Learning About Optocouplers


As a long term goal I'm wanting to connect an Arduino to a toy car driven by an electric motor. While there may be alternative approaches I decided to try to use an optocoupler (opto-isolator) to make it all work. While I discovered a number of pages that talked about various implementations of this idea I didn't find one that put all the details together in one place in such a way that it "clicked" for me. This page hopes to document what I've learned so that someone else might learn from it.

I find it helpful to be able to view schematics and images side-by-side to be able to picture how a particular circuit is supposed to look, so that's my aim here.

Getting started

My initial goal was to get a simple LED circuit controlled by another circuit through an optocoupler.

For reasons I can't remember (probably availability) I ended up purchasing some 4N25 phototransistor optocouplers from a local Christchurch component supplier. (Note that the datasheet linked is more recent than what I used and refers to the "-M" variety that come in white packages rather than black.)

@@ TODO: To be continued


Circuit photos