# 6n135 Optocoupler 24vac input

#### Tom544

Joined Mar 14, 2016
29
#1, I connected the 6n135 optocoupler on my breadboard with 5vdc. pin8 >5v, pin5>GND, pin6>Vo with 1K pullup resistor. Input side pin2 >5v thu 220 ohm current limiting resistor and pin3 > GND. I get 15.9 mA on input side, with output (High in = Low out).

#2, I kept all the same on output side and connected 24vac (26.2 vac, 37v rms) to pin2 thur 2.2 K resistor and a diode and pin3 to the other side. I get 5.0 mA of current on input and pulsed output.

#3, I changed the diode from series to parallel across pins 2 & 3. with 2.2 K resistor in series with the 24vac input I get .18 mA on the input and pulsed output.

#4, I connected 24vdc to pins 2 & 3 with a 2.2k resistor in series and I get 10.1 mA. 24/.01 = 2.4k (ok) The lowest current was 6.5 mA to get a steady output.

Why am I getting the low current readings on my meter for #2 & 3? Because of the half wave DC input?
Which is the better way to go for connecting the diode if needed?
I believe 10-15 mA should be good on the input. The Output will go to an Arduino Uno pin #7 and input will be 24vac from HVAC system when completed.
Thanks for any help!
http://www.vishay.com/docs/83604/6n135.pdf

#### Alec_t

Joined Sep 17, 2013
14,234
If I've understood your circuit description correctly, both #2 and #3 should give much the same results; an average input diode current of about 8mA.
Here's a simulation:

Your low current readings are probably due to your meter not responding correctly to the weird waveform it is seeing.

#### Tom544

Joined Mar 14, 2016
29
Alec, I believe the waveform is affecting the meter reading. Which way to connect the diode is the best?
On your diagram, V1 or V2? or it doesn't matter?
Thanks!

#### Alec_t

Joined Sep 17, 2013
14,234
Doesn't matter.