plc help

[Lancie1]

What is your rationale for going to a PLC ?

Glenn,

....which have to come on at particular times for particular time periods.

 

[bce123]

Look at the Automation Direct CLICK PLC

gets my vote

 

[danl]

hi folks and thanks for the many inputs here to my dilema thread!! to clarify, the solenoids i have to switch on and off for programed times are 24 vac, they just come that way they are sprinkler valves that draw about 2 amp. the two motors of course would have to be starter relays external but with a coil that the plc could handle. esntially, a controlling plc to have the capabilities of switching the valves, motor relays and seeing a few level switches. have real time programmable timming. etc. pretty much building my own delux sprinkler system because there isn't anything on the market already which i could afford. but even buying alot to build still beats a cost like that.so, here's what i'm lookin at 12 outputs, individually programed to handle 2 amp 24vac. 2 motor starter relays that have a relay coil compatable w/ what the plc put out for the coil relay activation. real time capabilities, and a few inputs externally powered matching the input range of the plc card. esentially a micro control plc and an input card and an output card of sorts? i'll do some lookin where lancie suggested also. thanks folks, always welcome suggestions!!

 

[Lancie1]

Here's what i'm lookin at: 12 outputs, individually programed to handle 2 amp 24vac, 2 motor starter relays that have a relay coil compatable w/ what the plc output for the coil relay activation, real-time capabilities, and a few inputs externally powered matching the input range of the plc card.

The Click (and many other brands and models) can handle all of that. Cost may be an issue, so shop carefully and buy only what you need. Do not buy a 2-amp PLC output to handle a 2-amp AC solenoid valve. Get at least 2 times the solenoid running current to allow for the initial in-rush current. Otherwise you will burn out your Output module.

...2 motor starter relays that have a relay coil compatable w/ what the plc output for the coil relay activation,...

If you buy PLC relay output modules, then you can use nearly any AC voltage to power your external relays. PLCs allow you to choose the voltage that you apply to the PLC relay. You just need to choose an output module that has a range that covers all the voltages that you need to use. Many (including the Click) have a range of 12 to 264 volts AC that can be applied to the PLC relay output coils and contacts.

 

[DwSoFt]

What is your rationale for going to a PLC ? If you just want to control the pumps with switches, hard-wired relays may be cheaper. Once built, the PLC system would be easier to modify or adjuat by editing the program.

he is running it automated, with a timeclock.
he could use a regular old time clock and relays too if he wanted to. but maybe he wants to practice his plc skills haha.

i would deff reccomend the automation direct plcs for such a simple setup. altho i think getting dc voltage added into the equation is a waste of time and money. [K]EEP T IMPLE TUPID lol. id get a 120vac plc, and them a simple 120 to 24vac transformer for the solenoids.

 

[Lancie1]

i think getting dc voltage added into the equation is a waste of time and money. [K]EEP T IMPLE TUPID lol. id get a 120vac plc,

Yes, maybe a waste, for you, me, electricians, and others.

But what about for Danl? I hesitate to recommend 120 volt equipment (bare 120 volt terminals can kill, adults, pets, and kids) without knowing the skill level and knowledge of the recipient. Based on his questions, and planned use, maybe yes, maybe no.

Yes this system is for my back yard.

 

[DwSoFt]

Yes, maybe a waste, for you, me, electricians, and others.

But what about for Danl? I hesitate to recommend 120 volt equipment (bare 120 volt terminals can kill, adults, pets, and kids) without knowing the skill level and knowledge of the recipient. Based on his questions, and planned use, maybe yes, maybe no.

Ah, fair enough, I agree that bare 120v terminals can kill in the right situation. I just neglected to think of that. I figured since he was thinking of doing a plc on his own, he would know how to protect everyone else from harm as well. My bad. If that's the case we should also have someone qualified install the dc power supply so that he doesn't touch the 120 at all. But yes I do understand that it is good practice to reccomend the lower voltages for safety and lower skill level.

 

[danl]

it's ok guys. i'm a tech. i've wired all kinds of stuff. besides i work around 12.7kva all the time. heck my chillers where i work are 1460v. don't worry about the 120v! i'm just trying to build a simple plc that will allow 24 hr 360 day repeat programming but require alot of outputs and just a few inputs. these outputs will control irrigation solenois and two motor starting relays.

 

[danl]

i was looking at the click as suggested above. now that's really some neat stuff!

 

[Lancie1]

It's ok guys. I'm a tech. I've wired all kinds of stuff.

Great, it is good to know that you know what you are doing. Is there anyone else living in your house that could put their fingers across the 120 volt exposed terminals of your PLC? Is there any need to install your PLC into a cabinet or a locked closet? We electrical types often forget that the the only thing the next guy/girl coming into the room knows about electricity is how to turn on a light switch. Make it safe for all who will be exposed to it. Enough said on that.

Yes, I think the Click is a good fit, and it does have a real-time clock that could be used to control your sprinklers. There are also other brands that will work. What I like about Automation Direct is that anyone can order online and know exactly what it will cost up-front.

 

[danl]

seeing that the click system is limited in output amps, it is doubtful that this or any other system would have an output rating to power as many solenoids up at the same time as would be required by my application which is five plus a motor starter. so, an outside transformer will have to be used along with relays to actually power the solenoids.

 

[danl]

and thats fine. the plc would still be running the show..... relays, s.d. transformers etc are no big deal. time to invest in a nema 4 box!

 

[danl]

neat sights you mentened here. automation direct is amazing.

 

[danl]

all this stuff is going to be going into a shed i built which is actually the pump house. (walk in) but a nema will be used so as no one will tamper w/ the circuits.

 

[Lancie1]

Seeing that the click system is limited in output amps, it is doubtful that this or any other system would have an output rating to power as many solenoids up at the same time as would be required by my application...

Doubtful, but possible if you use some of the Click Isolated Relay 7-AMP Output modules for your heavy current users, and the normal 1-Amp built-in outputs for the low-current loads. Remember, the Click relay outputs do not take their power from the PLC. Instead, they take power from your power supply to the output module terminals (whether it be 120 volts or 24 volts). The Click output relays simply have to have contact ratings to handle the connected load. This has nothing to do with the internal power rating of the PLC CPU. There is a maximum current rating for all the outputs on each module (due to the limited total heat dissipation of the module).

This is not rocket science for an experienced tech like yourself. All you need to do is add up your current loads, and then look at combinations of Click modules that will handle that load current.