IO Modules

kellwein

Member
Join Date
Jun 2018
Location
St. Louis
Posts
7
What is the difference between a protected IO module and a regular IO module?
Are there any differences in how they can function or if they can or cannot input or output different signals?
- Also, I'm brand new to the field.
 
Without any more information about what modules you are referring to, here are some guesses:
Current overload protection - output modules.
Overvoltage protection - any module.
Environmental protection (coating) - any module.
 
Lol - not an exam question.

I am interning at a company and have been to this website a few times to get random answers to things. Today I registered so I could ask random questions of my own and get second opinions from others.

I am sorta going through a spreadsheet template and filling in my inputs and outputs. In this spreadsheet they have a
1794-OA16; Flex I/O, 16 Point, 110VAC Output Module
and
1794-OB16P; Flex I/O, 16 Point, 24VDC Protected Output Module

I understand that they are different Voltages and types of voltage but was wondering what the differences between their functions would be?
Should certain devices be protected over others?
Why would one not protect their outputs?
What does it even mean for the output to be protect?
 
If you have access to the Knowledgebase, (which if your company has a tech connect contract you can get access), Look up answer ID 18520
 
1794-OA16:
Module outputs are not fused. Fusing is recommended. If fusing is desired, you must supply external fusing (1.6 A, 250V AC slow-blow) or use the 1794-TBNF terminal base, if recommended.

1794-OB16P:

The output current is electronically limited to 1.5A and thermally reacts to the short circuit by removing power to the circuit. When the temperature of the transistor is greater than 150C, the transistor will turn off which in turn will turn off the output point. When the transistor cools to 130C, it will turn on again. This also reduces heat, allowing a longer, controlled surge current.
 
An Allen Bradley Protected DC output module limits the output current (1.5 amps with the 1794-OB16P) to prevent the circuit from getting to hot and shuts the power down in the event of a short.
 
Okay, I think all of this helps me get a basic understanding.
- Are there any devices that don't normally use the protected IO or some that always need them?
- Are they purely based on user preference according to the design?
 
It's mostly user preference or design requirements.

In my experience, DC outputs with over-current protection are very useful when the outputs are field devices with cabling that's at risk of damage (and thus short circuits). Anything with a festoon or cable track, or where cables can be pinched or struck by machine elements is a good candidate for protected DC outputs.

When I have wiring that's entirely inside a control cabinet, the odds of miswiring or damage are low, and I don't usually use protected outputs.

In recent years, DC distribution devices have also become popular that use "solid state fusing". I like to use those to divide bulk power provided to different parts or functions of a machine or control system, so that a short or overload on one part won't take down the power for another part. The Murr "MICO" products and the Puls "PISA" devices are the ones I've used.
 

Similar Topics

Hi First post here! I admit I am not too used to handle interrupt OBs in Siemens. I have a customer who has been buying a standardized solution...
Replies
4
Views
210
Hi everybody! I have 2 Mitsubishi Q series PLCs that have built-in IP addresses of 192.168.3.xx and both of them have Ethernet modules...
Replies
9
Views
790
I have a Conveyor System Running Balluff Remote Ethernet blocks Topography has ethernet going through Master-2 to Master-1 (BNI...
Replies
5
Views
368
Hi All, I just wanted to confirm something regarding this module. What I understood from the manual, is that if RS-485 mode is selected (jumper...
Replies
2
Views
338
Dear Members; We are going to design a Simplex Control System With Following: 1. 24 Digital Inputs (SIL 2) 2. 24 Digital Outputs (SIL 2) 3. 4...
Replies
14
Views
1,055
Back
Top Bottom