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- The transistors Q1,Q2,Q3 and Q4 form the bridge circuit. Generally these are power transistors capable of handling high current.Q5 and Q6 drive the bridge. when the 'A' is made high and 'B' low, transistor Q5 is on and it makes Q1 and Q4 on. The current flows from vcc to ground through Q1,motor and Q4.hence the motor rotates in forward direction.
- When 'A' is made low and 'B' high the transistor Q6 is on and it makes the Q3 and Q2 on.The current flow from vcc to ground through Q3,motor and Q2.hence the motor rotates in reverse direction.
- When both 'A' and 'B' are low all the transistors are cutoff.
- Making both 'A and 'B' high simultaneously should be avoided.
The circuit doesn't work fine. When you connect resistors across the terminals its fine but when you connect a dc motor then it wont work. NO VOLTAGE ARRIVES ACROSS THE MOTOR TERMINALS!!
ReplyDeleteWhat about, you have connected the emitters of Q1 and Q3 and collectors of Q2 and Q4 to the motor coils,
ReplyDeleteweren't you have used the collectors of all transistors???
Shohaib1@gmail.com
I doesn't work, you have to make the correct analysis
ReplyDeletethanks for the info. i'll appreciate this note.
ReplyDeleteSince the voltage drop across the motor is (I'm assuming) higher than the voltage available from your inputs ( A & B ), you will need a PNP transistor for transistors Q1 ,Q3 ,Q5 , and Q6 instead of a NPN transistor.
ReplyDeleteYou also might want to throw in a nice big 200+ uF capacitor in parallel with the circuit to eat up any inductive EMF that that your motor will spit back out to you, so you don't fry anything when you overload it.
Also make sure that A and B are NEVER on at the same time. You'll short your circuit and things will burn up...I mean, unless you want things to burn up.