Fire Station Automation: Relays, Contact Closure, etc.

[FireAutomation]

Hello,

I'm working on a fire station automation project, and I've got some questions about some of the more inexpensive PLC's out there (like an Omron Zen, or Click PLC):

Upon a momentary contact closure, I need to accomplish the following:

Switch a single balanced audio line to an amplifier (it sits in off position otherwise)

Provide contact closure for another relay that operates a bank of lights

Provide contact closure for a garage door opener

Provide contact closure for an audible tone generator


I am a novice with PLC's, and I'm having a tough time figuring out the input output capability, and relay capability.

For the audio problem above, I'd use a double pole, double throw relay normally, I'm wondering if the PLC can accomplish that on its own? It seems foolish to have to use a relay with a PLC since it can do that job itself.

The contact closures I imagine are no big deal? The tone generator has a common output, and requires contact closure to an input, the same goes for the garage door and light relay.

Any help is appreciated

 

[itsmoked]

Buy a smart relay with dry contacts. Just use them directly if the loads are acceptable. If the loads are close to the smart relay's rating use the smart relay contacts to run an external relay.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FireAutomation]

I neglected to mention that the audio needs to stay engaged for 3 minutes... That's why I was leaning towards a plc.

 

[itsmoked]

Same thing. That has no bearing on this. You can program a smart relay to stay on for months.

Check this:

http://www.factorymation.com/s.nl/sc.2/category.22/.f

Siemens and others make this same style device. They have better programming software too, but you have to pay for it I believe.

You have enough in the link above to completely design and test your job without buying anything. You can download the actual software which provides simulation.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Beware of "Momentary" closures on PLC inputs. For some PLCs an input must stay high until it is scanned to be recognized. Scan time may depend on the size of the program.
Also, your insurance company may require the use of "Listed" PLCs or controllers. Many of the small economy model PLCs are not acceptable to the insurance underwriters for "Mission Critical" applications.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[FireAutomation]

Hi Bill,

The radio contact closure lasts for one second, hopefully that's long enough.

I took the Teco Genie II software, and programmed it how I'd like to see it run -- do you have any fears over that unit?

I've got it setup to where if power failure occurs, the normally closed contact will allow the audio to go through for a dispatch.

I've seen these systems designed before using all mechanical timers and whatnot, I was hoping that a PLC/PLR would be a better solution for the four or five contact closures and timers that I'll need.

Any information is appreciated.

 

[itsmoked]

I have used those particular units about 12 times. I have only seen one failure and it was entirely caused by me. I inadvertently set it up in a situation where the contacts feeding a large solenoid could find themselves opening and closing several hundred times a second for about half a minute. This fried the PLC's contacts in very short order. I was able to shift to a second pair of contacts and the system continues to operate correctly.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FireAutomation]

Keith,

Sounds great, I'll place an order and test out my program. I certainly like the function based programming over the logic ladder.

Second question,

Studies show that fading in audio alarms for firefighters is critical when they're asleep. A sudden alarm can cause bad health effects and startle these people while waking up for an emergency call.

I'm looking at using a Valcom 9927A paging tone generator:

http://www.valcom.com/techsupport/ringer_ts/tonegenerator.htm

The unit can make several different tones using contact closure.

I'd like to fade its audio output in, the only thing I can think of is something like a digital potentiometer. Does anyone have a better idea, or something simple that too can operate off of contact closure? Is this something a PLC or similar device can do? I'm at a loss on this one.

Thank you.

 

[itsmoked]

Not an easy fix..

For that smart relay you can get an expansion module that is transistor output. This gives you four outputs.

Google "digital volume control" and find a unit that takes pulses to step its volume up/down.

Another idea might be to build a resistor divider then use the smart relay's dry contacts to short the diver out in several steps.

You could also use an analog voltage volume control that takes in a voltage and changes the gain. Use a transistor-out to make a crude PWM voltage output to use for controlling the the aforementioned volume control.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[edshere]

itsmoked....its been along time since i've heard people talk about voltage dividers and transistors. Lets just can this PLC stuff and do this project with PIC chips and ohms law...... Good Times.

 

[itsmoked]

Indeed!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FireAutomation]

Sounds like a challenge. Nothing commercially available that takes care of this to my research, if anyone else knows of something, I'd appreciate it.

Thank you!

 

[Skogsgurra]

Come on! Firemen afraid of an alarm!?

Get real.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[edshere]

Seriously though, if you don't want to use the programmable relay like Itsmoked suggested, you could use a Micrologix 1000 or a GE Versamx Micro processor for almost as cheap. But then you would have to find software. I think Ge has a trial of Proficy Machine Edition that you have to reinstall every four days, but you could use it.

http://buyplcparts.com/index.php?main_page=product_info&cPath=1_9_25_18&products_id=5

I still like the IC idea better.

Ed

 

[jraef]

The Siemens LOGO! programmable relay has an option for an analog output module if that's what you mean. The latest version also has the ability to do a PWM output built-in to the basic unit if that is something that you can easily adapt to "fade".


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