AB SLC 500 cable

rowens

Member
Join Date
Aug 2003
Location
south carolina
Posts
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I am new to Allen Bradley .
I have a SLC 500 unit that I need to setup communication to and upload the program to a laptop for a backup and to use as a learning tool for AB software.
The Cat # of the unit is 1747-l40A .
I have the RS linx and Rs logic softwares.
The laptop has serial and paraell ports and 1784-pcmk card.
I also have P/N 96993801-AO1 cable with an adapter for 9 pin to a mini round 8 pin connection.
the problem is that I find on the plc a connection similar to a phone jack.
What do I need to communicate and how should I setup the laptop for this particular plc.
banghead
I appreciate any help.

Thanks in advance
Richard
 
The pcmk card gives you alot of options. If you order cable 1784-pcm4/b from ab, you can communicate from pcmk card to processor.

To configure driver for this:
Open linx
Select communications
Select configure drivers
Click down arrow under available driver types
Select 1784-pcmk for dh+/dh485 devices
Click add new
Name driver click ok
In configure screen change network type from dhplus to dh485
Select ok

Make sure you select your driver when you open rs logix 500.

I think you have to have a 1747 pic converter to communicate with the processor through its serial port.
 
Last edited:
Hold the phone, there, Mike.

Your assuming that the PCMK card he's got is a Series B (capable of talking DH+/DH485/RIO) and not the series A (DH+ only). I couldn't tell from that part number which he has.

I would also ask Richard to verify that he's got RSLogix500, not RSLogix5.

He'll also need to verify that the version of RSLinx is high enough to support his operating system, especially if he's going to go the 1747-PIC route instead of the PCMK route (a PIC on eBay runs about $50, which is way less then a new 1747-PCM4/B cable.
 
the card is a series B.
yes I have a current version of rslogix 500.
the cable that I have is labeled 1784-pcmc/b on one end and on the other end vc-p965 with an additional number mdc2601. the adapter with it is not identified. is there an adapter I can use in place of this one?
I appreciate all ideas.
thanks again :)
 
... more details ...

as Allen says: do NOT try to rig an adaptor for this ...

the reason that you need another cable is because of that little gray box in the middle ... the 1784-PCM5/B cable that you already have has "special magic" in its little gray box which converts the PCMK card's signal into DH+ signals ...

the 1784-PCM4/B cable that you need will have a different version of the "special magic" in its little gray box which will convert the PCMK card's signal into DH-485 signals ...

major point: different cables have different magic in their boxes ...

and incidentally the existing adaptor that you’re describing sounds like a part number 1784-CP7 ...

and as Allen has already said, you can buy a 1747-PIC module (usually quite a bit cheaper than the 1784-PCM4/B cable) to fit between your computer's serial port and the "phone type" connector on the SLC processor ... the PIC module also has a gray box with "special magic" in it ... and this particular "special magic" will be able to convert the computer's RS-232 signals into DH-485 signals ...

ugly picture department: suppose someone makes a "home brew" cable to go between their computer's serial port and the "phone type" jack on the front of the processor ... guess what happens to the computer's serial port? ... do NOT do this! ... a damaged serial port and/or mother board is the usual result ... that's because some of the pins on the processor's communciations port carry 24VDC ... your computer's serial port (and nearby components on the mother board) usually run at something around 3 to 5VDC ...
 
your computer's serial port (and nearby components on the mother board) usually run at something around 3 to 5VDC ...

I dont mean to nit pick about a point unrelated to the topic (I will anyway though), but your serial port operates between -15V and 15V actually... -5V to -15V being a logical 1, and 5V to 15V being a logical zero. It is the parallel port that is 0-5V.

And it should also be optically isolated from your mother board. That being said, I still doubt you are going to get a good result from that home brew cable you are talking about.


🤾
 
I dont mean to nit pick about a point unrelated to the topic (I will anyway though), but your serial port operates between -15V and 15V actually...

I'll bite, where does this power source on a PC come from? PC power supplies are 12vdc and 5 vdc, how do you obtain 15vdc + or -?

Ron Beaufort made a "GOOD POINT", a PC isnt meant to have 24vdc from an external source applied indiscriminately on serial or parallel port connections.

It has a tendency to LET THE SMOKE OUT...which we all know is not desirable.
 
I'll bite, where does this power source on a PC come from? PC power supplies are 12vdc and 5 vdc, how do you obtain 15vdc + or -?

Are you sure there isnt a + or - 15V coming out of there going to the mother board? I have never really looked to closely (there is a reason why I didnt go into IT). A quick search on google will verify the + or - 15V, ive also seen it on an oscilloscope.

I wonder what a USB runs at? + - 12V or 15V too? Have you seen all those things you can plug into them now, like fans, and lights.


Ron Beaufort made a "GOOD POINT", a PC isnt meant to have 24vdc from an external source applied indiscriminately on serial or parallel port connections.

In anycase, we can agree on that!
 
I was trying to stay away, but I think I need to comment:

Any PC inside has +/-12V. In legacy systems this voltage used by serial ports.
Nowdays they using charge pump type ICs like MAX202E or MAX3243E which converts +5V to +/-10V internally using pumps and small capacitors.
All chips with letter "E" have ESD 15KV protection.

There are no optical insulation on serial ports on consumer level computers.

Sure if you put 24V to a serial port you will damage it, like you will damage 24V PLC input by connecting 120VAC signal;)

Steve Crotty: USB running at +5V.


In any case I don't see a problem using "home brewed" cable if I know who made it and tested.

No one tells us that we are making "home brewed" PLC cabinet or built custom made equipement - really think - wee DO.

Custom cable manufacturers are same OEM as we are and they mostly doing better jobs than large super power houses.
 

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