Newbee

Hello. I am a novice as far as plc's are concerned. i have installed a few machines that are controled by plc's so i understand the principles but used a contractor for the programming/faultfinding.
I am looking for a new job and the agency guy has asked my if i have basic plc fault finding skills (not with a laptop) just general. i am quite computer literate and an electrical engineer by trade but i am not sure what exactly he means. i have an interview next week. could anyone help me with pointers to what i will be asked???
any help would be much appreciated.
Strider

Try Clicking on "learn PLCs" at the top of this page.
Spend some time and go through the threads on this forum. Youll find lots of very good links.

Cheers for that elevmike. Yeh there is a lot of good info and links on here.
My interview is tomorow and i feel more confident that i will be able to answer his questions. the only thing is what does he mean by NON laptop faultfinding? I guess he means checking ip/op devices like sensors,motors,encoders etc. any other advice before i dig my suit out and go into the lions den?
Cheers.
Strider

non laptop fault finding

Hello Strider,

NON laptop faultfinding

Click to expand...

I would guess the above means not going through the ladder logic analyzing the cause of a problem and start tracing from there.

To me basic troubleshooting for PLC is knowing the hardware (power supply, CPU, I/O's) and their operations (not related to programming) like for example AB PLC has key switch to select from run mode to program mode and to reset the PLC is to simply toggle the switch back and forth (this can be done using the laptop). Most PLC manuals have maintenance/troubleshooting procedure on it.

Good Luck!!

Vic Jasareno

and don't forget the little LED's on the front of the I/O modules ... he'll probably expect you to know how to interpret these ... and how they relate to the on-off status of the real-world devices ...

When you do it without a Laptop you must figure that the big control panel with all the relays and counters and timers are in another room.

Just like in the old days.

You read the paper schematic and test the feild devices to see if they work well and give you the expected signals.

Since those relay panels worked before they should be still working today !

BUT, the paper schematic is not the representation of the hardwired relays AND those relays do not exist. They are virtual. Da PLC!

And besides, whats nice, like Ron Beaufort just mentionned, you even don't always have to take out your DVM, there are nice little LEDs to "tell" you the states of the devices (most of the time anyway).

Soooo, if you could read an electrical schematic, you could troubleshoot the PLC without the Laptop... almost.

striderman,
So, give us an update. How did the job interview come out? What did the agency guy really mean by "basic plc fault finding skills (not with a laptop)"? I am always interested to know new ways to find PLC faults.