Interview Question Ideas?

[ganutenator]

I'm tasked w/ coming up w/ interview questions for my customer for a plc programmer.

I have tons of ideas, but I am afraid I may tailor them too specific to my history and be unfair.

Figured I may as well send a feeler out there and see if the community has any good ones.

Customer is not looking for an entry level plc programmer. so the should be medium to hard level.

 

[AustralIan]

"What is your plctalk.net username?"

 

[ganutenator]

"What is your plctalk.net username?"

lol

I'd never get a job if I answered that truthfully.

 

[keithkyll]

I figured out the avatar ("Duck Tape"), but confused about user name. Please give a hint.

 

[ganutenator]

I figured out the avatar ("Duck Tape"), but confused about user name. Please give a hint.

There was this really good old school mentor when I installed equipment that used the word ganutenator in place of what-ya-ma call it or thing a ma jig. He was always yelling at me to bring the gnutenator.

kind of borrowed it from him.

wish i spelled it gnutenator though instead.

 

[James Mcquade]

Get with your customer and see what plc's, hmi's, and scada packages he has.

these are my answers.
1. when a machine is down what's the first thing you would do?
ask the operator what's wrong
how is the machine supposed to operate.
has any maintenance been done on the equipment.
any sensors changed
any valves changed.

2. when you connect to a plc, what would your steps be to trouble shoot the machine.
find the master copy and make a copy to work with.
go online - if the code matches, keep going. if not, upload the program to
the pc and compare the plc programs to see what changed. look at the
differences and work from there.
have the operator reset the machine and see where it stops, look at the plc code to find the problem.

3 general questions to start with, then work your way into more detailed questions. if they can't answer basic questions, that's a flag.

4 MOST important, what steps do you take when modifying a plc program while the machine is running?
make the edits
ensure the operator and all maintenance people are clear
have someone at the e-stop
test the edits
if all goes well after a few cycles, accept the edits
keep monitoring the system for 30-60 minutes


We each can ask questions unique to our own experiences, ask typical questions, and as I said, basic questions first, then get into more detailed stuff if you are comfortable with their basic question answers.

hope this helps,
james

 

[James Mcquade]

another question.

when is a machine the most dangerous?

when it's first turned on.
why it that?
if the machine is turned on for the first time, valves can be wired backwards, or piped backwards.

when the plc is put into run for the first time, it does what you tell it to, not what you want it to do.

how do you debug plc I/O when the plc has the program downloaded into it for the first time? have the plc in program mode and debug the I/o manually, that's how we usually do it.

james

 

[jraef]

How do you spell PLC?

It seems as though I run across a LOT of people who would have failed that question...

 

[rootboy]

"What is your plctalk.net username?"

Wait a moment, I'll look it up...

 

[rootboy]

Give them a set of prints. and have them write a program for it. On the spot.

 

[cardosocea]

How do you spell PLC?

It seems as though I run across a LOT of people who would have failed that question...

The course I took in Uni that teached PLC's actually had this as a question. LOL

What is the role for? Is the guy going to support the system already running and do minor mods and mostly troubleshooting or is the guy going to be heavily developing?
This would be a determining factor in the questions asked as it usually requires a different mindset.

If the guy is in a supporting role, I would go through different fault scenarios such as program faults, sensor faults and so on and check if his steps made sense, but also what would be his action if he was required to bypass safety critical equipment. Most people want a PLC programmer so they can run a machine to the ground by deactivating safeties as they break down. Ensuring that this guy would know where to draw the line would be valuable.

If looking for a developer, perhaps ask about the different possible languages to program and see if he's an Allen Bradley Fundamentalist that only writes ladder, or if he can see the strong points of each language and organizational features (AOI, UDT, OB, FB, DB, etc...). This will give you an idea of how aware he is of the people troubleshooting the plant as well as reusing code, thus reducing the testing time.

 

[janner_10]

Anyone worth their weight would turn up with laptop in hand with a current program they had written.

Supported by photos, videos and wiring diagrams of the machine.

They would be able to talk you through each part of the program and what it did along with any problems they encountered and how they over came them.

At least thats what I did. My boss said in my interview nobody had bought their laptop into the interview amongst the other candidates. I walked out pretty confident the job was in the bag. Turned out it was.

 

[VAN]

Anyone worth their weight would turn up with laptop in hand with a current program they had written.

Out of curiosity why do you have a laptop with a Siemens/Rockwell license? I would feel uncomfortable taking my employee laptop from a current company to a new company. Same reason I don't keep code from past companies, if I developed it before I can recreate without copying it.

 

[janner_10]

Out of curiosity why do you have a laptop with a Siemens/Rockwell license? I would feel uncomfortable taking my employee laptop from a current company to a new company. Same reason I don't keep code from past companies, if I developed it before I can recreate without copying it.

I downloaded a trial version of TIA on my personal laptop for that very same reason. Not that there was any interest in the code as I went from a Siemens employer to a Rockwell employer, but it provided a great show and tell aid.

 

[James Mcquade]

janner_10,

taking a laptop to an interview is very risky in my opinion.
The company could claim you are stealing the laptop, copy the information, or report you to your current / former companies.

in my last position working for a defense contractor, no way am I going to carry that information somewhere! Non disclosure agreements, non-compete agreements. those can hurt you if your not careful

james