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Mechatronics Design Assignment
Autonomous Liquid Temperature Controlling System
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Contents: Introduction
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Project Design
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Project Working
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Testing and Result
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Discussions
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References
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Appendix
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Introduction: We built an autonomous liquid temperature control system for our Mechatronics design. The design is fully autonomous and mainly aimed at the controlling action without human intervention. Our design can be used by companies as heat exchangers or liquids temperature regulators.
In chemical companies (mainly but can be used at homes, offices, hospitals and schools to control the liquid ‘s temperature depending upon the desired value assigned) various liquid substances are needed to be cooled down to a particular level before being further processed, this is the place where we can implement our design as by controlling the values of a heat exchanger (heat exchanger is a device which is used to regulate the heat of two substances using the concept of heat transfer, it has 2 parts, the inner part is made up of many thin tubes through which hot liquids flow, through the outer part cooler water or liquid flows, heat is exchanged between two different substances, hot substance loses its heat to the cooler substances) and also the design can be used to get a regulated or desired temperature output (liquid), without using the heat exchanger, which is the temperature of the liquid is maintained by mixing cooler liquid the hot liquid (same).
For our assignment we would be focusing mainly on the second part which is liquid’s temperature regulator, whose main function is maintaining the temperature of liquid in a vessel, below a certain range of temperature using the 2 LM35DZ temperature sensors (they are the ones which detects the temperature change in the 2 liquids vessels, 1 RC servo motor (required to open and close the valve or clit for allowing the liquid to flow from one vessel to other), 1 DC geared motor (required to cool down the liquid as by attaching a fan or a stirrer to it), PIC 16F877A (the brains of the system which decides when to open the valve and allow the cooling process to start and stop) and 16x2 LCD (which is used to display the temperatures in the 2 different vessels).
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We are going to explain about the system developed below with the aid of software’s such as MPLAB, Proteus, Lab View and Autodesk Inventor. Final step would be developing the prototype of the design described. In the end the developer would tell the limitations faced and the suggestion to improve the design for further use.
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Project Design: Overall Design
1. Objectives:
The main objective is to construct a system which autonomously regulates or controls the temperature. Many companies specifically, chemical companies requires water at set temperature for cleaning purposes, boilers, cooling purposes etc. To meet that demand they can flow 2 ways:
The first way is they use some kind of cooling source which works continuously, keeping the temperature of the water at defined temperature. But, for the cooling system, the need for electricity is high, which is expensive.
The other way is that they use cool water from some source in company and mix it together with the hot water, and then they can mix the two together using some kind or mixer or cool it by using fan until the temperature comes down to the desired limit and then stop. This method has low electricity consumptions and results are got faster than the previous which has to get the temperature down by cooling continuously.
The system we want to construct can be even used in schools, hospitals etc. If somebody wants to have bath in summer and the tank is containing hot water, the temperature sensor detects the temperature and opens the valve from the other cool water source using the servo motor, so that it can mix the water from that source with cool water using the mixer attached to dc geared motor or can cool down the mixed water using fan. Any of the two methods can be used. Once the temperature comes to the range defined by the user, computation done by the microcontroller. The dc geared motor stops and the servo motor closes the valve, hence closing the source of the water from cool water tank to the tank which had hot water.
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So the developers have to make a system which can work as defined above, as the system is more economical and gives faster results.
Actually the system was designed for using the cool water source to cool the hot water without using any fan or mixer. As, the assignment demanded to have a dc geared motor. We put up the fan or mixer to increase the speed of cooling.
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2. Function:
The system design is fairly simple as this is the first time the developers are using the microcontrollers, if would have more time to experiment, the developers could have come up with more complex system. This system is for easy understanding, and gaining basic knowledge about Mechatronics design.
The system consists of 2 LM35DZ temperature sensors whose input is the temperature of the liquids or water in Tank A and Tank B. The output of these sensors is analog voltage signals which go into PIC16F877A microcontroller. The temperature sensors are connected to the ADC ports of the microcontroller, which takes in the analog signal and gives out digital values across specified ports.
Across the defined output port of the microcontroller, LCD is connected with takes the values of the temperature sensor and displays them, which change as the temperature of liquids in Tank A and Tank B change.
