Project Report DAS

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1. INTRODUCTION:

This project implements a high speed data acquisition, Logging and Controlling system

using ATMega16, ATMega8 microcontrollers and RS-485. Our main focus for this project was

to take analog or digital data from sensors which are distributed across very large area.

Maintaining the records of the data is important task when analyzing manually the status of

system; this is done with help of database record. Displaying every instant value to the operator

is being done with the help of visual basic user interface. Controlling an event when some

physical quantity has reached above its maximum limit or below its minimum limit is being done

with the help of control feature for every sensor.

Every sensor is connected to Atmega8 controller’s ADC through its signal conditioning circuit.

We have taken three Atmega8 modules which are connected to a main controller module which

is having Atmega16 controller. When any sensor give data to the Atmega8 it is converted to its

digital equivalent and transferred to the main controller which is connected to PC through RS-

485 interfacing. It is important to use RS-485 interface as it reduces the noise interference which

is very common in industries. The data coming from sensors is regularly being displayed on the

computer through the visual basic 6.0 software. There is also an option of controlling a particular

physical quantity which is being sensed regularly. This is with the help of control option being

provided in the software.

We have used RS-485 and RS-232 protocols to transfer data from slave to computer. Between

the slave and master controller there is RS-485 interface while between main controller and the

computer we have used RS-232 interface. Line drivers IC’s are used for this conversion.

The major design challenge we have encountered is with integration of all slave controllers with

master controller. As the master controller must know from which slave controller the data is

coming, this is done by making a data frame of 6bytes.this data frame contains address of the

slave, data from the slave, start and end reorganization of the frame. After this it becomes easy to

recognize the frame and give that frame to appropriate field in the user interface.

Our original proposal was to do this work in wireless medium but due budget constraints we

have to take simple RS-485 interface to complete the task. Project every part is built in such a

manner that we can extend the slave controllers as well its data frame width with some simple

modifications.

2. HIGH LEVEL DESIGN :

i. Rationale:

Original idea was to build some set of data acquisition and signal conversion system for aircrafts.

It was prepared to do with the wireless medium but due to budget constraint we have to switch to

wire medium. Even after that also the project can be used in any environment where there is the

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requirement of data sensing from the physical quantity and taking the appropriate control action

according to that data.

ii. Logical structure:

Block diagram for DAQ

MASTER DEVICE

ATMEGA 16

PC

USB

PORT

USB TO

UART

CONVER

TER

SLAVE

DEVICE

ATMEGA 8

SLAVE

DEVICE

ATMEGA 8

SLAVE

DEVICE

ATMEGA 8

RESISTOR

SENSOR

LIGHT

SENSOR

TEMPERATURE

SENSOR

3

iii. Hardware/software tradeoffs:

As the software (VB6.0) is getting the data from USART buffer which is 16 times faster than the

hardware, there no much trade-off requirement for communication. At the run time hardware is

providing the data at sufficient speed which is being taken from the software easily accurately.

iv. Standards:

We have used two standards for data communication. That are RS-485 between the slave

controllers and the main controller and RS-232 between the main controller and pc. Protocols

study:

a) RS-232 protocol

Communication as defined in the RS232 standard is an asynchronous serial

communication method. The word serial means, that the information is sent one bit at a time.

Asynchronous tells us that the information is not sent in predefined time slots. Data transfer can

start at any given time and it is the task of the receiver to detect when a message starts and ends.

Asynchronous communication has some advantages and disadvantages, which are both discussed

in the next paragraph.

Devices, which use serial cables for their communication, are split into two categories.

These are DCE (Data Communications Equipment) and DTE (Data Terminal Equipment.) Data

Communications Equipments are devices such as modem, TA adapter, plotter etc while Data

Terminal Equipment are Computer or Terminal.

The electrical specification of the serial port is contained in the EIA (Electronics Industry

Association) RS232C standard. It states many parameters such as -

1. A "Space" (logic 0) will be between +3 and +25 Volts.

2. A "Mark" (Logic 1) will be between -3 and -25 Volts.

3. The region between +3 and -3 volts is undefined.

4. An open circuit voltage should never exceed 25 volts. (In Reference to GND)

5. A short circuit current should not exceed 500mA. The driver should be able to handle this

without damage. (Take note of this one!)

Serial Ports come in two "sizes". There are the D-Type 25 pin connector and the D-Type

9 pin connector both of which are male on the back of the PC, thus you will require a female

connector on your device. Below is a table of pin connections for the 9 pin and 25 pin D-Type

connectors.

Table various serial port pins

D-Type-

9 pin no.

D-Type-

25 pin no.

Pin outs Function

3 2 RD Receive Data (Serial data input)

2 3 RD Transmit Data (Serial data output)

4

7 4 RTS Request to send (acknowledge to modem that UART

is ready to exchange data

8 5 CTS Clear to send (i.e.; modem is ready to exchange data)

6 6 DSR Data ready state (UART establishes a link)

5 7 SG Signal ground

1 8 DCD Data Carrier detect (This line is active when modem

detects a carrier

4 20 DTR Data Terminal Ready.

9 22 RI Ring Indicator (Becomes active when modem detects

ringing signal from PSTN

Null Modems

A Null Modem is used to connect two DTE's together. This is commonly used as a cheap way to

network games or to transfer files between computers using Zmodem Protocol, Xmodem

Protocol etc. This can also be used with many Microprocessor Development Systems.

Above is preferred method of wiring a Null Modem. It only requires 3 wires (TD, RD &

SG) to be wired straight through thus is more cost effective to use with long cable runs. The

theory of operation is reasonably easy. The aim is to make to computer think it is talking to a

modem rather than another computer. Any data transmitted from the first computer must be

received by the second thus TD is connected to RD. The second computer must have the same

set-up thus RD is connected to TD. Signal Ground (SG) must also be connected so both grounds

are common to each computer.

The Data Terminal Ready is looped back to Data Set Ready and Carrier Detect on both

computers. When the Data Terminal Ready is asserted active, then the Data Set Ready and

Carrier Detect immediately become active. At this point the computer thinks the Virtual Modem

to which it is connected is ready and has detected the carrier of the other modem.

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All left to worry about now is the Request to send and Clear To Send. As both computers

communicate together at the same speed, flow control is not needed thus these two lines are also

linked together on each computer. When the computer wishes to send data, it asserts the Request

to send high and as it's hooked together with the Clear to Send, It immediately gets a reply that it

is ok to send and does so.

Notice that the ring indicator is not connected to anything of each end. This line is only

used to tell the computer that there is a ringing signal on the phone line. As we don't have a

modem connected to the phone line this is left disconnected.

RS232 bit streams

The RS232 standard describes a communication method where information is sent bit by

bit on a physical channel. The information must be broken up in data words. The length of a data

word is variable. On PC's a length between 5 and 8 bits can be selected. This length is the

information length of each word. For proper transfer additional bits are added for

synchronization and error checking purposes. It is important, that the transmitter and receiver use

the same number of bits. Otherwise, the data word may be misinterpreted, or not recognized at

all.

With synchronous communication, a clock or trigger signal must be present which

indicates the beginning of each transfer. The absence of a clock signal makes an asynchronous

communication channel cheaper to operate. Less line is necessary in the cable. A disadvantage is

that the receiver can start at the wrong moment receiving the information. Re-synchronization is

then needed which costs time. All data received in the resynchronization period is lost. Another

disadvantage is that extra bits are needed in the data stream to indicate the start and end of useful

information. These extra bits take up bandwidth.

