How to Use the Omron NX System Units

Hello this is Ray Marquiss, Senior Application Engineer with Valin Corporation, and you may know me from some of my very famous videos about using Omron and Intelligent Actuator products in automation applications. This video is going to discuss the use of Omron NX system units which are used when you're using the Omron, NJ or NX PLC's, or Ethercat couplers or Ethernet/IP couplers.

The NX system units are of the type that we see here. There is an additional NX unit power supply unit, an additional IO Power supply unit, an IO Power Supply Connection unit, and a shield connection unit. The Shield Connection unit is pretty self explanatory, so I don't cover it in this presentation. I've also listed the part numbers for these types of units so that you can take a screenshot and keep it handy for your reference. NX system units perform a function other than some IO.  They don't do communication, they don't do digital inputs, they don't do digital outputs, they don't do analog, anything like that.  It's just an accessory unit to help with the power system that you use on your CPU or your coupler.

The additional NX unit Power Supply Unit, which is just a really mouthful of a name, is used to power the NX units themselves. Basically, I think of them as powering the intelligence or the circuitry inside the IO units. The additional IO power supply units are used to connect and distribute power to your IO devices as well as to the outputs of the NX units.  If you have NX output units and you don't have an additional IO Power supply unit when you need one, then you will get no output power from your digital outputs and another outputs as well.  The IO power Supply Connection Unit is a convenience unit. It's used to connect power for your IO devices directly to the rack where your NX IO units are on the coupler or the PLC.

I've listed the part numbers here for you for the three different types of units that we're going to cover so that you can refer back to it or take a screenshot of it for future reference, but you may hear me reference in an NX-PD unit, or an NX-PF unit, or an NX-PC unit. Or I might say a PD unit or PF unit or PC unit, and those all mean the same thing. It's just an abbreviated version of the complete part number.

If you look at a system that has an NX PLC, like an NX102 or an NX1P, this very complicated diagram is in all the manuals about four times, but if you just trace it out, starting with the power supply and then following the colored lines, it becomes simple. We’ll start with the dark blue line. That comes from the power supply and goes into the unit power supply terminals on the PLC. Once it's connected there, it's going to power up the PLC and the internal circuits.  Then it's going to bus some of that power through contacts on the side of the NX PLC out to your NX IO units. And so that power is bussed right from the CPU with the same power supply that you connect to the CPU. This is represented by the light blue lines in the graphic, with the arrow pointing up.

If you follow the red line, this is our additional IO Power supply unit.  This is going to provide power for your devices like sensors or solenoids or relays, and it's also going to provide the power that will switch through your output units. In this example, we see that we have the first NXPF unit, which is a requirement when you have an NX series PLC, you must have one of those. If you continue following the red line, you'll notice that it goes out to 2nd NX-PF0730 and that's because, through calculations that I'm going to show you later, it was determined that another power supply unit was needed in this application.  It's connected to the same power supply as the first NX-PF0730.
If we go back and talk about the next unit power that comes through the dark blue line and then through the CPU to the light blue line, you'll notice that it goes to the right and then stops at another NX-PD1000. Another additional NX Unit Power Supply Unit. That's because when we created our hardware configuration in Sysmac Studio, it popped up a warning that said we needed to add this NX-PD1000 in order to power up the units that we had in there. This will be shown in a slide later on.

If you're using a coupler, it's a little bit different.  Here we see a coupler, and you can see that on the coupler itself, there are terminals for both types of power.  There's connection for the internal circuit power and connection for the IO power. And so you do not need an NX-PF unit when you're using a coupler unless you exceed the capacity of the contacts in the coupler here.  We'll see how to calculate that in a little bit.

Here's a slide that shows the use of the IO power Supply connection units. Those are the units that I said in the beginning were sort of for convenience so that you can connect all of your wires for your devices to the same place that you're connecting the output wires from your devices or the input wires for devices.  If you look here we have a transistor output unit in a three wire device. Let's say it's some kind of solenoid, and it needs to be powered as well as switched. So you can see that the transistor output unit connects output 12 to the three wire device, and then we've added IO Power Supply connection units so that we can connect the ground and the voltage to the device to power it up right here at the same unit. So, rather than creating a bunch of terminal blocks in your panel that are for bussing or splitting the 24 Volt power supply out so that you can make multiple connections to the same power supply, we provide that capability with these units added to the node or the PLC that you're creating with the NX units on it.

Down at the bottom I've got the part numbers again for you.  The PC-0020 is for the voltage connection, the PC-0010 is for the G Connection, the ground connection, and then the PC-0030 has IOG and IOV.  Every output or input unit that Omron sells has a wiring diagram like this to give you examples of how to wire it up and give you all the specs.  We’ll be looking at parts of those in a minute. Just to note, some of the output units have IOV, IOG or both connections on them already. As you can see in this unit, the transistor output unit OD3121, which is just a four point unit.  Since it has so much space because it's only using four points instead of eight or 16, it has the IOV and IOG connections right on the transistor output unit itself, so you can land those wires right there. You don't need those additional PC units.

