I have an optocoupler that has a max forward voltage of 1.65 and a max reverse voltage of 6.0 does this mean i can only apply a max of 1.65v to the collector? or can i apply 5v? I get confused about forward a reverse voltages.

 

The input to the opto-coupler is an LED so you will need a current limiting resistor to avoid exceeding the maximum current applied to the input.

Applying a reverse voltage in excess of the rated 6V should be avoid also.

hgmjr

 

The foreward voltage is the voltage necessary to place the internal LED into conduction. As long as there is that much voltage present, the LED will emit light. Then it's a matter of limiting current to less than the maximum rating with resistors.

The reverse voltage is the greatest voltage the LED can withstand in reverse bias. More than 6 volts will send the LED into avalanche conduction and destroy it.

 

Thank you that makes sense to me, the textbook answer i got online did not make that much sense. So if I were to put a 5v signal from an AVR for no more then 2 seconds the chip can withstand it especially if i put a pull down resistor on it.

 

If the voltage is in the reverse direction, then a resistor will not help. Add a diode in series with the LED to block the reverse voltage.

 

What is the part number of your optocoupler?