Data bits are sent with a predefined frequency, the baud rate. Both the transmitter and

receiver must be programmed to use the same bit frequency. After the first bit is received, the

receiver calculates at which moments the other data bits will be received. It will check the line

voltage levels at those moments.

With RS232, the line voltage level can have two states. The on state is also known as

mark, the off state as space. No other line states are possible. When the line is idle, it is kept in

the mark state.

Start bit

RS232 defines an asynchronous type of communication. This means, that sending of a

data word can start on each moment. If starting at each moment is possible, this can pose some

problems for the receiver to know which the first bit to receive is. To overcome this problem,

each data word is started with an attention bit. The space line level always identifies this

attention bit, also known as the start bit. Because the line is in mark state when idle, the receiver

easily recognizes the start bit.

Data bits

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Directly following the start bit, the data bits are sent. A bit value 1 causes the line to go in mark

state; the bit value 0 is represented by a space. The least significant bit is always the first bit sent.

Parity bit

For error detecting purposes, it is possible to add an extra bit to the data word automatically. The

transmitter calculates the value of the bit depending on the information sent. The receiver

performs the same calculation and checks if the actual parity bit value corresponds to the

calculated value.

Stop bits

Framing means, that all the data bits and parity bit are contained in a frame of start and stop bits.

The period of time lying between the start and stop bits are a constant defined by the baud rate

and number of data and parity bits. The start bit has always space value, the stop bit always mark

value. If the receiver detects a value other than mark when the stop bit should be present on the

line, it knows that there is a synchronization failure. This causes a framing error condition in the

receiving UART.

The stop bit identifying the end of a data frame can have different lengths. Actually, it is not a

real bit but a minimum period of time the line must be idle (mark state) at the end of each word.

On PC's this period can have three lengths: the time equal to 1, 1.5 or 2 bits. 1.5 bits is only used

with data words of 5 bits length and 2 only for longer words. A stop bit length of 1 bit is possible

for all data word sizes.

b) RS485 Protocol:

RS485 is the most versatile communication standard in the standard series defined by the EIA, as

it performs well on all four points. That is why RS485 is currently a widely used communication

interface in data acquisition and control applications where multiple nodes communicate with

each other.

Differential signals withRS485

Longer distances and higher bit rates

One of the main problems with RS232 is the lack of immunity for noise on the signal

lines. The transmitter and receiver compare the voltages of the data- and handshake lines with

one common zero line. Shifts in the ground level can have disastrous effects. Therefore the

trigger level of the RS232 interface is set relatively high at ±3 Volt. Noise is easily picked up

and limits both the maximum distance and communication speed. With RS485 on the contrary

there is no such thing as a common zero as a signal reference. Several volts difference in the

ground level of the RS485 transmitter and receiver does not cause any problems. The RS485

signals are floating and each signal is transmitted over a Sig+ line and a Sig- line. The RS485

receiver compares the voltage difference between both lines, instead of the absolute voltage level

on a signal line. This works well and prevents the existence of ground loops, a common source

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of communication problems. The best results are achieved if the Sig+ and Sig- lines are twisted.

The image below explains why.

In the picture above, noise is generated by magnetic fields from the environment. The

picture shows the magnetic field lines and the noise current in the RS485 data lines that is the

result of that magnetic field. In the straight cable, all noise current is flowing in the same

direction, practically generating a looping current just like in an ordinary transformer. When the

cable is twisted, we see that in some parts of the signal lines the direction of the noise current is

the opposite from the current in other parts of the cable. Because of this, the resulting noise

current is many factors lower than with an ordinary straight cable. Shielding—which is a

common method to prevent noise in RS232 lines—tries to keep hostile magnetic fields away

from the signal lines. Twisted pairs in RS485 communication however adds immunity which is a

much better way to fight noise. Differential signals and twisting allows RS485 to communicate

over much longer communication distances than achievable with RS232. With RS485

communication distances of 1200 m are possible.

Differential signal lines also allow higher bit rates than possible with non-differential

connections. Therefore RS485 can overcome the practical communication speed limit of RS232.

Currently RS485 drivers are produced that can achieve a bit rate of 35 mbps.

Table Characteristics of RS485 compared to RS232

RS232 RS485

Differential No Yes

Max no. Of drivers Max

no. Of receivers

1 1 32 32

Half duplex

Full duplex

Half duplex Full

duplex

Network Topology Point-to-point Multi point

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Max speed at 12m Max

speed at 1200 m

20kbps (1kbps) 35Mbps

100kbps

Receiver input resistance 3-7kohm 12kohm

Driver load impedance 3-7kohm 54ohm

Receiver input range ±15 V –7-12 V

Max driver output voltage ±25 V –7-12 V

Max distance 15m 1200m

We see that the speed of the differential interface RS485 is far superior to the single ended

version of RS232. To avoid reflections on longer cables it is necessary to use appropriate

termination resistors.

RS485 can be used in situations with a severe ground level shift of several volts, where at

the same time high bit rates are possible because the transition between logical 0 and logical 1 is

only a few hundred-mill volts.

Network topology with RS485:

Network topology is probably the reason why RS485 is now the favourite in data acquisition and

control applications. RS485 is the only of the interfaces capable of internetworking multiple

transmitters and receivers in the same network. When using the default RS485 receivers with an

input resistance of 12 kΩ it is possible to connect 32 devices to the network. Currently available

high-resistance RS485 inputs allow this number to be expanded to 256. RS485 repeaters are also

available which make it possible to increase the number of nodes to several thousands, spanning

multiple kilometres. It is the reason why RS485 is so popular with computers, PLCs, micro

controllers and intelligent sensors in scientific and technical applications.

In the picture above, the general network topology of RS485 is shown. N nodes are connected in

a multipoint RS485 network. For higher speeds and longer lines, the termination resistances are

necessary on both ends of the line to eliminate reflections. The RS485 network must be designed

as one line with multiple drops, not as a star. Although total cable length maybe shorter in a star

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configuration, adequate termination is not possible anymore and signal quality may degrade

significantly.

RS485 COMMUNICATION

RS485 functionality

All the senders on the RS485 bus are in tri-state with high impedance. In most high-level

protocols, one of the nodes is defined as a master, which sends queries or commands over the

RS485 bus. All other nodes receive these data. Depending of the information in the sent data,

zero or more nodes on the line respond to the master. In this situation, bandwidth can be used for

almost 100%. There are other implementations of RS485 networks where every node can start a

data session on its own. This is comparable with the way Ethernet networks function. Because

there is a chance of data collision with this implementation, theory tells us that in this case only

37% of the bandwidth will be effectively used. With such an implementation of a RS485

network it is necessary that there is error detection implemented in the higher-level protocol to

detect the data corruption and resend the information at a later time.

There is no need for the senders to explicitly turn the RS485 driver on or off. RS485

drivers automatically return to their high impedance tri-state within a few microseconds after the

data has been sent. Therefore it is not needed to have delays between the data packets on the

RS485 bus.

RS485 is used as the electrical layer for many well-known interface standards for

Modbus. Therefore RS485 will be in use for many years in the future.

