data consecutively a micro SD card shown in fig. 5 is used with an adapter in this controller. The microSD memory Card is a functionally compatible with the SD Memory Card but is smaller in dimensions [10]. The microSD memory Card com-munication is based on an advance 8-pin interface and the microSD memory Card host interface supports regular SD or miniSD Memory Card Adapter and operates as an SD Memo-ry Card. The capacity of micro SD/TransFlash memory cards currently range in storage size from 64 MB (megabytes) to 8GB (gigabytes) and upward [11]. In this project a 2GB micro SD card is used and to interface the SD card with PIC18F4520 an adapter is also used.
WORKING PRINCIPLE
The PIC microcontroller 18F4520 always senses the room tem-perature and outdoor temperature using its 10 bit A/D con-verter. It also monitors the battery voltage level as well. It is important because the Fan Unit will not work if the BTS bat-tery voltage is under some certain specified level. The control-ler also maintains the room temperature under a predeter-mined value by controlling the Fan Unit and Filter unit opera-tion. It also controls the movement of louver. If the BTS room temperature is not under a tolarent level then the controller gives priority to AC rather than Fan and Filter Unit. One of the major operations of this controller is to store the room temper-ature and outdoor temperature data with relevant time and date in to a micro SD card. Fig. 9 shows the overall system.
CONCLUSION
FCU is an environment friendly ventilation system for BTS rooms. It not only reduces the emission of carbon-di-oxide (CO2) in environment but also saves electricity in a great deal. The whole package of FCU is not very costly and it could be an affordable choice for a developing country like Bangladesh. Its data acquisition system is an advance feature which not only helps to monitor the BTS room environment but also can provide ideas how to improve the function of the FCU system. So replacing an Air Conditioner with a Free Cooling Unit will be a profitable choice for our environment and economy as well.