Protected Digital Outputs
neilot said:
Thanks Geospark. just one thing, I have observed our IO's here uses Flex IO for Digital input, analog input, analog output. And also uses Point IO for Digital output or relay output. whats the specific purpose specially for digital output uses point IO?
Hi neilot,
Without knowing your application(s), what each module is doing, the number of points per module, and type of each module, it would be difficult to say why any of the modules were specifically selected. To be clear, are you saying the same application(s) have both Flex I/O Inputs and Point I/O Outputs?
Seeing as you are specifically asking about digital outputs, here is one example of why you might choose Point I/O over Flex I/O for digital outputs.
Both platforms support digital outputs, so why might someone use Point I/O instead of Flex I/O for digital outputs?
Let's say you want an 8-point Digital DC Output Module and you require electronic fuse, electronic protection and diagnostics.
Flex I/O...
The Standard Flex I/O Digital DC Output Modules, such as the 1794-OB8, provide no electronic protection. Some 1794 digital output modules (6 when I checked) provide electronically protected outputs with individual electronic fuses on each output, such as a 1794-OB8EP. Under short circuit or overcurrent conditions, the faulted output turns off and remains off, and the fault condition is latched. If the fault condition is cleared the module fault can be unlatched through a module pushbutton reset (certain modules only), resetting the fault diagnostic bit via programming software, or power cycling the module.
There is no 1794-OB8
D, or similar i.e. there are no 8-point Diagnostic Digital DC Output Modules, which provide LED status of protected faults on the front of the module. You could select the 16-point 1794-OB16
D Digital DC Output Module, but this just provides diagnostic features for wiring faults, such as open wire, short circuit, or reverse power bit. While they do provide a thermal shut down for short circuits, this is for module protection, not per-point protection.
Therefore, Flex I/O cannot be selected for an 8-point electronically protected, diagnostic digital output module.
Point I/O...
All Point I/O Digital Output Modules are electronically protected against short circuit, overcurrent, over-temperature or open wire on their outputs.
The Standard Point I/O Digital DC Output Modules, such as the 1734-OB8, use basic electronic protection as a "Protected Module" feature i.e. it protects the module as a whole. For instance, a short circuit on one output will take the whole module offline. However, the Standard modules do not have indication of these faults, and they must be removed and refitted to clear the latched module protection fault.
The Enhanced Point I/O Digital DC Output Modules, such as a 1734-OB8
E, provide "Point Protected" short circuit, overcurrent, over-temperature or open wire protection i.e. each output has a separate electronic fuse, which, in the event of a fault, will turn that output off only. Enhanced modules also provide diagnostics and indicate these faults on their LEDs. They may be power cycled or reset in software - the latter allowing the module, and its healthy outputs, to remain functional through the fault.
These modules also have a user-selectable Latch Fault and Auto Restart feature. If the fault condition is cleared the module fault can be unlatched through the RSLogix 5000 module profile, resetting the fault diagnostic bit in programming or power cycling the module. The Auto Restart feature allows you to define the action of an output on a short circuit or overcurrent condition, either "shut off" or "try to turn on".
So basically, all Point I/O Digital DC Output Modules have electronic protection as standard. So the 1734-OB8 (protected, no diagnostics) or the 1734-OB8E (protected with diagnostics) would be a suitable choice.
That's just one example which also provides some more detail on some of the differences between what these two I/O platforms have to offer.
Some other reasons they were selected could be a personal preference, space considerations, expansion capable, more modern I/O platform, etc.
Regards,
George