I loaded PC boards as summer jobs during college. Paid twice minimum wage! A really good high school electronics course meant I could easily read resistor codes, and a Manpower rep at a job fair said, “Want to be employed tomorrow?” 😄 Got me through college! And yes, I was usually the only male. 😂

At one point I had the idea of building a large matrix display with micro incandescent bulbs, 1.2V/15mA per bulb or so (still sitting in a drawer..) - I stopped when I realized that soldering 800 flimsy wires to my 2.5x2.5m framed wire grid and also programming the graphic functions was a bit tedious. But what helped to increase the response time of the bulbs was to preheat them with a current that didn't make them glow, or to scan them fast with a pulse width that also didn't make them glow just yet. As far as I remember this way it was not necessary to bump up the voltage this much. (So in case of an error they wouldn't break because of the overvoltage.)

A great candidate to have a watchdog set up, as a crashed sketch could end up dumping the filament "overvoltage" without the "PWM" style lower average voltage if any outputs get stuck on

What i am missing (or did not see?) is something for emergency shutdown of the filament power when something with the mux goes wrong. Just a random software crash may kill the expensive display quicker than the watchdog timer would kick in....

It would be very nice for a nightstand clock. Analog voltage dimming for night time, tubes would last forever if not pushed that hard.

Props to the ladies including you Fran.

love these old displays, some of my older MPH police radar units have these displays, I have always liked the way they looked.

On my 100% DCI-P3 displays it looks very much warm like an incandescent and very orange at 5V!

I'm not sure if the 5 ms and 2 ms mentioned were per digit or per the entire display. I suspect "per digit." You have to get above the human eye "flicker fusion threshold." Long ago we might have called this "persistence", but that term also means how long an image may be perceived after it was gone, so the more specific term is now used. It is about 60 to 90 Hz for humans. If "per digit", 5 ms would be 35 ms to scan the entire display which is about 29 Hz and "flicker" would be expected. At 2 ms it is 14 ms for the entire display which is about 71 Hz and probably barely fast enough for at least many humans. But if certain other animals are watching this, such as an owl or a house fly, they will still see a flicker. You have to be a bit careful designing such things as not all humans are identical and if you use yourself as the test subject, somebody else might still see flicker.

The nerdy parts are the best! Always loving you taking deep dives WaaaaaaaaaaaaaayDownInsiiiiiiiiide :)

I could be wrong, but i dont believe solder flows over the component side during wave soldering.

I probably would have added a few lines to the arduino to change the timing from a button input or similar.

How much effort would it be to drive them all individually? Might be a fun challenge

NEVER multiplex vintage displays if you have the option to do direct-drive. As a longtime creator of clocks using nixie, numitron, NIMO, etc devices, the last thing you want to do is reduce the operating life of a device that is no longer manufactured. In the old days, multiplexing was done because the drive electronics was expensive. Today, the electronics portion is dirt-cheap compared to the cost of the tubes, so saving a few dollars on the IC's doesn't make much sense if your tubes cost hundreds of dollars apiece. For example, the gigantic, though butt-ugly 14-segment 7971 nixie tubes are going for 200USD apiece now, and the few NIMO tubes I've seen were over $300, and those were untested. A six-tube clock is a hefty investment, so treat your tubes as best you possibly can. Why is multiplexing bad ? Simple. When you multiplex, you can see the brightness goes down. To offset this, the current must be increased in order to increase the brightness. With gas-filled tubes, the wearout mechanism (generally sputtering) is exponentially proportional to the current. Incandescent tubes undergo thermal shock, from cold turn-on as well as thermal cycling. Similar wearout problems can be expected from multiplexing fluorescent and electroluminescent displays. Some displays, notably gas-discharge panels and multicharacter displays, require multiplexing because the number of pins disallows direct-drive, so in those cases you have no choice. I add circuity to limit display currents to safe values, such as using current regulators on my nixie clocks, and filament preheat/cooldown on the incandescent/NIMO ones. Knock-on-wood, nothing has died yet.

Hi Fran! I want to get into electronics doing hands on projects for beginners. I'm looking for a good starter kit. The AM Tech kit looks good, but the founder has been idle for about a year. I'm not sure if he is in business anymore and he had a successful launch. Can you recommend a good kit with components, circuit projects, data sheets, etc.?

Most camera's have an IR filter. Would a camera without one pick up the true color of the filaments at lower voltages?

Fran has a real soft spot for display systems

Shrunkified 😂 👏 👍 Edit: I’ve never heard a better one word description. Tnxs!

Would the cost of one diode block be 40x more expensive? It might be possible that producing this block would be only 3x more expensive than same amount of discrete diodes. ICs weren´t that much integrated at that time. Encapsulating a single diode vs. encapsulating a dozen diodes should not be a factor of 40! Still a valid point of cost saving by using ICs.

I've always had a bit of a facination with electronics. However it is comparable to brain surgery...lol

I love these "weird, crazy videos"! Love you too! Thanks for sharing!

Very cool!

Thank you so very much Fran for sharing this, very relaxing fran cad..i enjoyed your content. . Looking forward to seeing your next video 😊

Wow, thank you!

I have a few hours free if you like me to debug FranCad. Funny that the "boring" part of the video was what I wanted to learn about most. I have some ICs that I wanted to use for multiplexing, shift registers actually IIRC, but I have never gotten them to work. Been a while since I tried, maybe I wasn't using diodes. Funny that that I do digital programming and analog electronics, but I know nothing about analog programming and digital electronics.

The flicker was lovely, Happy days.

I am incredibly jealous of your B-7971 display, but I'm glad you're continuing your Numitron video!!

If you're multiplexing with overdrive and the processor locks up, I guess you run the risk of burning out a display?

1800k

Awesome as always Fran! Another scheme for multiplexing I am using 74hc244 tri-state buffers with the outputs tied together. BCD inputs would be controlled by a CD4017 which is pulsed by a 555 timer at the frequency of your choice. The 4017 fires the OE pins of the tri-state buffers like a distributor cap on a car. A "good" way to run those pesky VFD tubes with all of the digits inside one tube like an old microwave oven. Arduino would be easier of course, but this is another "easy" option. I'm kind of new to this, but I believe that most multiplexing is an integral part of the IC's or micro- controller(s) being used. A 74hc244 has 8 channels with two OE (low output enable) pins on each so that would allow you to only use seven of them to control the segments and possibly a decimal point. If not, be sure to tie one of the inputs low or high. Hope this helps someone out there. Comments welcome.

Neat explaining how it works, only need one BCD to 7 segment decoder IC.

When I grow up, I’ll own a nixie clock 😎

@Franlab. Is that a Yamaha drum machine in your theme music?