are any of the EEs around here familiar with programmable logic controllers? i've been trying to use one with my senior design and haven't had much luck getting it to work properly.

i looked online for some sort of guide on how to wire these things up to relays and whatnot and have met with minimal success.

if someone has any knowledge he can share, i'd be grateful. i'd be even more grateful if someone could drop by broughton on monday and maybe tell me what i'm doing wrong.

4/21/2006 8:05:55 PM

I program invensys plc's at work. Send me a schematic of what you're trying to do. What plc are you using and what do you use to program it? I'm guessing you're trying to hook up to a triac output

4/21/2006 11:21:15 PM

you just fill in the dots where the lines cross

4/22/2006 12:09:24 AM

^?

^^i'm using the same plc as the one in this thread (Mitsubishi FX1s - 20MR - ES/UL):
http://thewolfweb.com/message_topic.aspx?topic=93964

the plc is what i'm using to control the extension/retraction of several hydraulic cylinders. the plc is supposed to energize solenoid valves through dpdt relays. i'm pretty confident that i've set up the wiring to and from the relays correctly.

i also got my ladder logic worked out, but when i tested the program out, i couldn't get any of my outputs to work. i think my trouble is with wiring the plc to everything else...i'm not savvy on the subject.

this is a block diagram of what i'm doing:

cylinder 3 extends until contact switch 1 activates. cylinder 3 stops and cylinders 1 extend for a certain time. then cylinders 2 extend until contact switch 2 activates. all the cylinders then retract in sequence.

4/22/2006 12:31:57 AM

haha, those plc's they give you for ME senior design are damn pieces of shit and old as hell.

Klang brought in a guy that helped us with the plc's. I forget his name and if you haven't met him go hit up Klang to find out who he is.

4/22/2006 2:27:11 AM

okay so they are relay outputs.
Stupid question, do you have power to the common side of the relay of the PLC?

4/22/2006 9:12:59 AM

do you have it wired somewhat like this

4/22/2006 11:30:47 AM

if i recall correctly, this is sort of what my wiring looks like. I only put in one relay for simplicity

4/22/2006 6:57:57 PM

is the plc a micro unit or full size? as some of the miro sized ones need a pilo relay between them and the main relay, as the coil on many full size relays will kill a small plc's outputs. I have worked with small stuff from stamp II size up to allen bradley and GE rack mount units.

4/23/2006 12:52:29 PM

i'm going to assume it's a full sized one. nobody else in the class has been using any sort of intermediary relays.

Quote :

"Stupid question, do you have power to the common side of the relay of the PLC?"

i assume you're asking if i have the plc itself plugged into a power source, yeah, i have the ground, neutral, and live connections plugged into the wall...i forgot to put that in my diagram, i guess

4/23/2006 2:18:26 PM

Hey UberCool,

On Monday, let's just switch your logic to sink and I can help you out completely

How's that sound?

4/23/2006 6:33:42 PM

Looks like you have all your commons wired to +24 on the plc,, assuming the comons listed are feeds for the outputs, your relay coil is hooked from +24 on one side always fed to a 24 volt swtiched feed on the other side. Try checking both feed to ground, if one is hot all the time and the other goes hot when you energize the plc, all you need to do is feed the common side of the relays off of ground or dc 0V

4/23/2006 9:00:38 PM

you sure you have all the logic written correctly?? are the lights (i'm assuming it has them??) coming on to prove the PLC is attemping to close a particular output circuit??

4/23/2006 9:12:26 PM

I wasn't refering to the plc power, but the relay outputs on the plc tied to common, which it looks like that is wired correctly. Our electrians miss that one more than anything. Just use a volt meter across the coil of your relay and again on the cylinders. It shouldn't be that difficult to figure out.

4/23/2006 9:33:39 PM