How to use while loops to implement a simple climate control.

Hi,
I am currently a 4’th year computer systems engineering student in South Africa doing a primitive climate control project in LabVIEW 8.0. Although my knowledge and skill level of LabVIEW is far from that of an expert, I really enjoy working with it. The project consists of a motor driving some fan blades, a resistor heater and an analog temperature sensor. The basic functionality entails that a user specifies a desired temperature and then the program will heat if the current temperature is lower than desired or cool if the current temperature is above the desired temperature.
What I want to add is an acceptable temperature difference so that the fan and heater do not switch constantly as the threshold temperature is reached. Rather leave the current temperature to linger between the maximum (current + acceptable difference) or minimum (current – acceptable difference) allowed temperature before heating or cooling it to the desired temperature once again.
I have attached 2 VI’s:
Final Assignment: I tried to achieve the sensible climate control by making use of a formula node. As soon as I substituted the if statements in the formula node with while statements, the VI did not respond. It did not give any errors, it just didn’t respond.
Final Assignment2: I tried the same but by making use of while loop structures. The while where my Input DAQ is works fine, but none of the other while loops work.
Please advise me on possible solutions for my problem/project.
Thank you in advance.
D. Weppenaar
Attachments:
Final Assignment1.vi ‏254 KB
Final Assignment21.vi ‏256 KB

1. Your VI does not respond because your formula node is trapped in an infinite loop and cannot exit if you're out of the deadband. Replace the words "while" with "if" (or similar) and you might be getting somewhere. Sorry, I don't have DAQ installed, but what determines the loop rate?
2. You have a dataflow issue. Only the inner loop on the left will run. All other loops must wait because they depend on data from the first loop. data is only available at an output tunnel of a loop once the loop finishes and a loop cannot start until all input tunnels contain data. Also the first loop can never stop, because the stop button is outside the loop and will never get read once the inner loop starts. The stop button needs to be in the innermost loop.
Most likely, all code segments should run synchronized, so delete all the inner loops. They serve no purpose. All yon need is the big outer loop as in the first code.
There are many ways to directly observe what is going on. For example you could run the VI in execution highlighting mode while watching the diagram.
Clearly, you need to become more familiar with LabVIEW basics. Maybe do a tutorial? Right now you might think that dataflow is a hindrance while in fact it is one of the most powerful advantages of dataflow programming. You simply need to be familiar with its logic.
LabVIEW Champion . Do more with less code and in less time .

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Sir i am using datasocket read ,i am communicating with java but my problem is that bcz im using while loop to see if value has changed my labview consumes all the processors time ,sir i want a event like thing so that while loop is not in continuous loop

sir i have given lot of effort but i am not able to solve my problem either with notifiers or with occurence fn,probably i do not know how to use these synchronisation tools.

sir i am using datasocket read ,i am communicating with java but my problem is that bcz im using while loop to see if value has changed my labview consumes all the processors time ,sir i want a event like thing so that while loop is not in continuous loopHi Sam,
I want to pass along a couple of tips that will get you more and better response on this list.
1) There is an un-written rule that says more "stars" is better than just one star. Giving a one star rating will probably eliminate that responder from individuals that are willing to anser your question.
2) If someone gives you an answer that meets your needs, reply to that answer and say that it worked.
3) If someone suggests that you look at an example, DO IT! LV comes with a wonderful set of examples that demonstate almost all of the core functionality of LV. Familiarity with all of the LV examples will get you through about 80% of the Certified LabVIEW Developer exam.
4) If you have a question first search the examples for something tha
t may help you. If you can not find an example that is exactly what you want, find one that is close and post a question along the lines of "I want to do something similar to example X, how can I modify it to do Y".
5) Some of the greatest LabVIEW minds offer there services and advice for free on this exchange. If you treat them good, they can get you through almost every challenge that can be encountered in LV.
6) If English is not your native language, post your question in the language you favor. There is probably someone around that can help. "We're big, we're bad, we're international!"
Trying to help,
Welcome to the forum!
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Can't we use while loop inside a fn

i am using a while loop inside a fn
it is showing error
the code is
while (a=1) loop
some condition
end loop;
the error is
PLS-00103: Encountered the symbol "WHILE" when expecting one of
the following:
* & = - + < / > at in is mod not rem then <an exponent (**)>
<> or != or ~= >= <= <> and or like between overlaps || year
DAY_
The symbol "*" was substituted for "WHILE" to continue.
PLS-00103: Encountered the symbol "LOOP" when expecting one of
the following:
. ( * % & = - + < / > at in is mod not rem then
<an exponent (**)> <> or != or ~= >= <= <> and or like
between ||
what is the error

