As the subject says, can an Allen Bradley SLC 500 processor read/write to a
PLC 5, 1771, rack and I/O modules? For my home brew experimentation
projects I like a SLC 500 rack and modules but sometimes I the variety and
bargains I find in 1771 racks and specialty modules. Since most are
controled by BTW & BTR, thought perhaps a SLC 500 could use them. I haven't
ever tried this so I'm not sure.
Well, it's maybe as much a toy and learning tool as anything else, but I
have some projects in mind that I want to try. I'm also wanting to teach my
son about PLC's and controls, I'm hoping to give him a head start by time
he's job hunting, he's 11 now so PLC 5's and SLC 500 might be out of date by
then but the concepts seem to apply.
One project is to use the analog I/O for analog circuit control, I've been
interested in making a multi-port battery charger using analog outputs to
control a switch mode power supply and read the battery charge voltage and
current with the analog inputs for both constant current and constant
voltage charging. The PLC seems like a nice platform for control and to be
able to see what is happening in the program.
Another project is to control my electric Brinkman smoker monitoring meat
temperature and internal temperature of the smoker. I plan to do ramp and
soak, I have ramp and soak temperature controls but they don't wait on the
setpoint to be reached, they just change the setpoint over time and if the
meat never gets to temperature I'd never know unless I watched it. I can
program the PLC for maximum internal smoker temperature until the meat
reaches the setpoint temperature and then set for 140 deg. F keep warm
temperature. Yes, I'm just playing but also enjoying some pulled pork BBQ
Yet another possible future project(s) include making a molding press for
rubber molding and plastic injection molding. I have a home machine shop
including a CNC lathe and CNC mill, I think it would be fun to make molds
using CAD CAM software and the CNC machines. Then using cylinders, valves,
and temperature control make rubber or plastic molded items(I work in a tire
plant and can get samples for cheap and consult with the chemists for the
properties I want). If I make something profitable, great, maybe a little
extra income, if not, no big deal, the education and experience would be
In other words, I guess I'm just wanting a more deluxe Lego Mindstorm :-)
I'm underemployed so I come up with projects for a more interesting and fun
challenge (Crossword puzzles could save me a lot of money).
I don't know of enough details on how it works, but I know at work we have a
mixing line where part of it has a SLC 500 and other parts have PLC 5's,
they somehow message each other to synchronize one with the other. Also, on
Allen Bradley's documentation of the 1771 ASB Remote I/O adapter it
mentioned communicating with SLC 500's but I don't know to what extent. I'm
not sure if a SLC 500 can BTW and BTR a card in a 1771 rack or not though.
I looked on eBay at the SLC 500 and PLC 5 options, added up the parts I
wanted plus shipping. A PLC 5/40 setup with digital and analog I/O was
cheaper than the equivalent SLC 5/04 so I bought:
1771 A2B rack, 8 slot with power supply, 4ea. 32 point DC input modules,
4ea. 32 point relay output modules for about $50 shipped.
PLC 5/40 processor for $125 shipped
Analog Input card, 16 single ended or 8 differential around $50 shipped
Analog Output card, 8 outputs, voltage out, around $50 shipped
My grand Total was around $280 (I spend a little more than the lego
mindstorm costs :-)
I also like that many discrete I/O modules are available on eBay for around
$20 shipped and quite a variety of modules can be bought for $50 or less.
You found some good bargains, especially on the 5/40 processor. We'll be
seeing PLC-5 hardware on the surplus market for a long time as old machines
are either scrapped or upgraded with new PLC's. I considered using a PLC
to control model railroad signalling, but we normally use just 5 or 12 vdc
those modules are harder to find.
An SLC-500 can do block transfers but it's either very clunky or sort of
clunky depending on the OS version. The earlier versions require direct
manipulation of M0 and M1 files, while the later versions implement the
BTW and BTR instructions. It's been at least 10 years, but I've done it
the old way to the 1746-HCSE high speed counter and over RIO to
a Mettler-Toledo scale and PanelView terminals.
There are at least three ways for SLC-500 and PLC-5 processors to
directly communicate: DH+ between a 5/04 and any PLC-5; Ethernet
between a 5/05 and a PLC-5 with integral Ethernet or the Ethernet
module; and serial DF1 between a 5/03, 5/04 or 5/05 and any PLC-5
except the original four "classic" processors which lacked RS-232
ports. That doesn't count the various bridge modules that go between
That rack I bought with 4ea 32 point relay cards and 4ea 32 point DC in
cards might work with model RR signaling. If so, they had two available and
another one was still listed. It was $29 "Buy it Now" and shipping for me
was $20.69. I thought 256 I/O, a remote I/O adapter, 8-Slot rack, and power
supply for $50 shipped sounds like a pretty good deal.
At work on our mixing lines we have multiple Mettler-Toledo JagXtreme
scales. I was originally looking for a SLC 5/03 or 5/04 but after seeing
the bargians on 1771 cards I wondered if I could use the 1771 rack with the
SLC 500. But then finding a good price on a PLC 5/40 should take care of
I'm still looking for a SLC 500 rack and 5/04 processor, if nothing else I
should be able to get the 1771 card data to the 5/04 by DH+. I think a SLC
500 rack would be more portable for bench tinkering.
A little update- I found an additional 16 slot rack with 5ea 16 point AC
Triac output cards and 8ea 16 point input cards (6 AC and 2 DC), plus a PLC
5/30 and power supply, all for $85 with shipping and taxes, and it all
works! I don't find many bargains like that!
I just found a panelview 550 (in "good" condition for $100 shipped) that
will do DH-485 protocol over the RS-232 port of a SLC 5/03, /04, or /05.
So, my plan is to try using the panelview with a SLC 5/04 on the RS-232 port
and connect to the PLC 5's through the SLC5/04's DH+ port.
Additional cards I bought so far are an RTD input card for temperature
control and a 1771-IXHR high resolution thermocouple milliVolt input card.
I became interested in the IXHR card because in the mV mode it has a zoom
feature that zooms in on a +-30mV range to a 1uV resolution, that should
work for load cells at least with a little bit of instrumentation
amplification as needed.
So far the biggest inconvenience is swapping from one PLC to the other on my
COM port, I wish I could pass through one PLC 5 with DH+ and program either
or both from one COM connection, just like you can with a PCMK card.
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