counter instruction ?s

[Rube]

Well I guess I'm gonna have to try that Monday when I get around a processor because I still don't understand the need for the T4:2/DN bit in the parallel output branch.
Maybe a lesson in it for me.

 

[Kick-It-Up]

You need to look at the conditions that allow the timers to energize and think of how this piece of equipment would operate.

Are things moving for a time or to a position?

A hint would be that the fault timer is half the length of the two cycle timers, which could only work for one of the two above scenarios.

 

[Kick-It-Up]

Well I guess I'm gonna have to try that Monday when I get around a processor because I still don't understand the need for the T4:2/DN bit in the parallel output branch.
Maybe a lesson in it for me.

It is there to energize the fault light when the timer times out, without it the fault light would be on as soon as the rung becomes true which would then de-energize the rung by de-energizing the forward and recline relays.

 

[Rube]

You beat me to it KIU--I got it now


Long week.

 

[Ron Beaufort]

please do not laugh if i am in error

no, we're not laughing – but whether you're in error or not isn't the point ... you're going too deep ... don't look at the operation of the whole program ... just answer the questions below ...

instant replay:

(1) we'll reset the counter when ________________ ...

specifically, what does the ONE rung which controls the RESet "say" about when the counter will be reset? ...

(2) what type of rung construction is responsible for maintaining the Auto Cycle Start bit B3:0/0 in the ON condition? ...


did your class study this type of rung construction? (please answer "yes" or "no") ... if you covered this type of construction, what "name" did you use to describe it? ...

(3) in an Allen-Bradley processor, what ALWAYS happens to this type of rung construction EVERY time that the processor starts up? (as in after a power failure has been restored) ...


answer those "hint" questions correctly – then and ONLY then – will you be ready to figure out what DIFFERENT conditions you want use for triggering a counter reset operation ...

post your answers to the questions above – the forum members will help ...

tip: we're not really interested in how the "complete" program works ... we're just interested in what makes the reset operation take place ...

earlier I offered to talk you through this by phone ... why haven't you called? ... if you can't afford the call, just send me another email with your phone number and I'll place the call from my end ... we can have this done tonight ...

 

[Mickey]

The suns in your eyes mickey

No,no see my avatar I'm wearing shades. It's the drink ( V-8 juice) sitting next to me.
My grandson says I'm the fix-it guy, I haven't lost everything and if I have I don't remember having it in the first place.

 

[plcnovice34]

sorry i have been out , i sent you an email with my number in it or i can call you

 

[Ron Beaufort]

I just got off the phone with our friend plcnovice34 – and I'm quite sure that "we've made contact with the material" ...

and the answers to the "hint" questions are:

(1) we'll reset the counter when: bit/box B3:0/0 contains a ZERO ...

(2) what type of rung construction is responsible for maintaining the Auto Cycle Start bit B3:0/0 in the ON condition? ... it's a "seal-in" construction

(3) in an Allen-Bradley processor, what ALWAYS happens to this type of rung construction EVERY time that the processor starts up? (as in after a power failure has been restored) ... a "seal-in" rung will always turn off – so the bit/box of its "output" will have a status of ZERO

now then ... if you carry that logic through to its ultimate conclusion, it should be obvious that the existing "reset" rung will not allow the counter to maintain its count after a power failure ...

so ... we need to "tweak" the conditions that control the "reset" rung ...

we worked through those over the phone step-by-step, and came up with two separate ways to correct the problem ... I'm not going to post those here – mainly because I don’t want to give away the answers to some other instructor's educational material ...

follow up note to plcnovice34 ... since you don't have a processor to work with at home, there's a link below which SHOULD allow you to download a free and legal demo version of some Allen-Bradley software – and also an Emulator which MIGHT prove useful to you ... personally, I've never tried the Emulator – but give it a shot and see if it helps ... let us know how that goes ...


http://www.ab.com/programmablecontrol/plc/micrologix/downloads.html

good luck with your studies ...

 

[plcnovice34]

thank you Ron for all your help, i tried the links but its not downloading on my computer.you definitely educated me on plcs