November 1, 2010
Hi, I have been trying to get this h bridge right for almost a month now, ( see attached pdf)
I have a 1K res in front of the opto isolators Collector for current limiting. The opto isolator's LED is powered by a micro-controller. According to my code. When 1 is high 4 is high and when 2 is high 3 is high.
So current has to flow from 1 to 4 and from 2 to 3 according to me respectively depending on what is high. But guess what, if the base has no power, then current flows freely from collector to emitter and the other way round as well. So it has no effect if I put a high on the base. And then one of the FET's goes up in smoke if I did not jet put a high on the base, or I can put a high on the base, no difference.
Can some one please help me with this. I am on the edge of loosing all hope.