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v. Packet structure:

We have made a protocol for the data frame in which there is 6 bytes field is there. First

byte is start of bit, second is address byte, third is control byte, fourth and fifth is for data bytes

and sixth byte is of end of frame.

STX ADDRESS CONTROL

DATA

DATA DATA ETX

Description:

• STX is start of header it act as starting mark for packet.

• ADDRESS is the address for the slave from which communication is to be done.

• CONTROL DATA contains control signal which is to be from PC to slaves in order to

control certain devices.

• Next two bytes carries data from slaves to PC.

• ETX act as end point of packet.

3. CIRCUIT DESCRIPTION:

1. Schematic diagram and PCB layout for the slave controllers is as shown below. The

project layout is made with the help of EAGLE 5.5.0 (PCB layout making software).

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Slave controller schematic.

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Slave controller track side layout.

Description:

1. Atmega8 is the controller used.

2. USART RxD and TxD pins are connected to data in and data out of 75176B (line driver IC)

which converts RS-232 signals into RS-485.

3. 5v constant power supply is used.

4. Separate headers for ISP and ports are provided.isp header is used for burning the controller.

5. Crystal oscillator and the Reset circuitry is connected to the appropriate controller pins.

2. Schematic diagram for main controller is as shown below. This is also made with

EAGLE 5.5.0 (PCB layout making software).

13

Master controller schematic.

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Master controller track side layout.

Description:

1. Atmega16 is used as the main controller.

2. Multiplexer 74155N and De -multiplexer 74LS153N IC’s are used to switch between rs-232

and rs-485 communication interfaces.

3.75176b is used to convert rs-232 signals into rs-485 protocol communication.

4.5v power supply is used.

5. Various headers are taken to take the port output and input.isp header is provided for burning

process.

6. Crystal oscillator and the Reset circuitry is connected to the appropriate controller pins.

USB to serial converter:

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We designed the system to be connected to pc via USB port, for this purpose we

developed USB to UART (AVR-CDC) converter module. AVR-CDC is a USB-RS232C

interface using the CDC (Communication Device Class) protocol. Although the bulk endpoint

required for CDC is not allowed within the low-speed USB standard, it works fine on major

platforms.

Features:

• No dedicated driver necessary. OS loads a built-in driver ("usbser.sys" on Windows).

• Very low cost. This is the cheapest solution for the USB-RS232C interface.

On Windows, an INF file is required to load the pre-installed driver when the device is

connected for the first time. The virtual COM port appears after the connection established.

The Vcc should be lower than 3.6V to meet the USB standard. Use a quartz crystal instead of

a ceramic resonator for stable connection. ATmega8/48/88 can achieve the higher transfer rate

(e.g. 38400bps) using the internal USART.

All information about AVR-CDC USB-RS232C interface is obtained from link

http://www.recursion.jp/avrcdc/index.html.

USB to Serial converter Schematic

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USB to Serial Converter track side layout

Description :

1. There is a header SL 1 which connects RxD and TxD pins to the serial cable.

2. Output from the PC is given to COM port which is connected to the USB port of the USB

to Serial Converter.

3. Crystal oscillator is connected to the appropriate controller pin.

4. HARDWARE DESIGN:

i. Data aquisition system:

All the modules connected in the proper manner is shown below. Total setup is working

accurately according to the requirement.

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Data Acquisition system set-up

ii. Slave controller:

The diagram shown below is of slave controller board. All the IC’s and headers used are

shown in the diagram. ADC header is used to connect the sensor output to the slave

controller. ISP header is used to programmed the slave controller with the help of USB

programmer. 75176B is the line driver IC used to convert RS-485 protocol into RS-232

protocol and vice-versa.

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Slave controller board

iii. Main controller:

The diagram shown below is of main controller board. All the IC’s and headers used are

shown in the diagram. ISP header is used to program the main controller with the help of

USB programmer. 75176B is the line driver IC used to convert RS-485 protocol into RS-

232 protocol and vice-versa. 75LS153N is the multiplexer IC used to multiplex the

signals from serial port and RS-485 and the vice versa. 75LS155 is the demultiplexer IC

used to demultiplex the signals from serial port and RS-485 and vice versa.

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Master controller board

iv. Sensor assembly:

We have used three sensors in our project. They are, light intensity sensor, temperature

sensor and trim pot. They are giving their data to the respective ADC of the slave

controller.

a) LDR (Light Dependent Resistors):

The resistance of the Light Dependent Resistor (LDR) varies according to the amount of

light that falls on it. The relationship between the resistance RL and light intensity Lux for a

typical LDR is

RL = 500 / Lux Kohm

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With the LDR connected to 5V through a 3.3K resistor, the output voltage of the LDR is

Vo = 5*RL / (RL+R)

Reworking the equation, we obtain the light intensity

Lux = (2500/Vo - 500)/R

For a low cost LDR, at the same light intensity, the part to part variation in resistance can be as

high as 50%.

Lux is a derived unit based on lumen, and lumen is a derived unit based on candela.

One lux is equal to one lumen per square metre, where 4π lumens is the total luminous flux of a

light source of one candela of luminous intensity:

1 lx = 1 lm·m-2 = 1 cd·sr·m–2.

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As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.

Luminance.

TABLE FOR TYPICAL VALUES OF LUX METER

Typical

value(LUX)

Area & conditions

10-5 lux Light from Sirius, the brightest star in the night sky

10-4 lux Total starlight, overcast sky

50 lux Family living room

80 lux Hallway/toilet

100 lux Very dark overcast day

320 lux Recommended office lighting (Australia)

400 lux Sunrise or sunset on a clear day. Well-lit office area

500 lux

Lighting level for an office according to the European law UNI

EN 12464

1,000 lux Overcast day]; typical TV studio lighting

10,000–

25,000 lux

Full daylight (not direct sun)[

32,000–

130,000 lux

Direct sunlight

b) Temperature Sensor - The LM35:

The LM35 is an integrated circuit sensor that can be used to measure temperature with an

electrical output proportional to the temperature (in ºC)

Features

• You can measure temperature more accurately than a using a thermistor.

• The sensor circuitry is sealed and not subject to oxidation, etc.

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• The LM35 generates a higher output voltage than thermocouples and may not require that

the output voltage be amplified.

• It has an output voltage that is proportional to the Celsius temperature. The scale factor is

.01V/ ºC

• The LM35 does not require any external calibration or trimming and maintains an

accuracy of +/-0.4 ºC at room temperature and +/- 0.8 ºC over a range of 0 ºC to +100 ºC.

• Another important characteristic of the LM35DZ is that it draws only 60 micro amps

from its supply and possesses a low self-heating capability. The sensor self-heating

causes less than 0.1 º C temperatures rise in still air.

LM35 Temperature IC

The LM35 comes in many different packages, including the following.

• TO-92 plastic transistor-like package,

• T0-46 metal can transistor-like package

• 8-lead surface mount SO-8 small outline package

• TO-202 package. (Shown in the picture above).

Connections for LM35DZ

Typical circuit is shown below

In this circuit, parameter values commonly used are:

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• Vc = 4 to 30v

• 5v or 12 v are typical values used.

• Ra = Vc *1000000Ω

• Actually, it can range from 80 KΩ to 600 KΩ, but most just use 80 KΩ.