Here's a note about the NX PF0730.  These are the NX-PF units, and also about the IO connection units. What we're saying here is that when you provide the NX-PF0730 and you connect the power to it, that provides power through that red line that we were discussing earlier. The power to power up your devices through the NX PC units is also provided along this same path. And so the power that goes through those connection units is also used in calculating how many NX-PF0730s, or NX-PF units, you need.

A note about the NJ CPUs: the NJ CPUs do not allow NX IO units can be connected to the side of them like the NX CPUs do. NX IO units are used with the NJ PLC over Ethercat using an Ethercat coupler. 

Another note about NX1P PLC use. If you look at the spec sheet for NX1P, you can see that it says that you can attach 8 NX units to the CPU itself. That's eight NX units Max, and any NX unit that starts with “NX”, whether it's an input or an output or one of our system units, counts towards that max. So if I had one output unit and two system units, that would be 3 units total. So just remember that these system units count in the number of units that you can use when attached to a PLC.

How many do I need if I am building my system? Do I need to add additional NX unit power supply units?  Those are the NX-PD1000s, and that depends on the configuration. This one’s easy because you can check for the NX unit power supply requirements in Sysmac Studio. In other words, if you go into Sysmac Studio and you configure your hardware with the NX units that you're going to be using, then it will show you if you need additional NX-PD units. When it comes to the NX-PF units, how many you need is going to be determined based on a few factors. If you're using an NX102 or NX1P, you need at least one of these. You have to have one if you're using one of those PLC's. If you're using only Ethercat or Ethernet/IP couplers, you don't need at least one. You may need one, but it's not required that you absolutely have one. And then after that first one that's kind of required for the NX102 and NX1P, you have to do calculations to determine how many units you can connect to one NX-PF unit, and there's a manual number W578 that goes through that.  We're going to go through it here as well.

As far as the NX-PD units, in order to determine how many of those you need: if you create your configuration in Sysmac Studio, as I've done here in this graphic, you'll see some exclamation marks that I've circled here and then you'll see power supply power and available power that I've also circled in the information window that you'll see while you're doing this. What that means, the red circle on the right, means I've used 11.05 watts out of 10 watts available from the connection that I've got to the power supply, so I need to add an NX-PD unit here in order to be able to power up those last two modules on the right. In the bottom graphic you can see I've added the NX-PD unit and those exclamation marks have gone away. And if I click on that power unit I can see that I'm using 1.65 out of 10 watts of available power for that particular NX-PD unit. It's the additional one that I've added.  So it's really easy just put your configuration in Sysmac Studio and you'll be able to determine if you need NX-PD units.

As far as figuring out how many additional IO power supply units you need, those are the NXPF units, the only one hard and fast rule for these is that you must have at least one when you're using an NX1P or an NX102 [only mandatory on NX1P if connecting NX units to the end of the CPU]. The need for additional units is calculated using info from the specifications for the NX IO units and for the input and output devices connected, so I can help you with what you need for the NX IO units, but as far as the input and output devices go, you must get those spec sheets on your own. We're going to add up all the current consumed by the PF0730 itself, any NX input units, any NX output units, all your connected devices and then, it's not shown on here, but also we need to add up power used by any other NX system units, normally the NX-PC units.

I’ve got a very simple example that we're going to go through. And it's from Omron’s manual, but the Omron manual is incomplete at this time, so I've fleshed this out a little bit more. This example uses 4 laser measurement sensors from Omron’s product line, called the Omron  ZX2-LDA11, and I've got spec sheets for it on the following page.  It doesn't matter if this [NX-PF0730] is connected to a CPU or wherever it's connected, we are calculating whether we need additional NX-PF units based on what we see here, which is we've got two IO units connected to an NX-PF unit. And then we've got our devices.  So we've got the four laser measurement sensors, and we'll see how we calculate this all out.

Up until now, we've been talking about the system units, and one of the types of system units we mentioned was the NX-PC units. Those are those connection units. And you notice in the graphic for the previous slide, there were no NX-PC units in there and the question could be why not? Why didn't we have those in that example? And why aren’t we going to worry about them while we go through this example?  But the answer is simple, and that is that the input unit and output unit selected for the example have the IOV and the IOG connection built into them like I had shown in an earlier slide. So those will be providing power to power up the sensors that we're going to be talking about, and there's going to be a part of the calculation that includes how much power is going to come through those connection points?

