Electronic Basics #32: Relays & Optocouplers

  • Published on Oct 29, 2017
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    In this episode of Electronic Basics I will show you how a Relay and Optocoupler works and when it makes sense to use them. Along the way you will see a couple of practical examples and find out how to control these two components properly.
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Comments • 401

  • John Ripper
    John Ripper 21 day ago

    Can you please make the circuit drawings visible straightly please? This angle type paper drawing looks cool but is nauseating. Thank you.

  • Kadir K
    Kadir K 2 months ago

    thanks a lot!

  • ash0787
    ash0787 3 months ago

    optocoupler are COOL, I kinda guessed what it does though after seeing a video where someone used one in a coil gun design.

  • Pocketcraft006
    Pocketcraft006 3 months ago

    The only basic video that i understand

  • M Vijay Kumar
    M Vijay Kumar 4 months ago

    Please creat video on smpc type inverter

  • jassim javed
    jassim javed 4 months ago

    One thing I didn't understand is if the relay is galvanically isolated then why do voltage spikes of 255V occur at the push button?

    • Marcin Malcher
      Marcin Malcher 4 months ago

      The voltage spikes occur on the coil side of the relay, and that's where the button is. The reason for them is that as soon as the coil is disconnected it starts acting as a current source, and as the current has nowhere to go it creates those spikes.

  • Jeepudon J
    Jeepudon J 4 months ago

    Very gooddddddd explain thank so much you make very good explain for me a+++

  • Joao Carlos
    Joao Carlos 6 months ago +1

    1:10 Portugal!

  • kempossible Privateinvestigator

    Thank you for your videos! I have learned so much frim you. When it comes to quality, you are definitely king! Thanks!

  • Ehtesham Nisar Ahmed
    Ehtesham Nisar Ahmed 7 months ago

    Nice work as always
    Many years, i am in the field of automation.
    Initially, i was using arduino with mechanical relays but always an error due to spike voltage even with flyback diode.
    After that i started with TRAIC BTA41 which can sustain upto 40Amp.
    My system is working fine
    I also used this traic with stm32 works great.
    In my opinion, Traic is much superior than mechanical relay.
    A tutorial on this topic from your side will be highly appreciated.

  • nicholas berzsenyi
    nicholas berzsenyi 8 months ago

    It's a decoder, not an encoder

  • Nikita Makstadt
    Nikita Makstadt 8 months ago +2

    Mega Mind, you should go to NASA

  • Halo Fan
    Halo Fan 8 months ago

    They sound like electro magnetic transistors

  • arduino guy
    arduino guy 8 months ago

    Sir I don't understand 1 thing which is that a relay is same as wire. so a relay shouldn't have a power loss.

    • Alberto Gregory
      Alberto Gregory 8 months ago

      arduino guy power loss of a normal copper wire i think.

  • Mitchell
    Mitchell 8 months ago

    Damn, I just want to make circuits just like I did in minecraft and on a switchboard during physics class. I can't find anything on how to do that and this seems quite difficult to understand for a beginner.

  • Herman Brooks
    Herman Brooks 9 months ago

    The first 3 months when i was starting at electronics i didn't understand a word you say in your videos, now when i watch your videos again it all makes a lot more sence. Your videos are great for people who already know how those things work and need more detailed explanation to truly master the use of it

  • Bharatha
    Bharatha 9 months ago

    excellent video!

  • prabhat kumar
    prabhat kumar 9 months ago

    Great as always !!

  • Charlis Iyeli-Eney
    Charlis Iyeli-Eney 9 months ago

    Thanks man great Videos

  • indra verboden
    indra verboden 10 months ago

    Bisaan si akang eta

  • Gautam Ahuja
    Gautam Ahuja 10 months ago

    really nailed it man. awesome and so easy explanation. thank you man.

  • rst
    rst 10 months ago

    Why won't you connect a switch or an aplifier directly to the led circuit? Without using a relay?

  • Денис Иванов
    Денис Иванов 11 months ago

    Никуя не понял

    ODFPV 11 months ago

    Man I f'ing love the way you break things down.

  • ari pratama
    ari pratama Year ago

    I have a problem with opto isolator in my circuit it is still respond to command but only give weak current output around 2ma. I connect the output to drive 12v relay. Why is like that?

  • Shrey Sharma
    Shrey Sharma Year ago

    Hello sir
    I want to know if i can use a BTA41 triac with Moc 3021 optocoupler IC to control heavy loads such as Air conditioners, refrigerators, microwave ovens etc. or the appliances whose current ratings are more than 10Amps and power ratings are nearly 2KW and if this combination isn't the right one then please guide me 😃

    • Simhadri Gedi
      Simhadri Gedi 5 months ago

      and the relay also available at low cost compared with BTA41 and MOC3021

    • Simhadri Gedi
      Simhadri Gedi 5 months ago

      my dear sir the above combination is only for pwm application not for load on and off purpose .My opinion is choose 30A relay is best choice for your heavy loads controlling purpose

  • Prithvi Raj
    Prithvi Raj Year ago

    I am controlling a AC appliance with ardduino (5v) , what should I use - relay / solid state relay , help me with it

  • killaken2000
    killaken2000 Year ago


  • FS TECH Fazal Subhan

    Superb keep it up😘

  • nathanas64
    nathanas64 Year ago

    Thorough analysis! Really appreciate these videos!

