Set/reset function

Mia · May 6, 2013

Hi,

I'm struggling a little here with a stupid function that I'm sure has a very easy answer.

Using the program iTrilogi I can't find a set/reset function for the outputs!! Does this program not have that? is there any other way I can do this??

Please help!!

Mia

dbh6 · May 6, 2013

Welcome to the forum, I have never used a iTrilogi program but if you can't find set/ reset which is basically a latch/unlatch you can roll out your own. You can do this by "sealing in" the output that you want to stay on until the reset is pressed that unlatches the latched output. If you want an example, just simply search in the search field "seal in" and you should find tons of examples.

Ron Beaufort · May 6, 2013

let's be careful here ...

I have ZERO experience with the software that you mentioned – but be careful ...

in an Allen-Bradley system when you use a "seal-in" type construction, then the output will NOT turn back on again after a power-down situation ... but with an actual Latch/Unlatch construction the output CAN indeed come back on unexpectedly ...

so ...

the question that you need to ask yourself is this: do I really want the output to "come back on again" at power-up? ... or not? ...

part of the problem is that many programmers use the terms "latch" and "seal-in" interchangeably ... they are not the same thing – and the differences between the two programming methods can lead to "surprises" ...

surprises in this particular area can be expensive – and dangerous ...

the thread below discusses most of the concepts involved for Allen-Bradley and Automation Direct ... whether either one of these works the same way that your software works remains to be seen – but you really need to explore the basic ideas ...

http://www.plctalk.net/qanda/showthread.php?p=71786&postcount=1

good luck with your project ...

Lancie1 · May 6, 2013

The iTriLogic instruction that locks in a bit output is called "Latch".

I warn you against overuse of Latch (as most beginners do). It is much better if you learn the constuction of ONE TriLogic Out instruction with a seal-in or self-latch, that can turn on and turn off an Output, without the need for a second rung to turn it off or Clear.

glenncovington · May 6, 2013

It is a [Latch] function with a [Clear].

Mia · May 6, 2013

Hi!

I actually found the Latch/clear function, but it did not solve my problem..

I'm trying to make a sfc controlling 4 motors (each in 2 directions). testing this in 3 step, I made a program (attached pics).. the problem is that when I want to simulate, I get a warning that motor2_fw and motor3_fw are already energized.. And I just can figure out why! I thought the step kinda deactivated itself when the transition moves on to the next step...??

any suggestions? :Z

glenncovington · May 6, 2013

In rung 13 are the outputs supposed to be all for reverse. Two are for rev and two are for FWD. The two FWD outputs are also in rung 10.

Mia · May 6, 2013

well I want to run all the motors fwd in the first step, and then run 2 of them fwd and 2 of them rev.. I tried to use latch/clear as well, but I still have the same problem. It's like I cant "clear" them between each steps..

glenncovington · May 6, 2013

It is a better practice in my opinion to only use physical outputs one time in the program. Make the varying conditions that you want for the output to operate in the rung but only have the output once.

In the case of your program the scan evaluates the output as not true in rung 10 when S2 or r2 is not true and then evaluates the same output as true in rung 13 when S3 is true and S2 is not.

Essentially turning the output on and off during the same scan.

wimpiesplc · May 6, 2013

Mia said:
.. the problem is that when I want to simulate, I get a warning that motor2_fw and motor3_fw are already energized.. And I just can figure out why!

glenncovington said:
...
In the case of your program the scan evaluates the output as not true in rung 10 when S2 or r2 is not true and then evaluates the same output as true in rung 13 when S3 is true and S2 is not.

Essentially turning the output on and off during the same scan.

Some systems don't allow multiple assignments of same output. I don't know 'iTrilogi', maybe it would be possible, but I guess that the warning you get shows it's not.

iant · May 6, 2013

Ok, I had to look up that PLC to remind me.
Also do not trust the SSR outputs to handle more than 0.5 Amp resistive load. then have the device out in the field 550 Km away from support.
(NOT MY DESIGN)
I have only interogated it once.
these are a PCB style PLC and only very basic.
RULE OF THUMB, Cheap PLC's - you can not use outputs twice.
(ofcourse you can with AB and other newer PLC's)
where posible I would recomend avoiding this practice.

Lancie1 · May 6, 2013

(1) I'm trying to ... control 4 motors (each in 2 directions).

(2) I want to run all the motors FORWARD in the first step,... [for xx seconds, or until Switch S1 is turned on, or when and for how long?]

(3) Then run 2 motors FORWARD, and run 2 motors in REVERSE...[for xx seconds, or until Switch S2 is turned on, or when and for how long?]

I downloaded i-TriLogic, and can help you, if you will explain the following:

For Step 1, how long should each motor should run, and when should the change to Step 2 be made?

How long should Step 2 run, and when it should change to Step 3 (or if this is the last step, when should all motors stop and the system be shut down?

Lancie1 · May 6, 2013

Here is an attempt to organize your program, and define what it does.

Step 1: When S1 is ON, run all 4 motors Forward for 5 seconds.
Step 2: When S2 is ON, run MC1 and MC2 Forward, and run MC3 and MC4 Reverse.
Step 3: When S3 is ON, run MC1 and MC2 Reverse, and run MC3 and MC4 Forward.

Set/reset function

Mia

Member

dbh6

Lifetime Supporting Member

Ron Beaufort

Lifetime Supporting Member

Lancie1

Lifetime Supporting Member

glenncovington

Lifetime Supporting Member

Mia

Member

glenncovington

Lifetime Supporting Member

Mia

Member

glenncovington

Lifetime Supporting Member

wimpiesplc

Member

iant

Lifetime Supporting Member + Moderator

Lancie1

Lifetime Supporting Member

Lancie1

Lifetime Supporting Member

Similar Topics