What to study work in control field (was: Dears)

[panic mode]

lol... i am not sure how to approach this but let me try:

i don't know what work expectations in your area are. i know that here, regardless what I know, I have to learn new things all the time, forever.
there is very little likelihood of finding a job as "PLC programmer" and only do that task. or PLC and HMI. or just a robot...

to get into this line of work i can suggest few things as bare minimum:
- learn how to read between lines and do your own research, without this, look for another job
- get really good with multimeter, without good troubleshooting skill, look for another job
- make sure you are expert in Ohms Law etc or look for another job
- if you are serious about this, get serious; what plc software did you download and try already?
- make sure you know how to interface devices by looking at whatever little info is in datasheets (often just block diagrams), this includes digital, analog, and line driver circuits.
- make sure you know how to shift logic level (say from TTL to 24VDC and the other way around)
- make sure you know how to use and create diagrams (learning AutoCad is quite useful - it is used all the time to exchange information)
- make sure you are familiar with at least one PLC commonly used in your area
- make sure you are familiar with at least one HMI (usually from same maker as PLC)
- make sure you are familiar with at least one fieldbus (Profibus, DeviceNet...) or at least have the idea
- make sure you are good in using RS232 (get two serial ports, connect them with cross over cable or so called null modem cable and send some messages and data over)
- make sure you know how to quickly network 3-4 ethernet devices (computers or whatever)
- lookup : reed switch, inductive proxy, diffused photo eye, photo eye with background suppression, polarized retro-reflective photoeye.
- lookup : solenoid valve, reed switch, cylinder, check valve, pressure regulator
- lookup : transient suppression, flywheel diode, relay, contactor, reversing contactor, overload relay, soft start, VFD
- lookup : PNP, NPN, optocoupler, quadrature encoder, LVDT
- lookup : your local Electrical Code (teaches you what is allowed and what is mandatory, teaches wire colors, wire and fuse sizing, grounding and bonding, etc.) this should be available as a course
- lookup : E-Stop, light curtain, two hand control, laser scanner, safety categories, dual channel, muting, monitoring
- lookup : servo amplifier, pulse train, quadrature encoder, limit switch, homing, overtravel
- lookup : sensor cordsets, M12, M8 are most common; M12 is standard and common for all types of sensors; M8 comes in two versions - usually 3-pin for inductive sensors, 4-pin for optical sensor which makes troubleshooting messy (you cannot just swap two nearest sensors to test if one of cables is bad)

this should be enough to get you started or employer interested. more you can learn on job.
as you can see this can be lumped into:
- programming
- sensors
- networking
- safety
- motion
- pneumatics
- design
- troubleshooting

most of those things you can do from home. if you can pay a visit to one of the companies. if anything tell them that you are customer looking for a small machine for your own business and that you are interested if they can make one for you, then ask all you like - freebee tour... ;-)

oh, one moer thing, make sure you are good in your current field (it is actually very closely related to what you want):

wow that's awesome,
... if you graduated from an electronics department you can only work on mucrocontroller...

if this is your field, prove it. make your own PCB with microcontroller and couple of relays and digital inputs, add one stepper motor.
connect it to PC using RS232 or SB or Ethernet. write PC program that allows you to control relays and stepper motor and read signals on inputs.
That is a great exercise and it will help you sail smoothly though "PLC/HMI/Sensors" waters. Also it will be nice proof for your potential employer that you are capable to make things from scrath. integrating systems using off the shelf components like PLCs and HMIs is usually easier.

 

[panic mode]

so you need a new job? do a practice run, select few parts, choose cad of your choice and make a diagram. post it here for discussion. do a program. for example you can pick any software and write program (we don't need to download it to plc, it is enough to see the code).

good example would be simple pick and place machine (gantry style) with only X and Z motion and gripper. X and Y cylinders are on center-closed valves, gripper is on single solenoid valve, and under gantry is belt driven conveyor run by motor. all three have reed switches for extended and retracted position. there is green indicator lamp "Running", red indicator "Jammed", buzzer, photoeye "Part present" and buttons "Start", "Stop" and "Reset Fault".

nothing happens until start is pressed. when start is pressed machine enters Run mode and everything is operational. pressing stop or detection of fault stops the machine. starting machine when fault is present shall not be allowed, to clear the fault, press "Reset Fault" button. clearing fault does not resume Run mode, to enter Run mode, operator is expected to press Start button again.

