Data Logger

The data logger is a standalone unit for capturing data from different RF sources and routing it to the central server PC through 802.15.4 network. This unit accepts queries from central server and then responds by sending the appropriate results back to the server. The system has an in built data collecting feature which collects the data from different sources periodically, using a polling mechanism and is independent of server PC.

The data logger has a Jennic wireless module directly incorporated into it. This wireless module operates in the license free 2.4 GHz band. Besides, the system also has a 802.15.4 wireless modem for communicating with the remote server. The data logger has a embedded micro controller which carries out the function of collecting data from the remote units via the wireless module, storing the collected data in an external non volatile memory and retrieving the collected data and transmitting it to remote server via 802.15.4 wireless whenever the remote application demands it.

System Interface

The system consists of a main data logger PCB and on board incorporated RF Arrays wireless module which acts as a co-ordinator. The wireless network interface is through 2.4GHz license free band from the coordinator to the router/end device. The coordinator initiates the network while the router/end device joins the network. The end device itself acts as the router and is connected to the utility meters from where the data has to be read. The high power wireless module incorporates the 802.15.4 network and is capable of sending the data over a distance of 1Km LOS using Whip Antenna (3 dBi gain) and in 5 kms LOS using high gain antenna (14 dBi gain) as per the geographical location. The wireless modules connect using the tree/star topology.

The 802.15.4 modem in the data logger connects to the remote server PC.

The data logger has the RFARRAYS wireless module (RIM511) directly incorporated into it. This module has the Jennic micro controller JN5139 + RF Arrays RF Front End RIF211 along with SMA connector for the whip/High Gain Antenna. The high power module has power output of 18dBm and receiver sensitivity of -103dBm.The module operates in the license free 2.4GHz frequency band. Furthermore it has 16 channels for selection of operation and the module can be set for the best frequency channel (least activity) at initialization. High gain antennas are useful for extending the range of 2.4 GHz wireless modules. The 802.15.4 Modem with high gain antenna improves the link budget and hence increase the range significantly.

User Interface

The default user interface is through the remote Graphical User Interface (on PC) as it is connected to the data logger through the 802.15.4 modem. The interface can be modified by connecting a com check software in lieu of GUI through the serial port. This is useful in debugging and testing the product. This is possible because the data logger accepts the command through the serial port and is transparent as to the device connected to the serial port.

Product functionality

The system is able to connect wirelessly to the utility meter for reading the energy parameters like voltage, current, p.f, Kwh etc. The routers connected to the meters read the energy parameters from the meter using the serial port. This data is then transmitted to the data logger via the RF wireless network. The co-ordinator in the data logger then relays this data to the embedded micro controller using the serial port as the intra controller communication. The embedded micro controller is a 32-bit ARM controller capable of running at a speed of 72Mhz

The embedded controller does the function of gathering the required data by sending a query to the Jennic coordinator. This query requests the coordinator to get the specific all data from the respective meters which are connected to it. After getting the data the coordinator then transfers the data via the serial interface to the micro controller.

The micro controller then stores the data in the external storage for retrieval later. There are two modes of data collection: Scan mode and the instant data collection. In scan mode the data logger scans the meters connected to it in a periodic fashion every 1hour, 3 hours, 24 hours etc. In instant data collection the data logger sends the data of the particular meter as requested by the remote server.

An internal battery backup for the entire DL system in case of power failure, when the power is transferred from the battery. Hence there is a uninterrupted operation of the data logger which gives complete storage without missing any data. The battery backup lasts for 6-8 hours without recharge.

Data logger has an inbuilt RTC for getting the current date and time. There is also a coin cell within the data logger PCB which helps the RTC to run uninterrupted in case of power supply failure. One month data can be stored in the data logger for all meters. A total of 300 energy meters can be connected to the Data logger for data collection and data monitoring.

Embedded board characteristics:

Micro controller: 32 bit ARM micro controller STM32F103RB
Jennic module: High power module using JN5139 micro controller
External memory: 8MB EEPROM
Serial ports: USART (3 Nos)
Power supply: 3.3 Vdc, 250 mA
Battery: 3V Li-ion coin cell
Electrical parameters for Data logger
Mains Voltage : 230 VAC , 50Hz
Mains Current : < 1Amp
Voltage for micro controller board : 3.3Vdc, 250mA
Voltage for GSM : 9Vdc,350m A
Note : D.C voltage for micro controller board, GSM generated internally using the 230 Vac.
Mechanical: Enclosure Dimensions : 262mm (L) x 210mm (W) x 110mm (H)
Environmental : Operating Temperature : -40°C to 85°C