Wiring? (for PLC system-but not PLC related)

grnmon97

Member
Join Date
Nov 2007
Location
MA
Posts
14
I am attempting to design a machine that will use Qty 8 - PNP 10-24VDC through beam photo sensors as inputs and am trying to ease the wiring to the PLC. Can I use a terminal block to distribute 10-24VDC (+/-) to these sensors? and send a single wire to the PLC common? And perhaps supply power to solenoid valve (type not determined) outputs x8 as well? The sensor transmitter and receiver combination consume 48mA max current and the 24vdc power supply specs say DC output current is 0-12A.

Any help is greatly appreciated...
Bill
 
I do not see that being a problem. An easier way would depend on what type of PLC you are going to be using. You might be able to use somekind of remote I/O and have a single network cable back to the PLC.
 
Thanks Moltra. I am new to PLC's. Learning on my own to automate a process at my workplace. Therefore, funds are minimal, and every aspect is a new learning experience. Such as... I don't know what to look for in a terminal block. From what I have read, Terminal blocks sound like glorified wire connectors, but I want to connect 8 wires(Sensor+) to one (Power Supply+). Any suggestions where to shop?
 
We use alot of Phoenix Contact in our Panel shop. They have all the terminal blocks, shorting combs etc that you need to build any kind of panel. They also have power supplies and relays/signal isolators etc. They have reps everywhere so I would give your local one a call and have him fetch a catalog over. I've found their quality excellent.

AB do this stuff too but its usually alot more expensive.
 
Greetings grnmon97 ...

I'm not sure exactly what you're asking ... are you planning to hook the OUTPUT wires of all eight sensors together (into ONE wire) - and then connect that ONE wire to just ONE of the inputs on a PLC? ... basic idea: when ANY sensor sees its target, then the ONE PLC input turns ON ... is that what you're doing? ...

if that's what you're trying to do, then you MIGHT have a problem ... the trick is that some DC sensors do NOT turn completely OFF when the target is removed ... instead, they usually continue to allow a small trickle of current to flow - even when they're OFF ... usually that doesn't make much difference - because usually the PLC input won't react to that small trickle of "off state" or "leakage" current ...

but ...

if you hook up EIGHT sensors in parallel, then there MIGHT be enough leakage current flowing to fool the PLC into thinking that the input is ON - even though all of the sensors are actually OFF ...

if (as you say) your funds are limited, the best plan of attack is to give us the specific brands and model numbers of the equipment (sensors and PLC) that you're planning to use ... we can help you go over the specifications and try to head off any potential problems ... basic idea: the specs should tell how much "off state" current flows through each sensor - and how much current the PLC will regard as an OFF signal ...

if I've just misunderstood what you're up to, then just ignore this post and party on ... good luck with your project ...
 
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Bill,

Which PLC have you chosen for your project? I see from previous posts that you were working with a SLC150-LP151, which of course is an AC input/output model.

To answer your initial question, yes, it would certainly be preferrable to terminate your 3-wire sensor cables into a terminal block. The block can be wired to:
  1. Recieve & distribute 24VDC from the power supply to the sensors.
  2. Supply each PLC input with a PNP sensor output.
  3. Supply the PLC with the DC common used by the sensors.
Remote I/O as suggested by Moltra would certainly reduce wiring near the PLC, but based on your previous posts and this question, I think a direct wiring approach would best provide what you need to learn at the moment.

CeCo3
 
Greetings to you as well,Ron...
I would have 8 separate Inputs to the PLC (from the 3 wire sensor)but want to reduce the power wiring if possible. I purchased a Siemens 6EP1334-2AA00 24VDC Power supply and would like to power my I/O's from this. The Inputs will be Keyence PZ-G51 thru-beam sensors and I am currently using a AB SLC150 PLC but am looking to upgrade to a Direct Logic DO-06dr PLC. The process is for parts to activate solenoid valves when sensed by breakage of the thru-beams.
What I need to know is how can I distribute the 24VDC to each of the sensors and solenoid valves without wire nuts and electrical tape. I am REALLY new to all of this. In other words, I don't know what a terminal block does or how many types of Blocks there are.
Maybe there are even better ways.
ANY and ALL help is GREATLY appreciated!
Bill
 
CeCo3,
Thanks! I am using the AB SLC150, currently and am using relays from the sensor to switch the AC current. As you may have seen, in my last post, I am looking into the DL-06DR PLC as an upgrade. Any suggestions?

Please allow me to dig deeper into your answers about the Terminal Blocks...
You say that the terminal block can be wired to do what I want... Does that mean any block? Is there a certain type of block that I must look for?
Would it be possible to wire the sensors with M12 connectors on both ends and plug the sensor output m12 connector into a Terminal Block to get the same result? or am I reaching?

