Point IO rack size

the_msp

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Looking to install a E/IP Point IO rack at maximum capacity (63 modules). Been reading up a few things, am I correct in saying that;


  • Get the series B AENT(R) as series A is flaky with 63 modules installed
  • AENT(R) can take 8 modules
  • Follow the 1st 8 with 1734-EP24DC
  • 1734-EP24DC can take up to 17 modules
Would a 1734-FPD do the same job as an EP24DC if I put 24Vdc into it? Or is it purely for use when you want to say install a 230VAC input module in the rack?
 
If it's that much I/O, I would personally be looking for a higher-density platform. But that's not what you asked !

The 1734-FPD is purely for isolating the Field Power bus. It doesn't inject power to the POINTBus to run the modules like the 1734-EP24DC or 1734-EPAC do.
 
Hi,

The AENT is able to provide 1000mA for module bus power, and the AENTR 800mA. Each Point I/O module is (typically) 75 mA (some vary depending on type). So just add the EP24DC wherever you need to add more bus power.

As Ken said, the FPD is used to supply field output power independent of the AENT/EP power supply - maybe for separately supplied/protected outputs for example.

Regards,

Rob

2014-12-07_014239.png
 
OK Thanks. So I would use the FPD if say I wanted all my outputs grouped together, so that an e-stop would kill all outputs? (By having the FPD supply fed from the contacts of an E-stop relay)
 
Yes, the 1734-FPD is how you separate segments of the I/O power bus.

I use them to isolate my analog from my discrete (optional), or isolate my AC from DC (essential).
 
Point I/O Adapter Connection Limits

Sorry for the late reply. I read this the other day, but only got back to reply to it today...

the_msp said:
Looking to install a E/IP Point IO rack at maximum capacity... (63 modules)...

Personally, I'm with Ken on this one. I would not be too keen on adding the full complement of 63 modules to any Point I/O adapter when they can be possibly better segregated or indeed, where another platform might suit better - but if needs must, here are some further considerations...

The maximum of 63 modules for a Point I/O adapter is known as a "hard" limit. This basically means "...it is possible, but only if...". As well as power distribution and current draw considerations, you may also have connection limitations to consider here. The AENT has a limit of 5 "rack optimized connections" and 20 "direct connections". Only one of those 5 "rack optimized connections" can be an "owner" of the I/O modules i.e. can read/write to the modules.

It all depends on the bigger picture...

What mix of 63 I/O modules do you intend to add to the rack?
How many separate devices will need to communicate with the rack, or parts of the rack?
If more than one, then how many of them need to be an "owner" of unique I/O data within the rack?

If you were adding say, 63 digital I/O modules, then you could have one "rack optimized connection" from one "owner" controller to all 63 I/O modules. Similarly, up to four other "listen-only" controllers could use a "rack optimized connection" to the same 63 I/O modules. i.e. they can read the status of the 63 modules, but cannot write to them. This would be fine if you are only adding 63 digital I/O modules, and only looking to "own" the 63 modules from one controller.

As Point I/O is a distributed system, a user could be locating a lot of I/O together in one remote area, such as in the same enclosure, and then attempting to access parts of that I/O data from different controllers. If all placed in the same rack i.e. all under the same adapter, it may be possible that there are some modules, or groups of modules in that same rack, which will require a different "owner" to the other rack members.

If, for instance, 20 of 63 digital I/O modules require a unique "owner" who can read/write them, and the remainder of the modules require a different "owner" who can read/write them, then the first 20 would use up the one available "owner rack optimized connection" for the adapter. This means the remaining modules cannot be separately "owned" while residing under this same adapter. They would have to be placed in their own rack under another adapter. Or, one controller would have to own all 63 modules, and then indirectly use produced/consumed or messaging between other controllers that require ownership of some of the I/O data.

This adds complexity to the system, whereas splitting out ownership across separate Point I/O racks would simplify the setup. The trade-off is that you use more adapters, and it limits the number of modules per rack according to the ownership requirements.

Example layout...

63 digital I/O modules
A mix of 6 data users (Owner/Listen-Only)
All Point I/O to be installed in the same enclosure.
How many AENT(R) adapters will be required to segregate ownership?

1 Adapter = 5 rack optimized connections - 1 x Owner and 4 x Listen-Only, 20 direct connections
Owner = Controller that can read and write to modules under the same adapter in the same rack.
Listen-Only = Controller than can read I/O status only.

Controllers and their uniquely required access within the 63 modules:
Controller 1 = 07 Digital Input and 03 Digital Output modules (10 modules)
Controller 2 = 10 Digital Input modules (10 modules)
Controller 3 = 10 Digital Input modules (10 modules)
Controller 4 = 10 Digital Input modules (10 modules)
Controller 5 = 05 Digital Input and 05 Digital Output modules (10 modules)
Controller 6 = 04 Digital Input and 09 Digital Output modules (13 modules)

Controller 1 needs to write to Output modules, so it will require an owner connection. So it will use the one "owner rack optimized connection" available for the first adapter. This leaves 4 "listen-only rack optimized connections" free on the first adapter.

