View Full Version : Doubt regarding H bridge

02-17-2005, 11:56 PM
Hi Friends,
I created the H bridge circuit myself using BC547 and BC558 transistors. But when i give the digital inputs the motor is not rotating. When i turn the motor a bit then only it starts to roate. I dont know why.What must be the reason.

Thanks a lot

With warm Regds,

02-18-2005, 06:41 AM
A classic case of a motor needing high starting torque and not getting it. Motors require higher starting torque which translates to higher current drawn in the beginning of its motion. If that current is not provided the motor wont turn until it is nudged. You might actually hear some noise from the motor.

a) Use a motor that requires lesser current
b) Use PN2222A transistor instead of BC547 and PN2907A instead of BC558

02-19-2005, 12:11 PM
Hey pal,
Thanks for ypur suggestion. I planned to get the transistor u told me. But the problem is tht it is not available in the shops. Can u tell me some other substitutes which is popularly available or some more additions to the circuit such that it will drive the motor.
Thanks in advance,
With Warm Regds,

02-21-2005, 09:05 AM
Hi dude,

Ur profile shows that you are in chennai ant its impossible that u didnt find the transistors there. check out majestic (next to texonics) or electronica (the philips dealer shop painted in blue somewhere to the left of supreme) or rotek ( wil be expensive and should be the last option) - all these shops are in ritchie street. Look around and ur sure to find them.


03-26-2005, 02:22 PM
Hi Buddy,

Have you heard of LMD18245T it is a 3A/36V H bridge IC from National , It may not be available in shops but you can always get free samples from www.national.com . This being the same IC used for driving Mars Rovers, The guys at national never deny this request and the IC is damn good. Got speed control due to an integrated DAC and also got direxion control wid brake. This is the godfather of driver ICs. btw L293d does the work too !!

Ranjit Puri
Vivekanand Engineering college
Mumbai University

03-26-2005, 04:34 PM
Neat IC ..

Thanks for the post ranjt...seems pretty good from what you're saying
I'd love to get one of those


09-02-2005, 04:58 PM
u can use 2N6107 and D880

I used it

connect 150Kohm to base of transistor and digital input

the one I used


Bibin John

12-01-2005, 09:36 AM
Hi ppl,
Here is another one worth trying... MC33886 ... from freescale. Very easy to interface and has humongous ampereage. use the HSOP package only the other one is a big mess to solder.

Regz .. Ranjit

12-11-2005, 12:50 AM
use l293d
or lmd18200
or uln2803