You folks that help out with posts such as mine are AWESOME! Thanks for your help!
 
yes it is possible to connect the sensors to the I/O block and run one comm cable back. I agree with the Phoenix contacts info. If you contact phoenix and tell them what you have and what you want to do they will spec out which I/O block you will need. Wago will do the same, both are very good at helping people.

The terminal block will allow you to power all the sensors off 2 wires from the DC power supply. Just make sure you do not overload the power supply. You will just have to run the signal wire back to the plc for each sensor or connect them to the I/O block.
 
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Since you're looking at converting that SLC150 to a DO-06, one possible terminal block (and, yes, any terminal block can do what you're wanting...) would be AutomationDirect's DN-T12 line, then use their jumper bars to link as many together as you need.

Setup a group of them to be your 24+, then another group to be your 24-.

Then also use terminal blocks between your plc inputs/outputs and your devices. Wire directly between the input/outputs to a group of terminal blocks, then wire your field devices to the other side of the terminal blocks.
 
Bill,

Check out this post. It has some great panel pictures and if you scroll down to the third & fourth posts from Eric, you can see a row of terminal blocks in the lower right corner.

Terminal blocks are designed to organize and simplify wiring in control systems. There are many types, shapes, sizes and colors and they can perform a variety of functions as well. Typically they will be connected one next to the other on a common "DIN Rail." This A-B pocket guide can give you a taste of what is out there and there are many manufacturers.

As far as M12 connectors go, yes you could keep the connectors, but that will add cost. At some point the M12s must ultimately terminate into a wired connection (the PLC input) somewhere. If you need to retain the M12s, I'm sure Banner and others make terminal blocks that interconnect multiple M12s to a wired cable (with and without a connector plug on the other end).

Nothing wrong with being REALLY new to industrial controls, but make sure your boss knows that, too!

CeCo3
 
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yep, I just misunderstood what you were saying about the sensor connections ...



Automation Direct (the same place that sells the AD PLC you mentioned) also has the “wiring” stuff you’re talking about ... I personally haven’t used them - but I’m sure some of the other forum members can guide you ...



click this link and then go to the “Terminal Blocks and Wiring Solutions” menu selection ...



if you’re REALLY new, here’s a snapshot that I just took of one common type of wiring layout ... basic ideas: run a strip of DIN rail ... snap terminal blocks on the rail ... run a strip of wiring duct parallel to both sides of the terminal strips ... if done correctly, this will keep the wires neat and professional looking - and make for easier component troubleshooting and replacement in the future ... note: the pictures are from some of the equipment that my students use for lab exercises and not actual industrial wiring - but they should give you the general idea ...



rail.jpg




the shot below shows the idea behind the “shorting combs” mentioned by SLC_Integrator which can be used to tie several adjacent terminal blocks together electrically ... you can just use short pieces of wire for the same purpose - but the combs (some call them “fans”) are usually worth the money on larger projects ...



comb.jpg





quick question: are you SURE that this project is going to work - or are you sticking your neck out on the chopping block as you spend the bo$$’s money? ... if you just want to test out the basic ideas, most of us “been-bit-before” guys would do some “breadboard” experiments first - by hooking all of the components together (usually with wire nuts, baling wire, duck tape, bubblegum, etc.) ... we usually don’t shell out money for “neatness” until (and unless) we already know that the rig is going to actually do what we want it to do ...



good luck - and keep us posted ... wish I had more time to play ... looks like OZEE and others already had the AD source idea ...
 
Thank you all, once again. I think I am catching on now. Thanks for the pictures Ron. That really got the point across. I have looked at the panels pictures before and have been VERY impressed with Eric's work.
Fortunately for the owner of my company, and unfortunately for my wife, I am doing this research and design on my own as I am too busy during work hours to put in the time. That is where the limited funds come in. I am testing theory with little chunks at a time on smaller scales and if I gain confidence that it can work, I will look for the big bucks to manufacture from the company and then perhaps look to manufacture for others. In addition to the full time job/family/machine design, I am also on the 20 year plan at a local Community College studying Mechanical Engineering, because I like to learn.. So any knowledge gained from this experience will be a plus.

The only ??? that I have with whether or not the system will work is finding an automatic spray gun that will spray adhesive for my process. Typically these are designed for accurate application of paint, not messy coverage of adhesive. I am in contact with vendors of such products and they make me believe it is all possible, so that is where I stand today. Before I find the spray gun that will work, I will leave the details beyond the solenoid valves out of the equation. But this has been a tremendous help!
Thank you again.
 

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