TIP41/TIP42 H bridge with arduino

[warrad]

i try to design an h bridge to drive 24 v / 5 amps motor(for a wheelchair) and connect it to arduino , i design a circuit and attached it with this post , i use TIP41/TIP42 and 2N2222 transistors in my design and i use these data form the data sheet :

HFE for the TIP41=15
V(BE) = 2 V
and for the 2N2222
HFE = 30
V(BE)=2.6
are these data correct ???
and this is the schematic...


in addition i need to just control the direction of rotation with no speed control

with thanks

 

[ericgibbs]

hi W.

What purpose do Q3 and Q4 serve, they are always turned ON.

E.

 

[warrad]

thanks for you E.
if Q6 turned on then Q1 will turn on too,thus the current will take the bath of Q4 , and the same is applies on Q3...

 

[ericgibbs]

thanks for you E.
if Q6 turned on then Q1 will turn on too,thus the current will take the bath of Q4 , and the same is applies on Q3...

hi W,
I see that.

But Q3 will be On and Q6 current will flow thru Q3.???

 

[warrad]

oops ... you are right ... i will modify the schematic ... thanks a lot but abut the calculations of the resistors and the value i used from the data sheet its correct ??

 

[ericgibbs]

oops ... you are right ... i will modify the schematic ... thanks a lot but abut the calculations of the resistors and the value i used from the data sheet its correct ??

hi,
Regarding your calculations, as they are incomplete its not easy to say they are right.


A point to note:
You have Q6 and Q1 as emitter followers.

This means the emitter of Q1 to the motor can never rise above 5V - [2 *0.7V ]... thats assuming the arduino is outputting 5V.

Each emitter of Q1 and Q6 'loses' a 0.7V drop. OK.??

 

[alec_t]

As Q1 and Q2 are being used in emitter-follower mode and you don't have a level-shifter stage between the Arduino and the all-NPN H-bridge the maximum voltage applied to the motor (ignoring the fact that Q3 and Q4 will shunt current to ground) will be the Arduino output voltage (5V) - Q6Vbe - Q1Vbe = ~3.8V.

Edit: Eric's post crossed with mine (again!). We're obviously thinking along the same lines.

 

[warrad]

thanks for all ... i look in the circuit and i will do some modification and re post it a gain >>> thanks for you a gain

 

[Nigel Goodwin]

thanks for all ... i look in the circuit and i will do some modification and re post it a gain >>> thanks for you a gain

Just a quick tip - to use the transistors as switches (which is what you want), the outputs should be from the collectors, NOT the emitters.

For an example of a small H-bridge for a little robot with full description, check my website here: