Use of timer: what's the code to indicate that its period of time is expired?

I created a timer with a period of 30 seconds: the program has to execute some tasks if this period is passed. How do i write the code for expressing the fact that the period is passed?

Answer 1

[Doug Hull]

It is not clear what you are asing, but this is a primer on timers.

video

[Umberto]

I didnt't find the answer. Here is my code

V = xlsread('data.xls', 1, 'C2:C1002');      %import data from Excel

t = timer('Period', 30, 'TimerFcn', @(~,~)calculate(V, g, n, Vmin, Vmax));
function  calculate(V, g, n, Vmin, Vmax)
for i=1:n
   if V(i) < Vmin
       start(t);
       if %30 seconds have passed
            V(i) = V(i)+ g;
       end

     elseif V(i) > Vmax
         start(t);
         if %30 seconds have passed
              V(i) = V(i)- g;    
         end

     elseif (V(i) >= Vmin && V(i) <= Vmax)
         stop(t);
     end    
  end

how do I express in code the sentence "30 seconds have passed"?

Answer 2

[Sean de Wolski]

One thing you could be do would be to toc a tic that was started earlier. However, the best approach would be to get the InstantPeriod from the timer object

function timerNSeconds

T = timer('Period',10,... %period
          'ExecutionMode','fixedRate',... %{singleShot,fixedRate,fixedSpacing,fixedDelay}
          'BusyMode','drop',... %{drop, error, queue}
          'TasksToExecute',2,...          
          'StartDelay',0,...
          'TimerFcn',@(src,evt)tfcn(src,evt,pi),...
          'StartFcn',[],...
          'StopFcn',[],...
          'ErrorFcn',[]);

start(T);

end
function tfcn(src,evt,piapprox)

      pause(10) %comment this line to have it not exceed
      pi
      if get(src,'InstantPeriod') > 10
          disp('Period exceeded 10');
      end

end

Uncomment the pause to see it working with not exceeding the 10s.

[Umberto]

Do I need "src" and "evt" parameters in my code instead of @(~,~) to make it work?

[Jan]

@Umberto: Simply try it by your own.

[Umberto]

I tried but there's another problem with my code. The error message is "the value assigned to variable 't' might be unused". How can I solve it?

[Sean de Wolski]

That's just a code analyzer warning telling you it thinks you're doing something weird. (It tends to be right)

[Umberto]

I just can't find out where the problem is, why variable t is unused? I tried

function  calculate(t, V, g, n, Vmin, Vmax)

but it doesn't work

[Jan]

What does "it doesn't work" exactly mean? We cannot guess these details. We want to help, so please let us and explain the occurring problem.

[Sean de Wolski]

What I have above works, so what have you changed to make it not work?

[Umberto]

The function "calculate" isn't executed by the program. I know it because i wrote

function  calculate(t, V, g, n, Vmin, Vmax)
disp('now executing function');

but i don't see this message in the outputs.

[Umberto]

@Sean I changed it because i need to use my algorithm. Now i have this code

function simulation
%%parameters
Vnom =      3850;    
s =         0.01;         
delay =     30;       
g =         50;           
n =         1000;           
Vmin =      Vnom*(1-s);
Vmax =      Vnom*(1+s);
V = xlsread('data.xls', 1, 'C2:C1002');      %import data from Excel

t = timer('Period', delay,... %period
          'ExecutionMode','fixedRate',... %{singleShot,fixedRate,fixedSpacing,fixedDelay}
          'BusyMode','drop',... %{drop, error, queue}
          'StartDelay',0,...
          'TimerFcn',@(src,evt)calculate(V, g, n, Vmin, Vmax),...
          'StartFcn',[],...
          'StopFcn',[],...
          'ErrorFcn',[]);
end
function  calculate(t, src, V, g, n, Vmin, Vmax)
disp('now executing function');
for i=1:n
   if V(i) < Vmin
       start(t);
       if get(src,'InstantPeriod') > delay
            V(i) = V(i)+ g;
       end

     elseif V(i) > Vmax
         start(t);
         if get(src,'InstantPeriod') > delay
              V(i) = V(i)- g;    
         end

     elseif (V(i) >= Vmin && V(i) <= Vmax)
         stop(t);
     end    
  end 
  xlswrite('data.xls', V, 1, 'E2:E1002');
  end

Also you put start(t) before the timer function: i need to start the timer only if V(i) < Vmin or if V(i) > Vmax

[Sean de Wolski]

The problem looks like the calling syntax for setting up the timerfcn is different than the calling syntax for calculate().

[Umberto]

Do you have any suggestions to solve it?

[Sean de Wolski]

Use the same calling syntax...

calculate(t, src, V, g, n, Vmin, Vmax)

v.

calculate(V, g, n, Vmin, Vmax),...

[Umberto]

I used the same syntax calculate (V, g, n, Vmin, Vmax) but I still have the same problem.

[Jan]

@Umberto: Please do not let us guess, what your problem is. Formerly you told us, that there is the message, that "t" is unused. Now you have removed the "t" and get the same message? This is impossible. So please do not assume, that we use crystal balls, but explain the problem exactly and post the relevant part of the code.

[Umberto]

function simulation
V = xlsread('data.xls', 1, 'C2:C1002');      %import data from Excel

t = timer('Period', delay,... %period
          'ExecutionMode','fixedRate',... %{singleShot,fixedRate,fixedSpacing,fixedDelay}
          'BusyMode','drop',... %{drop, error, queue}
          'StartDelay',0,...
          'TimerFcn',@(src,evt)calculate(V, g, n, Vmin, Vmax),...
          'StartFcn',[],...
          'StopFcn',[],...
          'ErrorFcn',[]);
end
function  calculate(V, g, n, Vmin, Vmax)
disp('now executing function');
for i=1:n
   if V(i) < Vmin
       start(t);
       if get(src,'InstantPeriod') > delay
            V(i) = V(i)+ g;
       end

     elseif V(i) > Vmax
         start(t);
         if get(src,'InstantPeriod') > delay
              V(i) = V(i)- g;    
         end

     elseif (V(i) >= Vmin && V(i) <= Vmax)
         stop(t);
     end    
  end

I have 2 problems:

1)error message "variable t might be unused"

2)the function calculate isn't executed by the program because I don't see the message 'now executing function' in the outputs.

[Sean de Wolski]

So what you're trying to do here isn;t working for a few reasons.

First, t is scoped to the parent function simulation so that is why it does not exist in the subfunction calculate.

Second, I don't understand why you want to start the timer inside of its timerfcn. That doesn't make sense to me.

Third, you are not passing src into calculate(). Thus it will error, you need to pass in src like I did in my original.

[Umberto]

Ok I understood what you mean and I made some changes: I passed src into calculate() and started the timer before calculate(). However i need to use t into function calculate and I didn't manage to do it, i get "Undefined function or variable 't'" error message. Is there a way solve this problem?

[Sean de Wolski]

src and t are the same thing. They're both handles to your timer.

[Umberto]

But if I pass src to calculate() then why I get the "Undefined function or variable 't'" message?

[Sean de Wolski]

Because you don't pass t!!!! You've renamed it to src even though it is the same thing. You call it t instead if you wish; it's just a good programming practice to call the handle of the source object of a callback src or similar.