ive never used an opto isolator before, and im thinking it will be the best thing to use for a project im working on.

my local supply has a few of these on the shelf, and im just curious how to use them. pins 1,2,4 and 5 are no-brainers, but i dont know what to do with the base connection.

say i wanted to use the transistor to control a cmos gate....i would tie the emmiter to gnd, and a 1k resistor between Vdd and the collector. what do i do with the base pin?

 

You just leave the base open. You will find that a larger pullup will work better, as the 1K value will probably not let the transistor go to 0 volts. See if 47 K doesn't work better.

 

here is a link to a circuit posted in another thread on how to connect it with test function for the base..... post #15 here >>http://forum.allaboutcircuits.com/showthread.php?t=29326&highlight=Optocoupler&page=2

 

cool! thanks guys, much appreciated.