Sequencing Machine Steps in an Allen Bradley Micrologix PLC
This sample program shows examples of sequencing machines using cascading timers, counters, manipulating words, multiplication, sequencers, and by gremlins possessing your machine.
You will need RsLogix 500, RsLinx and either RsEmulate or one of our trainers this sample program. Click here for instructions on how to download, install, and operate RsLogix 500 and RsEmulate.
Everyone knows that I don't believe in using non-real world examples such as washing machines, elevators, and traffic lights to teach students how to program PLCs. When students come out of school, they either start off in the shallow end of the pool under a veteran or get thrown into the deep end with a big project and either have to sink or swim. I think these exercises prepare you for the kiddie pool. But the kiddie pool is warm for some reason, so let's see if we can warm those brains up a little with this sample programs.
I've chosen the 1960s Mercury Cougar sequential tail light problem to work with. You can do a quick google of "cougar tail lights" to see videos of how they operated. I didn't review the original wiring diagrams to assure that the samples function as they originally did:
- If the brake light is pressed, all of tail lights must turn on.
- If the emergency flashers are on, all of the tail lights must flash together as long as the brake light is not pressed.
- If the left or right turn signal is selected and the emergency flashers are not on, the tail lights should turn on in order from inside to middle to outside, then turn off and repeat.