Hi,i use a circuit in order to observe if a device is under the net of 220 volt.
But ,when i do not have 220v i take an instant sign that i have 220v.Can anybody help me?
The optocoupler TIL 111 ensure the isolation between the net of 220v and 8051.
I have to mention that the output of optocoupler is a pulse current,for this reason i use the capacitor c1 that makes the T1 transistor to have an output of 5v continuity .
i use this rutin with the method of polling.
where i do wrong?
SETB P1.2
MOV A,P1
ANL A,#00000100b
JNZ SIG
CALL sign_on
JMP EXIT
SIG: CALL sign_off
EXIT: END

______________________5v
| R3
|_//_______________out
R1 R2 | _|_ |
_//_//____1 | c1 ___ _|
| | _|___|_5 |_____|/ T1
~ 220v | | IC1 | | |>
| D1 /_ |_______| | |
|________|____| |_______| |
2 4 | R4 |
|_//__|
_|_gnd

Where:
R1,R2=100K
R3=5K6
R4=1M
C1=100n
D1=1N4148
T1=BC550C
IC1=TIL111 Optocoupler

thank you for any help