Now comes, the actuators which are the hands and legs of the system. We have RC servo motor which is connected to a slit (valve) in the Tank A. When the temperature is above 50 C the servo motor moves right (2.35ms) and cause the slit to move aside let the cool water from Tank A to flow into hot water Tank B. While at same time the dc geared motor is given command to run at full speed when the temperature in above 50 C and mix hot and cool water or cool the mixed water using fan, anything can be chosen as they are replaceable.
When the temperature drops below 50 C the servo motor attached to Tank A turn left (0ms) and causing the slit to close and stopping the flow of cool water into the Tank B having hot water, while at same time the dc geared motor stops. This remains until the temperature increases again above 50 C.
8 This is the basic function of the system designed. Improvements will be suggested at end, which can be done once the developers have time to research more and experiment using the microcontroller and other IC’s.
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Mechanical: 1. 3D Design of the System:
Tank B
Tank A
Slit
Mixer
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12 2. Components Used Mechanical:
Developer wanted to use the design created by him on Autodesk inventor as can be seen above. But, as this is scale down model of the actual concept which developer had in mind, very simple and easy methods have been used for reaching the result according to the function described above. Due to limitations on money, time and experience developers concept had setback.
Hard Plastic Containers:
Developer has chosen to use 2 hard plastic containers to simulate TANK A and TANK B. The Tank A has been represented by a hard plastic glass of volume 200 ml and Tank B has been represented by big hard plastic glass of 650 ml.
The hard plastic glass (tank A) is put at some height above hard plastic glass so that water can easily flow from A to B with using any sorts of pump. The volume of tank B is chosen to be greater as our system doesn’t have an effective feedback system mainly because the sensor required to detect the water level in tank B (ultrasonic sensor) wasn’t functioning well when tried to detect water level. So to protect from over flow of water we used bigger tank B compared to tank A. The other change in the design happened at very last stage, which is the day of submission. The valve needed to open and close water flow from tank A to B could not be found. The developer planned to use a tap as valve but could not connect to his plastic container and when he tried to use the slit as valve, the water rushing out came directly on the servo motor, which could damage it.
So finally after many tries and many failures, the developer planned to modify his concept a bit. Instead of the valve for opening and closing of the tank A using the servo motor, the user connected (attached) the servo motor to the outside of Tank A with Tape, so whenever the opening of the valve is needed to be simulated, the servo will rotate and with it would the Tank A pouring its contents directly into Tank B.
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Electrical: 1. Components Used Electrical:
LM35DZ Temperature Sensors:
For our assignment we are using Two LM35DZ sensors to measure the temperatures in tank A and tank B. Below are some of the characteristics and properties of the LM35DZ. The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to +110°C range (−10° with improved accuracy).
Features
Calibrated directly in ° Celsius (Centigrade)
Linear + 10.0 mV/°C scale factor
0.5°C accuracy guarantee able (at +25°C)
Rated for full −55° to +150°C range
Suitable for remote applications
Low cost due to wafer-level trimming
Operates from 4 to 30 volts
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Less than 60 μA current drain
Low self-heating, 0.08°C in still air
Nonlinearity only ±1⁄4°C typical
Low impedance output, 0.1 W for 1 mA load
PIC 16F877A Microcontroller:
Microcontroller is the brain of the system; all the decisions are taken by it autonomously. We are using this particular series of PIC microcontroller because:
It is very simple yet very powerful to use
It can be programmed and reprogrammed numerous times
It is small in size while have sufficient input/ output ports
It has low current consumption
It has onboard multichannel analog to digital convertor
It has in- built PWM function
15 Below are some of the features present in the PIC 16F877A, its pin and block diagram:
Pin Count
40 pin - PDIP
Program Memory
14KB or 8K 14-bit Flash
Max Crystal Speed
20MHz
RAM bytes
368
EEPROM bytes
256
Timers
2 x 8 bit, 1 x 16-bit
Digital Communication
1xA/E/USART, 1 x MSSP(SPI/I2C)
Capture/ Compare/ PWM
2 x CCP
ADC
8ch, 10-bit
Comparators
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(Register File Map)
18 Analog to Digital Converter (ADC):
The ADC is used to convert analog signals (input) to digital output, for our system we use 2 LM35DZ sensors whose outputs are analog voltage values. Therefore to convert them and use for various purposes we use ADC which is an integrated module inside the PIC 16F877A.
