R7008E-­‐Industrial

 Automation  Examination  
LP4  2014  
George  Nikolakopoulos  

Problem  1  [5  Points]  

 
In  an  assembly  line  there  is  a  conveyor  belt,  which  transfers  objects  being  placed  
in   constant   distances   among   them,   as   it   has   been   indicated   in   the   following  
figure.    

 
 
Automation  Specifications    
 
-­‐ The   motion   of   the   conveyor   belt   is   generated   by   a   three-­‐phase   motor,  
with  a  direct  start  and  a  thermal  protection.  Upon  a  fault  a  sound  alarm  
should   start   with   the   option   of   muting   the   sound,   by   pressing   a   mute  
switch.  
-­‐ By  pressing  a  START  button,  the  conveyor  belt  starts  moving  clockwise  
-­‐ This  motion  is  being  carried  for  T1=1  sec  and  then  it  stops  for  T2=5  sec  
-­‐ After  the  elapse  of  T2,  the  motion  is  carried  on  again  for  T1,  stops  for  T2,  
and   the   whole   process   is   kept   repeating,   until   a   STOP   button   is   being  
pressed  (pulse  movement)  
-­‐ When  the  conveyor  is  in  motion  a  green  light  H1  should  be  turned  on  and  
flashing  with  a  period  of  T4=0.5  sec  
-­‐ When  the  conveyor  is  in  stop  a  red  light  H2  should  be  constantly  turned  
on  
-­‐ The  whole  operation  is  repeated  in  an  automatic  mode    
 
Questions  
 
1. Design  the  low  power  circuit  for  solving  the  described  automation  [4  Points]  
2. Design  the  high  voltage  circuit  [0.5  Points]  
3. Design  the  PLC  program  for  this  automation  [0.5  Points]  
 
 
 
 
 

  1  
 R7008E-­‐Industrial  Automation  Examination  
LP4  2014  
George  Nikolakopoulos  

Problem  2  [5  Points]  

 
Consider  the  tank  installation  as  it  is  being  presented  in  the  following  Figure.  A  
supply   digital   valve   is   controlling   the   liquid   in   the   tank.   Tow   electrical   pumps   (A  
and   B)   are   being   utilized   for   emptying   the   tank,   while   the   pumps   are   being  
controlled  by  relays  in  an  On/Off  mode.  For  this  application  of  particular  interest  
are   the   three   height   control   points   E1,   E2   and   E3   that   initiate   specific   operations  
for  the  electrical  pumps.    

 
Automation  Specifications    
 
-­‐ By  pressing  the  START  button  the  supply  valve  switch  on  and  allows  the  
flow  of  liquid  in  the  tank.  
-­‐ A  STOP  button  should  close  the  supply  valve.  
-­‐ A  selection  of  manual  and  automatic  mode  should  exist  
-­‐ In   the   manual   mode   the   user   should   be   able   to   manually   start   and   stop  
the  electrical  pumps  
-­‐ In  the  automatic  mode  the  following  procedure  should  be  followed:    
o When  E1  detects  liquid,  the  pump  A  should  start  operating  
o When   E2   detects   liquid,   the   operation   of   pump   A   should   be  
terminated  and  the  operation  of  pump  B  should  be  started.  
o When   E3   detects   liquid,   both   pumps   A   and   B   should   be   in  
operation   to   avoid   an   overflow.   Moreover,   in   this   case   an   overflow  
sound  S1  and  a  red  light  indication  alarm  H1  should  be  initiated.  
o In   the   faulty   case,   which   is   the   case   where   the   hierarchical  
sequence   for   energizing   E1,   E2   and   E3   is   not   followed   (E1   gets  
energized,  then  E2  and  E3  in  the  end)  then  a  sensory  faulty  orange  
lamp  H2  should  turn  on.  

  2  
 R7008E-­‐Industrial  Automation  Examination  
LP4  2014  
George  Nikolakopoulos  

 
Questions  
 
1. Select   and   indicate   the   position   of   the   appropriate   sensory   equipment   for  
detecting   the   E1,   E2   and   E3   liquid   levels.   Explain   why   you   have   selected   this  
type  of  sensor/s.  [0.5  Point]  
2. Design  the  low  power  circuit  for  solving  the  described  automation  [4  Points]  
3. Design   the   PLC   wiring   diagram   to   the   sensors   and   actuators   and   the  
corresponding  program  for  this  automation  [0.5  Points]  
 
Problem  3  [5  Points]  
 
Consider   the   following   screw   moving   table   and   the   two   limit   switches   h   and   k   as  
it  has  been  indicated  in  the  figure.  The  movement  of  the  table  is  being  performed  
by  controlling  the  rotation  of  the  DC  motor.  For  this  application  we  would  like  to  
have   the   table   being   moving   from   point   A   to   point   B   with   the   following  
functionalities.  

