LabVIEW
HELP WITH A TRAFFIC LIGHT THAT RUNS FOR 2 MINS
Solved!
The simplest...
Use a milisecond timer to get a time reference.
Divide it by 1000 to get seconds.
Use a quotient and remainder with x the time, 120 as y.
Use the remainder as an input for your logic.
Put a wait ms in the loop, or it will drain one CPU thread.
An alternative is to:
use a shift register with a counter.
Increment it each cycle.
Give the loop a 1 sec. wait, use the Q&R with 120 and use the R for the logic
Put R in the right shift register.
This is all OK-ish for a test, but not how you make a LabVIEW program. Just saying, if you're going to add more (and more), you need a strategy...
Think "what if"... What if you have 10 colors? What if you have 10 RGB lights? What if the timing is different for each of them?
Search LabVIEW like a graph! 
Here's the edited program from previous owner, I couldn't get the traffic light running continuously.
It does not run forever because the loop terminates around iteration 120. So try to find a math function that starts over from zero instead, without stopping the loop.
Also:
- The sequence structure serves no purpose. Remove it!
- There is no need for any local variable if you place the terminal correctly. Also make sure to pick the correct mechanical action.
- Your timer is not in seconds and has the wrong representation.
- Your wait constant has the wrong representation.
- Most of the code is overly complicated and could be simplified dramatically.
- ...
@altenbach wrote:
It does not run forever because the loop terminates around iteration 120. So try to find a math function that starts over from zero instead, without stopping the loop.
Alternatively, put a 2nd loop around everything.
The inner while loop then turns out to be a for loop, with 122 wired to N. The abort Boolean can still terminate the for loop inner, using the Conditional Terminal.
Be careful with using the loop iterator. With a wait of 100 ms, your code will stop working after 6 years and 9 months. If you lower the wait to 10, it will be 248 days... On a single cycled timed loop on an FPGA, which is where you want to control traffic lights, it won't make a minute.
wiebe@CARYA wrote:
@altenbach wrote:
It does not run forever because the loop terminates around iteration 120. So try to find a math function that starts over from zero instead, without stopping the loop.
Alternatively, put a 2nd loop around everything.
I don't like loop stacks containing the bulk of the code (see also) 😄
All you needs is a fully scalable and maintainable state machine! Use diagram constants to define the colors and times for each color, so they can be tuned without having to touch the main code (Or read them form a configuration file at program start). Now you just have three states (and maybe an "out of service" state, etc.) where each state knows how long to last (in real milliseconds) until it should go to the next state. All state code is the same, differing only in color and duration, allowing you to reuse the bulk of the code. You can even expand the code later to e.g. switch the cycle lengths according to time of day and traffic volume.
Why don't you search the forum for better examples? I am sure there are many!
@altenbach wrote:
Why don't you search the forum for better examples? I am sure there are many!
Have a look here for some basic ideas.
