Akif KC

Controls Designing

8 posts in this topic

Hi all,

Hope everyone is doing good. I have this question about how to be good in designing the Controls. I never did controls designing from the scratch, always took over the designing from the seniors. Now I am in a plant where I don't have any senior controls people, and I badly want to learn how to design a controls system so we don't have to outsource it. Can someone here please tell me how should I do that? I mean is there any course I have to take? or can I learn that myself somehow? Please assist me. Thank you very much.

Akif.

 

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Design practices must be within constraints of the applicable standards in your place of business and client location. 

 

One can learn theory at school or university but everything discussed there is purely academic. When you start wrestling with real product, you need to find out what standards are applicable. You probably want to look up local national electrical standard. Some places do have electrical standard but it's use is voluntary. Also there may be specific standards that your clients insist on. 

 

Here in Canada, there is CEC or Canadian Electrical Code. One can buy book or better sign up for a course at one of colleges. This will introduce you to a standard and how to read and interpret it... Unlike material in college (that explains how to solve various circuits), this tells you what the trade standards are, how big wire mist be, how to do proper grounding and bonding, when and how to derate wire size, how to size conduit, how to select and apply circuit protection and much more. 

Next you need to practice somewhere good... Guy that does all kind of hacks in his garage is probably not the best mentor (he may know a lot but he does not play by the rules). Try finding an integrator, preferably someone catering to automotive because they will be cranking out tons of panels fast and they don't fool around because automotive clients are generally very knowledgeable and - they know what they want. 

Then you need to apply all learned to design circuits. That involves reading datasheets, making selections, sizing circuits, applying CEC, etc. 

Here it is also required to approve equipment before use (law requires that employers provide safe workplace for everyone). This means getting electrical inspection done by one of approved labs, and performing safety risk analysis. 

 

I used to interview controls candidates and I would ask them many questions about circuits, CEC, math, programming, networking etc. 

 

For someone wanting to do design I would ask something like:

You need to design something that can lift 750L tank of water 25m in 42sec. Tank etc.  weighs 180kg. Client is supplying 600VAC 3phase power. There is no PLC, there are just push buttons and relays. Draw entire circuit, size all components. 5min is enough, 10min is generous time but if someone takes twice as long and still gets right solution - we can still talk... 

 

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Wow, that is a really good reply. Thank you very much for your valuable reply. I am almost new in the field, trying to learn everything fast as possible, which I don't know whether it is possible. Was doing Co-op in an integration company and learned a lot of new things from there as you mentioned. Then got a good offer from a manufacturing plant , and here its just me, and I wanted to learn myself now. Kind of in that position where I want  to do the Automation projects myself, but I never designed an entire cell before myself, so company ends up outsourcing the project. I wanted to somehow learn this, which I know mainly comes through experience.

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On 5/23/2017 at 5:01 PM, panic mode said:

For someone wanting to do design I would ask something like:

You need to design something that can lift 750L tank of water 25m in 42sec. Tank etc.  weighs 180kg. Client is supplying 600VAC 3phase power. There is no PLC, there are just push buttons and relays. Draw entire circuit, size all components. 5min is enough, 10min is generous time but if someone takes twice as long and still gets right solution - we can still talk... 

 

If you don't mind explaining, what would be the correct way to go about solving that problem? and what would be some necessary information required for the needed components?

Thanks ,

Ryan

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Correct way is to calculate things using very simple highschool physics. Same is repeated in first year of university. Since it us only using basics it us fair game for anyone... And quick way to weed out slackers and wannabes.

Knowing water density and weight of tank you get mass of payload. Using mentioned elevation you get potential energy. Using that as work figure and time to do the work you get power.

And you want to give yourself some safety margin so you bump that power up ... Say 30%... 

Now that you have power and know supply voltage, you can select motor, size fuses and draw simple motor circuit with necessary controls. 

Someone that paid attention in school, has basic math skills, has seen motor circuits and has familiarity with applicable standard can do it quickly and show that he is the candidate you want hired. Others can go back to school to catch up or should consider different line of work 

The point is that nobody is perfect and knowing or remembering everything. Offering some help us acceptable too. Getting someone trip on derivation or proof of Maxwells equations may trip most candidates and that is not the point  

But if someone does not understand the basics, that is not just a red flag, the interview is over.

Everyone need to decide what is it that they expect from a candidate.  If you are hiring a programmer and he does not know about data types, difference in passing parameter by value and by reference, arrays, pointers etc. It means he does not know the basics. There is no point in asking him about more advanced topics.

My questions are all about the bottom line and things mentioned in candidates resume. No point in asking about things he did not mention. And he better know enough about things that he did mention.

Don't mean to crucify the candidate. And will happily accept inexperience, or various gaps. I will give then chance to learn at work (that is expected and required). But i do not tolerate deception. That is my bottom line 

 

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How do you get to carnage hall : PRACTICE !

 Are you doing your own drawings too ?

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Quote

carnage hall

Don't you just love spell check? What does one practice to get into carnage hall? 

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