Temperature measurement

• We need to use a voltmeter to sense Vout.

• The output voltage is converted to temperature by a simple conversion factor.

• The sensor has a sensitivity of 10mV / ºC.

• Use a conversion factor that is the reciprocal that is 100 ºC/V.

• The general equation used to convert output voltage to temperature is:

• Temperature ( ºC) = Vout * (100 ºC/V)

• So if Vout is 1V , then, Temperature = 100 ºC

• The output voltage varies linearly with temperature.

c) Resistance sensor:

Potentiometers are passive transducers. It has three legs; moving nut provides variance in

resistance.

Trim pot

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From the circuit the resistance RL given by

RL = ( Vout / Vcc ) * R

So we need only to measure Vout to measure resistance.

Rl

R

25

Sensor elements board

v. USB to serial converter:

We designed the system to be connected to pc via USB port for this purpose we

developed USB to UART (AVR-CDC) converter module. AVR-CDC is a USB-RS232C

interface using the CDC (Communication Device Class) protocol. Although the bulk endpoint

required for CDC is not allowed within the low-speed USB standard, it works fine on major

platforms.

Features:

• No dedicated driver necessary. OS loads a built-in driver ("usbser.sys" on Windows).

• Very low cost. This is the cheapest solution for the USB-RS232C interface.

On Windows, an INF file is required to load the pre-installed driver when the device is

connected for the first time. The virtual COM port appears after the connection established.

The Vcc should be lower than 3.6V to meet the USB standard. Use a quartz crystal instead of

a ceramic resonator for stable connection. ATmega8/48/88 can achieve the higher transfer rate

(e.g. 38400bps) using the internal USART.

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All information about AVR-CDC USB-RS232C interface is obtained from


USB to Serial converter

vi. AVR DOPER USB PROGRAMMER:

For programming the microcontroller we have developed AVR-Doper USB programmer.

Circuits and PCB layout can be obtained from site

http://rototron.info/default.aspx?Page=USBAVR/USBAVR.aspx.

AVR-Doper is an STK500 compatible In-System Programmer (ISP) and High Voltage

Serial Programmer (HVSP).It simply consists of an ATMega48 or an ATMega8 and a couple of

passive components. The programmer uses a firmware-only USB driver; no special USB

controller is needed. All firmware and USB drivers and can be downloaded from

http://www.obdev.at/products/vusb/avrdoper.html

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USB ISP Programmer

USB ISP programmer pin out

Atmega 8

ISP connector

74HC126 IC USB connector

Power supply forward jumper

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Features:

• HVSP allows using RESET pin for I/O, which is especially beneficial on 8 and 14 pin

devices.

• Simple hardware which can be built on a single sided PCB. No special USB chips are

needed.

• Compatible to Atmel's STK500 with built-in USB to Serial converter.

• Adjustable ISP clock allows flashing of devices clocked at very low rate, e.g. 32 kHz.

• ISP clock can be lowered with a jumper (if the programmer software does not support

setting the ISP clock).

• Second USB to Serial converter for processing debug output from the target.

• Uses USB power supply, no external supply required.

• Open Source (including firmware and schematics).

5. SOFTWARE DESIGN:

i. Visual basic 6.0

Visual Basic 6 is Microsoft’s one of the greatest version of the Visual Basic

programming language. Although writing programs can be a tedious chore at times,

Visual Basic reduces the effort required on your part and makes programming enjoyable.

Visual Basic makes many aspects of programming as simple as dragging graphic objects

onto the screen with your mouse.

Much of creating a Visual Basic program requires placing graphic objects on the screen

and setting attributes for those objects that determine how the objects are to look and

behave. Visual Basic is truly the only programming language today that beginning

programmers can learn easily. In addition, Visual Basic allows advanced programmers to

create powerful Windows applications.

Visual Basic is an enjoyable language due to its visual environment. Much of building a

Windows program in Visual Basic requires dragging and dropping graphic objects onto

the screen from a toolbox which houses those objects. Your

Windows program appears before your eyes as you add the objects. Visual Basic is one

of the first programming languages to incorporate a true WYSIWYG (What You See Is

What You Get) environment. The program that you build looks like the program users

see when they run the program from Windows.

Visual Basic is based on a language named BASIC. Visual Basic is visual and uses a

simple BASIC-like programming language, yet Visual Basic enables you to create

powerful Windows programs.

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Visual Basic’s visual nature is more important than its programming language in many

ways. The visual interface provides your program’s character and interacts with the user.

The programming language works behind the scenes to connect the visual elements.

ii. AVR studio as IDE

AVR Studio is an Integrated Development Environment (IDE) for writing and debugging AVR

applications in Windows 9x/ME/NT/2000/XP/VISTA environments. AVR Studio provides a

project management tool, source file editor, simulator, assembler and front-end for C/C++,

programming, emulation and on-chip debugging.AVR Studio supports the complete range of

ATMEL AVR tools and each release will always contain the latest updates for both the tools and

support of new AVR devices.

AVR Studio 4 has a modular architecture which allows even more interaction with 3rd party

software vendors. GUI plug-ins and other modules can be written and hooked to the system.

Please contact us if you are interested in more information about this.

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6. DATA FLOW DIAGRAM:

FLOW CHART FOR VB PORGRAM

N Y

Create packets for slave

device’s address at regular

intervals and send them to

master device.

Wait to receive packets from

master device.

According to address of packet

obtained data bytes and

calculate sensor output and

display them on screen.

Put control signal on control

bytes in packet and send packet

to desired slave through master.

Receive packet from master and

discard it.

If user generates

control signal from

screen

Initialize COM port in VB program

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FLOW CHART FOR MASTER DEVICE

N

Y

Initialize UART with baud rate

57600

Enable RS232 port & receive

packets from computer

Enable RS 485 as Tx &

broadcast packets to all slaves.

Enable RS485 port as rx &Wait

until reply from slaves.

Receive packet from slave.

Enable RS 232 port & transmit

packet to computer.

Discard packet

If packet address

matches with

connected

slaves.

32

FLOW CHART FOR SLAVE DEVICE

ADC complete ISR

Initialize UART with baud rate 57600 &

RX complete interrupt also initialize ADC

with ADC complete interrupt.

Enable RS 485 as Rx

Do nothing and call ADC &

UART RX complete ISR when

ADIF & RXC flags are set.

ADC complete ISR

Return

Copy REGISTER ADCL &

ADCH to tempH& tempL

33

N

Y

RXC complete ISR

RXC complete ISR

Receive packet from slave.

Copy ADC data to data byte of

packet.

If address

matches

Enable RS 485 port as tx and

transmit whole packet.

Enable RS 485 port as Rx

Return

34

7. PROGRAMMING LOGIC:

i. Program for slave controllers:

#include <stdlib.h>

#include <avr/io.h>

#include <util/delay.h>

#include <avr/interrupt.h> //Including header files

#define STX 0x02

#define ETX 0x04

#define pack_length 0x06

void USART_Init(unsigned long int); //function to initialise USART.

void ADC_Init(void); //initialise ADC in free running mode.

void RS485_Tx_en(void); //function to enable RS-485 as tx

void RS485_Rx_en(void); //function to enable RS-485 as Rx

unsigned char USART_Receive(void); //function to rx single character

void USART_Transmit( unsigned char); //function to tx single character

void PACKET_RX(void); //0 for rs-232 & 1 for rs485

void PACKET_TX(void); //0 for rs-232 & 1 for rs485

unsigned char Address_Check(void); //function to check for right address

void read_control_sig(void); //function to read control signal from packet.

