# MOC3021 optocoupler not working ( or not working , a bit confused )

## My Understanding

As far as my understanding of MOC3021 optocoupler goes, it should latch pins 4 and 6 whenever there's a current flow between pins 1 and 3.

# The Confusion

## Image 1 - D1 not glowing and D2 glowing

So, in this image no current flows between pins 1 and 3, however pins 4 and 6 is latched.

Same happens on the breadboard except that even the LED between 4 and 6 isn't glowing either on the breadboard ( unlike the simulation ).

## Update : Yes increasing current works out fine

Actually it's part of an arduino circuit in which I would be giving an output from an arduino pin to this, and there won't be any LED ( not white one for sure as I came to know now that it requires more voltage ).

So, perhaps it would be fine with an arduino pin, this was just to check the components before hand. Also , since MOC3021 has 15 mA forward current, so 5V would do the work ( as high in arduino pin would give 5V ). I suppose even 3.3V would do the work.

Thanks all .

### I am a newbie in this field , so it's great to get those tidbits of info.

• Try to increase the input current to 20mA – G36 Nov 22 '18 at 17:52
• Your diagram shows a red LED but it looks white in the picture, White LEDs have a much higher forward voltage than red, it's almost a miracle it lights up at all. – Finbarr Nov 22 '18 at 17:59
• I only buy the MOC3023 because it requires less current. My memory says that you need $5\:\text{mA}$ for the MOC3023, $10\:\text{mA}$ for the MOC3022, and $15\:\text{mA}$ for the MOC3021. And in all cases I plan on $1.5\:\text{V}$ for the emitter diode. – jonk Nov 22 '18 at 17:59
• That's a great piece of info Finbarr and jonk, I am a newbie in this field , so it's great to get those tidbits of info. – Sizu Taylorventuresllc Nov 22 '18 at 18:15