simple logic test

JohnRatHolten

Member
Join Date
Jul 2012
Location
St.Louis
Posts
101
Hey All,

I'm looking for a simple "can this guy read logic or not" kind of test.

Here's the scenario;

I'm the "controls" guy in a manufacturing facility maintenance shop,
I'm kind of the lead sparky (I use to take offense to that term, but hey,
it is what it is, I'm not an EE, and I don't get to spend all my time programming,
but I have been working around controls for over 25 years, and think
(hope) I know a little bit).

Seems like every few months the maintenance manager comes through
the shop, giving some prospective "new guy" a tour, and inevitably they stop
by my workbench for an introduction...... and of course, he knows all about
PLC's and stuff.....

I thought it would be interesting to have some sort of simple logic diagram,
maybe just 8 or 10 rungs of basic binary ladder functions (no FB's or math
so it would be applicable to any programming language), but involved enough
that it makes you think......

I could hand the guy this drawing and say,
"okay, if you enable input 1, what happens"?

Can the guy read logic or not?

I started to make something up, but I have a hard time being objective about it,
I wrote it, so I know how it works, but is it meaningful?

Anybody out there got anything like this?

Regards
JohnR
 
I don't have anything special but I have been known to ask the question what is x = x + 1? Usually if they have any programming skills whatsoever they can answer this quickly. If you get the blank stare or "what do you mean" they haven't programmed before. Just my opinion.
 
There are plenty of PLC logic problem examples that you could use. It might be better to use part of a typical program that is actually running in your plant, for example the PLC rungs that control a Forward-Reverse motor, or a conveyor with several interlocks. In other words, something that he should know and should be able to answer after a minute studying the logic.

If you use some bit of logic that does not exist anywhere in your plant, the job seeker may feel it is unfair and that it was a set-up to trip him up. He could very easily come back with "where is this used in your plant"? Then you are in the spotlight if you are forced to say "we don't use that here, it was just a test" (in other words a trap). But if it is valid and it is being used, then it is something that he would need to know if he gets a job there. Then he has no beef if he does not understand what you gave him.
 
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I was interviewed for a job once where they give me some switches, a 24V battery, a buzzer, and a light to wire up... can't remember the detail. A good little test for electrical relay knowledge. They also had me draw a ladder on a white board for similar logic.

I thought it was a good way to separate out those who heard a PLC sale pitch once vs those who actually know something.
 
I had a test at a previous job i interviewed for. It had several rungs of code, but i don't remember all the details. it had a light that would come on if a integer was equal to some random number and a pushbutton was pressed. Then they had a bunch of buttons on a panelview that would add like 7, 10, 100, -1, -50 and some other amounts or if some were pressed while holding a push button. It also had greater than functions to reset the integer if it got too high, and had a counter on the buttons that would reset the integer if the buttons were pressed too many times. Object was to figure out the sequence you had to press the buttons in to make the light come on without changing any code.

I wish i still had that code, it was a pretty fun test.
 
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make a 2B OR 2B (sorry can not overscore) and a coil with a ?
if the guy says impossible to have a ? he is good.
if he says this is impossible ask him why.
if he says TRUE then hire him.
just kidding but sometimes it is very simple.

as most of the new guys learn not ladder but structured text or C the questions are somewhat difficult for we (old boys).
ask him where ladder is still a good use (if he says in safety he is good)
dont ask him what you do know, do ask him what you dont know. like servo or communication etc.
 
In one job interview that I had they took me out to one of there production machines and gave me a laptop. I had to open up RSLinx and RSLogix 500 and get online with the PLC. Once I was online they asked me why a bit in the program wasn't energized and I had to trace the logic back and tell them what was not turned on for the bit to be true.
 
Once I was online they asked me why a bit in the program wasn't energized and I had to trace the logic back and tell them what was not turned on for the bit to be true.
That was a relevant test for what you would actually be doing at the plant. I hate those tests with theoretical questions that will never come up on the job.
 
Hey All,

Just thought I'd bump this thread to share a new caveat to our maintenance hiring practices.

It has been handed down from our HR lady, that we cannot present potential maintenance candidates with any sort of aptitude testing.

Since we are an Equal Opportunity Employer, presenting candidates with a test would;

"give a qualified candidate an unfair advantage over an un-qualified candidate"..........



What's this world coming to???

regards,
JohnR
 
Hey All,

Just thought I'd bump this thread to share a new caveat to our maintenance hiring practices.

It has been handed down from our HR lady, that we cannot present potential maintenance candidates with any sort of aptitude testing.

Since we are an Equal Opportunity Employer, presenting candidates with a test would;

"give a qualified candidate an unfair advantage over an un-qualified candidate"..........



What's this world coming to???

regards,
JohnR

Wow. I don't know what else to say about that. It sounds like the HR lady needs to interview for her job again.
 
Hey All,

Just thought I'd bump this thread to share a new caveat to our maintenance hiring practices.

It has been handed down from our HR lady, that we cannot present potential maintenance candidates with any sort of aptitude testing.

Since we are an Equal Opportunity Employer, presenting candidates with a test would;

"give a qualified candidate an unfair advantage over an un-qualified candidate"..........


What's this world coming to???

regards,
JohnR




OK, I'll bite.
You are joking right????
 
I agree with shooter. Ask them their weak points. It is a good quality to know what knowledge you are lacking on.

Also, it is a shame you can't do an aptitude test. We have written tests, but they are cake if you can trace a line. I got my position because I set up a test bench one day after work, wired it all up safely and set up a motor and VFD and started doing analog controls on it for a speed reference.

People who want it will tend to shine, though a little encouragement won't hurt.
 
I usually tell stories and then ask a question. "How would you have done that?" or This is what we are going to do..."How would you actually do it?" I tend to get some amazingly bad answers but when I get a good one that is the guy I tend to hire. Were I to hire a PLC programmer (Allen Bradley) I am thinking that a question related to relating to Ron Beaufort's light and switch box (from his videos) would tell you what level they are at. Even if they cannot give you the correct answer the thought process they use will tell you how smart, experienced, and knowledgeable the candidate is.
 

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