Hello
I am trying to make a switch to control LED
In this schematic below
I am trying to operate the Opto-Isolators so the D9 Led could light up.
Me and my friend asume that If same voltage connected(Yellow Circle) the output will be 0v(Blue Circle) Is that true??
My friend tell me that it must have Resistor connect to ground (Red Circle) It that neccesary ? If yes, Why?
Thank for help.
I am trying to make a switch to control LED
In this schematic below
I am trying to operate the Opto-Isolators so the D9 Led could light up.
Me and my friend asume that If same voltage connected(Yellow Circle) the output will be 0v(Blue Circle) Is that true??
My friend tell me that it must have Resistor connect to ground (Red Circle) It that neccesary ? If yes, Why?
Thank for help.