Beginner question..

[Helloworld25]

So I work for a company that doesn’t allow code change without going through a lot of people. Anyway my question is I have a sensor and when it gets blocked for 4 seconds it outputs a blue jam light. We’ll it goes un-noticed by employees so i wanted to add a jam horn to sound off what I was originally going to do was request changing the code to just simply output the existing horn in a near by area and the light both. The light is 120v I was just going to wire a 120v alarm horn in parallel with the light so when the light output is triggered by the plc the horn also goes off. Some more info the light runs to a remote I/O but I can tie in the horn in the junction box right next to pilot light. Is this a bad idea? Will it work? Or should I just go the long route. Sorry if this is a dumb question I’m relatively new to PLCs. Any help would be appreciated.

 

[Steve Bailey]

Conceptually, no problem. The one thing to check is whether the PLC output can handle the additional current the horn will draw.

 

[Mark-]

And also check if the light has a "lamp/light test", command in the logic and if it does, is it OK for the horn to also sound for a lamp test.

 

[Jeev]

Also check if the audible being constantly on with the light is going to cause employees to direct profanities at you. Perhaps consider a unit that can modulate and/or adjust volume in hardware.

 

[Helloworld25]

Also check if the audible being constantly on with the light is going to cause employees to direct profanities at you. Perhaps consider a unit that can modulate and/or adjust volume in hardware.

That was also a concern of mine. The alarm is continuous, I told my co-workers it’s going to be constant alarm, although the light blinks I think that’s just the internal circuitry of the light creating the flash one of my co-workers thinks the alarm will sound with the light. I think the opposite. So if I have wago remote I/O being communicated to the PLC over profibus I just need to find out the current rating of that and make sure my light and horn doesn’t exceed that?

 

[Mickey]

Let the PLC control a relay (double pole). One pole for the light the other for the horn.

 

[James Mcquade]

if it is company policy not to change the program without going through channels, then that is what you need to do. sounds like there won't be any program changes, but i would still go through the proper channels and present what you propose. pros and cons.
i worked at a company where no changes could be made unless approved by me, the engineering manager, the line manager, and supervisor. there were a lot of changes being made that changed the quality of the product. since then, only only 4 people were allowed to make changes and it had to be documented.
Quality was excellent after that rule.
james

 

[parky]

I would personally use a seperate output & turn the horn on in say a 3 second on 3 second off, perhaps even have a mute button it will depend on how the operators react, some examples are will ignore it if it goes off after a time, if it stays on until fault cleared or pulse (the latter 2 might encourage operators to accidently on purpose swipe it with a lump of metal

 

[dummy_bit]

I feel your pain. I had to do that up until 5 years ago. Now we have a plc backup system that overwrites any changes made.

Can you make wiring changes? I'd do what mikey said

Let the PLC control a relay (double pole). One pole for the light the other for the horn.

Hopefully they left you some spare wires in that junction box and enough room in the remote I/O box for a relay...

 

[IO_Rack]

I work for a highly regulated business where all changes are approved, qualified and documented.

There is nothing wrong with this. No matter how simple the change is, do exactly what you want to do. Edit your drawings, make program changes then test. You may find you want a lot more than you think. Maybe you'll want to pulse the horn. Maybe a horn silence button.

BTW.... if we were to change the wiring, that would require a change order as well.

 

[TheWaterboy]

Pharma industry has entered the chat . . .

 

[PreLC]

plc backup system that overwrites any changes made.

Automated downloads? O_O

 

[Aardwizz]

BTW.... if we were to change the wiring, that would require a change order as well.

Absolutely.

@Helloworld25 :
The reason for "going through a lot of people" is to do a risk assessment. As Steve Bailey pointed out, perhaps there is not enough oomph in the output to drive both the light and the horn.

If you just make your change, you could potentially not gain the horn, but also loose the light, making the situation worse instead of better.

Just as you're coming to this site for a sanity check, that "through a lot of people" serves the same function. Do not bypass it, no matter how inconvenient or how "safe" or "minor" the change you think your improvement is.

This is not just paperwork for the sake of paperwork, or because of some overbearing, blind-and-stupid government regulation.

Yeah, it sucks, having your hands tied. Wanting to do good things and being unable to. But that's the rules of the company / industry that you are in. Either you need to change and accept it, or change company / industries.