//Globle variable delaration.

unsigned char data_packet[6],data_counter=0,temp_dataH=0,temp_dataL=0;

const unsigned char Device_Address = 0x36; //for temperature sensor.

char i=0,j=0,k=0;

short isEndTwo=0;

ISR(ADC_vect) //ISR to handle ADC complete

interrupt.

temp_dataL = ADCL; //copy ADCL to temp_dataL

temp_dataH = ADCH; //copy ADCH to temp_dataH

ISR(USART_RXC_vect) //ISR to handle RXC complete

interrupt.

PACKET_RX(); //receive packet from master

data_packet[3] = temp_dataH; //copy ADC data to packet.

data_packet[4] = temp_dataL;

//_delay_ms(500);

35

if(Address_Check() && isEndTwo)

read_control_sig(); //if address matches then read control signal

PACKET_TX(); //tx packet to master.

RS485_Rx_en(); //enable RS-485 as rx

int main (void)

DDRB=0x3F; //make portB outport.

DDRC=0x00; //make portC inport for ADC.

DDRD=0xFF; //make portD outport for controls.

USART_Init(57600); //set baud rate

RS485_Rx_en(); //enable RS-485 as rx

ADC_Init(); //init. & start ADC

sei(); //enable globle interrupt flags.

while(1) //wait until interrupted.

return 0;

/////////////////////////////*FUNCTION DECLARATION*/////////////////////////

void USART_Init( unsigned long int baud)

baud = (((12000000l / (baud * 16UL))) - 1); //calculate vulue for UBRR register

UBRRH = (unsigned char)(baud>>8); // Set baud rate

UBRRL = (unsigned char)baud;

UCSRB |= (1<<RXEN)|(1<<TXEN)|(1<<RXCIE); // Enable receiver and transmitter

UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1); //Set frame format: 8 data, 1 stop

bit & asynchronous comm.

void ADC_Init(void)

ADCSRA |= (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // Set ADC prescalar to 128 -

125KHz sample rate @ 16MHz

ADMUX |= (1 << REFS0); // Set ADC reference to AVCC

36

ADMUX |= (0 << REFS1); // Set ADC reference to AVCC

ADMUX |= (0 << ADLAR); // Right adjust ADC result to allow easy 8 bit

reading

// No MUX values needed to be changed to use ADC0

ADCSRA |= (1 << ADFR); // Set ADC to Free-Running Mode

ADCSRA |= (1 << ADEN); // Enable ADC

ADCSRA |= (1 << ADIE); //Enable ADC interrupt

ADCSRA |= (1 << ADSC); // 1 to Start A2D Conversions

void PACKET_RX(void)

j=0;

data_counter = 0;

for(k=0;k<=5;k++)

data_packet[k]= 0; //flush data_packet.

while(j<=5) //condition to take care of correct data

reception

i = USART_Receive(); //receive first

if(i == STX) //start of packet.

do

data_packet[data_counter++] = i;

i = USART_Receive(); //receive until whole packet rxd

while(!(data_counter == (pack_length-1)));

if(i==ETX)

data_packet[data_counter] = i; //

isEndTwo=1;

else

isEndTwo=0;

break;

j++;

37

void PACKET_TX(void)

RS485_Tx_en() ;

data_counter = 0;

do

USART_Transmit( data_packet[data_counter++] ); //code to tx data packet.

//_delay_ms(500);


USART_Transmit( data_packet[data_counter] );

unsigned char Address_Check(void)

if(data_packet[1]==Device_Address) //if packet address matches with device add.

return 1 else 0

return 1;

else

return 0;

void read_control_sig(void) //reads control signal & latches control to portD

if(data_packet[2]=='1')

PORTD = 0x04;

if(data_packet[2]=='2')

PORTD = 0x00;

unsigned char USART_Receive( void )

while ( !(UCSRA & (1<<RXC)) ); // Wait for data to be received

return UDR; // Get and return received data from buffer

void USART_Transmit( unsigned char data )

UDR = data; // Put data into buffer, sends the data

38

while(!(UCSRA & (1<<TXC)));

UCSRA &= 0xfd; // Wait for empty transmit buffer

void RS485_Tx_en(void)

PORTB =0x03; //write portB to select RS485 as tx

void RS485_Rx_en(void)

PORTB =0x00; //write portB to select RS485 as rx

ii. Program for main controller:

#include <stdlib.h>

#include<string.h>

#include <avr/io.h>

#include<util/delay.h> //Including header files

#define STX 0x02

#define ETX 0x04

#define pack_length 0x06

void USART_Init(unsigned long int); //To initialise USART.

unsigned char USART_Receive(void); //To receive char from USART

void USART_Transmit( unsigned char); //To receive char from USART

void PACKET_RX(unsigned char); //0 for rs-232 & 1 for rs485

void PACKET_TX(unsigned char); //0 for rs-232 & 1 for rs485

//Globle variable delaration.

unsigned char data_packet[6],data_counter=0,i=0,j=0 ;

int main (void)

DDRA=0xFF; ////make portd outport to select RS-485.

USART_Init(57600);

while(1)

39

while(1)

PACKET_RX(0); //rx from computer.

if(data_packet[1]=='6' | data_packet[1]=='7' | data_packet[1]=='8')

break; //if packet address does not matches with connected

slaves then break

PACKET_TX(1); //tx to slaves.

PACKET_RX(1); //rx from slaves

PACKET_TX(0); //tx to computer.

return 0;

/////////////////////////////*FUNCTION DECLARATION*/////////////////////////

void USART_Init( unsigned long int baud)

baud = (((12000000l / (baud * 16UL))) - 1);

UBRRH = (unsigned char)(baud>>8); // Set baud rate

UBRRL = (unsigned char)baud;

UCSRB |= (1<<RXEN)|(1<<TXEN); // Enable receiver and transmitter

UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1); //Set frame format: 8 data, 1 stop

bit

void PACKET_RX(unsigned char port)

unsigned char i=0,j=0;

data_counter = 0;

if(port==0) //check & select rs232 port.

PORTA =0x00;

else if(port == 1) //check & select rs485 port

PORTA =0x0c;

while(j<=5)

i = USART_Receive();

if(i == STX) //start of packet.

do

data_packet[data_counter++] = i;

40

i = USART_Receive();


data_packet[data_counter] = i; //end of packet

break;

j++;

void PACKET_TX(unsigned char port1)

data_counter = 0;

if(port1==0) //check & select rs232 port.

