Help please...

maxine

Member
Join Date
Aug 2003
Location
Toronto
Posts
13
I bought an AB plc-5 system (PLC-5/15 and 16 points I/O cards) I cannot use the outputs addresses from 00 to 07, only from 10 to 17). Please help me... Thanks.
 
What do you mean you can't use them? Do they physically not work? What model card is it? I think more info is needed to help.
 
Let's say I put in my ladder diagram O:002/00 and when the rung is true nothing happend(in lights), I changed the output to O:002/10 and then the output O:002/00 turns on.
The plc is a PLC5/15 frm. R, series B and the cards are 1771-IAD and 1771-OAD..
 
Sounds like an addressing mode problem to me. Try setting the system to 1-slot addressing and try the lower-byte outputs again.
 
Doesnt the physical location with AB PLC5 also represent the address? Isnt slot 0 is normally an input card or can it be either...I forget now its been so long. I remember grouping inputs first then outputs for "housekeeping" purposes mainly but thought there was another reason for it....guess I need to RTFM again. I also remember them in order input, ouput, input, output and so on...for some reason I have always thought the first slot (0) had to be an input.

I go RTFM now.
 
I Bet........

I bet 5 bucks you are missing a physical jumper wire on the card itself. Double check that first......
 
A weakness of the PLC5 design is the connectors in the chassis where the i/o modules are inserted. If you are unfortunate, you can experience that a module does not respond or responds "strangely". This because the pins in the connectors doesnt have sufficient contact. Remedy: Power down, and remove and insert the module repeatedly - 3 or 4 times (that will give the pins a good massage).

Also try to change the module in question with a similar module in another slot, and see if the error follows the slot or the module.
 
Just a thought!

Is all your output assignment is in ladder 2? If it is not, you need to call a Jump Sub Routine to the specific ladder for the PLC to scan it.

lad.jpg
 
maxine

Sounds like you will need to change out your chassis. You would get something like that if the chassis dip switches were set for 1/2 slot addressing and you were using 16 point modules, where you should have 1 slot addressing.
1/2 slot would look at the bit as 0 and the 16 point card would see the same bit as 10.

Ron, the only time you need to place your inputs and outputs in spicific locations is with complementary I/O and some intelligent modules.

Roger
 
Go check the part number on the chassis. If it's a "1771-AxB", where the X is the number of slots, then you have a Series B chassis and can look elsewhere for the addressing problem.

If there are only two letters after the "1771-" in the part number, then you have an old 8-bit chassis that was built for the PLC-2 (probably it has a date code before 1986). It won't work with the 16-bit I/O modules.

This is definitely a backplane configuration problem. Keep looking !
 

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