PLC Test

My boss asked me to make up a PLC test using RS Logix 500 structure for new applicants but I am not sure what are the common tests out there, so wondering if somebody has idea what to write and what not to write?
Thanks in advance

What do you want to test? Their ability to solve problems or their ability with logix500?
Search the forum - there are plenty of discussions on this subject.

Both,I want to make sure they can use RS Logix and also to solve quick troubleshooting problems.

believe it or not
getting online is a good test....
not to loose the tags
make sure RSLinx is shutdown first.
there are a number of small problems that the inexperienced will fall into.
At the end of the day understanding ladder logic is similar to relay logic.
the hardest question is what level of knowledge do you want or need from the new employee. In a fully established plant, do you want someone to reprogram all your machines or do you want the person to find which input is not working.
Is this company a machine manufacturer, do you need a GUN programmer?

what you need to do is to ask around in the plant to see what a lot of the common problems are. what basic skills would the maintenance personnel expect from a newbie.

use pushbuttons and switches with good and bad contacts.
see if you have a plc output card with a blown fuse in the card or a bad output.

TEST the person using a triac output using a wiggy ( mechanical volt meter with a load if you didn'nt know what a wiggy is). IMO very important. i got bit once using the bosses wiggy, didn't use it ever again. used a fluke 87.

use contactors and overloads
use n.o. and n.c. prox switches and have the wrong one wired in.

use the incorrect contacts in the plc program.

do as others have said as well.

also see if they can use wireless. our plant has a lot of wireless here.

regards,
james

another good test is to locate the bit that is getting overwritten earlier in logic.

use a switch or pot with intermittent contact on a test jig and have them locate that the problem is NOT in the PLC. (its always the program isn't it?)

Scaling analogs.

Going online gets most people
Design a holding/seal-in circuit using real inputs/outputs
with the stop button NC contacts. This helps create an understanding
of xic/xio

They should know what a "force" is and how to use it. What can be forced & what cannot.

Also, how to program a simple "free-running" timer.

How to create a simple "flip-flop" (bi-stable multivibrator in old-school lingo). This is a very commonly asked question on this forum.

The list is endless, depending the particular skills you need.

My take on it is rather different.

I wrote up a flowchart for one of our most used, yet more difficult to initially grasp, assembly processes in the plant, an I/O chart and a blank program (I did however, fill in the I/O for them-- I'm not completely heartless). The applicant then has to write a program for the process. No time limit.

It's rather like the Kobayashi Maru, in that it's kinda like a no-win scenario, but it's also a test of character-- which is really what I'm after aside from what they know. I've had an applicant walk out cursing after 15 minutes (apparently it called him out on his programming skill claims), and another work at it for 90 minutes and wanted to keep at it even when I stopped him. You can guess which one I hired.

Using this test has given me two good fellows to work with, who I don't have to completely handhold as if he were an apprentice. Some training still goes on (finer nuances of networking and routing, for example), but in the end, there will be two guys going from just good to excellent.

I would throw a double-coil or two in the logic. Maybe some MCR instructions. And put a condition or two in the JSR on a subroutine or two. These three things are in my experience the most common reasons you'll see a program not acting like it's "supposed to." If you're looking for physical troubleshooting testing, a former boss of mine like to do the following:

- Put an un-stripped wire in a terminal so only the insulation makes contact.
- Pull a neutral off a relay and hide it in the wire duct.
- Take a jumper or two out of a terminal strip.
- Take the bulb out of a pilot light.