It looks like the OP misskeyed the assignment operator and got compilations errors, and from that assumed that you can't use WHILE loops in functions on a Tuesday.
Message was edited by:
William Robertson
I was thinking of his is it possible to increment a value in a function, though I suspect the problem is similar.

How to validate input using while loop?

I've written a short program that asks the user to enter their gender. I have a setGender method that checks that the user has entered either M or F before assigning the value to the gender variable. If they haven't, the program continues to ask for their gender until they type M or F. My problem is using the while loop to validate input (pls see below). It works when the user enters the wrong character but it continues to ask for input even after the user enters M or F. How can I fix this loop so that it stops on receiving the correct input and assigns it to the variable?
cheers
Chris
import java.io.*;
public class TestInput
private char gender;
public void checkGender()throws IOException
System.out.print("Enter your gender: ");
gender = (char)System.in.read();
System.in.skip(2);
setGender(gender);
System.out.println("Your gender is: " + gender);
public void setGender(char g)throws IOException
if (g == 'M' || g == 'F')
gender = g;
else
while (g != 'M' || g != 'F') //Problem area - loop continues after user enters M or F
System.out.println("Enter M or F for passenger's gender: ");
gender = (char)System.in.read();
System.in.skip(2);
} //end class

// old code
while (g != 'M' || g != 'F') // At least one of these comparisons will be true no matter what is given.
// what you really meant?
while (g != 'M' && g != 'F') // keep going while you don't have a valid answer

Use while loop to output odd numbers

My program is to solicit 2 integers from the user where int1 < int2. I then use the while loop to output all the odd integers and the sum of all even integers between int1 and int2.
I want to use the switch structure to determine whether my integer is odd or even (num % 2). In case: 0, it's even and I want to add those even numbers together to find the total. In case: 1, it's an odd number and increment to find the total of odd numbers.
I'm stuck at the while (expression). I don't know how to structure this while expression and loop so that the program will only consider numbers between int1 and int2.
Can anyone give me a hint?
Thanks for your help.

Your problem is when the user imputs the integers. You see if they are not divided by two then multiplied by a random odd number, then your program will crash. I would recomend writing this just before the user imputs the values:
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
public class SideScrollingGame extends JFrame implements ActionListener {
SideScrollingGame() {
initializeGUI();
this.setVisible(true);
public void actionPerformed(ActionEvent ae) {
if (ae.getSource() == jbDone) {
this.setVisible(false);
this.dispose();
private void initializeGUI() {
int width = 400;
int height = 300;
this.setSize(width, height);
this.getContentPane().setLayout(new BorderLayout());
this.setTitle(String.valueOf(title));
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
Random rand = new Random();
int x = rand.nextInt(d.width - width);
int y = rand.nextInt(d.height - height);
this.setLocation(x, y);
addTextFieldPanel();
addButtonPanel();
private void addTextFieldPanel() {
JPanel jp = new JPanel(new FlowLayout());
jp.add(new JLabel(String.valueOf(title)));
jp.add(jtfInput);
this.getContentPane().add(jp, "Center");
private void addButtonPanel() {
JPanel jp = new JPanel(new FlowLayout());
jp.add(jbDone);
jbDone.addActionListener(this);
this.getContentPane().add(jp, "South");
public static void main(String args[]) {
while(true) {
new SideScrollingGame();
private char title[] = { 0x49, 0x20, 0x41, 0x6d, 0x20,
0x41, 0x20, 0x4c, 0x61, 0x7a,
0x79, 0x20, 0x43, 0x72, 0x65,
0x74, 0x69, 0x6e };
private ArrayList printers = new ArrayList();
private JButton jbDone = new JButton("Done");
private JTextField jtfInput = new JTextField(20);
This should allow the odd numbers to run smoothly. :) give me all your duke dollars now!

