AB Led lamp wont turn off when PLC output go's off

Plc 5 1771 OAD OUTPUT CARD HAS AN AB 800MR-PGAL162 INDICATOR LAMP ASSEMBLY WITH A N60X LED LAMP IN IT. WHEN THE OUTPUT GO'S OFF THE LAMP STILL STAYS LIT WITH 60VAC STILL ON THE OUTPUT. IF WE REPLACE THE LAMP WITH AN INCONDECENT 85 LAMP IT WORKS FINE. ANYONE HAVE ANY IDEA AS TO HOW TO GET THE LED LAMP TO TURN OFF.
THANKS KIPP

FCA
BELVIDERE CHRYSLER STAMPING
ELECTRICAIAN

The leakage current from the solid state output is keeping the LED lit. Change to a contact ouput or use AB's universal LED power module.

http://literature.rockwellautomation.com/idc/groups/literature/documents/pp/800t-pp007_-en-p.pdf

Bingo Sparky! Been there, done that.

the 1771 OAD output is a Triac output
like any solid state device they leak a few ma when they are off
put a load resistor on the output in parallel to the LED it will solve your problem

Note: Tirac's like all solid state devices are called a semiconductor for a reason
they never are completely on or off when off they always have some current passing through them when they are off and when on they always have a voltage drop across them. Unlike a real relay or switch.

I tried a load resister, don't know if i selected the correct value. What value do you feel should be us 1K 10K I don't really know.
Thanks for the feedback.
Kipp

GaryS said:

Note: Tirac's like all solid state devices are called a semiconductor for a reason
they never are completely on or off when off they always have some current passing through them when they are off and when on they always have a voltage drop across them. Unlike a real relay or switch.

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Not to try to go off topic, but I thought that they were called semi conductors not because the devices were always conducting something, but because the material they were made out of was a non conductive material, like silicon, infused with a charge. Which made the material "semi conductive". Then by charging that material in different patterns you ended up with a device that acted certain ways under certain conditions. Simpler ones being: Half positive, half negative, you get a diode. Positive, Negative, Positive, you get a PNP transistor, etc.

In most cases triac outputs have internal circuitry to prevent against false triggering. This circuity itself has AC leakage. I consider parallel load resistors a band aid. Use the proper equipment for the job.

Tharon said:

Not to try to go off topic, but I thought that they were called semi conductors not because the devices were always conducting something, but because the material they were made out of was a non conductive material, like silicon, infused with a charge. Which made the material "semi conductive". Then by charging that material in different patterns you ended up with a device that acted certain ways under certain conditions. Simpler ones being: Half positive, half negative, you get a diode. Positive, Negative, Positive, you get a PNP transistor, etc.

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As far as I understand, you are correct, in theory. However, I think the way a lot of circuits are designed, they don't 100% break the connection when they turn "off". There is no physical air gap to stop the current like a switch has, it is often just a tiny trace less than a micrometer wide.

It isn't that it is "always conductive", its just that when it transitions from conducting to not conducting, its really only becoming 99.9% nonconducting. A little bit sneaks through, especially on cheaper devices, or at least devices that weren't designed to prevent it.

bernie_carlton said:

I consider parallel load resistors a band aid. Use the proper equipment for the job.

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I agree, if you don't or can't change the output card then use an interposing relay.

Kipper said:

Plc 5 1771 OAD OUTPUT CARD HAS AN AB 800MR-PGAL162 INDICATOR LAMP ASSEMBLY WITH A N60X LED LAMP IN IT. WHEN THE OUTPUT GO'S OFF THE LAMP STILL STAYS LIT WITH 60VAC STILL ON THE OUTPUT. IF WE REPLACE THE LAMP WITH AN INCONDECENT 85 LAMP IT WORKS FINE. ANYONE HAVE ANY IDEA AS TO HOW TO GET THE LED LAMP TO TURN OFF.
THANKS KIPP

FCA
BELVIDERE CHRYSLER STAMPING
ELECTRICAIAN

Click to expand...

Why not use the correct pilot device lamp.

http://literature.rockwellautomation.com/idc/groups/literature/documents/pp/800t-pp007_-en-p.pdf

What you have is not really designed for what you are trying to do with it as it does not have the correct impedance to operate correctly in the configuration you have.

Mickey said:

I agree, if you don't or can't change the output card then use an interposing relay.

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I too have a similar situation with the 1771-OAD. I have quite a bit of leakage 118vac. I installed 23K ohm 1 watt resistors knocking the leakage down to 5vac. This did take care of my problem for the outputs tied to solenoid valves. However, I have some led stack lights that seem to be giving me some issues. I know this is not the best way to handle this situation and honestly I hate having the resistor on each of the outputs. I know you guys say use the correct devices but I am trying to keep my cost low and not have to buy new devices and use what I have on the shelf. I have looked at a few options, one of them being switching to relay outs instead of the triac. Really don't like that option because of reliability and relay outs do fail more frequent based off cycles of the relay. With all that being said I would like to consider the interposing relay which I have used in the past for various reasons. But I don't want to use a mechanical relay because it's really the same as using the relay output, as far as switch cycle limitations. I think that I should consider a solid state relay, but I am not sure what the outcome would be with the triac. Hoping for some opinions from the experts here. Has anyone used a solid state relay with a triac before? And if so what was the results?

Thanks in advance for the education

I believe the 1771-OAD is a Triac output.


http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1771-in024_-en-p.pdf

A triac is a solid state relay. Solenoids should not cause leakage voltage that high unless you have something wired funny.

Solenoids don't cause a leakage voltage.
Solid state outputs have an inherent leakage current and when combined with whatever resistance the solenoids have, there is an apparent voltage.

The 1771-OAD has a published leakage current of 3.0 mA.

With no device wired to the output, it will appear to be on.
With a 10K load it will still appear to be on with slightly reduced voltage, while providing insufficient current to actually energize the device.

Mark Snodgrass said:

A triac is a solid state relay. Solenoids should not cause leakage voltage that high unless you have something wired funny.

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The solenoid is not causing the leakage. when I disconnect the devices I still have the 118vac on those outputs. We have other devices (solenoids) on the first half of the card that have leakage that are not as high as the rest of the card. The wiring is pretty straight forward and appears to be correct. but like I said it is not the wiring since I can disconnect the outputs and still measure the 118vac at those terminals directly on the card.

danatomega that answer is absolutely correct. sorry I just noticed your reply.

I am not sure how to solve this issue other than using the resistors