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

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Umberto 2013-4-3

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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?

回答（2 个）

Doug Hull 2013-4-3

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编辑：Doug Hull 2013-4-3

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

video

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Umberto 2013-4-4

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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"?

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Sean de Wolski 2013-4-4

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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.

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Umberto 2013-4-9

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@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

Umberto 2013-4-12

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

Sean de Wolski 2013-4-12

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.

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