Dear everyone.thank you for open my question. i have a problem in my project. the diagram is shown in the jpeg picture.my problem is about the 4N26. as shown in the picture, when the input of the full wave rectufier is 8VAC single phase, the output of the 4N25 are very low which is not detectable by the hc11 microcontroller. after i increase the input voltage to 16VAC, the output value of the 4N26 are still remain same or just increaly very slightly. when i remove the AC supply to the rectifier, i get the same value at the output 4N25. how could this can happen? since the AC supply already removed? how to solve it? what i want in my project is when the input of the rectifier increase, the output of the 4N26 also will increase. meaning input AC source of VAC should propotional to the output of the 4N26. the 5 V supply is supply from the microcontroller, and the range which the microcontrooler can acceprt from the output 4N26 is form 0 to 5V. any mistake in my circuit? the first ua741 and TL081 are use a peak detector to detect the peak voltage form the full wave rectifier. very thank you for your solution.
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