One thing that i usually do when i program is to write test routines for the program.
Test routines are useful because:
1 - you can check how the code is running and if he has some bugs, debugging it without doing some physical damage to the plant.
2 - you can check if the model of the machine in your mind is similar to the real machine, seeing how the code is going and what is still needed to complete the machine.
3 - other people that read the program checks how "it should work" through the test utility, for example what input you should expect if the motor starts running, or how you control an analogic output coming from a PID, or simulate movements whit motors and encoders, and so on.
On PLC there are simulators (i often use RSEmulate of Allen Bradley, because we often use their plcs) that can execute programs and "force" input and output, so let's see how to use them.
I do an example with a ladder program:
I have a motor (O:0/0) that starts when i press a button (I:0/0).
The motor is connected toan encoder (I:0.1) and when encoder is arrived at 14 the motor must stop his run.
There is an alarm sensor (I:0/1) that must block the motor if the encoder fail.
This is a way to do the program:
And this is how i test the inputs and encoders.
It's actually easy not only to test the entire application in this way, but also to see what should happen when the motor starts, and when it should stop.
If you upload a program with a Test Routine (that of course is disabled), you can also understand in a easier way how the program works and save a lot of time, and there is not necessity of calling the constructor's assistance (that fired is main programmer 10 days ago and that is still searching for a cheap one, as usually).
I add a solution for RsLogix 500, that can be emulated and tested with RsEmulate 500.
For Siemens users, try to do this with the simulator of Step 7, and if you can't force Inputs automatically, just use a DB and put in parallel test bits / words and merkers.
Hope this post can be useful for someone, the program for RsLogix 500 can be found here:
http://www.mesta-automation.com/Downloads/ProcessSimulation.rar
Test routines are useful because:
1 - you can check how the code is running and if he has some bugs, debugging it without doing some physical damage to the plant.
2 - you can check if the model of the machine in your mind is similar to the real machine, seeing how the code is going and what is still needed to complete the machine.
3 - other people that read the program checks how "it should work" through the test utility, for example what input you should expect if the motor starts running, or how you control an analogic output coming from a PID, or simulate movements whit motors and encoders, and so on.
On PLC there are simulators (i often use RSEmulate of Allen Bradley, because we often use their plcs) that can execute programs and "force" input and output, so let's see how to use them.
I do an example with a ladder program:
I have a motor (O:0/0) that starts when i press a button (I:0/0).
The motor is connected toan encoder (I:0.1) and when encoder is arrived at 14 the motor must stop his run.
There is an alarm sensor (I:0/1) that must block the motor if the encoder fail.
This is a way to do the program:
And this is how i test the inputs and encoders.
If you upload a program with a Test Routine (that of course is disabled), you can also understand in a easier way how the program works and save a lot of time, and there is not necessity of calling the constructor's assistance (that fired is main programmer 10 days ago and that is still searching for a cheap one, as usually).
I add a solution for RsLogix 500, that can be emulated and tested with RsEmulate 500.
For Siemens users, try to do this with the simulator of Step 7, and if you can't force Inputs automatically, just use a DB and put in parallel test bits / words and merkers.
Hope this post can be useful for someone, the program for RsLogix 500 can be found here:
http://www.mesta-automation.com/Downloads/ProcessSimulation.rar
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