How Optocouplers Work and How to Use Them - DC To Daylight

[@7alfatech860]

Hi Derek, thank you for not oversimplifying the topic! I really appreciate how you show the derivation of the values from the data sheet, etc. In addition, it is great to hear some industry level concerns too, like longevity, which most presenters simply gloss over.

[@AmRadPodcast]

Thanks 7Alfa. Yes, it always kind of bugs me that the long-term reliability stuff is left out in the text, but then again we don't usually consider designing stuff to work the same 40 years out. -Derek

[@t1d100]

I enjoy Derek's teaching style.

[@AmRadPodcast]

Thank you very much! -Derek

[@justovision]

Another use: Optocouplers are part of the MIDI standard to prevent ground loops between devices.

[@AmRadPodcast]

I hadn't considered that, but I would like to play with MIDI someday. My wife has an old keyboard with a MIDI output, now to think of an interesting project! -Derek

[@tinkmarshino]

I like your show. though it is still way above my head it gives me incentives to understand the subject for the day.. and is one of the best things I have found to help me learn.. The old sink or swim routine.. it has always worked for my though at 70 it is getting a bit harder but I still find it fun.. I thrive on a bit of challenge.. thanks guys.. you really have helped in my quest to learn electronics (at least the basics) carry on!

[@AmRadPodcast]

Hey tinkmarshino - This is great feedback, and it's cool to hear that these topics are helpful to someone learning on their own. Please keep coming back... I've got tons of back to basics stuff in the works. -Derek

[@rollahelp2619]

Thanks Derek; Excellent ! I'm also a great fan of opto-couplers, & have regularly used the MOC5007 series, as it has hysteresis, in the output stage, which provides a nice clean square switching transitions. I only recently came across the A817V, which provides a much smaller footprint, than the MOC5007, & as my circuits have lots of 4093s, then the opto output gets squared up anyway. I'm into automotive ignition & ECUs, with trigger wheel/flying magnet crank signals, & if there is any place an opto is required, to reduce noise, then automotive projects, have got to be right up there.

[@24tcwarrior]

Would you happen to have something that takes a 5V TTL input signal and output of a delta 100V square wave? I.e. -20V - 80V, 0V - 100V, etc. Or could you possibly point me in the right direction? I was looking to use a 4N25 Optoisolator.

[@SeanBZA]

Yes, useful as you can easily get inversion, even if you do not want isolation, or to interface to different voltage levels as well. Plus the simple way to do high side drive, though the on state voltage drop can make it bad with bipolar, but the mosfet driver versions are great for making N channel switches that are easy to interface although they are also going to be slew rate limited.

[@AmRadPodcast]

Hi SeanBZA. Interesting application as a high side driver. I hadn't considered that for the demonstration, but this may make a good future topic when I start poking around with FETs. Thanks for the feedback. -Derek

[@taintedmeat9740]

Nice equipment collection in the back ground !

[@fixitalex]

Back in the days we were making it the hard way with led and photo-transistor.

[@AmRadPodcast]

I once tried making an automatic dog feeder. I needed a way to determine if there was food in the dish, and ended up using an led to illuminate it, and a phototransistor to detect reflected light. It worked great... in the dark. That's when I learned about modulating the signal in order to work in daylight - back to the drawing board kid. :) -Derek

[@richardcletus6026]

Ive been trying to firgure out how and where to jam some PC817s into a guitar or pedal. Had no idea how they worked or how I could apply them, but I have a hunch now. Vague hunch, but I have a big pack of components and a breadboard. Time to get pragmatic.

[@grins047]

Super useful. Thank you!

[@LandMineFX]

For some reason, I'm having issues with pwm when connecting the LED side to an Arduino, and the transistor side to a guitar signal in a PC817 optocoupler. Any attempt to adjust the brightness of the internal LED introduces noise into the signal unless the LED is all the way off or all the way on. Wonder why?

[@OdinsCloud]

Good video, good channel!

Optocouplers are often used in the retroaction loop of switching power supplies, where they are probably biased. Does that mean that the regulation will get off as time goes? That might explain faults on old mains connected boards and PSUs?

[@arunsebastian4035]

can i use schmitt trigger optocouplers instead of NAND gate for switching ?

[@sarimbinwaseem]

What about high volatges? like 240V AC to micro controller.. I want to get signal from AC voltage to micro controller.. How can I calculate the RIN value.. acc to your formula it's 47K resistor.. will it work?

[@lordofelectrons4513]

Another use is dealing with noisy mechanical switches like a micro switch on the end of a long cable especially if that cable is conducting power or other signals.

[@paradiselost9946]

how about doing this for linear/analog? its strange, that with arduino etc being so popular, that interfacing and isolating an analog signal seems so overlooked... been waiting a month for hcnr200, got sick of it, been playing around with pc817s in a cross coupled feedback loop with some promising results... input drives the isolated output, thats fed back to the output LED to drive an isolated feedback loop in the input... im not actually concerned about precision, as long as its pretty close and its isolated... it all seems fairly linear so far...

[@greatscott36]

I'm confused, I see he uses the resister on the positive side but I look up circuits and it shows the other side, dose it matter witch side or...?

[@24tcwarrior]

It shouldn't matter because all you are doing is setting up a voltage divider to get the necessary Vf = 1.2V to drive the LED side.

[@loverboykimi]

Good Stuff! Thnks.

[@CABohol]

I made a DIY Vactrol VTL5C4 for my Audio limiter circuit.

[@AmRadPodcast]

Awesome. That sounds like a fun project. -Derek

[@Damaraja]

Cool 👌

[@assistantto007]

Galvianic?

[@Acein3055]

Good subject matter. Good narration. Good engineering design work. The overall video presentation is annoying because you keep switching the video back to showing you.

[@MAYERMAKES]

if your video had just come out a week earlier it would have saved an arduino....oh well

[@AmRadPodcast]

Oh no! Sorry to hear about your loss Clem. I hope you had a backup. -Derek