First, we're going to add up all the current used by the NX-PF units that we have, and right now we only have the one, and so it's 10 milliamps, and so I would keep a list similar to the one that you see on the page here, and I would add 10 milliamps into that.  You see that at the bottom of the page NX-PF unit current consumption from the IO power supply is 10 milliamps, and you can see that there's a spec for that in on the spec sheet: “current consumption from IO power supply”. The next step is to go to the Omron spec sheet for the ID3317 input unit, and if we look at the spec sheet on that, I've indicated with the red arrows that the input current we need for our calculation is listed there at 6 milliamps. The current consumption, which is also required for calculation as indicated in red at the bottom, and it says there's no consumption, so I'll add those into the chart at the bottom of the page by adding zero for the current consumption and six milliamps per point for the input current that we need.

Next, we go to the output unit, and we can see that the output unit has 10 milliamps current consumption from the IO power supply unit. I will add that into our chart down at the bottom for 10 milliamps. So we figured out all that we need to know about our NX IO units and our NX system units for this system for this example.

Here's a section of the spec sheet for the Omron laser amplifier. It's connected to a laser sensor, the ZX2-LDA11, and I have highlighted some stuff here to make it easier to understand. We have outputs from the sensor and they are rated at 50 milliamps per point, and those are in the orange. We have the inputs to the sensor which are also rated 50 milliamps per point, and they are highlighted in green.  Then we have one power supply right there, highlighted in red. The power for that is going to come from the NX-PF module. The rating for that part is 125 milliamps per sensor. In our example, we're going to have four sensors, but we're only going to use one input and one output from each one, just for the example. So imagine we're using the “pass judgment” output that you can see there, and we're going to use the pink line, which is the load off (that's the laser off input) to the amplifier.  Since we're using four of these sensors, and we're using one input and one output from each one, it's possible that you could get that pass output that we were just talking about to be on from each of the four sensors, so you could potentially have four of the outputs on at a time, meaning that four of the inputs on the input unit would be on at the same time, and when we are calculating these numbers, what you're doing is you want to calculate based on how many inputs or outputs are going to be on at the same time. It's not always the case where you calculate for the fact that every output is going to be on on an NX IO unit or every input is going to be on. It's not always that way.

Here's where I got that info for the sensor. You can see that the judgment outputs are 50 milliamps and the sensor power supply is 125 milliamps. Here I've highlighted them in red. I've made a chart that shows the inputs and the current consumption for those and also the outputs and the current consumption for those. I've got four points of inputs. Those are inputs on the NX units. So that would be going to an NX input module and they’re 50 milliamps per point. And then I've got four outputs going from the NX unit back to the laser sensors. And the connected loads draw 125 milliamps per sensor. And then each of the connected outputs draw 50 milliamps, so that's 50 million amps per point. If we add it all up, and I know that you probably weren't taking notes, but you can go back and rewind the video to the appropriate pages to confirm my numbers here, but the NXPF unit took 10 milliamps, the ID unit used 0 milliamps plus six milliamps per point, plus 50 milliamps per point for a total of 224 milliamps.  Then the NX-OD unit used 10 milliamps plus 125 milliamps x four points. That's for our laser sensor power, and then 50 milliamps x four points for a total of 710 milliamps.  That’s 10 milliamps plus 224 milliamps plus 710 milliamps to give us .944 amps.  A little less than an amp.  The maximum power that the NX-PF units can provide, or at least the PF0730 that I've chosen for this example, is rated at 10 amps. But when you're using it with the CPU, you can have only four amps or less on that unit.  We are at 0.9 amps, so we’re much lower than the four amp capacity. I've highlighted that note by the way, here in blue about using 4 amps, even though it's rated at 10 amps. If you're using it on a coupler, the assumption is that you could go up to 10 amps.

After you've calculated the current consumption, you need to calculate the voltage drop using the numbers that you came up with after you calculated the current consumption.  There is a chart in manual number W578, and in that chart it tells you if your current consumption total was one of these numbers between one and four amps, then you will use a voltage drop from the right hand column based on that. In our previous example, we came up with .944 amps, which is about an amp. And the chart shows us that it's a .02 volt drop per unit. We have two units, so we calculate .02 * 2 is equal to .04. We started with 24 volts and we subtract the .04 that we just came up with. And that is going to leave us with 23.06 volts. Now we need to check the specs on our connected devices to make sure that the resulting voltage after the voltage drop is sufficient for them.  If the voltage drop is too much then we need to add another NX-PF unit to reduce the voltage drop, even though we may not have exceeded the power, the current consumption available.

So when you're using an N series PLC or coupler, an NX-PD unit may be required and Sysmac Studio will advise you if one is required as you're configuring your hardware.  You can do that before you actually make your purchase or build your final bill of materials. When using an NX1P or an NX102, a PF unit is required. You have to have at least one and then you need to calculate if that's going to be the only one you need, or if you're going to add more. When you're using a coupler an NX-PF unit may be required if you calculate that you're going to exceed the ratings for that coupler and its connections on it.  So determine the number of PF units needed by performing the calculations that we just outlined and everything is going to be great. Your life is going to be wonderful and you'll be able to buy that new car and the great big house that you wanted.

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