Allen-Bradley / ControlLogix 1756

Every 1756 I/O module catalogue number, plus chassis, power supplies and the suffix decode. Current production and older generations.

ControlLogix is the large modular Rockwell platform and it is still in production, so this is a straightforward supply job quoted with a delivered lead time. We also carry surplus and used for the older 1756-L6x and L7x generations that are getting harder to find.

Read the suffix first

Rockwell states that certain 1756 catalogue numbers carry characters at the end that indicate additional features. This is the fastest way to tell two similar modules apart.

So a 1756-OB16IEF is an isolated, electronically fused, fast 16 point DC output, and a 1756-OB16IEFK is the conformal coated version of the same module.

Digital input modules

Digital output modules

Analog and HART modules

Each of these also exists in a conformal coated K version. The wider analog range covers voltage, current, RTD and thermocouple inputs and voltage and current outputs. Send us what you need.

Safety I/O

Two restrictions on these that matter.

The 1756-IB16S and 1756-OBV8S are only compatible with a Series C chassis. Fitting one into a Series A or B chassis will not work.

And because of its higher internal power dissipation, Rockwell says do not install a 1756-OBV8S next to any controller or communication module. That is a slot layout constraint, not just a purchasing one.

Safety modules also require specific RTBs or IFMs. Both have been agency certified using ControlLogix RTBs, so substituting a generic wiring system can invalidate the certification.

Chassis

Extended temperature versions are 1756-A5XT, A7XT, A10XT and the LXT variants. Conformal coated chassis carry a K, for example 1756-A13K. Chassis also carry series letters and the specifications differ between /B and /C.

Chassis are horizontal back-panel mount only and any module goes in any slot.

Power supplies

Each also exists in a K conformal coated version. A is AC and B is 24 V DC.

Sizing the supply, and why systems trip on startup

The 5.1 V rail is almost always the binding constraint. Most modules draw the bulk of their current there. Total output across all rails cannot exceed 75 W on the 75 series supplies.

A quick check. Count every module including the controller and comms modules and allow roughly 0.6 A at 5.1 V per module. If that lands above 5 A you need a PA75 or PB75 rather than a PA72 or PB72.

The 13 A supply is the better default, because it leaves headroom for the module someone adds in two years. Send us your module list and we will size it.

Controllers

The L7x controllers operate 0 to 60 degrees C. Note that if an XT module is used in a standard chassis it can only withstand the environment specified for the standard version. Mixing XT and standard hardware gives you standard ratings.

Three things to check before you order

Electronic keying

The controller checks module identity and revision against the project. If a replacement module has a different series or firmware revision from what the project expects, and keying is set to Exact Match, the module will not come online. It is physically identical and it still will not run.

Send us the series letter with the catalogue number, and the firmware revision if you know it.

RTBs and IFMs are not included

Rockwell states it plainly: 1756 standard I/O modules require either a Removable Terminal Block or a 1492 interface module to connect field wiring, and neither is included with the module. They must be ordered separately.

This is the single most common thing left off a ControlLogix order. Tell us the module and we will include the right RTB or IFM.

Studio 5000 version

Newer controllers require newer Studio 5000 Logix Designer, and a module too new for your software version may not appear in the catalogue at all.

What we can supply

Current production. Chassis, power supplies, 1756-L8x controllers, the full digital, analog, HART and safety I/O range, communication modules, RTBs and IFMs. Quoted with a delivered lead time.

Older generations. 1756-L6x and L7x controllers, earlier I/O module series and chassis series. Surplus and tested used.

That second point matters more than it sounds. If your project is built for a specific module revision, a used module of the right series is less disruptive than a new one that forces a keying change.

Related

Allen-Bradley overview. CompactLogix for the mid-range platform. PanelView for operator terminals.

Send us your catalogue numbers

For a new system, send the I/O list and we will specify chassis, supply, controller and RTBs as a complete rack with the supply sized properly.

For a replacement, send the catalogue number plus the series letter, and tell us your Studio 5000 version. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Rockwell Automation, Inc. Allen-Bradley, ControlLogix and Studio 5000 are trademarks of Rockwell Automation. All trademarks, brand names and catalogue numbers are the property of their respective owners and are used here for identification purposes only.