PORTA =0x00;

else if(port1 == 1) //check &select rs232 port

PORTA =0xcc;

do

USART_Transmit( data_packet[data_counter++] );


USART_Transmit( data_packet[data_counter] );

unsigned char USART_Receive( void )

while ( !(UCSRA & (1<<RXC)) ); // Wait for data to be received

return UDR; // Get and return received data from buffer

void USART_Transmit( unsigned char data )

UDR = data; // Put data into buffer, sends the data

while(!(UCSRA & (1<<TXC)));

UCSRA &= 0xfd; // Wait for empty transmit buffer

iii. Visual basic programming:

a) Programming for taking the data from sensors and storing in database:

41

'Global variable declarations

Public db As Database

Public rs As Recordset

Dim k As Integer

Public sno As Integer

Dim curx As Single

Public num_sensors As Byte

Dim numFrameReceived As Byte

Dim first_Address As Byte

Dim ch As Byte

Dim interval As Byte

Dim cury() As Single

Dim xRange(1) As Integer

Dim yRange(1) As Integer

Dim yscale As Integer

Dim xscale As Integer

Dim isFanOn As Boolean

Dim isControlOn As Boolean

Dim temp As Integer

***********Procedure of command button named

cmdshow*********************************

Private Sub cmdshow_Click()

If (rs.RecordCount) Then

Form2.Show

Else

MsgBox "There is no record in the database", vbExclamation, "Warning"

End If

End Sub

***********Procedure of command button named

controlcmd********************************

Private Sub controlcmd_Click()

If ((Val(Text1(2).Text) >= Val(Text1(0).Text)) And (Val(Text1(2).Text) <=

Val(Text1(1).Text))) Then

If (MSComm1.PortOpen) Then

sendFrame (49)

isControlOn = True

Else

MsgBox "Port is not open. Communication can't take place", vbExclamation, "DAQ"

End If

Else

MsgBox "Value of Set point must be between low limit and high limit", vbExclamation,

"DAQ"

42

End If

End Sub

***********Procedure of sendframe

function***************************************************

Private Sub sendFrame(controlData As Integer)

Dim ctr As Byte, f As Variant

Dim frame(5) As Byte

frame(0) = 49

frame(1) = 54

frame(2) = controlData

frame(3) = 0

frame(4) = 0

frame(5) = 50

For ctr = 0 To 5

f = Chr(frame(ctr))

MSComm1.Output = f

Next ctr

If (controlData = 49) Then

isFanOn = True

ImgFan.Visible = True

Else

isFanOn = False

ImgFan.Visible = False

End If

End Sub

***********Procedure of command button

deleterecord***************************************

Private Sub delreccmd_Click()

Dim Msg, Style, Title, Response, MyString

Dim i As Integer

Msg = "You will lose all previous records..Do you want to continue?"

Style = vbYesNo + vbExclamation + vbDefaultButton2

Title = "Confirmation Box"

Response = MsgBox(Msg, Style, Title)

If Response = vbYes Then

Call delRec

For i = 0 To 2

lblsensor(i).Caption = 0

Next

End If

End Sub

***********Procedure of delRec

function*******************************************************

Private Sub delRec()

db.Execute ("Delete from sensors_data")

rs.Close

43

Set rs = db.OpenRecordset("sensors_data", dbOpenDynaset)

Me.sno = 1

Call drawgrid

For ctr = 0 To length

cury(ctr) = yRange(1)

Next ctr

curx = xRange(0)

End Sub

***********Procedure of command button exit

************************************************

Private Sub exitcmd_Click()

rs.Close

db.Close

End

End Sub

***********Procedure of Form_Load

function**************************************************

Private Sub Form_Load()

Dim length As Byte, ctr As Byte

'Set number of sensors

num_sensors = 3

'Set address for first sensors

first_Address = 54

ch = first_Address

interval = 1

xRange(0) = 260

xRange(1) = 860

yRange(0) = 350

yRange(1) = 610

yscale = (yRange(1) - yRange(0)) / 10 'set no. of pixels for one Y part of 10

xscale = 40 'set no. of pixels for one X part of 10

temp = yscale

length = num_sensors - 1

ReDim cury(length) 'Dynamic allocation

Set db = OpenDatabase(App.Path & "\daq.mdb")

Set rs = db.OpenRecordset("sensors_data", dbOpenDynaset)

If (rs.AbsolutePosition = -1) Then

Me.sno = 1


cury(ctr) = yRange(1)

Next ctr

Else

rs.MoveLast


If (ctr = 1) Then

yscale = yscale / 5

44

End If

cury(ctr) = yRange(1) - rs.Fields(ctr + 2).value * (yscale / 10)

yscale = temp

Next ctr

Me.sno = rs.Fields("Sr No").value + 1

End If

curx = xRange(0)

VScroll1(0).value = Text1(0).Text

VScroll1(1).value = Text1(1).Text

End Sub

***********Procedure of drawgraph

function**************************************************

Private Sub drawgraph()

Dim x As Single

Dim y As Single

Dim ctr As Byte

x = curx + (xscale / 5)

If (x > xRange(1)) Then

Me.Cls

Call drawgrid

curx = xRange(0)

x = curx + (xscale / 5)

End If

rs.MoveLast

For ctr = 2 To (num_sensors + 1)

If (ctr = 3) Then

yscale = yscale / 5

End If

y = yRange(1) - (rs.Fields(ctr).value * (yscale / 10))

Line (curx, cury(ctr - 2))-(x, y), QBColor(9 + ctr)

cury(ctr - 2) = y

yscale = temp

Next ctr

curx = x

End Sub

***********Procedure of drawgrid

function**************************************************

Private Sub drawgrid()

Dim i As Integer

i = 0

Me.Line (xRange(0), yRange(0))-(xRange(1), yRange(1)), QBColor(0), BF

For x = xRange(0) To xRange(1) Step xscale

Line (x, yRange(0))-(x, yRange(1) + 5), QBColor(2)

CurrentX = CurrentX - (xscale \ 5)

CurrentY = CurrentY + 3

Me.Print i

45

i = i + 5

Next

i = 10

For y = (yRange(1) - temp) To yRange(0) Step -temp

Line (xRange(0) - 5, y)-(xRange(1), y), QBColor(2)

If (i = 100) Then

CurrentX = xRange(0) - 35

Else

CurrentX = xRange(0) - 30

End If

CurrentY = CurrentY - 3

Me.Print i

i = i + 10

Next

End Sub

***********Procedure of form_Paint

function**************************************************

Private Sub form_Paint()

'Variable Declarations

Dim x As Single

Dim i As Single

Dim j As Single

Dim value As Single

Dim c As Integer

Dim y() As Single

ReDim y(num_sensors - 1)

Call drawgrid 'Draws grid for graph

x = curx

For c = 0 To (num_sensors - 1)

y(c) = cury(c)

Next

If (x > xRange(0)) Then

For c = 2 To (num_sensors + 1)

CurrentX = x

CurrentY = y(c - 2)

rs.MoveLast

If (c = 3) Then

yscale = yscale / 5

End If

For i = x - (xscale \ 5) To (xRange(0) + 8) Step -(xscale \ 5)

rs.MovePrevious

value = Me.rs.Fields(c).value

46

j = yRange(1) - (value * (yscale / 10))

Line -(i, j), QBColor(9 + c)

Next

rs.MovePrevious

If (rs.BOF) Then

j = yRange(1)

Else

value = Me.rs.Fields(c).value

j = yRange(1) - (value * (yscale / 10))

End If

Line -(i, j), QBColor(9 + c)

yscale = temp

Next

End If

End Sub

***********Procedure of testSensor1Data

function********************************************

Private Sub testSensor1Data()

If (Val(lblsensor(0).Caption) >= VScroll1(0).value And Val(lblsensor(0).Caption) <=

VScroll1(1).value) Then

Shape1.FillColor = RGB(0, 255, 0)

