Micrologix 1400 Input table versus Input card

Wired a new prox to an unused input (/14) on channel 4.
I test the prox, and its light plus the indicator on the IQ16 DC Input card are tracking with the switch's activation... Prox sees part, lights come on; take away part, prox and card indicator lights go out.

But when I look at the Data Table for I:4/x, bit 14 is not changing from 0 to 1 when part activates the prox, even though the indicator on the card lights. DC supply for the prox is the same supply as the card's, of course.

Do I need to actually put an examine on/off in the program for the data table to reflect the state of the input on the card?

Thanks.

Data table is in RSLogix 500, in online mode?

If yes, is IQ16 configured in RSLogix?

drbitboy said:

Data table is in RSLogix 500, in online mode?

If yes, is IQ16 configured in RSLogix?

Click to expand...

Yes, and
Yes.

So do you have an expansion card you're plugging this into? 1762-IQ16?

If wired correctly, it should show up in the I data table as I:4.14 or I:4/14

Just to double check are you counting correctly?

Since AB starts with 0, so the built in discrete input is I:0

I'd check I:3/14 too.

That's always thrown me for a loop.

But if the card lights, it should show up in the data table.

You may have already checked but if this is a DC sensor did you wire PNP or NPN. Light on sensor will function but if the signal wire to the PLC is the wrong polarity it will not make the input go high.

Is the PLC is run mode?

If memory serves me, the SLC 500 family doesn't update the input data table while in Program mode. The PLC-5 and Logix 5000 families do, but I seem to remember that the 500 did not. I could be mistaken as it's been a while since I've used anything in the 500 family.

OG

glenncovington said:

You may have already checked but if this is a DC sensor did you wire PNP or NPN. Light on sensor will function but if the signal wire to the PLC is the wrong polarity it will not make the input go high.

Click to expand...

OP indicated light on input card functioned, not just sensor light.

Any chance the input is being forced off?

It would be unlikely that the card is inhibited (Ignore Configuration Error) but I am pretty sure that would also keep the data table from being updated with real world info from the card.

It sounds like you're looking at the data table in Logix500, but if you're actually putting an indicator on a HMI linked directly to the input, you might have to shift the address to see it. I encountered that with an I/O status screen on a PV800. I had to link to O:6/0 to reach O:1/0.

See this thread for great details from Geospark:
http://www.plctalk.net/qanda/showthread.php?t=119263

>Do I need to actually put an examine on/off in the program for the data table to reflect the state of the input on the card?

Click to expand...

Not in an A-B controller. I was very surprised the first time I used an Indramat CoDeSys controller to find that the base tag for a physical Input wouldn't update in the IDE view unless there was a user program reference to it.

That like to George's explanation is likely more detailed than you'd ever want to know. The MicroLogix designers staked out I/O memory to accommodate all the different base sizes and types, and organized them all in Slot 0.

That shouldn't affect your ability to look at them in RSLogix 500, but it might affect the addressing of HMI devices if you are directly addressing the I/O data table memory and they don't have a syntax that's specifically for the modern MicroLogix.

i can be wrong on this card, if i am someone correct me.
most inputs are optically connected to the plc card.
when an input turns on, it turns on a indicator light inside the card.
a photo cell then detects the light and activates the input circuitry.
this prevents the entire card from going bad if the wrong voltage is introduced to the input, only that input will go bad. they can go and do go bad.
i had one go bad 1 day after installation on a micrologix. we measured 24 volts at the input terminal and the plc did not see it.
your input may be bad.
regards,
james

Are you online?

5618 said:

It sounds like you're looking at the data table in Logix500, but if you're actually putting an indicator on a HMI linked directly to the input, you might have to shift the address to see it. I encountered that with an I/O status screen on a PV800. I had to link to O:6/0 to reach O:1/0.
[snip]

Click to expand...

No.

Turns out, the IQ16 had been moved a few years ago, and whoever moved it from slot 2 to slot 4, didn't also move its comments ("Grey Code") to slot 4... I saw the comment in slot 2, but since that wasn't the card I was trying to use, I paid it no mind at first. That was my mistake. There was an absolute encoder hooked to the first 10 bits of slot 4's IQ16, and apparently the grey code conversion uses all 16 input bits. Anyway, I found an unused bit on slot 2 (slot 3 is an output card, FWIW) and put my new signal wire from the DC prox on slot 2 (also changed the indicator's address in the automation direct HDMI), so it's all working fine now. I do wish using absolute encoders was documented more-fully in the command reference from rockwell; Thanks for the ideas, though.