24VAC Remote I/O Ethernet Adaptor

[ASF]

I have to shoehorn a small remote I/O rack (6xDI, 2xDO) into a machine that only has a three phase supply with no neutral, and uses a transformer for 24VAC controls.

Anyone know of an Ethernet/IP remote I/O solution that can handle 24VAC? I'd prefer to avoid a three phase DC power supply if I can, not least because there's no space.

The Ethernet/IP adaptor itself would need to be able to be powered with 24VAC, and the digital inputs would be 24VAC (unless the card can rectify it's own 24VDC and spit that out - the inputs are all dry contact). Digital outputs will just be driving relays so can be anything.

An AB solution would be ideal (talking back to a 5069 Compact Logix, and customer preference is AB) but open to other solutions.

 

[Saffa]

Haven't seen anything modern that is 24VAC in terms of remote IO.

Couldn't you throw a 24VAC to 24VDC PSU in, if the 24VAC transformer is big enough of course? Something like this...

https://www.powerstream.com/24vac-to-24vdc/

 

[Saffa]

Sorry i missed the fact that space is at a premium... hate those jobs when the cabinet was too small for the original gear, let alone the upgrade! Good luck.. there's always space on the side walls of the panel!

 

[JesperMP]

There are some very compact 24VAC to 24VDC PSUs.
For example Phoenix Contact STEP-PS/48AC/24DC/0.5.
Only 18 mm wide and sits on the DIN rail. Has 12W output, is that enough ? Wont be enough to drive valve coils, but you can have a remote IO module with relay contacts that drive valve coils from the 24VAC.

There are also many 2-phase or 3-phase AC to 24VDC PSUs, but probably not as compact as the module mentioned above.

 

[geniusintraining]

An AB solution would be ideal (talking back to a 5069 Compact Logix, and customer preference is AB) but open to other solutions.

Why not use Point I/O? https://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1734-sg001_-en-p.pdf

EDIT: I have never done it before but how about a CLICK? Not sure how hard it would be to connect to a CompactLogix but they list Ethernet/IP messaging https://www.automationdirect.com/ad...(stackable_micro_brick)/plc_units/c0-10dd2e-d

 

[OkiePC]

All Click PLCs require 24VDC for power. The P2000 series does offer a power supply that will accept 24VAC. I am not sure if a P2-550 supports Ethernet IP adapter mode, but I suspect it can.

https://www.automationdirect.com/ad...ble_controller)/base_power_supplies/p2-01dcac

https://www.automationdirect.com/ad...grammable_controller)/cpus_-a-_remotes/p2-550

But the smallest base they sell for it is 4 slots.

EDIT: Forum post about adapter mode:
https://community.automationdirect....n-between-compactlogix-controllogix-and-p3000

 

[geniusintraining]

I saw the OP 24 and never looked at the AC/DC part.. cant you just put in a bridge rectifier? then your world is wide open to options

 

[GaryS]

Why not use a 24VDC input and use a full wave bridge rectifier on each input
I have seen them small enough that it wouldn't take up any additional space

 

[ASF]

Thanks everyone. I'd prefer not to get into bridge rectifiers and tricks like that - it does need to be still "off the shelf" and "industrial" spec.

I like that Phoenix option, but it's 48VAC and I only have 415VAC and 24VAC. Doesn't appear that they have a 24VDC version. Makes sense - typically if you're going to rectify to 24VDC, you want to start somewhere around 28VDC.

Looks like it's going to be a three phase DC PS, and it's going to be ugly.

 

[ASF]

Haven't seen anything modern that is 24VAC in terms of remote IO.

Couldn't you throw a 24VAC to 24VDC PSU in, if the 24VAC transformer is big enough of course? Something like this...

https://www.powerstream.com/24vac-to-24vdc/

Something like this may be an option, I'm just hesitant because again, I need something off-the-shelf and industrial looking. I'm also not convinced 24VAC will really rectify to 24VDC properly. It'll probably be closer to 20VDC, and this job has enough complications without adding in "is my voltage high enough". Have you ever used one?

 

[AustralIan]

Siemens LOGO! has Modbus TCP, and 24VAC. Not sure your feelings on the modbus AOIs, or using a controller as RIO.

 

[ASF]

Siemens LOGO! has Modbus TCP, and 24VAC. Not sure your feelings on the modbus AOIs, or using a controller as RIO.

TBH this solution probably falls into the "just because you can, doesn't mean you should" basket.


Fortunately I have had a win - I've just learned that the machines have not yet had their power supplies run (or quoted). Which means I can specify a three phase + neutral supply, and solve all my problems at once. Just because the machine doesn't need a neutral, doesn't mean I can't have one!

 

[KirkC]

Since you are running an ethernet cable into the panel any way you could just inject the 24vdc onto the ethernet cable and un-inject it in the panel to power the remote IO. Use a passive POE injector.

https://www.amazon.com/BeElion-Pass...+a+passive+poe+injector&qid=1622419998&sr=8-6

 

[ASF]

Since you are running an ethernet cable into the panel any way you could just inject the 24vdc onto the ethernet cable and un-inject it in the panel to power the remote IO. Use a passive POE injector.

https://www.amazon.com/BeElion-Pass...+a+passive+poe+injector&qid=1622419998&sr=8-6

Now that's a creative idea! I like that!

 

[Saffa]

Something like this may be an option, I'm just hesitant because again, I need something off-the-shelf and industrial looking. I'm also not convinced 24VAC will really rectify to 24VDC properly. It'll probably be closer to 20VDC, and this job has enough complications without adding in "is my voltage high enough". Have you ever used one?

I haven't used that particular model but I have used 24VAC to other DC voltage converters before. Busy building a little irrigation valve control panel that is taking 24VAC to 48VDC and needs to be PELV. Helios Power do a range of these but not DIN rail mount. They generally contain a rectifier and buck-boost converter, so higher DC out than in is certainly possible

But if you can have a neutral then finding a slim single phase 24DC PSU is going to be cheaper and easier.

That 24V POE option is also an idea but you would want to check volt drop. Most POE devices have built in regulators to step the POE voltage down to something like 5V or whatever they internally need, so a bit of volt drop from 50m of thin ethernet cable isn't an issue for those.