DESIGN AN H-BRIDGE
DESIGN AN H-BRIDGE Before starting design you should know the following things 1. Type of motor you want to drive(it can be dc motor,stepper motor,servo motor) H-bridge is meant for DC motor, but here I am talking about the selection of transistor for the purpose. 2. Know the maximum ratings of the motor. Small DC motor will have 12v,250mA and some small steppers 24V,600mA. You should know this because you have to choose appropriate transistor. 3. Now you have Vmax and Imax ratings of the motor, so select a transistor(mostly power transistor with these ratings. i.e Maximum Collector Voltage should be greater than Vmax and Maximum Collector Current should be greater than Imax 4. If you are using PWM to drive the motor select a transistor which works with high frequency(less switching time), but mostly this condition is normally avoided.
see the transistor ratings of a normal transistor and power transistor
5. Before you choose the transistor you should be very well aware of the
ratings of the transistor. Search in google for its datasheet.
6. Mostly we go for h-bridge having two leads, for that you have to
use a PNP and an NPN transistor. See in the diagram
This is the ideal H-bridge
7. Remember the truth table of a normal H-bridge IC(like L293D,L298)
8. Verify your designed H-bridge with the truth table.If you are getting
any short circuits in any of the condition then your circuit is wrong.
9. If you are designing H-bridge only with NPN or PNP transistor(this
is mainly used for microcontroller and parallel port), see the
link below, there you can see the H-bridge designed with 4 NPN
transistors
see http://booksbybibin.14.forumer.com/viewtopic.php?t=54
10. Choose NPN and PNP transistor such that both transistors have identical
ratings. See some complementary pair like SK100 and SL100.
11. See one motor driving circuitary designed. Find fault in it
Now you find fault in the circuit. See when the condition P=Q=1(5V)
then VCC and ground gets short circuited. So this is not an ideal
H-bridge eventhough it works properly for all conditions except P=Q=1
12. See this H-bridge
This can be said as inverse H-bridge because, it When I1=I2=1 the
two ends of the motor will get 0V(It should be Vcc for normal H-bridge)
When I1=I2=0 the two ends of the motor will get VCC
(It should be ground for normal H-bridge)
13. Now you make your own H-bridge using NPN or both NPN and PNP transistor
according to your requirement. Remember the above points while designing
DESIGN AN H-BRIDGE Before starting design you should know the following things 1. Type of motor you want to drive(it can be dc motor,stepper motor,servo motor) H-bridge is meant for DC motor, but here I am talking about the selection of transistor for the purpose. 2. Know the maximum ratings of the motor. Small DC motor will have 12v,250mA and some small steppers 24V,600mA. You should know this because you have to choose appropriate transistor. 3. Now you have Vmax and Imax ratings of the motor, so select a transistor(mostly power transistor with these ratings. i.e Maximum Collector Voltage should be greater than Vmax and Maximum Collector Current should be greater than Imax 4. If you are using PWM to drive the motor select a transistor which works with high frequency(less switching time), but mostly this condition is normally avoided.
see the transistor ratings of a normal transistor and power transistor
5. Before you choose the transistor you should be very well aware of the
ratings of the transistor. Search in google for its datasheet.
6. Mostly we go for h-bridge having two leads, for that you have to
use a PNP and an NPN transistor. See in the diagram
This is the ideal H-bridge
7. Remember the truth table of a normal H-bridge IC(like L293D,L298)
8. Verify your designed H-bridge with the truth table.If you are getting
any short circuits in any of the condition then your circuit is wrong.
9. If you are designing H-bridge only with NPN or PNP transistor(this
is mainly used for microcontroller and parallel port), see the
link below, there you can see the H-bridge designed with 4 NPN
transistors
see http://booksbybibin.14.forumer.com/viewtopic.php?t=54
10. Choose NPN and PNP transistor such that both transistors have identical
ratings. See some complementary pair like SK100 and SL100.
11. See one motor driving circuitary designed. Find fault in it
Now you find fault in the circuit. See when the condition P=Q=1(5V)
then VCC and ground gets short circuited. So this is not an ideal
H-bridge eventhough it works properly for all conditions except P=Q=1
12. See this H-bridge
This can be said as inverse H-bridge because, it When I1=I2=1 the
two ends of the motor will get 0V(It should be Vcc for normal H-bridge)
When I1=I2=0 the two ends of the motor will get VCC
(It should be ground for normal H-bridge)
13. Now you make your own H-bridge using NPN or both NPN and PNP transistor
according to your requirement. Remember the above points while designing