23-04-2014, 02:45 PM
DATA ACQUISITION USING AT89c51 AND PCL-207
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ABSTRACT
A typical data acquisition system consists of individual sensors with necessary signal
conditioning, data conversion, data processing, multiplexing, data handling and associated
transmission, storage and display system.
In order to optimize the characteristics of a system in terms of performance, handling
capacity and cost, the relevant subsystem can be combined together. Analog data is generally
acquired and converted into the digital form for the purpose of processing, transmission and
display.
Rapid advances in Personal Computer (PC) hardware and software technologies have
resulted in easy and efficient adoption of PCs in various precise measurement and complex
control applications. A PC based measurement or control application requires conversion of real
world analog signal into digital format and transfer of digitized data into the PC. A data
acquisition system that performs conversion of analog signal to digital data and the digital data to
analog signal is interfaced to a pc to implement the functions of a measurement and control
instrumentation applications.
In this project we have used the electromagnetic sensor to acquire the data of a magnetic
disk angular velocity, which we have got in mili volts range. This has been further converted
approximately into the range of 5 volt by using an instrumentation amplifier of suitable gain
(~20).We then converted the analog voltage into digital by using ADC 0808 and the processing
part is done by using ATMEL89c51.In the second case we have used the data acquisition card
PCL-207 to interface the amplified output to PC.
INTRODUCTION
PC based Instrumentation System
The instrumentation systems have evolved over a period of time. Instrumentation systems are in
standalone or modular types. Traditionally, measurement and control are done using standalone
instruments. The measurement and control are automated by exchanging data between the
instruments and computers. There are several ways of exchange of measurement and control data
between computer and instruments. The GPIB, RS-232, USB and IEEE 1394 are the standard
interfaces provided in high performance standalone instruments for exchange of data. The
general form of PC based measurement system is shown below.
PC Interfaces
The DAQ hardware is available in different forms. The most common type is plug in type which
is inserted into one of the empty expansion bus slots on the motherboard. The hardware uses the
PC expansion bus for communication with the PC. The DAQ devices which are compatible with
PC serial port (RS232 compatible) and USB port are also more common. The DAQ system
support one of these interfaces for communication with the PC.
PC Interfaces
The DAQ hardware is available in different forms. The most common type is plug in type which
is inserted into one of the empty expansion bus slots on the motherboard. The hardware uses the
PC expansion bus for communication with the PC. The DAQ devices which are compatible with
PC serial port (RS232 compatible) and USB port are also more common. The DAQ system
support one of these interfaces for communication with the PC.
555 TIMER
The 555 monolithic timing circuits is a highly stable controller capable of producing
accurate time delays, or oscillation. In the time delay mode of operation, the time is precisely
controlled by one external resistor and capacitor. For a stable operation as an oscillator, the free
running frequency and the duty cycle are both accurately controlled with two external resistors
and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output
structure can source or sink up to 200 mA.