opto coupler

:?:

can help me guys how to use an opto coupler in a circuit.

i just experince repairing switch mode power supply I suspected a defective opto coupler, then I replace it (PC817). The Tv set powers on.

Another experince is when I check for resistance in the pin 4 (PC817) of a opto coupler the LED for stand by circuit the LED blinks.

Can you help with this guys Im confused on how a opto coupler used in a circuit like for example in the switch mode power supply, how a opto coupler isolates the high voltage section and low voltage section?

sorry for this question? I always want to explore more in electronics.

thanks. GOD BLESS YOU ALL.

It would really help to have a schematic of your application.

Sometimes opto-couplers are used in a linear mode to transmit linear signals across the isolation barrier, but more often they are used to transmit on/off control signals or modulated pulses (either pulse width or pulse rate information).

Measuring with an ohmmeter in circuit under voltage: not a good experience. The reaction (LED blinks) in this case understandable and lucky. (in worst case : bang!)
Without sematic and/or experience measuring is senseless.
If the circuit contain IC, the datasheet is helpful.

thanks guys for the post.

but how could so say that a opto coupler is defective?

jin29_neci said:

thanks guys for the post.

but how could so say that a opto coupler is defective?

Click to expand...

An opto-coupler is (usually) just an LED and a photo-transistor, it's simple enough to test statically - but for power supply use a static test doesn't prove much!. Far easier to test it by substitution.