The Analog-to-Digital (A/D) Converter module has five inputs for the 28-pin devices and eight for the 40/44-pin devices. The conversion of an analog input signal results in a corresponding 10-bit digital number. The A/D module has high and low-voltage reference input that is software selectable to some combination of VDD, VSS, RA2 or RA3. The A/D converter has a unique feature of being able to operate while the device is in Sleep mode. To operate in Sleep, the A/D clock must be derived from the A/D’s internal RC oscillator.
The A/D module has four registers. These registers are:
A/D Result High Register (ADRESH)
A/D Result Low Register (ADRESL)
A/D Control Register 0 (ADCON0)
A/D Control Register 1 (ADCON1)
The ADCON0 register controls the operation of the A/D module. The ADCON1 register, configures the functions of the port pins. The port pins can be configured as analog inputs (RA3 can also be the voltage reference) or as digital I/O.
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(ADCON0)
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(ADCON1)
21 The ADRESH: ADRESL registers contain the 10-bit result of the A/D conversion. When the A/D conversion is complete, the result is loaded into this A/D Result register pair, the GO/DONE bit (ADCON0<2>) is cleared and the A/D interrupt flag bit ADIF is set. The block diagram of the A/D module is shown below. After the A/D module has been configured as desired, the selected channel must be acquired before the conversion is started. The analog input channels must have their corresponding TRIS bits selected as inputs.
After acquisition time has elapsed, the A/D conversion can be started. To do an A/D Conversion, follow these steps:
1. Configure the A/D module:
Configure analog pins/voltage reference and digital I/O (ADCON1)
Select A/D input channel (ADCON0)
Select A/D conversion clock (ADCON0)
Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
Clear ADIF bit
Set ADIE bit
Set PEIE bit
Set GIE bit
3. Wait the required acquisition time.
4. Start conversion:
Set GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete by either:
Polling for the GO/DONE bit to be cleared (interrupts disabled); OR
Waiting for the A/D interrupt
22 6. Read A/D Result register pair (ADRESH: ADRESL), clear bit ADIF if required.
7. For the next conversion, go to step 1 or step 2 as required. The A/D conversion time per bit is defined as TAD.
(A/D Block Diagram)
23 The conversion process for ADC (10 bits) is as follow: ADC have 10 bits, so the number of outputs are = 210 = 1024 or 0 -1023 As we are using LM35DZ, 10mv output from the sensor = 1 C So, if output is 100mv, the temperature is as = 1 C\10 * 100 = 10 C
But, we are using the reference voltage as 1.024V So, resolution is 1.024\1024 = 1mv So, if LCD display 102.4 then it means the voltage is = 102.4*10mv=1.024v
Servo Motor:
For moving the value (but now tank A), we are using Servo Motor C36R from Cytron Technologies. The main advantage of servo motor over dc geared motor is to control the angle of rotation. The properties of C36R (180 degrees rotation angle) are as follow:
Speed (sec\60 deg)
0.16/4.8 V, 0.14/6 V
Torque (Kg/cm)
3.5/4.8 V, 4.5/ 6V
Features
Servos are controlled by sending them a pulse of variable width. The signal wire is used to send this pulse. The parameters for this pulse are that it has a minimum pulse, a maximum pulse, and a repetition rate. Given the rotation constraints of the servo, neutral is defined to be the position where the servo has exactly the same amount of potential rotation in the clockwise direction as it does in the counter clockwise direction. It is important to note that different servos will have different constraints on their rotation.
Control position through Pulse Code Modulation
Pulse width range: 0.5ms – 2.5ms
Come with servo horn and screw accessories
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Servos are controlled by sending them a pulse of variable width. The signal wire is used to send this pulse. The parameters for this pulse are that it has a minimum pulse, a maximum pulse, and a repetition rate. Given the rotation constraints of the servo, neutral is defined to be the position where the servo has exactly the same amount of potential rotation in the clockwise direction as it does in the counter clockwise direction. It is important to note that different servos will have different constraints on their rotation.
