Vacuum Tube Logic Hack Chat

Digital logic, the old-fashioned way

Wednesday, December 9, 2020 12:00 pm PST Local time zone:
Hack Chat
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David Lovett will host the Hack Chat on Wednesday, December 9, 2020 at noon Pacific Time

Time zones got you down? Here's a handy time converter!

Join Hack ChatFor most of us, circuits based on vacuum tubes are remnants of a technological history that is rapidly fading from our collective memory. To be sure, there are still applications for thermionic emission, especially in power electronics and specialized switching applications. But by and large, progress has left vacuum tubes in a cloud of silicon dust, leaving mainly audiophiles and antique radio enthusiasts to figure out the hows and whys of plates and grids and filaments.

But vacuum tubes aren't just for the analog world. Some folks like making tubes do tricks they haven't had to do in a long, long time, at least since the birth of the computer age. Vacuum tube digital electronics seems like a contradiction in terms, but David Lovett, aka Usagi Electric on YouTube, has fallen for it in a big way. His channel is dedicated to working through the analog building blocks of digital logic circuits using tubes almost exclusively. He has come up with unique circuits that don't require the high bias voltages typically needed, making the circuits easy to work with using equipment likely to be found in any solid-state experimenter's lab.

David will drop by the Hack Chat to share his enthusiasm for vacuum tube logic and his tips for exploring the sometimes strange world of flying electrons. Join us as we discuss how to set up your own vacuum tube experiments, learn what thermionic emission can teach us about solid-state electronics, and maybe even get a glimpse of what lies ahead in his lab.

  • Hack Chat Transcript, Part 2

    Dan Maloney12/09/2020 at 21:12 0 comments

    Boian Mitov1:04 PM
    Thank you @Usagi Electric (David) and @Dan Maloney :-)

    Usagi Electric (David)1:05 PM
    Thank you all for the excellent discussion! I don't actually have any plans though, so I'll be hanging around a bit more, haha

    And although we have no more chats until 2021, I just want to mention next week's "Holiday with Hackaday and Tindie" Remo hangout. It's like a big geeky holiday party online.

    Artem Kashkanov1:05 PM
    @Usagi Electric (David) Feel free to contact me with any contacts.

    It'll be Tuesday at 9:00AM Pacific if anyone is interested

    Usagi Electric (David)1:06 PM
    @Artem Kashkanov I will definitely take you up on that! After I read through all your projects in detail that is, haha

    Usagi Electric (David)1:07 PM
    Oof, 9 AM pacific is 7 AM here, not sure if I can pull myself out of bed that early

    @Dan Maloney so how do I look up this chat in the future?

    nubbie question

    Whoops, wait, I got that wrong -- noon pacific

    Sorry about that -- same time as Hack Chat, a day earlier.

  • Hack Chat Transcript, Part 1

    Dan Maloney12/09/2020 at 21:11 0 comments

    Hi everyone, welcome to the last Hack Chat of 2020! I'm Dan, I'll be moderating again today for David Lovett, aka Usagi Electric, and we're going to be talking about Vacuum Tube Logic, or pretty much anything about vacuum tube circuits.

    David, can you kick us off with a bit about how you got interested in vacuum tubes circuits?

    Usagi Electric (David)12:00 PM
    Sure thing!

    Jerry Isdale12:00 PM
    flat panel array antennas are amazing these days. You can fabricate somethat will pick up Blutooth from miles away

    curiousmarc12:01 PM
    Hello everyone

    Hi Marc! Welcome back!

    Usagi Electric (David)12:02 PM
    My father was an EE (although his profession was a pilot), so there was always a little bit of interest in old electronics in the house. But, growing up in the 80s, I got used to really low voltage stuff (even cutting my teeth on BEAM robotics, which is ultra low voltage stuff). So, I've always had this fear of high voltage, which kept me away from vintage stuff too much. I always thought tubes were gorgeous though, so earlier this year, I decided to finally give tubes a shot, only at low voltages. To my surprise, they worked decently well!

    curiousmarc12:03 PM
    For us non-Japanese speakers, what does Usagi mean (I think I get the Electric part)?

    Usagi Electric (David)12:04 PM
    Once I found that I could actually get the tubes to do stuff, it became this goal of mine to try to build something substantial out of tubes at low voltages. There's many times when 150V would have been much easier, but I'm nothing if not stubborn.

    Usagi Electric (David)12:04 PM
    Ah, yeah, Usagi just means "rabbit" in Japanese.

    curiousmarc12:05 PM
    Sweet. We have pet rabbits too. Ours are not electric though :-)

    Love the logo, BTW -- nice ears

    Usagi Electric (David)12:06 PM
    There's kind of a story there. My buddy and I are also huge into classic cars and while out drinking in an Izakaya in Nagoya one night, we came up with this joke idea to create a blog or something called "Usagi Motors" (うさぎモーターズ). It just kind of stuck, so I adapted it a bit for the electronics stuff

    Usagi Electric (David)12:06 PM
    Haha, thanks, that was a lot of fun to make.

    Usagi Electric (David)12:06 PM
    And Marc, that's awesome! Pet rabbits are fantastic animals! We've had a pet bunny for years now and I would take a bullet for her, haha

    MCCHAVEZ12:07 PM
    I'm not telling my daughter (who has a pet rabbit) or it will inspire her to get another just to name it rabbit in japaneese

    Usagi Electric (David)12:08 PM
    Haha, if she needs ideas for Japanese names, I can get my wife involved and you'll have a ton of rabbits before you know it

    Ethan Waldo12:08 PM
    This conversation is going down a rabbit hole...

    CJ Keithley12:08 PM
    so... what sort of logic circuits have you built using low voltage tubes?

    MCCHAVEZ12:08 PM
    now....back to electronics.

    tomcircuit joined the room.12:09 PM

    Yeah, I was going to ask just how low you've pushed the voltage in some of these circuits. Seems like you use 24 volts a lot -- have you found a floor?

    MCCHAVEZ12:09 PM
    it would be great to look at building some VT computers .... Mr. Carlson's lab has a nice session with a NOS opamp tube

    Usagi Electric (David)12:10 PM
    So, aside from the ones I've done videos on (SR, D, edge-D and T flip flops, a half adder and a full adder), I've also done a few combos of those build other things. Like mixing an XOR gate, a D Flip Flop and a Full Adder to build a bit-serial full adder.

    Usagi Electric (David)12:10 PM
    Though, I've kind of shelved that idea for now. I may return to it in the future

    MCCHAVEZ12:10 PM
    link to Mr. Carlson's lab on opanmp

    MCCHAVEZ12:10 PM

    Usagi Electric (David)12:11 PM
    Dan, I've actually done a bit of testing at just 6V, but not much. 6V is great because you just need one supply for the entire thing, but you really start running super tight margins. Swings of just 1V to 2V. It could work with if you build some hybrid stuff, using a microcontroller...

    Read more »

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