Sinking And Sourcing I/o What Is The Most Common?

WHEN DESIGNING A NEW PLC INSALLATION USING DC I/O WHAT IS THE MOST COMMON SINKING OR SOURCING? THANKS.

It is always a big confusion from various manufacturers about sink and source terminology. Ex: mitsubishi terminology is diffeent than A-B terminology.

The most common is Sinking Input and Sourcing Output based on A-B definition.
Sinking Input: A positive voltage signal from the sensor to the input =1. Sensor connected between +24V and input.

Sourcing output: A positive voltage from the output =1, Load connected between output and 0V.

It is your option to use Sinking or Sourcing base on your system

if you have encoder most of them working NPN so you need
Sinking or Sourcing ?

I think the definition should be NPN inputs mean the signal from
the sensor is (-) or PNP mean (+) same for outputs in that way
there is no confusion.

ArikBY,
The sinking/sourcing relationship is not necessarily as simple and straight forward as you suggest.

http://www.plcs.net/dcforum/DCForumID1/2645.html

MACI,
As far as Field Sensors (Inputs), there was a time (not long ago) when the selection was pretty limited. These days it seems that, for any given sensor, there is an NPN version, a PNP version, and quite often there is an NPN/PNP (selectable) version.

Also, not too long ago, some PLC's restricted the Input devices to one type or the other - at least, for a particular card. Some manufacturers provided both Sinking Cards and Sourcing Cards. That issue has just about disappeared. That is, these days, generally, PLC Inputs accept either type of input device.

Now, regarding Outputs, if you are using solid-state Outputs, they are either NPN-Sinking, or PNP-Sinking, or NPN-Sourcing, or PNP-Sourcing. Refer to the manual to determine the case for the particular PLC.

Of course, Relay Outputs don't care... as long as you are careful to maintain the proper relationship within any "grouped" Outputs.

As far as troubleshooting goes...
Each method has their own set of pluses and minuses. And in any case, you still have to determine the particular configuration before your readings make sense.

So, as far as which is more common in terms of a NEW construction, the real answer lays not in the historical evidence, but rather, in the current availability of the various versions.

Since there appears to be less and less difference between the availabilities of the various types, it boils down to cost. That would include the cost of the sensor and any extraneous expenses associated with the design and installation of the particular sensors - whatever those might be.

As far as which method is better...
It's getting to be more like "six-of-one or a half-dozen of the other".

Terry

What you say is not contradict what I said I try to make it simpel

when you talking in term of NPN or PNP about inputs and outputs

sinking/sourcing have no meaning when I purchase PLC I asking

NPN inputs and PNP outputs that describe exactly what I mean.
sinking/sourcing is somthing more philosophical.
As far as troubleshooting goes...because we are in most cases grounding the (-). in europe they use PNP for inputs and PNP for outputs
it make the system more safe.and reasonable.
that the reason you can find more and more PNP encoders something you hardly find before the CE.and other devices who working with PNP
output.
I find out that machine who made in Japan coming with NPN inputs and
the outputs can be either.
Whats common in US?

Most Japanese PLCs have selectable inputs (NPN or PNP dependant on the common) and NPN outputs (sinking). Most Europeans seem to go for PNP input and PNP output.
I am quite happy with NPN output but NPN input is a NO NO!!!! Ground a wire and turn on an input. Have seen some nasty results from that scenario.
ABs version of sinking/sourcing is definately different from all Japanese manufacturers. I agree NPN and PNP is more definative.
beerchug

That the idea with the PNP in and out. when you grounging a wire
if it is not (-) you get short cut .and evry thing stops.
that the idea behind CE.more safe.
you may ground the (+) too!!!!!(bad and confusing)
my opinion if you have mixed I/O dont ground nothing

Sink/Source, NPN/PNP, +Logic/-Logic

Then you throw in the IEC terms, Positive Logic and Negative Logic, it is no wonder that nubees get confused.

Out here in the automotive supplier market, PNP, (Sourcing or Positive Logic) is most common for inputs and outputs.

Thanks for all the great info on my I/O sinking sourcing question.

Thanks for all the great info.

Nowadays when I talk to a sales-Rep. I ALWAYS ask them for the schematic of the device.

I would ask them if a device is sourcing or sinking. They tell me things like "Well, its NPN" or its "PNP".

And when I tell them I don't give a darn about there technical knowledge (in a polite way of course ) they seem not to hunderstand my request.

They fail to know that with a different brands comes a different vocabulairy and that these words that are used are often the exact oposite from what there competition writes. I've even seen stuff like "The sourcing circuit" to find that the PLC card was the source.

They seem so certain about there statements but they only know one brand or two.

With the schematic it's so clear and easy to hunderstand. The other problem if find is that some manufacturers know only draw a blackbox type of schematic. If they don't show the load it even trickyer.