If (isFanOn And (Val(lblsensor(0).Caption) <= Val(VScroll1(2).value))) Then

sendFrame (50) 'off the fan

End If

controlcmd.Enabled = False

ElseIf (lblsensor(0).Caption < VScroll1(0).value) Then


controlcmd.Enabled = True

Else



End If

If (isFanOn And (Val(lblsensor(0).Caption) <= Val(VScroll1(2).value))) Then

sendFrame (50) 'off the fan

End If

End Sub


function********************************************


Dim value As Single

value = CSng(lblsensor(1).Caption)

If (value >= 0 And value <= 20) Then

DarkShape.FillColor = RGB(0, 255, 0)

OptimumShape.FillColor = RGB(255, 255, 255)

BrightShape.FillColor = RGB(255, 255, 255)

ElseIf (value >= 21 And value <= 70) Then

47




Else




End If

End Sub


function********************************************


Dim value As Single

value = CSng(lblsensor(2).Caption)

If (value >= 0 And value <= 30) Then

RngShape1.FillColor = RGB(0, 255, 0)



ElseIf (value >= 31 And value <= 60) Then




Else




End If

End Sub

***********Procedure of getbyte

function********************************************

Private Function getbyte() As Byte

Dim a As Byte

'wait as long as receive buffer is empty

While MSComm1.InBufferCount < 1

Wend

'get first 8-bits in variable a

a = Asc(MSComm1.Input)

getbyte = a

End Function

***********Procedure of lblsensor_Change

function******************************************

Private Sub lblsensor_Change(Index As Integer)

48

If (Index = 0) Then

Call testSensor1Data

ElseIf (Index = 1) Then


Else


End If

End Sub

***********Procedure of Timer_Timer

function******************************************

Private Sub Timer_Timer()

Dim ctr As Byte, f As Variant

Dim overflow As Integer


If (interval = 1) Then

frame(0) = 49

frame(1) = ch

frame(2) = 0

frame(3) = 0

frame(4) = 0

frame(5) = 50

While (MSComm1.InBufferCount)

a = getbyte()

Wend

For ctr = 0 To 5

f = Chr(frame(ctr))

MSComm1.Output = f

Next ctr

ch = ch + 1

While (MSComm1.InBufferCount = 0)

overflow = overflow + 1

If (overflow = 2000) Then

MsgBox "Data is not being received", vbCritical, "Error"

Call stop_comm 'Stop communication

Exit Sub

End If

Wend

Timer.interval = 1

Call mscomm1_OnComm

Else

interval = interval - 1

End If

End Sub

***********Procedure of mscomm1_OnComm

function***************************************

49

Private Sub mscomm1_OnComm()

'Variable Declarations

Dim data As Long

Dim sensors_data As Single

Dim ctr As Byte, Index As Byte, a As Byte, c As Byte


Dim v As Single

'Check whether data is received or not

If (MSComm1.CommEvent = comEvReceive) Then

a = getbyte()

If a = 49 Then

'Building frame

frame(0) = a

frame(1) = getbyte()





'concatnate frame(3) and frame(4) to get 16-bit data

data = 0

data = data + frame(3)

For ctr = 1 To 8

data = 2 * data

Next

data = data + frame(4)

'Now right shift 16-bit data to 6 places to get 10-bit data

For ctr = 1 To 6

data = data \ 2

Next

'set value of index based on the sensor's address ( i.e. frame(1))

Index = frame(1) - first_Address

If (Index = 0) Then

'convert 10-bit sensor-1 data into actual data using conversion formula

sensors_data = (data * 100) / 1024 'Temperature conversion formula

ElseIf (Index = 1) Then


50

v = 5 / 1024 * data

If (v < 0.5) Then

v = 0.5

End If

sensors_data = (250 / v) - 50 'Light Intensity conversion formula

Else


sensors_data = (data * 100) / 1024 'Resistance conversion formula

End If

'Display Data into appropriate field

lblsensor(Index).Caption = sensors_data

Else

MsgBox "There is some data loss in communication", vbCritical, "Error"

Call stop_comm 'Stop communication

Exit Sub

End If

numFrameReceived = numFrameReceived + 1

If (numFrameReceived = num_sensors) Then

'when data has been received from all the sensors, insert all sensor's data

'into database

rs.AddNew

rs.Fields("Sr No").value = Me.sno

rs.Fields("Time And Date").value = Now

For ctr = 2 To Form1.num_sensors + 1

rs.Fields(ctr).value = CSng(lblsensor(ctr - 2).Caption)

Next ctr

rs.Update

Me.sno = Me.sno + 1

' insertion completed

'Draw values on graph

Call drawgraph

'now reset values of variables, because recordings of this time has been completed

numFrameReceived = 0

ch = first_Address

Timer.Enabled = False

Timer.interval = 1000

Timer.Enabled = True

51

'Set Time delay in seconds between two recordings

interval = 1

End If

End If

End Sub

***********Procedure of command button start

************************************************

Private Sub startcmd_Click()

On Error GoTo ErrorHandler

MSComm1.CommPort = VScroll7.value

MSComm1.Settings = "57600,N,8,1"

MSComm1.InputLen = 1

MSComm1.PortOpen = True

startcmd.Enabled = False

stopcmd.Enabled = True

VScroll7.Enabled = False


Timer.Enabled = True

Exit Sub

ErrorHandler:

MsgBox Err.Description, vbExclamation, "Warning"

End Sub

***********Procedure of command button stop

************************************************

Private Sub stopcmd_Click()

Call stop_comm

End Sub

***********Procedure of stop_comm

function************************************************

Private Sub stop_comm()

VScroll7.Enabled = True

stopcmd.Enabled = False

startcmd.Enabled = True

MSComm1.PortOpen = False

controlcmd.Enabled = False

Timer.Enabled = False

End Sub

***********Procedure of txtchange

function************************************************

Private Sub txtchange(Index As Integer)

If (Val(Text1(Index).Text) Or Text1(Index).Text = "0") Then

If (Val(Text1(Index).Text) >= 0 And Val(Text1(Index).Text) <= 100) Then

VScroll1(Index).value = Val(Text1(Index).Text)

52

Else

MsgBox ("Value is out of range")

Text1(Index).Text = 0

End If

Else

If (Text1(Index).Text <> "") Then

MsgBox ("Invalid Value")

Text1(Index).Text = 0

End If

End If

End Sub

***********Procedure of Text1_Change

function**********************************************

Private Sub Text1_Change(Index As Integer)

Call txtchange(Index)

End Sub

***********Procedure of VScroll1_Change

function*******************************************

Private Sub VScroll1_Change(Index As Integer)

Text1(Index).Text = VScroll1(Index).value

If (Val(Text1(0).Text) > Val(Text1(1).Text)) Then

MsgBox "Low limit can't exceed High limit", vbExclamation, "Warning"

Text1(0).Text = Val(Text1(1).Text)

Else

If (lblsensor(0).Caption <> "") Then


End If

End If

End Sub

Private Sub VScroll7_Change()

Text7.Text = VScroll7.value

End Sub

b) Programming for making the database:

***********Procedure of setFlex function*******************************************

Public Sub setFlex()

Dim ctr As Byte

fg.TextMatrix(0, 0) = "Sr No"

fg.TextMatrix(0, 1) = "Time And Date"

