HELP! Scanning inputs and flashing related faults

Capper

Member
Join Date
Sep 2007
Location
Ontario
Posts
11
Hi All,

I've been struggling with an application which requires a buzzer to pulse a number of pulses to correspond with different alarms (1 pulse equals area A, 2 pulses area B, etc). I think I have to buzzer output portion working (haven't tested since the last round of changes) but am definitely struggling to have the program continuously scan the fault trigger inputs and alternately pulse the buzzer if there is more than one fault trigger present (if fault #1 and fault #3 inputs are both high pulse once, pause then pulse three times repeating until the fault inputs go low). I've searched and looked at the flasher program in the downloads area (couldn't find the output driving the bulb...) to no avail.

Any help would be appreciated!

Thanks
 
What EXACTLY is the program doing that you don't want it to do?

p.s. - Nice .pdf, most people's rendition is too small to be legible.
 
first determine the duty cycle of the pulse and then the dwell between repeats. a simple function could index thru a fault word and produce the sequence you need
 
Thanks for the reply and the compliment! The problem is cycling through the fault triggers (it won't) if I force the inputs on 2 or more of the faults it will just repeat the first it latched over and over...

I have overcomplicated it (see attached) and have it cycling through but it may repeat randomly and not index truly sequentially. I've heard of a tecnique called "sideways H" or something to that effect where the preceding rung latches the subsequent rung but didn't quite wrap my mind around it...

One phenomena I don't understand is the c5:0/dn bit would not trigger a reaction anywhere else in the file when it reset itself (like it scanned and updated before scanning the other rungs) I stretched it with another timer (getting messier). Next I cycled a counter in an attempt to scan one of the three trigger rungs sequentially, this turned out hit and miss.

I'm sure there is an easy way I don't see for the trees...
 
Okay, you nerd sniped me on this one :)

How about something like this? AreaAlarms is a DINT where every bit represents an alarm in an area (i.e. bit 1 high means area 1 alarm, bit 2 high means area 2 alarm, etc etc). Pointer is also a DINT (or INT or SINT if you really want).

An Area 1 alarm will pulse once, an Area 2 alarm will pulse twice and so on (lets hope there's never an alarm in area 31 ;)). In between each set of pulses there's a 3 second gap (or you can set WaitTimer to whatever gap you want).

I haven't tested it, but give it a shot and let me know how it goes!

Screen Shot 2015-11-27 at 9.18.16 am.jpg
 
I've just noted that you're using RSLogix500, not 5000 - so it'll look a little different as far as you will have to put all output instructions on parallel branches (instead of in series as I've done), but the concept will be the same.

Also, if you use an integer (N) for your AreaAlarms tag, make sure you change the GRT instruction to be Greater than 15 instead of greater than 31 lest you fault the PLC ;)
 
Thank you very much ASF & all those who took the time to comment! The concept worked well, I believe one of my problems was related to using the counter done bit to immediately reset the counter rather than resetting the counter just before using it as depicted by ASF. Secondly, the fact I never considered using the ADD to increment the pointer! I've learned a bunch on this one... I've attached a PDF of the final product. Thanks again!
 
For next time

Just so you know, A-B processor timers have a TT bit (Timer Timing), which is equivalent to what you have done with XIC EN and XIO DN. Either one works but TT is a little cleaner.

timer timing technique.jpg
 
Last edited:
No problem, and thanks for posting back the follow up!

Good fix on the issue with not annunciating the last pulse correctly too, that's one that catches me out annoyingly often ;)
 

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