The angle is determined by the duration of a pulse that is applied to the signal wire. This is called Pulse Width Modulation. The servo expects to see a pulse every 20 ms. The length of the pulse will determine how far the motor turns. For example, a 1.5 ms pulse will make the motor turn to the 90 degree position (neutral position). However, the exact correspondence between pulse width and servo varies from one servo manufacturer to another.1.5ms is not necessarily neutral or middle position.
The position pulse must be repeated to instruct the servo to stay in position. When a pulse is sent to a servo that is less than 1.5 ms the servo rotates to a position and holds its output shaft some number of degrees counterclockwise from the neutral point. When the pulse is wider than 1.5 ms the opposite occurs. The minimal width and the maximum width of pulse that will command the servo to turn to a valid position are functions of each servo. Different brands, and even different servos of the same brand, will have different maximum and minimums. Generally the minimum pulse will be about 1 ms wide.
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DC Geared Motor:
Developer would be using four SPG50-10K dc geared motors to provide the power to the fan or the mixer inside Tank B.
26 Below are the properties of this dc geared motor:
Voltage
12V DC
Output Power
3.4 W
Rated Speed
170 RPM
Rated Current
0.9 A
Rated Torque
196 mN.m
For controlling the DC Geared motor we are using the motor driver MD10B. It is designed to drive high current brush motor or application. It is designed for wide range of robotics and automotive applications. The board incorporates most of the components of the typical applications. With minimum interface, the board is ready to be plugged and play. Simply add in power, this driver is ready to drive high current motor. It has been designed with capabilities and features of:
Industrial grade PCB with heavy copper material for high current applications
Each component is soldered properly and tested
Support up to 10A maximum
5V logic level compatible inputs
12V as Vcc
PWM speed control up to 10KHz
Bi-directional control for 1 motor
Very low standby power consumption
System ground is isolated from motor’s power source with opto-isolator
4 Schottky diode as clamping diode
Dimension: 6cm x 4.5cm
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(Connection of the driver to MCU)
(Connection of driver without MCU)
29 LCD:
We are using 16*2 (LCD) for displaying the values of the temperature from the temperature sensors after the ADC conversion through PIC 16F877A.
Connections
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Project Working: My work in the group was defined to interfacing 2 LM35DZ temperature sensors with PIC 16F877A microcontroller, then getting the value to be displayed on the LCD, coding of DC geared motor, RC servo motor, LCD and ADC, lab view and PCB in PROTEUS. But I would be explaining only the temperature sensors and displaying the value onto the display.
Block Diagram:
32 Flow Chart:
33 Circuit Diagram:
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36 Above the developer has used PROTEUS to construct the circuit for interfacing the PIC 16F877A with the LCD and the 2 LM35DZ temperature sensors.
First the SK40C PIC 16F877A driver was used to run the circuit, which was in the testing stages. As the lecturer demanded SK40C circuit to be built on bread board or PCB we had to built the driver circuit ourselves.
Crystal X1 of frequency on 20 MHz is used to as clock; 12V DC power supply is supplied at Vpp which is connected in series with push button switch which is used to power on and off the PIC. The 2 LM35DZ temperature sensors output are connected to AN0 and AN1 (analog input channels) which are used for A to D conversion to give digital outputs. A potentiometer of 1k is used to create Vref for the ADC; the output of this potentiometer goes to AN3. The pins from number 7 to 14 (8 bits) on LCD are connected across PORTD of the PIC, which are 8 bits from D0 – D7. The enable pin on the LCD is connected to RA5; the RW (read/write) pin on LCD is connected to the ground, the RS (register select) pin on LCD is connected to RA2, VEE is connected to output of 1K potentiometer which is used to change the contrast, VDD is connected to +5V DC and VSS is connected to the ground. This is the main connection of the circuit which is used to get the input from temperatures sensors to the ADC port of PIC, change the analog signal from the sensors to digital and show the output in Celsius across the 16*2 LCD. The other main connection for the circuit is the RB0 which is connected to the enable of the RC servo motor and RE0 which is connected to PWM of the DC geared motor driver MD10B.