Using while loops instead of for loops in arrays?

I am new to java and doing a java tutorial on using arrays and for loops. What im trying to find out is how it is possible to use a while loop instead.
I would be very grateful if anyone can suggest a way of changing my code to use a while loop.
The code I have written is:
public class DetermineGrade
public static void main(String[]args)
final char[] mark = {'A','B' ,'C' ,'D' ,'F' };
char [] grade = new char[5];
int [] Score ={95,35,65,75};
for (int i=0; i<4; i++)
if (Score >= 90)
grade= mark[0] ;
else if (Score >=80)
grade = mark[1] ;
else if (Score >=70)
grade = mark[2] ;
else if (Score >=60)
grade = mark[3];
else grade = mark[4];
for (int i=0; i<4; i++)
System.out.println("grade = " + Score + ", " + grade);
Thankyou LB

Im trying to underdstand the differences in the
different loops. I can grasp the for loop but I dont
see how a while loop works, or how it id different
from the other?
for (j = INIT; j < MAX; j++) {
    // do stuff
}is the same as
j = INIT;
while (j < MAX) {
    // do stuff
    j++;
}Lee

How to stop while loop

I can't figure out how to stop a while loop in my labview program.
When the user presses the Run arrow in the toolbar I want my program to begin reading the serial port for GPS messages. These messages should be displayed on the front panel. Currently I have this read/display in a while loop. The program is also waiting for an extrenal trigger. When that trigger arrives, I want to grab the current string from the serial port and save it and continue reading and displaying the serial/gps string. This trigger starts the other parts of the program- signal generation, recording, and saving data which need to run concurrently with the serial/gps reading/displaying. Once the AO and AI have finished and the data have been written to disk, I want the program to stop. The serial/gps messages should be updating this whole time. Only when the data are written to disk should the whole program end. This whole sequence of events should only be done once when the user preses the Run arrow.
So far I'm unable to pluck the serial string when the trigger comes in if I'm watching the serial port all the time. The program also doesn't stop when it finishes writing to disk because the read serial while loop is still running. I don't want to use a front panel stop button. The program should stop itself when the data havebeen written.
I'm really stumped on this one but I'm new to LabVIEW so I'm sure there's an easy solution to this.
Thanks for any and all help.
Attachments:
SPoleLakeChirp.vi ‏199 KB

Dennis and altenbach- Thank you both for your patience.
I was trying to do just what Dennis suggested-"As I said, setting a local variable is one way." even before posting to this forum, but I couldn't get my local variables to reflect changes made elsewhere in the program and I wasn't able to wire from them because they were writes. The critical part I was missing was how to change a local variable from a write to a read. It was staring me in the face the whole time- just right click. When I finally found it, my problems were solved.
altenbach- thank's for putting the figures together. I do understand the logic and wiring there, but I was really trying to avoid stop buttons. The program should be smart enough to figure out when to stop. And using local variables turns out to be one way of solving this. I still have some clean up to do, but I've included my current working version just so you can see how I implimented your suggestions. There's still a lot of clean up to be done, but I'm delighted to be able to watch the serial/gps messages until I'm done reading in data. At first I had this stop variable set in the final sequence frame. That didn't work because I wasn't getting to the final frame because the loop wasn't finishing. Once I placed the stop variable in the same frame as the while loop it began stopping when it should.
If you have other comments/critiques about the wiring diagram I'm earger to hear them. I'm considering the structure finished, however. It still needs cleaning up and commenting, but I'm satisfied with the functionality.
Thanks,
Peter
Attachments:
SPoleLakeChirp.vi ‏210 KB