buzzer sounds for 3 seconds every time Run mode is started. conveyor waits for buzzer to complete plus two more seconds and then runs as long as there is no part present.
when 'part present' is made, conveyor pauses and waits until part is removed, then runs again to deliver next part.

pick and place runs independently of conveyor. it can start after 1second that run signal is active (does not need to wait for buzzer to finish or for conveyor to start running).

pick and place runs through sequence:
move Z up
move X to drop position
move Z down to drop position
open gripper for three seconds
move Z up,
move X to pick position
wait until part is present (same part brought there by belt conveyor, checked by one and only photoeye)
make sure gripper is open
move Z down
close gripper
done, go to first step

note
X axis moves only when gripper is up
gripper goes down open in pick position
pressing stop turns off all outputs, center closed valves cause cyclinder to maintain position, gripper will close because it is on single solenoid (energized to open)

fault is generated if any reedswitch is not made within 5 second that appropriate output was active.
for example there is need to lift gripper to upper Z position, output is energized but readswitch "gripper up" is not yet made. if this condition lasts 5 seconds or longer, fault bit is set.
when any of the fault bit is set, we set another bit - Alarm present (used to shut down Run mode).

circuit will also have estop, MCR relay and green illuminated "MCR reset" button.
pressing EStop kills power to outputs driving solenoids (motion) but not indicator and buzzer (announciation).

this is likely type of question you may expect to do in a PLC course.

 

[flinty]

that is afull guiding for me man i like that as i likr you you are so friendly helpfull person,
i'll do and study what you tell me in the 1st post of your last 2 .
and the funy part in post 2 i dont know if you expect me to answer or do that programm now but i promiss you and that is for me and i am completly Convinced with that i'll ask you to give your comments about that code you post.

finlay i wanna thatnk you for you great post and for your time you wast to help alost one like me ,cuz i was feel that i missed alot of something over here for example b4 i read this post
i visited an electronic doctor from my colledge after ignoring alot of calls i did it to him,
this doctor teach me microcontroller and i asked him like i asked you exactly and look what he tald me :
you need to study microcontroller again and i'll teach it to you as aprivate cource ,
then take androhit course and then study PLC level 1&2 then you will be qualified.

then i saw your post i think i know now what i need to learn ,that was it want to put my leg at that start of road ,and cuz of missed parts i didnt know which road will lead me ti what i want,

but you did it already,and i dont what to sya man but thatnk you very much.0;l\

thank you very much dude.

 

[Winterstone]

Hi flinty,

because I saw another posting from you regarding integrators and lowpass filters:

Don't forget that control loops do not only need microcontrollers, PCU's and other digital stuff (which was extensively discussed in this thread).

For my opinion, it is absolutely necessary to know also about analog controllers and system theory.
Keywords: Laplace transformation, transfer function, pole distribution, stability, stability margin, stabilization, Nyquist diagram, linear/non-linear loops,....

 

[flinty]

i studied analog control b4,but only theories .

you see that poet

 

[Winterstone]

i studied analog control b4,but only theories .

you see that poet

Please, can you translate ?

 

[JimB]

Please, can you translate ?

A childish variation of textspeak often used by those who just about speak English well enough to really mangle it in a silly attempt to make themselves look clever.

I know that the English language is complicated due to its multiple origins, but this sort of rubbish frequently practiced in Asian countries is no form of improvement.
I have even had the word "plz" instead of "please" in formal business communications. Not good.

Having said that, in German there is what appears to be a semi-formal short hand which can appear in official notices "u.s.w."

JimB

 

[panic mode]

und so weiter...

Mann, Ich habe Deutsch kaum benutzt in... Jahren. Schade...

 

[Mickster]

Please, can you translate ?

With today's TXTing laziness, shouldn't that have been written:

Plz cn u trnzl8?

 

[Jugurtha]

Some "l33t" stuff here

I always thought that boards should have a link to "How To Become a Hacker" (and indirectly to "How To Ask Questions The Smart Way".. Not just for the point Raymond makes about learning English, but also to get the whole philosophy. Though I think it's not easy to acquire that philosophy and that mindset.

PS: That's a good thread, I bookmarked it to look at it more thoroughly at a later time.

 

[flinty]

With today's TXTing laziness, shouldn't that have been written:

Plz cn u trnzl8?

so cute m8,you got me