Beginners Project - Traffic Light

Hello there,

My first "project" on my PLC course is programming a Trafficlight using a Micrologix 1000. I was able of elaborating one using 3 Timers (On-Delays), but have trouble looping the program so it starts over by itself.

Right now my system is something like this:

1. Start switch in ON position.
2. Activates TON 1 - T4:13
3. Timer (T4:13/TT) turns Green light for X seconds.
4. After X seconds TT goes off and DN activates a TON 2 - T4:14
5. Timer (T4:14/TT) turns Yellow light for X seconds.
6. After X seconds TT goes off and DN activates a TON 3 - T4:15
7. Timer (T4:15/TT) turns Red light for X seconds.
8. After X seconds TT goes off.

I tried several things but none have worked. I'm really just getting the hang of the programming so... I suppose it should be easy.

Thanks all!

Try using one timer with compare functions. (less then, greater then,Equal to,) Have your one timer reset itself to continue the trafic light operation. This should give you a good start.

Pohl said:

8. After X seconds TT goes off.

Click to expand...

You were almost there! You forgot to add "and DN resets the sequence" to that step.

Now, how can you make the DN bit reset the sequence?...

Hint:

1. Start switch in ON position... and sequence is NOT done



-Eric

Haha ok... good to know I was near completion. So I should imply by your "hint" that the START switch needs to be in off position! True. I tried doing the following:

- Using the same output name for the red light (O:0/7), I placed a N.C. contactor (?) so it would "open" the circuit for the duration of the red light (X seconds). This however, didn't work somehow, as the green light never turned on again. How can I accomplish this?

Thanks! I'm excited haha.

can you post your code...


pdf or logix file

Pohl said:

Hello there,

My first "project" on my PLC course is programming a Trafficlight using a Micrologix 1000. I was able of elaborating one using 3 Timers (On-Delays), but have trouble looping the program so it starts over by itself.

Right now my system is something like this:

1. Start switch in ON position.
2. Activates TON 1 - T4:13
3. Timer (T4:13/TT) turns Green light for X seconds.
4. After X seconds TT goes off and DN activates a TON 2 - T4:14
5. Timer (T4:14/TT) turns Yellow light for X seconds.
6. After X seconds TT goes off and DN activates a TON 3 - T4:15
7. Timer (T4:15/TT) turns Red light for X seconds.
8. After X seconds TT goes off.

I tried several things but none have worked. I'm really just getting the hang of the programming so... I suppose it should be easy.

Thanks all!

Click to expand...

As eric said

In your first rung in series with the START command - put something thats in your last rung thats NOT DONE until it times out

Also, you have done a traffic light for one direction. Usually, traffic lights control both East/West and North/South directions. How would you add the other direction to your program? Hint: You should only need four timers for both directions. A simple timing diagram is useful, to know what the other direction is doing, and what functions can be combined.

Another Method: You can do a two-direction traffic light with one timer, by using comparison instructions for each lamp rung.

Woohoo, we did it!

Thanks all guys, our next project is right up! And I'm going to need more help. Yay!