Part of Made in India,Design Innovation

Workshop,2015

A  Fresh  New  Experience  in  Project-­‐Making  &  Learning!

PHYSICS INVESTIGATORY PROJECT ON

H-BRIDGE USING TRANSISTORS

The  H-­‐Bridge  circuit  also  known  as  a  motor  driving  circuit  is  used  in  robo9cs  to  drive  motors  forwards  and  backwards.  You  can  make  an  H-­‐Bridge  circuit  and  control  the  direc9on  of  motor  rota9on  by  controlling  the  polarity  of  applied  voltage  across  its  terminals.

In  this  project,  you  will  need  a  breadboard,  four  transistors  (PNP1,  PNP2,  NPN1,  NPN2),  a  DC  motor,  four  diodes,  four  resistors  and  a  few  connec9ng  wires.  The  connec9ons  are  made  such  that  the  collectors  of  all  the  transistors  are  connected  to  the  motor  and  the  circuit  has  an  H-­‐like  configura9on  with  a  load  (motor)  at  the  center.

The  circuit  was  tested  by  giving  different  polari9es  to  different  base  resistors  (R1,  R2,  R3  and  R4)  and  the  behavior  of  the  motor  was  observed  at  each  condi9on  and  the  results  were  compared  to  the  following  output  table:

R1 R2 R3 R4 Direc+on  of  current

Effect  on  the  four  transistors

Effect  on  motor

Ground No  Supply No  Supply Vcc LeC  to  right PNP1  and  NPN2  turns  ON Motor  spins  clockwise

No  Supply Vcc Ground No  Supply Right  to  leC PNP2  and  NPN1  turns  ON Motor  spins  anHclockwise

Ground No  Supply Ground No  Supply -­‐ PNP1  and  PNP2  turns  ON Motor  breaks

No  Supply No  Supply No  Supply No  Supply -­‐ No  Supply Free  rotaHon

AQer  verifying  the  experimental  outputs  in  four  different  cases  of  the  inputs,  we  do  the  ‘path  of  current’  analysis  and  reason  out  the  motor  behavior  by  iden9fying  which  transistors  turn  ON  in  each  case  .  All  the  transistors  used  above  are  in  the  satura9on  region.

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