 
 
Automation  Specifications    
 
-­‐ By   supplying   power   to   the   system   (turning   on   the   supply   switch)   the  
table  immediately  starts  moving  to  the  right  (Delta  point)  
-­‐ During  the  movement  of  the  table  to  the  Alpha  or  Delta  position  the  press  
of  a  button  B0  should  stop  the  current  movement  
-­‐ By   pressing   the   M   button,   the   table   should   continue   moving   in   the  
direction   that   the   previous   movement   has   been   stopped   by   the   pressing  
of  the  B0  button  
-­‐ In  the  case  that  the  table  is  moving  towards  Delta,  the  pressing  of  a  button  
B1,  either  the  reach  of  the  limit  switch  k  should  reverse  the  movement  of  
the  table  to  the  left  
-­‐ In   the   case   that   the   table   is   moving   towards   Alpha,   the   pressing   of   a  
button   B2,   either   the   reach   of   the   limit   switch   h   should   reverse   the  
movement  of  the  table  to  the  right  
 
Questions  
 
1. Design  the  low  power  circuit  for  solving  the  described  automation  [5  Points]  
 
 

  3  
 R7008E-­‐Industrial  Automation  Examination  
LP4  2014  
George  Nikolakopoulos  

 
Problem  4  [6  Points]  
 
We   would   like   to   design   an   automation   for   the   selection   of   black   and   white  
metallic   balls   into   two   streams,   as   it   has   been   indicated   in   the   following   figure.  
The   process   is   happening   with   the   specially   designed   linear   moving   selector,  
which   is   solid   and   have   a   whole   in   the   middle   in   order   to   mechanically   allow   the  
displacement  of  only  one  ball  per  time.  
 

 
Automation  Specifications    
 
-­‐ The   black   coloured   balls   should   be   placed   in   the   black   balls   production  
line,   while   the   white   coloured   balls   should   be   placed   in   the   white   balls  
production  line,  as  it  is  indicated  in  the  figure  
-­‐ A   piston   should   drive   the   movement   of   this   specifically   designed   linear  
actuator  
-­‐ When  the  piston  is  in  full  extension,  it  is  assumed  that  the  ball  is  living  the  
piston  for  the  black  balls  line  
-­‐ When  the  piston  is  in  full  contraction,  it  is  assumed  that  the  ball  is  living  
the  piston  for  the  white  balls  line  
-­‐ Each   time   that   a   ball   is   entering   in   the   black   or   white   balls   lines,   it   should  
be  detected  in  order  to  allow  the  further  movement  of  the  piston  
-­‐ In  the  beginning  of  the  operation,  we  assume  that  the  piston  is  exactly  in  
the  middle  position  among  the  black  and  white  balls  lines,  while  we  also  
assume  that  it  is  equipped  with  an  already  known  coloured  ball.    
-­‐ The   automation   should   start   and   stop   by   pressing   START   and   STOP  
buttons  correspondingly.    

  4  
 R7008E-­‐Industrial  Automation  Examination  
LP4  2014  
George  Nikolakopoulos  

 
 
Questions  
 
1. Select   the   type   of   sensors   for:   a)   detecting   the   type   of   balls   and   b)   the  
movement  of  the  balls  in  the  white  and  black  lines.  Place  the  sensors  on  
the   correct   position   on   the   automation   and   explain   the  
utilization/operation  of  the  sensors  [0.5  Points]  
2. Select  the  type  of  cylinder  (double  or  single  actuation)  that  you  are  going  
to  use  in  this  automation.  Select  the  corresponding  pneumatic  valve  and  
present  the  pneumatic  circuit  that  you  are  going  to  utilize.  [0.5  Points]  
3. Design   the   low   power   circuit   for   solving   the   described   automation.   [5  
Points]    
 
Problem  5  [3  Points]  
 
Consider   an   automation   with   two   motors.   By   pressing   of   a   START   button   both  
motors  start  operating  on  the  same  time.  By  pressing  a  STOP  button,  one  of  the  
motors  stops  directly,  while  the  other  stops  after  the  elapse  of  additional  20sec.    
 
Questions  
 
1. Design   the   low   power   circuit   for   solving   the   described   automation.   [3  
Points]    
 

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