  • Malluvalasa Johnkumar

    Is it possible to connect the diode series to the indicator such that in order to avoid high voltages at the tap key by stopping current in reverse direction?????

  • amitgutpa7
    amitgutpa7 Year ago

    Can relay be attach with the 2 way switch??

  • Endri Bedini
    Endri Bedini Year ago

    Very well explained. Thank you.

  • Matthijs Bonke
    Matthijs Bonke Year ago

    Very helpfull. Thanks😊 greetings from the netherlands 🇳🇱

  • Tanmay Krishna V
    Tanmay Krishna V Year ago

    Are you a lefty

  • Anurag Chakraborty

    Your writing style and diagrams are lit...
    Perfect for satisfaction...!

  • Javier Ferrer
    Javier Ferrer Year ago

    Sweet video! Thank you.

  • Ash Powell
    Ash Powell Year ago

    Great video, thanks.
    I came onto this video through trying to understand the role of a CLM50 opto which is present and used to control compression in an amplifier I am repairing.
    Unfortunately this IC is EoL and expensive to source, can you offer an opinion on a suitable replacement?
    This is the device in question - www.rodaronline.com/images/productos/pdf/adjunto_715_1.pdf

  • Old Curmudgeon
    Old Curmudgeon Year ago

    For smaller form factor relays I've noticed datasheets indicating they aren't designed for high duty cycles. I have a 12vDC thermostat project where I plan to use mosfets & a quad opti-isolator IC due to space constraints. I located some tiny relays w/ contact rating of 2A which is about 2x the expected load, but the coils are about 800mW & the datasheet indicated they shouldn't be left on for long intervals. I'm still looking for a schematic of the existing thermostat's board to see how the switching is handled.

  • Crazy Maker
    Crazy Maker Year ago

    THis is not good explanation

  • Shafin 007
    Shafin 007 Year ago

    I still dont understand what's the use of relays, you're literally adding voltage so that it turns on and lets current pass to power the next device. so basically a wire?

    • pamdemonia
      pamdemonia 3 months ago

      More like a switch. The main reasons to use them are :
      A) you want to switch on and off something using a lower voltage than the voltage you are switching. (say, using the 5v available on a MCU board to turn on and off a standard household light.)
      B) you want to isolate the electrical system of the thing you are powering from the regular electrical system. Maybe due to harmonics or extra sensitive equipment or something.
      There are other reasons, but those are the two main ones I see in the world.

  • David Delaney
    David Delaney Year ago

    The outlets in Germany have to be expensive. I bet they are super safe, but damn, we pay about 1-3 dollars for an outlet.

  • Vikash deep
    Vikash deep Year ago

    Nice sir

  • Gandhi Meet
    Gandhi Meet Year ago

    Nice sir

  • diregremo
    diregremo Year ago

    Woah, what kind of bits were those?

  • Dan Vizuet
    Dan Vizuet Year ago

    Thanks a lot! :DD

  • Shubham Chavan
    Shubham Chavan Year ago

    in 8051 uc

  • Shubham Chavan
    Shubham Chavan Year ago

    how to learn programing language in microcontroller for beginners

  • Shubham Chavan
    Shubham Chavan Year ago

    very nice video sir

  • Ben Hadj Slimen Nader

    Good Job, I like your amazing presentation !

  • Yasir Shahzad
    Yasir Shahzad Year ago

    power supply unit in the product??

  • edidiong ekpo
    edidiong ekpo Year ago

    Great video

  • edidiong ekpo
    edidiong ekpo Year ago

    I love your videos.

  • polymetric
    polymetric Year ago

    Relays are good for relay big loads.

  • i u
    i u Year ago

    i was waiting for the time when you say " but there is a problem ", ha ha ha so getting used to it now, found it @3:45 . PS: you explain things just the best way i cold possibly think of. Keep up. Thanks.

  • Muhammad Aarif
    Muhammad Aarif Year ago

    Hello sir.. Can i use the mct2e optocoupler ic to switch my relay using esp 8266...NEED HELP

  • Shreyas Kulkarni
    Shreyas Kulkarni Year ago

    Optocoupler galvanically isolated? :/
    Maybe you ment optically isolated...

    • Johannes
      Johannes 4 months ago

      No, they also provide a galvanic isolation.

  • mayur chudasma
    mayur chudasma Year ago

    can we use 4n25 as voltage buffer by controlling irled current

  • Manoj Horo
    Manoj Horo Year ago

    You are awesome

  • Christian Tambe
    Christian Tambe Year ago

    Awesome video and clear explanation !