Controllers 2 - 4 do not need to write to any outputs, so they can use 3 of those 4 "listen-only rack optimized connections" available on the first adapter, leaving one free. So the modules for Controllers 2 - 4 can reside under the first adapter.

Controller 5 needs to write to Output modules, so it will require an owner connection. As the "owner rack optimized connection" is used on the first adapter, a second adapter must be used. This then leaves 4 "listen-only rack optimized connections" available on the second adapter.

Controller 6 also needs to write to Output modules, so it will also require an owner connection. So a third adapter must be used. Again, using the one "owner rack optimized connection" available to it, and leaving 4 "listen-only connections" free.

So 3 AENT(R) adapters are required to facilitate these 6 data users...

Adapter 1 = 40 Digital I/O modules (1 Owner/3 Listen-Only)
Adapter 2 = 10 Digital I/O modules (1 Owner)
Adapter 3 = 13 Digital I/O modules (1 Owner)

-----------------------------------------------------------

If not all Digital I/O modules?

Analog and Speciality modules each use one of the 20 "direct connections" available per adapter. This limits you to 20 analog or speciality modules per rack.

Example layout...

63 mixed modules
A mix of 4 data users (Owner/Listen-Only)
All Point I/O to be installed in the same enclosure.
How many AENT(R) adapters will be required to segregate ownership?

1 Adapter = 5 rack optimized connections - 1 x Owner and 4 x Listen-Only, 20 direct connections
Owner = Controller that can read and write to modules under the same adapter in the same rack.
Listen-Only = Controller than can read I/O status only.

Controllers and their uniquely required access within the 63 modules:
Controller 1 = 13 Digital I/O modules, 02 Encoder modules (15 modules)
Controller 2 = 20 Analog I/O modules (20 modules)
Controller 3 = 20 Analog I/O modules (20 modules)
Controller 4 = 05 RTD modules, 03 Counter In modules (8 modules)

Controller 1 needs to write to Output modules, so it will require an owner connection. So it will use the one "owner rack optimized connection" available for the first adapter. Controller 1 also has 2 encoder modules, which will use a "direct connection" each, leaving 18 free.

Controller 2 uses 20 Analog I/O modules. Each will use one "direct connection". 18 of these could use the remaining 18 available on the first adapter. However, this would mean the last 2 would have to go to a new adapter, so a separate adapter, using all of its 20 "direct connections" would be preferable here.

Controller 3 also uses 20 Analog I/O modules, which will require 20 "direct connections", so another adapter would be required here, again, using all of its "direct connections".

Controller 4 uses 8 speciality modules - 05 RTD and 03 Counter In modules. Each of these uses a "direct connection", so another adapter would be required here, using 8 and leaving 12 "direct connections" free on the last adapter.

So 4 AENT(R) adapters are required to facilitate these 4 data users...

Adapter 1 = 15 Digital I/O modules (1 Owner)
Adapter 2 = 20 Analog I/O modules (1 Owner)
Adapter 3 = 20 Analog I/O modules (1 Owner)
Adapter 4 = 08 Speciality modules (1 Owner)

These are just a couple of examples of how a slightly more complex arrangement can end up limiting how many connections can be used through the adapter, and hence, the maximum number of modules permitted per adapter.

Even if the above does not relate in any way to your intended setup, it's still no harm to know these things going forward.

TBC...
 
Some further detail...

Just a couple more specifics...

the_msp said:
...am I correct in saying that;

  • Get the series B AENT(R) as series A is flaky with 63 modules installed
    I'm not sure what you've heard or read, but the Series A AENT are not as good with noise immunity. Something that was rectified when designing the Series B AENT hardware. Some might argue that they are both "flaky" with 63 modules on their rack, but a lot depends on the mix of I/O, proper power distribution, and if relevant, proper handling of thermal dissipation. They can struggle in poorly ventilated tight spaces, but that goes for either Series A or B adapters. While we're on the "Series" side of things. Note: You must use Series C Point I/O modules with the AENT(R) adapter. Series A or B modules will not work.
  • AENT(R) can take 8 modules
    As quoted, the AENT(R) can provide 800mA of POINTBus current to modules to the right of it. If using standard digital I/O modules only, which typically draw 75mA each, then 800 / 75 = 10 modules maximum per AENT(R) adapter. The AENT does slightly better with 1000 / 75 = 13 modules maximum. However, if using relay output, analog, or some of the speciality modules, then their current draw can vary between 80 - 220mA. For example, the relay output module 1734-OX2 typically draws 100mA. So in this case, you could only use 8 modules with an AENT(R) adapter. If using an analog temperature input module 1734-IR2, they typically draw 220mA each. So you are restricted to using only 3 modules per AENT(R) adapter.
  • Follow the 1st 8 with 1734-EP24DC
    Again, the number of modules on the adapters power supply will vary depending on the modules used, but yes, use the EP24DC to power the next group of modules until its current capacity is reached.
  • 1734-EP24DC can take up to 17 modules
    The EP24DC provides an additional 1.3A POINTBus current to the modules to the right of it. The maximum of 17 modules per EP24DC is based on using the lower rated standard I/O modules, again, typically 75mA each. So that's 1300 / 75 = 17 modules maximum. So similar to the above, this maximum is determined by the mix of modules used.

the_msp said:
...Would a 1734-FPD do the same job as an EP24DC if I put 24Vdc into it? Or is it purely for use when you want to say install a 230VAC input module in the rack?

