i want to test HCPL 072 optocoupler

Thread Starter

Asad Saleem

Joined Nov 8, 2020
hello.. i dont know how to post my quetion so i m writing my question here..
i want to test HCPL 072 optocoupler but there are 2.4v on its VO pin without giving input signal to LED.. and when i give input signal then there are 5v on its VO pin..
i want to operate NPN transistor with optocoupler's VO pin.. but transistor turns on without giving input signal to optocoupler.. bcz there are already 2.4 volts..
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Joined Sep 17, 2013
Welcome to AAC!
Post a schematic of your setup, with all components labelled (e.g. R1 etc) so that we can see where the problem might lie.
If your circuit is on a breadboard then a close-up sharply-focussed picture too could be helpful.


Joined Jun 26, 2012
Be sure you are actually grounding VIn (pin 2) to GND (pin4) to turn the output off. The opto has internal drivers that probably won't work right if you just leave the VIn pin open. VDD1 and VDD2 must be OK on both sides of the opto to power the internal circuitry.
Here's the datasheet: