Simple isolation circuit using optoisolater, how come it doesnt works? Need help!?

Question

Hi guys, i am trying to do one simple isolation circuit, here is the schematics.

http://img99.imageshack.us/img99/597/pic1tc7.jpg

any idea why is it not working? basically i am using the left side to act as a trigger thingy and the right side vout as 5v when the left side is being triggered. which area did i went wrong?.?

Answer 1

It looks like it should work, but when the input is on, the output on pin 6 will go to zero, because the transistor will turn on.  In order to tell that it is on, you need a resistor from pin 6 to Vcc, because the optocoupler is not putting out a voltage, it is just changing its resistance.  Probably anything from 1K to 10K would work fine.  You don't have a value on R1; I assume you have a value that will give the correct current to turn on the LED.  I don't know what type of optocoupler it is, but probably about 1K or a little less would work there.

Answer 2

you are missing the schematic of the right part.

Circuit won't work without additional components. connect pin 5 to ground, pin 8 to +5, pin 6 to +5 via a 1000 ohm resistor, and pin 7 open (a 560 ohm resistor to ground from pin 7 may improve operation).

Look at the voltage at pin 6 for your output.

R1 should be about 330 ohms, look at the data sheet for more info on this.

If you had looked at the data sheet for the part it probably would have told you all of this information. Never use a part without reading the data sheet.

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