Below developer has shown the PCB layout generated using PROTEUS for the circuit shown above. The first PCB is the auto generated PCB which has 2 layers and the second PCB is the one made by the developer itself.
One of the toughest part of this assignment was generating this PCB as it took very long time to get it right, but still could not manage to get absolutely right PCB had to remove a potentiometer from the PCB to be able to complete it.
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39 Codes for MPLAB:
Below are the codes which the developer generated for the whole system. All codes were developed by me (help from cytron). MPLAB helps to interface the PIC to PC with help of USB driver. MPLAB is IDE which helps to write codes for the PIC. It uses Hi – Tech C Compiler for compiling all the codes written together. It can be built and then burned into the PIC using the USB burner.
//For interfacing the 2 temperature sensors with PIC 16F877A, displaying the output on LCD and //controlling the movement of the RC servo motor and DC geared motor with respect to change //in the voltage output from temperature sensors
#include
#include
Including the Libraries needed for this program…….
#include #include #include
#ifndef _XTAL_FREQ #define _XTAL_FREQ 20000000
Crystal frequency of 20 MHZ defined for oscillations……..
#endif
//===============configuration==============================
__CONFIG (0x3F32);
Setting up the PIC 16F877A for the codes……..
//===============define IO port=============================
#define
lcd
PORTD
#define
RS
RA2
#define
E
RA5
Assigning or Defining ……..
40 #define
CHANNEL0 0b10000001
// AN0
#define
CHANNEL1 0b10001001
// AN1
//==============FUNCTION PTOTOTYPE=========================
void e_pulse(void); void delay(unsigned short i); void send_char(unsigned char data);
Declaring the variables…….
void send_config(unsigned char data); void lcd_goto(unsigned char data); void lcd_clr(void); void dis_num(unsigned long data); void increment(unsigned long data); void read_adc(void); void motor_full(void); void motor_stop(void); void servo_one(void); void servo_two(void); unsigned short read_temp(void);
//====================MAIN================================
unsigned short result; unsigned short temp,tempA,tempB;
void main(void) { ADRESH=0;
//clear A/D result
ADRESL=0;
//clear A/D result
High and Low ADC registers
41 //setting ADCON1 Register ADCON1=0b11000101;
// A/D result right justified,
// configure RA2 and RA5 as digital I/O
TRISA=0b11011011;
//configure PORTA I/O direction
TRISB=0b00000000;
//configure PORTB as output
TRISC=0b00000000;
//configure PORTC as output
TRISD=0b00000000;
//configure PORTD as output
TRISE=0b00000000;
//configure PORTE as output
Assigning bits in ports which to be output and which to be input…..
PORTA=0; PORTB=0;
Clearing all the ports before using…….
PORTC=0; PORTD=0; PORTE=0; Configuring the LCD before use…… while(1) { send_config(0b00000001);
//clear display at lcd
send_config(0b00000010);
//Lcd Return to home
send_config(0b00000110);
//entry mode-cursor increase 1
send_config(0b00001100);
//diplay on, cursor off and cursor blink off
send_config(0b00111000);
//function set
lcd_goto(0);
//display character on LCD send_char(' ');
42 send_char('T'); To get TEMP A value to 1st line of LCD……….
send_char('E'); send_char('M'); send_char('P'); send_char('.'); send_char('A'); send_char('=');
lcd_goto(20);
//display character on LCD send_char(' '); send_char('T');
To get TEMP B value to 2nd line of LCD……….
send_char('E'); send_char('M'); send_char('P'); send_char('.'); send_char('B'); send_char('=');
while(1)
//infinity loop
{ //sensor A ADCON0=CHANNEL0;
//CHANNEL1=0b10001001
lcd_goto(8);
read_adc();
temp=read_temp(); dis_num(temp/10); send_char('.');
ADC 1 setup for TEMP A which is sensor 1 (Getting the actual value in Celsius)…….
