Point IO 1734 Allen Bradley - Input Sensor Hardware Installation Wiring Testing Programming Tutorial
Point IO is a critical component of a distributed control system. This hardware component from Rockwell Automation allows the end user to add nodes of inputs and outputs to their system within proximity of field devices. By doing so, costs of installation are reduced and the need of multiple PLCs is reduced if not eliminated in most situations.
From a practical standpoint, Point IO is a hardware block which communicates over ControlNet, DeviceNet or EtherNet and sends data to the master device. The master device is an Allen Bradley PLC which can be from the ControlLogix or the CompactLogix family. A major advantage of the Point IO platform is the fact that the user can pick the required input and output cards in order to satisfy the needs of their control system. In other words, the user may choose to have a very flexible node combination & save on the costs.
In this tutorial, we will be exploring the connections needed to add a SICK sensor to one of the inputs on the Point IO node. This procedure is the same for most sensors, relay based inputs and other devices commonly seen in a 24VDC based control system.
Working with Point IO Hardware
In this tutorial, we’re assuming that the user has established a connection to the Point IO hardware. Although you may still establish a connection to the sensor, the data sent to the PLC requires the network connection to be in place. Refer to the tutorial linked below in order to setup the connection over EtherNet/IP. Note that you may choose any other network based on your base module.
Point IO Hardware EtherNet Setup Tutorial
Here’s the hardware used for the purpose of the tutorial:
From left to right
The sensor we will be using is also displayed next to the Point IO module. It’s critical to understand the hardware characteristics of the devices wired to the Point IO nodes. Failure to select matching devices will result in damaged hardware which may be permanent.
The SICK sensor, the information of which can be seen in the image above, operates within DC 10 – 30V range. This means that we can select our input card to be the 1734-IB8. The reason for this of course is that our sensor is an input device and sends data to the card. Furthermore, it’s critical for use to note that the sensor is a PNP based device and that the 1734-IB8 card is SINKING. This concept is often misunderstood by engineers as well as technicians. The bottom line is that most North American systems will employ the PNP -> SINK scheme. Make sure that you match your devices properly. Otherwise, they simply won’t work together. To find out the type of device you’re dealing with, refer to the respective manuals & datasheets.
Wiring the Sensor to Point IO
Wiring a digital input into the 1734-IB8 card is straightforward. The card features 8 distinct inputs. Each input is tied into the terminal of the base which can be selected to be spring clamp or a screw terminal.
The SICK sensor we’ve discussed above has three critical connections which are common to many other input devices:
- 24VDC Power | Brown wire
- 0VDC Power | Blue wire
- Sensor Output | Black wire
Although the sensor may be powered from any source, the Point IO hardware allows the user to utilize certain terminals for 24VDC power for field devices. These terminals are located on the 1734-AENT or the 1734-EP24DC modules. Since there aren’t many terminals available for this purpose, it’s recommended to add distribution terminal blocks within the panel in order to accomodate other devices. However, for the purpose of our tutorial, we can land the blue and brown wires of the sensor directly onto the 1734-EP24DC power supply.
Lastly, the most important wire will carry the sensor signal to the Point IO hardware. Note that in reality, the sensor has two discrete outputs which are the opposite of each other. Depending of the need of the control system, the user may chose one output or the other. For many devices, the default output will be on the black wire; for some the white wire will carry a secondary output.
Testing Point IO Devices & the SICK Sensor
Now that the wiring is in place, it’s very easy to test the field device as well as the Point IO input functionality. This step is critical and has to take place before any machine is put into operation. It’s not rare to see sensors be miss-wired in the field as electricians land thousands of connections within a short period of time and thus mistakes can be made. Going through the equipment and making sure that the proper devices are landed on their respective inputs is critical. Furthermore, it’s not uncommon to receive defective or damaged parts from a supplier; testing is critical.
In order to test this specific sensor, it’s sufficient to place the reflector about 10 inches away and block the beam. By doing so, the sensor should transition between ON and OFF states and thus send the proper signal to the Point IO card. The visual indication of this transition can be seen on the sensor as well as the input card. The image below illustrates both of these locations.
Point IO in Studio & RSLogix 5000
The final step in this process is to make sure that the input we’re toggling comes into the PLC and can be seen in RSLogix & Studio 5000. Once we define the modules for the remote rack, we can navigate to the PLC scoped tags which will display the current status of the Point IO. In our case, the sensor should come in at PointIORack:1:1:I.0. Note that the 1 represents the first node within the module and the 0 represents the first input within that specific module.
For example, if we were to land the black wire into the second node into input #8, we should expect the PLC address to be PointIORack:1:2:I.7.
By toggling the sensor once again, we can observe the data transitioning between 0 and 1 on that specific address.
We’ve successfully integrated a SICK sensor into our Point IO module. At this point, other devices can be added to the same hardware & send data to the control system. By utilizing the Point IO platform, engineers are saving on installation costs while increasing system flexibility.
The SICK sensor we integrated is a simple digital input. However, the Point IO cards available for use are not limited to this type of input. There are AC cards, analog, timers & much more available. Make sure to read the documentation and select what’s appropriate for your specific application.
If you have any questions about this particular tutorial or Point IO in general, don’t hesitate to visit our forums.