Part of Made in India,Design Innovation

Workshop,2015

A  Fresh  New  Experience  in  

Project-­‐Making  and  Learning

PHYSICS INVESTIGATORY PROJECT ON

NOR GATE USING TRANSISTORS

Do  you  know  what  controls  the  mixing  machine  that  blends  ingredients?  The  concept  of  a  2-­‐input  NOR  gate  will  help  you  understand  this;  it  has  two  inputs  (A  and  B)  and  only  one  output  (Q).  Each  ingredient  is  stored  in  the  hopper.  Inside  the  hopper  a  proximity  switch  is  mounted  which  acts  as  a  sensor.  

If  the  level  of  any  of  the  ingredients  is  below  the  minimum  level,  the  corresponding  sensor  will  send  input  1  to  the  NOR  gate,  causing  the  output  to  go  low  and  hence,  the  mixer  turns  OFF.

However,  if  the  level  of  all  the  ingredients  is  above  the  minimum  level,  only  then  the  sensors  will  provide  inputs  0  to  the  NOR  gate,  causing  its  output  to  be  high  and  hence,  the  mixer  turns  on.

In  this  project,  you  will  make  a  NOR  gate  logic  circuit  using  two  transistors  (Q1  and  Q2),  four  resistors,  an  LED  and  a  few  connecSng  wires.  The  emiTer  of  Q1is  connected  to  the  emiTer  of  Q2.  Similarly,  the  collectors  of  the  two  transistors  are  connected  to  each  other.    Two  wires  are  connected  to  

the  leV  leg  of  the  base  resistors.  Each  connecSng  wire  represents  the  input.  This  input  could  be  either  1  or  0,  where  1  stands  for  Vcc  (posiSve/high  voltage)  and  0  stands  for  ground  (negaSve/low  voltage).

To  provide  the  respecSve  inputs,  the  truth  table  of  OR  gate  is  followed.  

Input  A   Input  B Output  Q0 0 10 1 01 0 01 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.  AVer  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,  innovaSon   and  high  producSon  value.  CoolJunk  has  been  featured   in   naSonal   and   internaSonal   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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