53

fg.ColWidth(0) = 700

fg.ColWidth(1) = 2000

For ctr = 2 To Form1.num_sensors + 1

fg.TextMatrix(0, ctr) = "Sensor" + CStr(ctr - 1)

fg.ColWidth(ctr) = 1500

Next

For ctr = 0 To (Form1.num_sensors + 1)

fg.Row = 0

fg.Col = ctr

fg.CellFontBold = True

fg.ColAlignment(ctr) = 3

Next ctr

End Sub

Sub fillGrid()

Dim T As Integer, ctr As Integer

Form1.rs.MoveFirst

Do While Not Form1.rs.EOF

T = T + 1

For ctr = 0 To (Form1.num_sensors + 1)

fg.TextMatrix(T, ctr) = Form1.rs.Fields(ctr)

Next ctr

totalrec.Caption = "Total Records: " + CStr(fg.Rows - 1)

Form1.rs.MoveNext

fg.Rows = fg.Rows + 1

Loop

Form1.rs.MoveFirst

End Sub

***********Procedure of fg_Click

function*******************************************

Private Sub fg_Click()

End Sub

Private Sub Form_Load()

fg.Cols = Form1.num_sensors + 2

Call setFlex

Call fillGrid

End Sub

54

8. Results of design:

i. Accuracy:

All the sensors are providing the output according to the formula provided in their datasheet. As

the network is RS-485 there is less interference of noise or radiations on the data. All the data

from the sensors is represented graphically and numerically in very user friendly manner with the

help of visual basic. Therefore results are shown accurately with only ±1% deviation from

original value.

ii. Speed of execution:

We have transmitted and receive the data at 9600baud to 57600baud. Our system works better at

the higher baud value than at the low values. Perfect execution occurs at 57600 baud.

iii. Graphical representation of data:

All the sensors output are shown graphically in the visual basic software. It gives the

comparative values for 75sec. which gives perfect sensing of low and high output values for a

particular sensor. It also gives the knowledge of values of different sensor output in a particular

span of time.

55

There is also separate text representation of sensors output which give their values in figure. This

shows the exact output value for every sensor at particular time in its respective text box.

iv. Database:

All the output values from all sensors are being stored in a database file named “daq.mdb”. There

is a separate column for the sr. no., date and time, sensor1, sensor2, sensor3 which shows the

sensors output value at a particular date and time. This record is very useful when we are

interested in knowing the value of any physical quantity at a particular date and time.

v. Usability:

This Data acquisition, logging and control system can be used in areas where there is

requirement of knowing the values of particular physical quantity. At present we are only

measuring the temperature, light intensity and trim pot resistance values but it can be extended to

every analog or digital sensors output value.

The system can be used especially in noisy industrial environment as the network is of RS-485

type which less interfere with the noise or radiation. The system is also capable of controlling

physical quantity which is being measured. This is shown in temperature sensor control in the

form 1 of visual basic. We are activating a fan when the temperature exceeds or go below a

particular value. Therefore we can control a physical quantity when required manually. It can

also extend to automatic control of physical quantity by some programming.

A database file is there to store the output value of sensors. A good user interface is provided for

seeing and controlling the sensors output values. This all makes this system to acquire, log as

well as control the sensors output value. This system can be used in all the industries where there

is requirement to sense and control a physical quantity.

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9. CONCLUSION:

Our main aim of this project is to take the sensors data and forward to the pc accurately with the

help of RS-485 network accurately. This is being fulfilled wholly and correctly.

We have taken simple sensor assembly as that of temperature sensor, light sensor and trim pot

which are giving values of respective physical quantity accurately. Temperature sensor is

converting the surrounding temperature into the voltage according the formula provided in the

data sheet. Light sensor is sensing the surrounding light intensity accurately and converting that

value into its respective voltage with the help of some biasing circuitry. Trim pot is giving its

resistance into voltage which is sensed accurately.

All the sensors are giving their data to the particular slave controller board which converts this

analog value into digital with help of their A/D converters. The 10 bit value corresponding to the

voltage is representing true physical quantity. That 10 bit value is taken into fourth and fifth byte

of 6byte data frame. All the slave controllers have their unique address from which they are

being recognized in the network.

As every data frame contains the address of respective slave controller therefore it is being

recognized easily at the main controller that from which slave controller data has came. The RS

485 network is taken for the common junction between main and slave controllers. Working of

this network is tested and it is working perfectly according to the requirement. The values of the

respective sensors is represented graphically and numerically on the form made in visual basic.

All the conversion and the representation of the quantity is working in the best manner which is

required.

The system is built in such a manner that the extension and the modifications can be done easily.

If there is requirement of any slave controller then it can be done by simply adding one more

address in our programming. if there is requirement of adding more sensors on any existing slave

controller then it can be done by simply adding two more bytes in the 6bytes frame in the data

area and modify the code accordingly.

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10. ERRORS & PRECAUTIONS:

The following errors are encountered from very beginning of our project development:

1. Baud rate is also one problem that at 9600baud the system is not responding accurately

while at 57600baud system is performing at its peak.

2. At first we have make the RS -485 junctions (where all the RS -485 lines from the slave

controllers come) open with no bias. Due to this there is reflection from that end and the

result at the hyper terminal is not the required one. Solution of this problem was the

introduction of one 120ohm resistor at the open end. This allows no reflected waves to

introduce again in the circuit. After this the results are accurate.

3. We have made all the power supplies to the slave, sensor assembly and the main

controller at one point. At first we think that it is enough to give the voltage of 8-9 v from

the adapter but when the system becomes hang again and again and giving the “data is

not being received” this makes to think more. After that by thinking that it is the loading

problem we have increased the power supply from the adapter to 11-12v and then this

makes the system to work properly.

4. While burning special attention should be paid on the fuse bits and lock bits settings. In

fuse bit settings if external clock frequency is set at 8 Mhz and you are using 12mhz

crystal oscillator then there will be wrong results. We should also see whether RC

oscillator is selected or not. If yes then it will make the onboard crystal oscillator

ineffective. Therefore first check the fuse bits and then make the burning procedure to go.

There must no lock bits should be selected.

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11. ESTIMATED COST:

Sr. No. Component Value Quantity Cost

1. Atmega8 5 80 * 5 = 400

2. Atmega16 1 160

3. 75176B 4 40* 4 =160

4. 74153N 1 50

5. 74LS155 1 45

6. 7805 4 40

7. Headers 130 130

8. LDR 1 10

9. Temperature

sensor

1 70

10. Trim Pot 1 10

11. Crystal

Oscillator

5 5 * 10 = 50

12. Resistors 15 15 * 1 = 15

13. Capacitors 30 30 * 1 = 30

14. Switches 8 8 * 2 =16

15. Connectors 30 30 * 2 = 60

16. USB cable &

connectors

30

17. Copper plate 1*1 feet*feet 80

18. Total 1356

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BIBLIOGRAPHY:

http://www.google.co.in


http://rototron.info/default.aspx?Page=USBAVR/USBAVR.aspx.

http://www.obdev.at/products/vusb/avrdoper.html

http://www.avrfreaks.com

http://www.atmel.com

http://www.alldatasheets.com

http://www.edutalks.org

Project Report DAS

Documents

Transcript of Project Report DAS