kekrahulik
Member
During the "no parts available" era of 2020-2022, we were told that a 1756-OBV8S would have better delivery than PointIO safety modules that we typically used. I got the 1756-OBV8S to work for a direct wire connection to a servo drive safe-off, but could not get it to pull in a 24V Coil Allen-Bradley 700S emergency stop relay. The Card Output just faulted every time it tried to pull in the relay (the relay would give a good "chunk" pull in before the fault). Luckily, the relay was for future use, so I shelved it...until now when I need to replace a bunch of hardwired 120V relays with Safety PLC controlled 24V relays.
As I search the AB knowledgebase, it looks like I'm not the first to struggle. One technote has you adding diodes to prevent faults if you are wiring in Bipolar mode - I am not. I have the card setup for sourcing, so the output wires to the relay coil+ and the relay coil- wires to 24V common.
Another technote makes it sound like you must use a SELV /PELV listed 24V power supply. Interesting that when I search AB for a SELC power supply, I don't seem to find any.
And finally, another technote makes it sound like these modules shouldn't have made it out the door at AB:
Summary
False Overload Faults with OBV8S/OBV8SK in Sourcing mode
Question
Why the OBV8S/OBV8SK module experience Overload Faults when the contactors are switching in Sourcing mode with safety or safety pulse test mode selected but there is no actual overloads observed ?
Environment
• 5069-OBV8S / 5069-OBV8SK V1.011
• 1756-OBV8S / 1756-OBV8SK V1.011
Answer
• 5069-OBV8S / 5069-OBV8SK : Firmware V2.011 and Add-On Profile V2.01 is now available on the Product Compatibility and Download Center to resolve this anomaly.
• 1756-OBV8S / 1756-OBV8SK V1.011 : Use an interposing contactor consuming less current, the anomaly will be resolved in a future firmware.
SO MY QUESTION TO THE GROUP:
1. Has anyone been successful with a 1756-OBV8S card? Any learnings?
2. Do I need to use a SELV power supply for it to function?
3. I just bought some 700-HN123 8-pin safety relays that I can use to pull in the larger 700S relays in case this is a load issue (haven't tried it yet). Has anyone else had to do this?
Of course, the delivery of the 1756-OBV8s ended up being a year delivery - so in hindsight, I should have just gone with PointIO.
As I search the AB knowledgebase, it looks like I'm not the first to struggle. One technote has you adding diodes to prevent faults if you are wiring in Bipolar mode - I am not. I have the card setup for sourcing, so the output wires to the relay coil+ and the relay coil- wires to 24V common.
Another technote makes it sound like you must use a SELV /PELV listed 24V power supply. Interesting that when I search AB for a SELC power supply, I don't seem to find any.
And finally, another technote makes it sound like these modules shouldn't have made it out the door at AB:
Summary
False Overload Faults with OBV8S/OBV8SK in Sourcing mode
Question
Why the OBV8S/OBV8SK module experience Overload Faults when the contactors are switching in Sourcing mode with safety or safety pulse test mode selected but there is no actual overloads observed ?
Environment
• 5069-OBV8S / 5069-OBV8SK V1.011
• 1756-OBV8S / 1756-OBV8SK V1.011
Answer
• 5069-OBV8S / 5069-OBV8SK : Firmware V2.011 and Add-On Profile V2.01 is now available on the Product Compatibility and Download Center to resolve this anomaly.
• 1756-OBV8S / 1756-OBV8SK V1.011 : Use an interposing contactor consuming less current, the anomaly will be resolved in a future firmware.
SO MY QUESTION TO THE GROUP:
1. Has anyone been successful with a 1756-OBV8S card? Any learnings?
2. Do I need to use a SELV power supply for it to function?
3. I just bought some 700-HN123 8-pin safety relays that I can use to pull in the larger 700S relays in case this is a load issue (haven't tried it yet). Has anyone else had to do this?
Of course, the delivery of the 1756-OBV8s ended up being a year delivery - so in hindsight, I should have just gone with PointIO.