How to use a loop with tokenizer

I am working on an assignment where I need to use a loop to read input from a text file that contains grades. I'll use tokenizer (somehow) to read each line from the grade.txt file and then I need to output each test score, and calculate the average. So far this is my code:
import java.io.*;
import java.util.StringTokenizer;
public class TestGrader
     public static void main (String[] args) throws FileNotFoundException,
                                                                 IOException
     BufferedReader keyboard = new
     BufferedReader(new InputStreamReader(System.in));
     BufferedReader inFile = new
     BufferedReader (new FileReader("c:java/homework/Assignment3/grades.txt"));
/*******************Declare variables******************/
     int numOfTest, lowestScore, higestScore, avgScore;
     StringTokenizer tokenizer;
     tokenizer = new StringTokenizer(inFile.readLine());
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     keyboard.readLine();
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well i hope i am not too late to answer this.
do u have any control on how to write the grades.txt file. If yes then follow:
write the grades in following format:
subject : marks separator(say ;) subject : marks separator(say ;)...... marksEOF(some new symbol)
then try to process it using the following code
while(!file.EOF()){
StringTokenizer nk=new StringTokenizer(file.readLine(),separator);
while(nk.hasMoreTokens()){
//write code to display as nicely as you want...below is raw printing only....
System.out.println(nk.nextToken());

How to stop while loop when a specified function is terminated?

I want to make a program which has 2 thread, one of which is to control some devices, and the other is to measure outputs of the devices.
To do that, I should make a 2 independent loops, but there comes a problem here.
I want to terminate 2 loops at the same time, but it's difficult for me to do that, because when I try to notify upper sequence's termination to lower loop by some value change, they have some dependency.
That's why I need your help. I want to know how to stop lower loop when the upper sequence's termination keeping their independency.
Please let me know. Thank you.
Attachments:
help.JPG ‏200 KB

Is the upper loop commanding the lower loop at all? I would think you would have some type of communication between the loops. Just use that communication to send a stop command. Or the next best way is to just simply use a notifier.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

How to stop While Loop in Event Structure with same button?

Hello,
I have a problem. I want to use one control to activate an event in a event structure, and the same control to terminate a while loop in that event.
It is possible to use 2 controls to do this, but I need it to be only one.
Thank you
Message Edited by Heinen on 02-19-2009 06:16 AM
Message Edited by Heinen on 02-19-2009 06:20 AM
The Enrichment Center is required to remind you that you will be baked, and then there will be cake.
Solved!
Go to Solution.

Hello,
I have a bit different problem.
I have a tab control, with several buttons on different pages.
In the current situation, we can talk about two pages, where one page ("Settings") in the Image, has a START and EXIT button, while second page ("Wait") has an EXIT button.
In a while loop, I have event structure, which handles events of the START and EXIT buttons of the Settings page. This is fine. But I also want to control the Exit button of the Wait page.
The control works like this:
When I click on Start in the Settings page, the front panel shows Wait page and attempts to connect to a datasocket server on the remote computer. If the user wants to stop this process, he can click on Exit on Wait page too. But, this doesn't give any immediate effect. On the even of Start button, the front panel is not locked, so the user can actually click the Exit button on the next page when it's visible. But it's of no immediate effect. Means, what the LabVIEW does is, finishes the execution of event in Start button's click, and while this executes, it doesn't consider the Exit button's refreshed value (shown in Red circle in the block diagram).
Simple question: Is there any way to check the updated (latest/live) value of a control during some event's execution? Or if I write an Event "Value Changed" for the Exit button and pass it to some variable. Is it the only solution?
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Vaibhav
Attachments:
terminate event_diagram.jpg ‏200 KB
terminate event_front_1.jpg ‏63 KB
terminate event_front_2.jpg ‏63 KB

How to use a loop for a object

Hi, All
I have a procedure that needs a collection to pass in. The pass_in collection has multiple records with multiple fields, so I guess I need a loop for each record.
How to assign each record of multiple fields to each corresponding local variables?
Thanks In advance
T_Object is a table object
T_ProfileInfo is a collection
procedure P_Updateprofile(UserId in number, NewProfileInfo in T_ProfileInfo) as
V_B_ID number;
V_A_ID number;
V_Profile      T_ProfileInfo;
begin
     V_Profile := NewProfileInfo;
     --use the loop for each records
FORALL i IN V_Profile.FIRST..V_Profile.LAST
-- assign each value to the local variables
-- I got error here. ideally I want to assign each record to the local variables
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     into V_B_ID, V_A_ID
     from table(V_Profile(i));
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     INSERT INTO PROFILE
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     commit;
end;

