MicroLogix1000 Outputs not working But has indication

Carbon Fibr · Jun 24, 2014

Hi all.
Ive made a small I:0/0 push button and a O:0/0 light program to test that my plc is working.

I got the bush button on a 24VDC and the light I've tried AC and DC always stays on or other outputs will just stay off.

In the program the pushbutton activates on the screen than makes the output true, the indication of output light turns on the PLC itself but the actual switching doesnt work.
Also i've done a continuity test between VDC and O:0/0 and their the same point? wha?
Its a 1761-L20BWA-5A

Any help would be appreciated thanks.

FactoryTalktotheHand · Jun 24, 2014

Sounds like the contact on O:0/0 welded shut. Is this a new PLC or a used one? If new, I'd try to return it under warranty. If it's not, then there was probably a power surge at some point in its life that welded the contacts together. If a relay contact is staying closed even when power is off, then the output is bad.

Carbon Fibr · Jun 24, 2014

I do not believe its welded closed, every output is giving me trouble.
Also when the PLC is de-energized the continuity between the VDC/VAC O:0/0 is not the same anymore.

I cant get one output to "switch" using a multimeter to test after changing output in the program once each output is energized.

dbh6 · Jun 24, 2014

Please attached a sketch of how you wired everything up, including the input wiring, and external power supply if used

Carbon Fibr · Jun 24, 2014

picture uploader

Mickey · Jun 24, 2014

You said you have checked continuity, have you checked the voltage at the output?
What is the voltage rating/requirement of your output (light)? Have you checked voltage acrossed it?

Carbon Fibr · Jun 24, 2014

when i push the button, the input and output lights turn on. Shouldn't i hear a click in the PLC of the relay outputs switching?

Carbon Fibr · Jun 24, 2014

yeah

The outputs are not sending any voltage out once energized, Its also 24VDC light and it does turn on; its not the light. That is for O:0/1, the light for O:0/0 is always on.

For some reason O:0/0 and O:0/7 are normally closed which are sending voltage without the output being energized. But when i De-Energize the PLC O:0/0 and O:07 become normally open.

gbradley · Jun 24, 2014

Do you have an actual load on the output, or are you just checking it with a meter?

Carbon Fibr · Jun 24, 2014

Little 24VDC light bulb. And a meter Yeah nothing big. Does the PLC require a big load to actuate the output??
My knowledge is that the vdc I input into the port beside the output will energize the output once switched from the program. That being said the output should now have 24VDC coming out no matter the size of the load.

dbh6 · Jun 24, 2014

quick observation, is your ground terminal grounded??, your wiring looks fine expect for the ground connection, it should be grounded. When you measure the voltage between O/1 output and 24vdc common you should get 24volts DC. Also as Mickey suggested what is the rating for your Light? i know you said its 24vdc, but at how many amps, i doubt you used a light bulb which pulls high amperage, but you never know

Carbon Fibr · Jun 24, 2014

It is not grounded, what would the ground have to do with it? Also the light turns on with the voltage applied doesn't show an amperage ratting. Also measuring voltage between O/1 and common of the DC is no voltage. I do know if it does actually work which is what I'm trying to make happen, is the pin O/1 and 24VDC - will have 24VDC.

Carbon Fibr · Jun 24, 2014

Is there something in the PLC that makes all outputs not work? Even though I'm getting output indication?
Also anyone got an answer to should I hear anything within the PLC once an output is energized?

gbradley · Jun 24, 2014

I think a 24V DC light bulb should be enough of a load, I think that you need 2.5 mA min. at 14V dc
Sometimes I get tripped up when I don't see a voltage when checking with a meter only.

dbh6 · Jun 24, 2014

Based on you part number 1761-L20BWA-5A, the BWA, the B represents that all inputs are 24VDC, the W means that for the Outputs they are relay outputs, so when the specific output is energized you "should" hear the relay pull in.

As for Grounding although it doesn't seem to be the culprit of the problem, i got this from the manual "
All devices connected to the user 24V power supply or to the
RS-232 channel must be referenced to chassis ground or
floating. Failure to follow this procedure may result in
property damage or personal injury.
Chassis ground, user 24V ground, and the RS-232 ground are
internally connected. You must connect the chassis ground
terminal screw to chassis ground prior to connecting any
device"

MicroLogix1000 Outputs not working But has indication

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