how can i simplify this logic

[xenu]

I'm using productivity 1000 plc for this. The process is simple i have a wheel with yarn wrapped around it made out of aluminum with evenly spaced screws tapped into it for a prox switch to detect rotation. the logic is simple if the prox switch is on for more than 3 seconds the machine will stop or if the prox switch is off for more than 3 seconds the machine will stop both indicate a broken yarn. I have 24 of these sensors on each machine but i am looking for a simpler way to write this. attached is an image of how i currently have 1 prox in the logic.

 

[joseph_e2]

What I've done in the past is to use 2 timers. One on each state of the sensor. If either timer's DONE bit turns on, the wheel is stalled and we "do something" about it.

If all of the sensors are wired to consecutive inputs, or otherwise gathered into 16-bit words, you can do a compare of current value to previous value.
I'm not familiar with the Productivity series, but I've attached screenshots from an AB PLC.

N.B.: I haven't tested these so I'm not 100% sure it'll work as intended, but it's at least close.

 

[5618]

I don't know what instructions are available in the Productivity line. I often use a single timer running when the motor is on, timer done is the alarm. Then I'll have something like one-shot rising or one-shot falling of the prox resets the accumulated value of the timer.

Edit: Okie's pic below - yeah, like that, add the motor to time up.

 

[OkiePC]

Another way with a regular timer:

 

[drbitboy]

Another way with a regular timer:

^ This


It can also be done with a TOF, but that's tomayto-tomahto.

 

[joseph_e2]

Another way with a regular timer:

One neat thing about that is that you can add branches for as many sensors as you need. At least until you hit any branch limit the PLC has...

 

[OkiePC]

...
Okie's pic below - yeah, like that, add the motor to time up.

Good catch. Thanks. I missed that.

 

[xenu]

Another way with a regular timer:

Wont this constantly reset the timer regardless of if the wheel is turning or not

 

[drbitboy]

Wont this constantly reset the timer regardless of if the wheel is turning or not

[Edited: I misread you question; fixed now]


No, the -|↑|- instruction detects a 0-to-1 transition, and the -|↓|- instruction detects a 1-to-0 transition, of the bit operand, and either transition event will reset the timer as long as the sensor detects a screw entering or leaving its proximity within 3s of the last transition event.

So the timer will never expire as long as the wheel keeps turning and generating transition events.

If, however, the wheel stops turning, then the timer not reset and after at most 3s the timer will expire and it is that timer expiry (.Done bit value is 1) that can be used to raise the alarm.

 

[xenu]

Thank you so much for your help that is exactly what i was looking for. for some reason i was overcomplicating it and could not see the easier solution thank you.