Automation tech

SergeDep · Apr 5, 2022

Hi all, I have a PLC5/15 with a 1771-OAD module at slot 5, O:5/15 and 16 are not in the program yet i get 120 vac out and the light for 15 and 16 are not on. I installed a new output module and they are booth still on with 120 vac with the lights off on the module. I did a search for those 2 addresses and they are not in the program yet. Could the problem be from the rach?

Mickey · Apr 5, 2022

See pdf, note "off state leakage"

James Mcquade · Apr 5, 2022

welcome to the forum.

the 1771-oad module is a triac output module.
with no load on the outputs, there will be voltage on the outputs. the scr component of the output requires a minimum load to turn the unit off. look at the specification sheet posted for the leakage current values. there is nothing wrong with the output cards or the plc rack.
regards,
james

JohnCalderwood · Apr 5, 2022

Ah, the joys I used to have teaching the techs about these modules.

Serge, as James says, they are fine. Connect a load to the outputs ( a relay or a light) and switch the outputs on and off...

arpus4KM · Apr 5, 2022

I believe you could use a low impedance voltage check (Lo-Z on fluke, or an SV225 adapter) and you would be able to see it off due to the small load on it.

plvlce · Apr 5, 2022

IanM8040 said:
I believe you could use a low impedance voltage check (Lo-Z on fluke, or an SV225 adapter) and you would be able to see it off due to the small load on it.

A Wiggy would also work. Are those still around these days?

arpus4KM · Apr 5, 2022

plvlce said:
A Wiggy would also work. Are those still around these days?

seen a few sitting around some old guys boxes. As funny as they are to see, I think it's still better than the testing done before handheld meters were available. I think there are some manuals out there explaining the difference in tingle and pain between 20-60-120-240v lines

SergeDep · Apr 5, 2022

Automation Tech

Hi All, thank you so much for your quick response, I tried an incandescent pilot light and sure enough it worked, problem solved.

Again thank you so much for a quick response you guys are great.

Have a great day.

Serge

SergeDep · Apr 5, 2022

Automartion Tech

I did have LED pilot lights installed and they were always on with the output off. For some reason I thought the 1771-OAD was a relay output module but when James mentioned a triac output module my light bulb also went on lol.

thanks again.

TWS · Apr 5, 2022

One of these should be in every tech's tool box (or at least one in the maintenance departments tool crib). https://www.grainger.com/product/1A...PgLlNFIPiLDXnTfmd6BoCVoAQAvD_BwE&gclsrc=aw.ds.

parky · Apr 5, 2022

Interesting about LED lights a bit off topic but we have a property in Thailand, two years ago we replaced all the lights with LED units, the originals were fluorescent types, these were troublesome due to the voltage dropping well below the 220v (poor distribution), with the LED units when turned off they still lit up (could only see this in darkness, I checked the wiring & it's fine but I suspect the low power of these units the pick up off the cables generates enough to power the LED's slightly, I intend to re-wire when we go back as there is no earths at all, only a 10 Amp supply (already replaced with 20A by the supplier as we requested), however, the only protection is one 10 Amp breaker makes me shudder.

arpus4KM · Apr 6, 2022

TWS said:
One of these should be in every tech's tool box (or at least one in the maintenance departments tool crib). https://www.grainger.com/product/1A...PgLlNFIPiLDXnTfmd6BoCVoAQAvD_BwE&gclsrc=aw.ds.

eh, maybe. Nowadays you can get good readings if you know how to use a multimeter right. you can capture peak waveform voltage of a 60hz sine wave with a fluke 87v good enough to know if the incoming power is clipped and causing problems. you can also catch momentary blips of highs and lows with it too...

provided you know what all the function are and what they are used for... that's where people kinda fall short.

James Mcquade · Apr 6, 2022

wiggy's are still for sale.
the big issue with them that i have is that they turn off the triac scr's. i used one and no voltage, then tried to remove the wire and got lit up. used my fluke and found voltage. haven't trusted or allowed one to be used since.
BUT, it's a big no no with are flash teachers.
it's an automatic write up or termination here if you are found with one.
sad, i used my ticker to id voltage in a bundle of wires, and they are a write up also.
james

I_Automation · Apr 6, 2022

parky said:
Interesting about LED lights a bit off topic but we have a property in Thailand, two years ago we replaced all the lights with LED units, the originals were fluorescent types, these were troublesome due to the voltage dropping well below the 220v (poor distribution), with the LED units when turned off they still lit up (could only see this in darkness,

There are a few billboards on a corner I frequently pass. The LED lights are timer controlled to turn off at 2:00AM. I am guessing the timer has TRIAC output, as all the lights randomly flash all night when off.

I first found this out when I connected a laser star projector to a TRIAC output. The leakage current is enough to build a charge in the LED driver until the LED lights up and drains it quickly, flashing like a strobe at a steady slow rate.

arpus4KM · Apr 6, 2022

LED being such a small load has messed with the auto industry too. Older cars that people put LED lights in for turn signals causes most cars to flash quickly like the lights are burned out...

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