Rank beginner wiring question

I am in the process of building up a PLC trainer for my own educational use. It consists of a Micrologix 1000 (1761-AWA) and a PanelView 300 Micro (powered by a SOLA 24VDC power supply). I am connecting simple switches (toggle, momentary, pushbutton, etc.) to the 6 inputs, and then will connect various indicator lamps and possibly a small ac motor to the 10 outputs.

My question is this: Do I need to fuse each of the outputs separately? Also, the wire color for the 24VDC to the PanelView, should it be blue?

Thank you...

Jim

Blue is standard for +vdc, brown for -vdc. Aside from color codes to keep things organized, just be safe. Fuses are cheap. Also, you can easily power indicator lamps straight off your outputs, but use a relay for the motor...use 24vdc to actuate the relay and provide 120vac to your motor (fused!) There was a previous discussion that can give you more info and links here:
plctalk archive

Thank you for the reply, info, and link.

Jim

jdmartin8 said:

possibly a small ac motor to the 10 outputs

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What size is the motor? I hope you're talking about a really small AC motor. Your best bet might be to use a relay (or motor starter) to control the motor and let the PLC control the relay.

jdmartin8 said:

Do I need to fuse each of the outputs separately?

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Most people do it to aid in troubleshooting when a fuse does blow. On a machine or process, if you only protect power to the outputs with one fuse, and an overcurrent condition occurs, you blow the fuse....but you don't know immediately which output caused the fuse to blow. If you fuse every output individually, and the fuse blows, you can usually easily tell which one it is.

I think for a trainer, individual fuses would not be necessary. I would however include some kind of overcurrent protection for the trainer.

jdmartin8 said:

Also, the wire color for the 24VDC to the PanelView, should it be blue?

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Blue is "pretty much" a standard in the US. Of course, according to NEC you can use any color other than green, white (natural grey), or bare

Edit: Darn it -- WwIDGIEwW beat me to it....

Thanks, "93". Good information. Yes, I apologizing for not stating that I WILL be using a motor starter relay, but the ac motor will be very small, and low rpm (actually a timing motor drive from one of the industrial water softeners that I work on.)

Thanks again...

Jim

One of us is confused. It could be me.

10 outputs and 6 inputs???

How about 10 in and 6 out.

Many times I would love more outs then ins, but have yet to see one.

regards.....casey

+,-vdc

Hi,
WwIDGIEwW wrote this:Blue is standard for +vdc, brown for -vdc
Is it realy so in USA? Here in Europe, brown is allways +, and blue, sometimes white is -vdc. Black is output,signal etc (sensors)
/mihaly

Casey,

In reply to your post #6, I am the one in error. I don't know what I was thinking ! (interpret as Senior moment). I knew it was 10 in and 6 out. Sorry 'bout that !!

Jim

colors

In reality the US does not have any national standard for color codes of wire (except for green and white).

If I had my way, everyone building control panel would start to use the NFPA79 Electrical Standard for Industrial Machinery (UL508A is similar). This standard recommends (but does not require):
ungrounded DC control - Blue
grounded DC control - White with blue stripe
ungrounded AC control- Red
line voltage - Black
grounded AC - White or gray

In reality the US does not have any national standard for color codes of wire (except for green and white).

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I guess that depends on how you look at it.
NFPA 79 Electrical Standard for Industrial Machinery.
This states BLUE for ungrounded DC conductors and BLUE with WHITE stripe for grounded DC conductors.

One issue with this is there is no requirement to ground either conductor of a 2 wire supply under 50 volts.

I am familiar with (and got into the habit of using) the European method of Brown for +DC and Blue for - DC. I am not sure if IEC 204-1 stipulates this or not. I know it stipulates Light BLUE for neutral conductors. I have just seen and used it so long now its become a habit.

I think I will check if this is stipulated in IEC, either way I am going to see about getting the brown/blue combination used by NFPA 79. I wonder what it takes to get standards modified and accepted?

In this case I would like to see all the wire colors standardized on the international level. The same applies to how indicator lights should work.

Personally I wouldnt care if any government (would be helpful if they all did) accepted the standards or not, as long as we were all working with the requirements. Of course....not going to happen anytime soon.

Dont let me get started on a rant about programming languages....ie whats the point of establishing 5 languages when they ARE NOT THE SAME from brand to brand....OK end rant.

Didnt mean to do any hijacking...is it safe to use that word on the net?

One additional question along the same lines. Since this trainer will only have 1 Micrologix 1000 (1761-AWA), 1 SOLA 24VDC power supply, and 1 Panelview 300 Micro, should I just put in one long terminal block, and bring all the wires to that? I.E., 120VAC, 24VDC, all the inputs, and all the outputs?

I know that for a trainer, it really doesn't matter, but if I'm going to do it, it might as well be the correct way.

Thanks again...

Jim

Ron,

NFPA79 is not a required standard. It is optional. However the 2005 National Electrical Code (NEC) will reference NFPA79 but only for industrial controls/machine wired by "users". The NEC does not apply to OEMs. UL 508A (Control Panels) uses similar color coding but again there is no national requirement for UL listing.

Didnt say there was

First and foremost lets understand something...NEC is not a national standard even though it uses the word National in its title. It is accepted by all 50 states but is also modified...therefore there is NO national standard for any wiring in the US. There are applicable codes by each governing body within the US. OSHA uses its own standards which may or may not coincide with NEC code. I have not seen where the Federal government requires NEC to be established verbatim.

I have long understood this.
NEC is not a required standard but it is a standard that state/local/insurance companies base their code on and accepted.

NFPA is a standard...government required NO, neither is NEC in itself.

We can quibble from now to doomsday on this.

Fact there is no NATIONAL standard in the US except what is covered in OSHA safety.

FACT, noone offers a viable standard, in the US, for machine wiring except NFPA. Recognized by the government or not its still a standard.

So you can reference NEC all you want but it is NOT a US (national) standard...it is an accepted standard "adopted" but modified in many cases in ALL 50 states and US territories.

Been here done this.
What does it take to make a standard accepted?

I think its time we obtain a standard. The wiring and indicator light issue is a small part of what many of us do, it would be so much easier if we all used the same colors for the same thing.

I can offer time, webspace, or what may be needed if any are interested in developing or recognizing a standard. I am not sure what is needed but I am game to try if any are interested.

Just make sure you isolate your 120VAC section from your 24VDC section. Make sure the wire you use for the 24VDC is rated for the highest voltage that it may contact. Don't use analog signals in this same wire duct, unless conductors are rated as similar, and drain is after this 'contact'.

In Canada the standard is similar to European. Brown for +24VDC, Blue for 0VDC. Negative (-) ungrounded dc power is not used very often (anymore). It floats, especially over long distance and near other conductors.

John

Re: Didnt say there was

rsdoran said:

First and foremost lets understand something, NEC is not a national standard...

I have long understood this.

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Wow, a change of heart since the last NFPA discussion...