43 dis_num(temp%10); send_char(0b11011111); send_char('C'); send_char(' '); send_char(' ');
tempA=temp;
//sensor B ADCON0=CHANNEL1;
//CHANNEL0=0b10000001
lcd_goto(28);
read_adc();
temp=read_temp(); dis_num(temp/10); send_char('.'); dis_num(temp%10); send_char(0b11011111); send_char('C'); send_char(' '); send_char(' ');
tempB=temp;
ADC 2 setup for TEMP B which is sensor 2 (Getting the actual value in Celsius)…….
44 if(tempB>500)
{
motor_full(); servo_one();
}
The command is used to call the delay for servo motor and dc geared motor if TEMP B is more than 50 C……..
else {
motor_stop(); servo_two();
}
delay(2000);
}
}
}
The command is used to call the delay for servo motor and dc geared motor if TEMP B is anything below 50 C…….
45 //==================subroutine LCD setting ==========================
void send_config(unsigned char data) { RS=0; lcd=data;
When no register is selected……
delay(500); e_pulse(); }
void e_pulse(void) { E=1;
When enable goes high and low (read and write)……….
delay(500); E=0; delay(500); }
void send_char(unsigned char data) { RS=1;
When register is selected………
lcd=data; delay(500); e_pulse(); }
void lcd_goto(unsigned char data) { if(data<16) {
46 send_config(0x80+data); } else { data=data-20; send_config(0xc0+data); } }
void lcd_clr(void) { RS=0; send_config(0x01); delay(600); }
void dis_num(unsigned long data) { unsigned char hundred_thousand; unsigned char ten_thousand; unsigned char thousand; unsigned char hundred; unsigned char tenth;
hundred_thousand = data/100000; data = data % 100000; ten_thousand = data/10000; data = data % 10000; thousand = data / 1000;
Converting the values got in Voltage to that needed to display as degrees C (related to linear characteristics of the LM35DX)………
47 data = data % 1000; hundred = data / 100; data = data % 100; tenth = data / 10; data = data % 10;
if(hundred_thousand>0) { send_char(hundred_thousand + 0x30);
//0x30 added to become ASCII code
send_char(ten_thousand + 0x30); send_char(thousand + 0x30); send_char(hundred + 0x30);
Binary output to ASCII which can be understood……..
send_char(tenth + 0x30); send_char(data + 0x30); }
else if(ten_thousand>0) { send_char(ten_thousand + 0x30);
//0x30 added to become ASCII code
send_char(thousand + 0x30); send_char(hundred + 0x30); send_char(tenth + 0x30); send_char(data + 0x30); } else if(thousand>0) { send_char(thousand + 0x30); //0x30 added to become ASCII code send_char(hundred + 0x30); send_char(tenth + 0x30); send_char(data + 0x30); }
48 else if(hundred>0) { send_char(hundred + 0x30); //0x30 added to become ASCII code send_char(tenth + 0x30); send_char(data + 0x30); } else if(tenth>0) { send_char(tenth + 0x30);
//0x30 added to become ASCII code
send_char(data + 0x30); } else send_char(data + 0x30); //0x30 added to become ASCII code }
void increment(unsigned long data) { unsigned short j; for(j=10;j>0;j--) {
lcd_goto(32); data=data+1; dis_num(data); delay(10000);
}
}
//==================subroutine ADC=========================
void read_adc(void) { unsigned short i;
49 unsigned long result_temp=0; for(i=2000;i>0;i-=1)
//looping 2000 times for getting average value
{ ADGO = 1;
//ADGO is the bit 2 of the ADCON0
while(ADGO==1);
//ADC start, ADGO=0 after finish
register
ADC progress result=ADRESH; result=result<<8;
//shift to left for 8 bit
result=result|ADRESL;
//10 bit result from ADC
result_temp+=result; } result = result_temp/2000;
//getting average value
}
unsigned short read_temp(void) { unsigned short temp; temp=result; return temp;
}
//==================subroutine DELAY==========================
void delay(unsigned short i) { for(;i>0;i--); }
Will continue until i=0…….
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//==================Motor full========================
void motor_full(void)
{
Subroutine to run the DC motor………
PORTE=0x01;
__delay_ms(10);
}
//==================Motor stop========================
void motor_stop(void) {
Subroutine to stop the DC motor……..