The guys have answered this pretty well, but just to add...

Another reason to use the FPD, is when you need more than 10A of field current. The adapter's power supply provides 10A maximum of field power. If more is required, you can add an FPD and wire a higher rated power supply.

the_msp said:
...So I would use the FPD if say I wanted all my outputs grouped together, so that an e-stop would kill all outputs? (By having the FPD supply fed from the contacts of an E-stop relay)

Sample E-Stop Rack Configuration for 2 groups of I/O using different supplies. Both supplies are separately interlocked through safety outputs on an E-Stop safety relay...

You can use the EP24DC and the FPD to segregate supplies as follows:
1. Install the Adapter Module in the left-most position.
2. To the right of the Adapter install the FPD for the isolated 24V DC or AC field power.
3. To the right of the FPD install the I/O modules required for the first group, up to the maximum allowable POINTBus current for the adapter.
4. To the right of the I/O modules install an EP24DC, allowing for an additional 1.3A of POINTBus current.
5. To the right of the EP24DC module install another FPD for the isolated 24V DC or AC field power.
6. Install the remaining I/O modules for the second group with POINTBus current totalling 1.3A or less.
7. Install 24VDC power to the adapter module and the EP24DC module.
8. Install the field power to the FPD adapters. Different power supplies (AC or DC) can be used, sourced through the E-Stop relays outputs.

During an E-Stop condition, the Point I/O modules can now remain powered and communicating on the network, without their field I/O power.

Regards,
George
 
Thanks Ken, and George for your comprehensive replies, I learned a few things. The intended application for this is not to control a plant but on my "plc wall" (think 8x4 sheet with trunking, din rail, every PLC I work with as a hot spare). It will be used for talking to other PLC's via digital IO (old PLCs such as SLC 150, new but no-brand PLCs with no ethernet comms). For SAT testing repeat order panels.

It will mainly talk to a CPX-L32E, in the near future I intend on adding a CLX rack too but I can either only have one talk to the point rack at a time or setup messaging between them.

My reasons for going point IO:

  • Have 2x AENTRs (Ser A) 2x FPDs, 6x IE2C (ser C), 2x OE2C (Ser C) left over surplus from a previous job
  • Flexibility, can swap modules as required and even if I max out my rack and want to setup something different, remove the terminals from the 1734-TB
  • Price, IMO cheaper to get 2x IB8 than a 16 input CPX card, by the time you wire it from the card to a din rail terminal as opposed to going straight into the point IO
The majority of the modules will be IB8 or OB8. All the modules I have are 75mA each. As the rack will be in open air I shouldn't have any issues with heat. Shouldn't be any issues with induced noise as I have very little AC.



How does the ARM module work? Do you set it to what you intend installing there, say an IB8, and you can reference the IO as if it was that card?
 
the_msp said:
...It will mainly talk to a CPX-L32E, in the near future I intend on adding a CLX rack too but I can either only have one talk to the point rack at a time or setup messaging between them...

...Have 2x AENTRs...

If you have two adapters then you could consider, now or in the future, splitting the I/O between them? This way you could have the two Logix controllers owning a rack each. That might work if each controller needs only own a certain amount of your overall I/O count at any one time. But if one controller needs to own all the I/O at the same time, then that's a non runner, and yes, you would have to indirectly own the I/O between the controllers.

the_msp said:
...IMO cheaper to get 2x IB8 than a 16 input CPX card, by the time you wire it from the card to a din rail terminal as opposed to going straight into the point IO...

I won't argue the price point, but you don't necessarily have to wire to terminals from the CompactLogix modules. You can also wire directly to the modules that have RTBs.

For breaking out 32-point I/O on a CompactLogix, we use the terminated modules (1769-XX32T) with the MIL socket, and drop down to termination with 1492 cables. Sometimes we use the IFM terminating modules for the field wiring. Making off the 40-pin socket headers on the other end of the cables is real fun! I'm looking at a couple in a box here I got yesterday that I have to make off for a project we're doing during the Christmas break.

the_msp said:
...How does the ARM module work? Do you set it to what you intend installing there, say an IB8,...

Yes, it is recommended to set the key on the mounting base and the Address Reserve Module (ARM) to the same as the future intended module.

the_msp said:
...you can reference the IO as if it was that card?

No, while the ARM produces one byte of I/O data, it does not consume any data. However, the data serves as no real use as the module for that slot in RSLogix 5000 should normally be set to Inhibit.

The ARM just reserves a node address/slot for a future I/O module and is not selectable under the I/O Configuration in RSLogix 5000. So you add the future intended module to that slot and then Inhibit it. This stops the controller from continually trying to connect to a module that is not communicating because it does not exist, potentially wasting connections.

When you eventually swap in the module proper, you simply remove the Inhibit and the module is ready to go.

Regards,
George
 

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