i have not connected lm358 ckt,
i want the output of T1(as in first diagram) to be given to MUC 8051 but the output is analog one..
how do i get the digital output???
to give the output of L1 and T1 to comparator, the output measures around 1.8v!!
please help... please
There's no LM358 in the first schematic, which is a purely analog circuit and will be best suited for an A/D-input.
No matter how much gain you add, there will always be a range where you have an analog transition.
mentioned, digital is merely analog driven to the extremes.
The op-amp circuit is also best suited for an A/D-input, but could be changed relatively easy (move the feedback resistor) to give a digital output, just change the negative feedback to be a positive feedback an adjust the value for a sensible shift point. That way the output signal will be either "1" or "0".
If you want to stay with transistors, let the photo transistor control a 2-transistor Schmitt-trigger and you will get approximately the same functionality.