PLC freaking out

[krugtech]

On the newer lasers we use networked PLC nodes. This saves a lot of wiring as only a power and data lead needs to be run around the machine. I've been having issues with this, specifically the power bus. Barley getting 18 volts at the end of the line w 24 volts in. This really freaks out the control. the solution is simple-

Just double up on the power wires, most of the loss is the termination module so simply pass the power to it but NOT through it-

Before-



After-



I had a machine yesterday that had 5 of these wired pass-through. Got about 6 volts back at the end of a string of 5 of these. Many "ghost" problems went away.

This is a selectron machine, the Allen Bradly is similar (device net) but they actually have double terminals that plug into the termination nodes, just have to make sure the installer/assembler took advantage of this.

Chris Krug

Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS

 

[MacGyverS2000]

How long are your power runs (or how small of gauge wiring) are you using that you'd lose 25% of your voltage?!! I'd fix the supply problem and not band-aid the rest of it.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[krugtech]

I see this as a better way to wire the machine. how do you see this as a bandaid?

Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS

 

[MacGyverS2000]

If your voltage is dropping 25% over the run, the wire gauge is way too small. A proper fix is to run the appropriately sized wire. If you double up wires, what happens when one comes loose? You start to get odd behavior... sometimes it works, sometimes it doesn't. Those terminals are not designed for power bus structures, so fix that, too.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[krugtech]

I guess I didn't make myself clear. When the system was new, the voltage drop was acceptable and it was wired as on the "before" drawing. This is the factory configuration. I agree these terminals are not the best for this application, that would be a design flaw, out of my control.

Picture the 24 volt buss going through about 10 of these as you said sub-par terminals, lets put a solenoid bank on the end of the line just to make sure we load each and every one of those termination modules. The power for that solenoid bank must go through the sub par connector, through the pins in the termination module, into a soldered trace on the PCB, back out soldered pins, into the sub par connector, to the wire that leads to the next termination module where the 24 volts gets to go through the hell I described above again...... not once but 4 more times.

These termination panels really cant take full bus load, so why make them? I'm NOT doubling the wires to increase gauge, this is a bus system, the wires i doubled up , one comes from power, the other goes on to power other nodes. By simply moving the incoming bus power wires to the same terminals as the outgoing bus wire, the incoming and outgoing bus power no longer has to go through the hell I described. I just reduced the current load on those sub par connectors and solder traces by 80%, which brings the load on them into very acceptable levels. I am copper on copper w my power bus right up to each and every node. Me and my friends like things like that.

I learned all this in the trenches, communication on the front line is a little different, sorry for the misunderstanding....

And as i said, it works to get rid of freaky PLC issues for an hour w a screwdriver.

Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS