Tuesday, November 30, 2021

HOW TO TEST OPTOCOUPLER ICs CHIPS test integrated circuit

 OPTO   COUPLER   TESTING   

Optocoupler  is one   type of  ICs , It   isolates input  and output section  by using  optical technology  this  feature  increase safety of  circuit.  Optocoupler  has many   part number , different  part number has different output type so before checking it   has to  use part number to  research with datasheet and find input type and output type.   How to check  Optocoupler it depends  on  device type inside the ICs.   There   are  many package of  Optocoupler , briefly ,  through hole and  SMD.  For  through hole type such as  DIP-6  which  has 6 pin   DIP-4  which   has  4   pin  etc.



test  integrated   circuit    OPTOCOUPLER    ICs
Optocoupler   MCT2E  DIP-6   Package



I   will    use MCT2E   for example testing.  After researching with datasheet we know input is LED
terminal   number .  1   is  Anode and  terminal  number 2  is  cathode , this case ,  we  will check it by using  the same method  as   LED checking.   The dot on ICs body mean that the first pin start from that.   The   output  is  a   transistor pin number  6 is  Base terminal ,  pin number  5 is  Collector terminal and  pin number   4   is Emitter terminal , so  checking method  it  has the  same method  as  transistor  checking.


Step  to  test   Optocoupler.
1.  Input   Checking.

2. Output  checking.
Good Optocoupler has the   good  checking results for  both input and output checking.

1)   Input   Checking.
Set   the multimeter  to  diode test  Function and  connect test leads   as   photo.
Picture  number  one  is  forward   biasing  to  LED so we will  see voltage across  LED  =   1.077V
mean LED is good condtion.

HOW   TO  TEST  OPTOCOUPLER    ICs
Good  LED   present voltage drop across when applying forward   bias.



Picture number 2  is  reverse   biasing  to  LED so we will  see  " OL " ( Over Limt)  display mean LED is   still good.

test    OPTOCOUPLER
Good  LED   present  " OL "   display  when applying reverse  bias.





If   it is  bad  LED (short )  the   display show  around 0.002V  as shown below.
and   the first  and the second   testing   will get the same results.

TEST  OPTOCOUPLER    ICs
Bad  LED (short )  the   display    show  around 0.002V    2  time.



If   it is  bad  LED (open )   the  display  show   " OL "
for    the first and  the second   testing   will get the same results.


OPTOCOUPLER
 Bad  LED (open )   the  display  show   " OL "   2 time

2)  Output  Checking  has  2  step to do ( the same method  as  transistor  checking )
     2.1   Check B-C  and  B-E terminal as  shown on  photo below  ,  it  has  4  times measurement.
-  Good transistor output ...when checking  B-C  and  B-E terminal  it  display  high resistance  1 time and  " OL"   for the second  testing.
-   Open circuit .....display  " OL"   for  the both measurement.
-   Shorted Circuit.....display  " 0 ohm "  for   the  both measurement.
-   Leak ......display  some  resistance  for  both measurement but not the same resistance   value.

TEST  OPTOCOUPLER
B-C terminal testing show high resistance value for the fist measurement.
This good  B-C terminal .



OPTOCOUPLER
B-C    terminal testing show  " OL"   for    the second   measurement.
This good  B-C terminal 



TEST  OPTOCOUPLER
B-E terminal testing show high resistance value for the fist measurement.
This good  B-E terminal 



OPTOCOUPLER
B-E    terminal testing show  " OL"   for    the second   measurement.
This good  B-E  terminal.

 

2.2   Check   C-E   terminal  as shown on   photo below ,   it   has  to  measure  2   times.
Good transistor output   when checking   C-E   terminal  ...display " OL" or  very high resistance.
for the both measurement  ( test and switch test  leads )
-   Shorted Circuit.....display  " 0 ohm "  for  the both measurement.
-   Leak ......display  some  resistance  for  both measurement but not  the same resistance   value.


TEST  OPTOCOUPLER
C-E   checking , good transistor display  " OL"   for the first and the  second measurement.



OPTOCOUPLER
C-E   checking , good transistor display  " OL"   for  the  first  and   the  second measurement.



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