Data logger

INTRODUCTION

First we will see what is a data logger 

Data logger :

• A data logger, also called parameter monitor, is a portable measurement instrument that is capable of autonomously monitoring and recording physical parameters over a defined period of time.
• The digital data can be retrieved, viewed and evaluated after it has been recorded.
• Data loggers are provided with real time clocks to record the date and time of acquisition.
• The advantage of data loggers is that they can operate independently of a computer, unlike many other types of data acquisition devices.

Where it is used :

In environments like factories, power plants and transformers in electricity substations, controlling temperature to a safe value is important. Supervisory and control systems are used to monitor the temperature and other physical parameters on a centralised machine whereby one can monitor and control the remote devices.

Choice of Data Loggers : 

      Choice of Data Loggers can be based on many factors, such as:

• Cost
• Ease of use : set-up, readability, download data, analysis, etc.
• Temperature range/Its sensitivity towards various factors
• Accuracy and precision - degree of agreement of recorded temperature with actual
• Response time – the time it takes to response towards various parameters
• Shock and vibration resistance
• Water resistance – humidity, condensation, etc.
• Size, weight, mounting
• Number of Inputs: Data logger should be capable of handling many channels
• Memory : Depending on the data rate ,as higher the data rate higher the memory required, Therefore when specifying a data logger it is important to determine the sample rate and the sample duration which can be used to calculate the required memory

BLOCK DIAGRAM :

Description:- 

The objective of this work is to use data logging for temperature,Humidity & light measurement. In order to meet the above requirements, a low cost, versatile, portable data logger is designed.
                         A microcontroller based data logger has been developed for measuring temperature,Humidity & light at different input channels of ADC. 
                         The device is designed to receive data from temperature,Humidity and light sensors and to store the results on external non-volatile SD-Card for post process analysis. 
                          An integrated Graphical Liquid crystal display (GLCD) is also used for real time display of data acquired from various sensors.
                          In the present work, Parameters indicated by three channels are displayed on GLCD with the help of touch pannel after the intervals of time.
                        Based on these results, the accuracy of the channels is noted and by comparing them, the most accurate one among these is found.

System Design

LPC2148 :- The system is implemented on ARM7 microcontroller

 Why we are using ARM7 :

1.Low power Consumption.

2.fast execution per watt.

3. Good backward compatibility. 

These are some features of lpc-2148 :

•8 kB to 40 kB of on-chip static RAM and 32 kB to 512 kB of on-chip flash memory.

•128-bit wide interface enables high-speed 60 MHz operation.

•In-System Programming/In-Application Programming (ISP/IAP) via on-chip boot loader software.

•Embedded ICE RT and Embedded Trace interfaces offer real-time debugging with the on-chip Real Monitor software

•Single 10-bit DAC provides variable analog output 

•Two 8-channel 10-bit ADCs provide a total of up to 16 analog inputs, with conversion times as low as 2.44 ms per channel.

•Two 32-bit timers/external event counters

•PWM unit (six outputs) and watchdog.

•Low power Real-Time Clock (RTC) with independent power and 32 kHz clock input.

•Multiple serial interfaces including two UARTs, two Fast I2C-bus (400 kbit/s),

•SPI and SSP with buffering and variable data length capabilities.

 

GLCD :-

        The Graphical LCD as the name suggests is a type of LCD which can display graphics, images as well as text. The graphical representation of any data presents good understanding than just characters..

            Here we are using  OLED Display, Graphics 128x64 - 3.3V, SPI

These displays are small, only about 1" diameter, but very readable due to the

high contrast of an OLED display. This display is made of 128x64 individual

OLED pixels, each one is turned on or off by the controller chip. Because the

display makes its own light, no backlight is required. This reduces the power required to run the OLED and is why the display has such high contrast.

Features

· High Visibility during Daytime

Pin outs

· Current consumption only 20mA suitable for battery operation

· 3.3V operation with SPI high speed

· Only uses MCU 5 pins

· Digital Contrast adjustment