Simple reset timer program?

[joeholick]

I need a better understanding of the reset function for wiring a specific circuit for my dad's shop. I understand simple logic and the concept fairly well (I think!??)

Basically, a trigger on a liquid plastic dispensing gun/pump is pulled, and when the trigger is released, an output needs to be energized 5 minutes after the trigger has been released, (which will set off an alarm to remind to flush the gun), at that point the employee will need to press another switch to reset the system to fill the next mold which will of course also need to stop the alarm from sounding.

It's an extremely simple program until I add this variable - The user could pull the trigger again before the 5 minute countdown is up which needs to start the program again and ready for another mold, instead of setting off the alarm.

If the employee pulls the trigger again before the alarm goes off to fill another mold, (before the resin has started to cure in the nozzle which is at 5 minutes) the timer needs to reset from the most recent mold fill, if in fact the trigger is pulled again before the 5 minute countdown has completed.

After I have a better understanding of how that should be done, I would also like to be able to make the "5 minute" countdown variable, and be able to set at several different intervals such as; 2,3,4,5,6,7,8,9,& 10 minutes, so they can set the alarm to go off earlier in the summer when the resin cures quicker.

I am thinking a relay will latch on which will input a timer, but how should the reset part integrate?

Thank you everyone!

Joe.

 

[MarkNightingale]

Joe,

Which PLC are you using, and when you say you want to be able to make the time changeable, how will you do this, with an HMI? if so which one.

If you post what you have got so far people will be more likely to help you out and guide you in the right direction.

Mark

 

[joeholick]

Ah yes, I apologize. I have a decent supply of Allen Bradley SLC500 series modules and use Logix500 for programming. The I/O cards can be configured to match what this circuit requires, as I have at least one of (almost) everything. As far as making the time variable, we can just leave that stage out at least for now, I was hoping to use something simple like a several input rotating switch with each input setting the time of the timer.

Thanks again.

 

[Saffa]

You can simply use the (RES) output instruction to reset the timer (it's only parameter is the timer you wish to Reset - check RSlogix help if you need).

Add it to a rung which is energized when the gun trigger input is pulled, and your timer's accumulator should be reset back to zero.

As for the different timer settings, if you've got plenty of digital inputs to use then a rotary switch would work fine. Depending on which input is made, you can use the MOV instruction to copy the preset time (1, 2, 3, 4, 5 min etc) to the timer's Preset Value (T4:0.PRE for example).

 

[MarkNightingale]

Joe,

There is no need to use a reset for your counter. A reset would only be needed if you were using a RTO which is not necessary in your program.

Basically when the trigger is released, you need to start a timer. If the trigger is pressed again the timer will restart from 0, until the trigger is released again, which will then start the timer timing.

If the timer.dn bit comes on then sound the alarm.

Mark

 

[joeholick]

Joe,


Basically when the trigger is released, you need to start a timer. If the trigger is pressed again the timer will restart from 0, until the trigger is released again, which will then start the timer timing.


Mark

Okay excellent. I thought I was making it over complicated. My question now is, how do you get a timer to stay on from a momentary switch? Program a latching circuit? Can this all be done with one microswitch on the trigger?

 

[MarkNightingale]

Joe,

Is the switch on the trigger not on all of the time the mould is being filled.

If not yes you can use a 'seal in' piece of logic, but for that you will need something which will stop the 'seal in' logic.

Think of a simple start/stop 'seal in' logic.

Mark

 

[joeholick]

Okay, I think I totally have it figured out. I have never heard the term 'seal in.' I have only been studying PLCs for 2 weeks, never knew what they existed before then, but I googled the term and it is similar or actually synonymous with the latching relay I am try to explain. Thank you for confirming my suspicions Mark!

Joe.

 

[MarkNightingale]

Joe,

No problem.

Keep us updated and if you need anything else you know where we are

Mark

 

[joeholick]

You can simply use the (RES) output instruction to reset the timer (it's only parameter is the timer you wish to Reset - check RSlogix help if you need).

Add it to a rung which is energized when the gun trigger input is pulled, and your timer's accumulator should be reset back to zero.

As for the different timer settings, if you've got plenty of digital inputs to use then a rotary switch would work fine. Depending on which input is made, you can use the MOV instruction to copy the preset time (1, 2, 3, 4, 5 min etc) to the timer's Preset Value (T4:0.PRE for example).

This configuration works like a charm. And as for the rotary switch, I think that is the perfect idea, although, is it possible to use an analog input and set the timer for the alarm to a variable time within set limits?

As for now the system is working like a charm! I have not incorporated the variable alarm set off time. Any good tutorials on understanding how to use the move function?

Thanks guys!

 

[Lancie1]

This configuration works like a charm. And as for the rotary switch, I think that is the perfect idea, although, is it possible to use an analog input and set the timer for the alarm to a variable time within set limits?

Yes, it could be done with an analog input. It could be done with a digital input that represents each possible time setting (defined external to the PLC program). Another method that was popular long ago was using a thumbwheel switch to input a BCD (binary-coded decimal) number to your SLC digital inputs. Using a BCD 4-digit rotary thumbwheel switch allows inputing 15 time settings (plus 0) to the PLC, but using only 4 digital inputs. You can do the BCD inputs without the thumbwheel coding, and you have to decode the inputs inside your PLC program.

 

[joeholick]

Yes, it could be done with an analog input. It could be done with a digital input that represents each possible time setting (defined external to the PLC program). Another method that was popular long ago was using a thumbwheel switch to input a BCD (binary-coded decimal) number to your SLC digital inputs. Using a BCD 4-digit rotary thumbwheel switch allows inputing 15 time settings (plus 0) to the PLC, but using only 4 digital inputs. You can do the BCD inputs without the thumbwheel coding, and you have to decode the inputs inside your PLC program.

Could you please elaborate on the BCD thumb wheel? I think we have decided on a Micrologix 1000 so I only have 6 inputs and need 3 for the flush system, or I could get by with just 2 on the flush, but would rather not.

 

[alan_505]

A BCD thumbwheel switch will use four inputs per digit from 0000 to 1010, where each input represents the binary value of its position. 0001 = 1, 0010 = 2, 0011 = 3 and son on until you have used all 4 bits, this will count from 0 to 15.


Alan

 

[joeholick]

Thanks Alan. That makes sense. Now how the heck do I make sense of all these different inputs to change my timer? AH?!

 

[alan_505]

You could read the inputs that you are using and put that value into a N7 word (you could use the MOV or the MVM command) and use that word with the EQU command to MOV your time values into the timer preset.