PORTE=0x00;
__delay_ms(10);
}
//==================Servo one========================
void servo_one(void) { PORTB=0x01;
__delay_ms(2.35);
Subroutine to move servo motor to right……
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CLRWDT();
PORTB=0x00;
__delay_ms(17.65);
}
//==================Servo two========================
void servo_two(void) { PORTB=0x01;
__delay_ms(1);
CLRWDT();
PORTB=0x00;
__delay_ms(19);
}
Subroutine to move servo motor to the left…….
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Testing and Result:
Testing Method:
For the testing the circuit which is the sensor circuit and LCD display circuit, the developer used the Proteus software to simulate the circuit first. After the circuit worked good the developer went ahead with the constructions on the bread board using the SK40C circuit to place the PIC. After that went good the developer used the construct the SK40C circuit on bread board himself and tested it, after it being also successful the developer used the PCB to construct the circuit.
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Result Obtained:
The circuit worked well in all the stages. Developer was very sure his system would come out with flying colors but in the end while doing the design, in hurry the developer connected the PIC to 12V power supply than 5V power supply and the IC burned. So in end the user had to show the design using the bread board.
The sensors were working fine they put out voltage which was converted to digital value using ADC in PIC and then in end displayed the changing values on LCD.
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LABVIEW: Lab VIEW is a graphical programming language that uses icons instead of lines of text to create applications. In contrast to text-based programming languages, where instructions determine program execution, Lab VIEW uses dataflow programming, where the flow of data determines execution. In Lab VIEW, you build a user interface with a set of tools and objects. The user interface is known as the front panel. You then add code using graphical representations of functions to control the front panel objects. The block diagram contains this code. In some ways, the block diagram resembles a flowchart.
Lab VIEW programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments, such as oscilloscopes and multimeters. Every VI uses functions that manipulate input from the user interface or other sources and display that information or move it to other files or other computers.
Below we have made the block diagrams which we use to test the signals from the temperature sensor LM35DZ. The signal from the sensor is interfaced with the laptop using a DAC (data acquisition card). Once the signal comes from sensor it is in mille volts, we multiple it by 100 using multiplier as, per 10mV (0.01V) change in the voltage from the sensor is equal to 1 degree Celsius. So, if we have 0.02V from sensor we multiply it by 100 which is equal to 2, which in turn is 2 degree Celsius. The output of the multiplier goes to the thermometer, numeric display and wave form graph to see the simulation of change in temperature.
One part of the output from multiplier goes into the greater than and equal to comparator. We have compared the output of the multiplier with 50, which is the minimum temperature our system will come to action. If the output of multiplier is above 50, the LED would light up which indicates that the temperature is more than 50 degree Celsius.
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(Panel when there is no input to the data acquisition card)
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(Value on connecting to the LM35 sensor) (Wrongly Done)
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Discussion: The developer learnt a lot about the Mechatronics design from this assignment, he learnt to code in C language and assembly language; he got familiarized with MPLAB, learnt how to use Proteus and develop PCB and at last the Lab View for getting signal to PC from sensor.
Developer also learnt a lot about PIC 16F877A, DC geared motor, servo motor, temperature sensors and LCD. All this would be very useful for him for his FYP.
Suggestion
For the future the developer suggest using the Liquid level sensor the ultrasonic sensor to measure the contents of tank B, protecting it from overflowing. Then using pump to feedback water to tank A if due to any reason it gets hotter than tank B. And the last would be using a timer in the circuit to protect continuous running of dc motor in hot temperature of tank B.
References:
www.Cytron.com accessed on 2nd May,2011
http://sine.ni.com accessed on 3nd May,2011
http://forum.allaboutcircuits.com accessed on 3nd May,2011
http://extremeelectronics.co.in/microchip-pic-tutorials/interfacing-lm35temperature-sensor-with-pic-microcontroller/ accessed on 5nd May,2011
http://en.wikipedia.org/wiki/Operators_in_C_and_C accessed on 5nd May,2011
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Appendix: (Extra Info on LCD used)
FLOW CHART FOR LCD INITIALIZATION
FLOW CHART TO DISPLAY ASCII CHARACTER
