Part of Made in India,Design Innovation

Workshop,2015

A  Fresh  New  Experience  in  

Project-­‐Making  and  Learning

PHYSICS INVESTIGATORY PROJECT ON

NAND GATE USING TRANSISTORS

Do  you  know  the  working  behind  the  door  closure  system  of  a  car?  The  concept  of  a  NAND  gate  will  help  you  infer  it’s  working;  it  has  two  inputs  (A  and  B)  and  only  one  output  (Q).  The  ECU  (electronic  control  unit)  of  the  car  is  designed  such  that  the  driver  gets  a  visual  indicaNon  if  any  car  door  is  open;  it  helps  avoid  accident  and  injury  to  the  passengers.  

Let  us  assume  that  there  are  two  doors  in  a  car  and  the  above  system  is  installed.  When  any  of  the  switches  is  open  due  to  the  door  posiNon,  the  NAND  gate  energies  the  lamp  inside  the  car,  hence  warning  the  driver.

In  this  project,  you  will  make  a  NAND  gate  logic  circuit  using  two  transistors  (Q1  and  Q2),  four  resistors,  an  LED  and  a  few  connecNng  wires.  The  emiTer  of  Q1  is  connected  to  the  collector  of  Q2.  The  collector  of  Q1  is  connected  to  Vcc  (posiNve/high  voltage)  while  the  emiTer  of  Q2  is  connected  to  ground  (negaNve/low  voltage).  Two  connecNng  wires  are  connected  to  the  leW  leg  of  the  base  

resistors.  Each  connecNng  wire  represents  the  input.  This  input  could  be  either  1  or  0,  where  1  stands  for  Vcc  and  0  stands  for  ground.

To  provide  the  inputs;  the  truth  table  of  the  NAND-­‐gate  was  followed.

Input  A Input  B Output  Q0 0 10 1 11 0 11 1 0

On  providing  the  inputs,  if  the  LED  glows  this  means  output  Q  =  1  or  high.  If  the  LED  does  not  glow,  the  output  Q  =  0  or  low.  AWer  verifying  the  experimental  outputs  in  four  different  cases  of  the  inputs,  we  do  the  ‘path  of  current’  analysis  and  reason  out  why  the  LED  glows  in  each  case.

Have  a  look  at  our  Project  Kit!

CoolJunk   is   India's   fastest   growing  DIY   (do-­‐it-­‐yourself)   kits   company   focused   on   project-­‐based   learning   in  science,   engineering   and   technology.  Having   20,000   users   in   India,  US,   Singapore,   Middle   East   and   New  Zealand,  the  CoolJunk  kits  are  known   for  quality,  innovaNon   and  high  producNon  value.  CoolJunk  has  been  featured   in   naNonal   and   internaNonal   journals   including   Wallstreet,   Yourstory,   Hindu   Business   Line,  NextBigWhat  and  was  tagged  as  the  coolest  Indian  start-­‐up  in  IAN  Bootcamp-­‐2011.  

For  more  projects  visit  our  website:  CoolJunk  

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