Replacing an Allen Bradley SLC150 with a SLC 5/04


Thread Starter


It is not possible to shut the equipment/line down to change processors. Windows of opportunity exists where some I/O wires can be moved from the SLC150 to the SLC5/04. This will mean that, before the changeover is complete, the machine's control code will be executing from two different PLCs.

Will one-shots work? Suppose the SLC150 finishes its scan and generates one-shot output. The 5/04 gets this output and is told to execute a one-shot
scan, reset and wait unit told to execute another one-shot scan.

The idea is that once all I/O wiring has been moved to the 5/04, then the one-shot interface can be removed along with the SLC150.

Anyone have any ideas?
Try this:
Wire the outputs of the SLC5/04 to fused terminal blocks such as AB 1492-WFB. This is good practice anyways. Leave the fused terminal
blocks open and fuses out, and connect your field wiring in parallel with the outpus of the SLC-100. Be careful, don't get electro-zapped.
Wire inputs of both PLCs in parallel as well. Since you have a SLC-150 I assume there is no analog. Wiring the plc card end usually take
the most time, so pre-wire the PLC card end on the bench and leave long enough wires reach anywhere in your panel, that way you can attach
these during your windows of opportunity. With the fuse terminal blocks open, go ahead and let the SLC5/04 execute its program and you can do any debugging, it "thinks" its in control, but its not. Then simply insert the fuses and close the fused terminal blocks and shut off the SLC150. If the fused terminal blocks are impossible, then force off the outputs of the SLC5/04 but go ahead and wire it in parallel. You can still debug, then remove forces. If you try to do it a few points at a time you're bound to have down time anyways as you take the SLC-150 off line to modify and relaod its program since it cannot be programmed online.

Jeremy Pollard

A bad sat afternoon but here goes.

Convert the code into the 5/04 - done apply enables in each of the output rungs in the 5/04 with proper grouping move the o/p's one or a group at a time so that part of the control is split between the two
finish the job

an SLC 150 doesn't have that many I/O -why the hassle? Just asking
Pretend the thing blew up and change it out:) Good luck.
Sheesh we make some things so hard - dont know who we is/are but sounds wierd thats all.

Cheers from:

Jeremy Pollard, CET
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Bob Peterson

As I recall, the SLC150 did not allow online programming. So to add oneshots to it would require a shutdown. Might as well just bite the bullet and find a time when it can be shutdown for a few hours and just do it then.

Bob Peterson