Timer Logic Question

[Pnut q 0]

Hello Im working on a homework assignment in the Goodheart Wilcox Programmable Logic Controllers book. Here is the problem. I need help specifically with the third scenario. Use a switch for reset. Close the temperature switch TSW to start the following sequence of events. 1. Motor #1 runs for 3 seconds. 2. Motor #2 runs for 5 seconds. 3. Finally a bell will ring 3 times within six seconds. ( Can some help me with the logic to make an output energize 3 times in six seconds?)

[Cookie Monster 2]

Timed Horn.RSS There are many ways to get this result. The comparrison statements make it easy for my maintenance crew to read through the logic. Edited 1 Oct 2013 by Cookie Monster

[Pnut q 0]

Thank you, this looks good. My instructor hasn't taught us equal to logic yet, but he will be happy that I inquired online an answer. Do you know of a way that the same could be accomplished from using just ton, tof, xic, or xio? I figured out how to make the light flash repeatedly but I really didn't have any control of it.

[Michael Lloyd 85]

No... you need outputs too. Try OTL and OTU

[Cookie Monster 2]

If you wanted to just use timers to accomplish this it could get very messy. T4:1 is triggered once M2 has stopped. T4:1/DN would start T4:2 and so on. This would make the logic very confusing and hard to read, cascading timers and using the .TT bit to trigger the horn would work. This can be done, but I wouldn't recommend using 6 individual timers just for three short triggers of the output. Edited 2 Oct 2013 by Cookie Monster

[daba 4]

I would go with Cookie Monster's approach. The reasoning is simple, there is absolutely no need to use separate timers, since they do not need to be used concurrently. Use only one timer, and comparison instructions (EQU, NEQ, LES, GRT, LEQ, GEQ, etc., but the most useful is LIM) inspecting the timer's accumulator (.ACC). Now it is easy, change the number ranges below to suit the timer's timebase setting (I've assumed 1 second here)... LIM 0 Timer.ACC 2 OTE Motor#1 (note that 0-2 is 3 seconds!) LIM 3 Timer.ACC 7 OTE Motor#2 The question doesn't specify how long the bell should ring for, it just says it should ring 3 times in six seconds, so the simplest solution is 1 second on, 1 second off, repeated 3 times EQU 8 Timer.ACC OTE Bell EQU 10 Timer.ACC EQU 12 Timer.ACC Note the above is a 3-level parallel branch for the EQU instructions. Now put this into actual PLC code... good luck with your assignment.