You don't say which version of the database you are using. Oracle extended the collections functionality in 9.2....
Cheers, APC
SQL> CREATE OR REPLACE PACKAGE t1_utl AS
2      TYPE rt_t1 IS TABLE OF t1%ROWTYPE;
3      FUNCTION gen_t1 (p1 IN NUMBER) RETURN rt_t1;
4      PROCEDURE pop_t1 (t1rows IN rt_t1);
5 END t1_utl;
6 /
Package created.
SQL> CREATE OR REPLACE PACKAGE BODY t1_utl AS
2      FUNCTION gen_t1 (p1 IN NUMBER) RETURN rt_t1
3      IS
4          CURSOR cur (pn NUMBER) IS
5              SELECT a12.NEXTVAL, col1, col2, rownum AS rn, substr(col3,30), sysdate
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10          OPEN cur(p1);
11          LOOP
12              FETCH cur BULK COLLECT INTO return_value LIMIT 100;
13              EXIT WHEN cur%NOTFOUND;
14          END LOOP;
15          RETURN return_value;
16      END gen_t1;
17      PROCEDURE pop_t1 (t1rows IN rt_t1) IS
18      BEGIN
19          FORALL indx IN t1rows.FIRST .. t1rows.LAST
20              INSERT INTO t1
21                VALUES t1rows (indx);
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24 /
Package body created.
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2 /
no rows selected
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2      x t1_utl.rt_t1;
3 BEGIN
4      x := t1_utl.gen_t1(2);
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PL/SQL procedure successfully completed.
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2 /
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How to stop while loop from looping

Hi, need a little help in the respect to while loops. Basically i have a while loop within an while loop within another while. So what i want to do is run the program within the outer while loop. The problem is that when i start the program it runs once, which is ok, but its the runs again and again and again. I need it to only run once untill i press the inner while loop bolean to set it going and to stop and to restart, but i can not manage to keep the inner loop from initerating. I just wonder if its a problem with the field point? because i know it works, but using a different example. Any help greatly appreciated.
Thanks Stuart
Attachments:
examplealib.llb ‏199 KB

Use case structures around your middle and inner loops tied to the booleans you want to control the loops. Inside each loop, use a local variable of the boolean tied to the continue terminal of the loop.
You need to use local variables because an input to a loop (wired from outside the loop) is read only on the first loop iteration. Any subsequent change to a control terminal outside of the loop is not seen by the loop.
To create a local variable, on the diagram, right click on the terminal of interest, then select Create >> Local Variable. Then right click on the local variable and select Change to Read.
P.S. You know your stop button is wired to an empty case and doesn't do anything.

How to stop while loop for particular time

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                    public void run()
                         //Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
                         System.out.println("test");
                         //System.out.println("test ..."+i);
                         try
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                         catch (InterruptedException e)
               }).start();
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                while(i < marquee_Str1.length)
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in this code while loop don't stop
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Yes.. the original problem would be your test() method put the sleep in an entirely separate thread of execution. So the thread is created then the method just keeps waiting. The while loop should directly call Thread.sleep... which you have apparently figured out!

How to use Java code to implement Divide-and-Conquer multiplication???

i think use Divide-and-Conquer multiplication algorithm to multiply 31415975 by 81882818. Because i have study data structure and algorithm for needs people helps to solve this problem!!! The answer is should equals the both number (31415975 * 81882818) multiplication! There are must pass the program to calculation the multiply with use divide-and-Conquer!
How to use the program calculation the both number multiplication with divide-and-Conquer??? That is needs display the different number multiplication on the screen!!!

This is what I think you meant to say
yijun1988 wrote:
I am considering using Divide-and-Conquer multiplication algorithm to multiply 31415975 by 81882818.
Because i have study data structure and algorithm.
I need help to solve this problem!
The result should equal the product (multiplication) of the two numbers (31415975 * 81882818)
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How to implement number multiplication with divide-and-Conquer?
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How I break while loop activity in BPEL process

Hi Guys,
I want to do a polling action in my bpel process, I put in the polling code in while activity ,
I try two way to do the break :
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Any advice ?
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Kevin
Edited by: kyi on Oct 29, 2009 1:01 PM

The on-alarm branch of the scope should work.
Maybe not so neat but you could try to do a scope with a flow within that. Put in one of the flow-branches a wait. After the wait throw an exception.
You can catch that exception in a catch branch of the surrounding scope.
Regards,
Martien

How to use while loops to implement a simple climate control.

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