Kewl display

On Sat, 21 May 2016 10:41:18 -0400 (EDT), bitrex Gave us:

Real nixie tube 'vintage clocks' are way kewler.

There were all sorts of crazy numeric display technologies.

Nixie

Incandescent 7-segment tubes (gas pumps)

Magnetically flipped metal plates or disks (airports)

Veeder-root linked cylinders with motors, noisy

Electro-luminescent. Got ugly as some segments wore out

Edge-lit plastic sheet stack, incandescent (GR counters)

Seven neon bulbs

CRT 7-segment (HP9100 calculator)

LED 7-segment, some monolithic (HP35)

LED dot matrix, some with built-in decoders

VF, still used but not so common

Incandescent matrix (scoreboards)

E-ink, moving particles

Electrochromics

Oled.

and there must be more.

So far, LCDs win.

I bet you could write a novel in 7-segment text. Someone once wrote a novel without using the letter E.

SRS still uses 7-segment LEDs in their instruments. It takes a lot of driver electronics. It's funny some times when they try to spell stuff.

I like VFDs. They're great for outdoors (like EV charge port displays!) because they're easily readable in direct sunlight and at odd angles, and cheaper and more durable than a backlit LCD panel.

I remember when I was a kid in the early 1980s I had an electronic tennis video game that used a multicolor VFD display. I guess color LCDs weren't in the cards for consumer electronics yet, so they had a custom VFD made with all the sprites for the players and ball positions laid out and sequentially illuminated as needed. It was crude but still really fun.

Two related questions that you might be able to answer so I don't have to start a new thread:

Any idea how they did the scrolling message board in Times Square circa 1940s? The one that you can find famous films of on YT saying things like "WAR IN EUROPE ENDS" and such. It looks like they were incandescent bulbs, it must have been a huge feat of technology to control all that in the tube/relay era.

And for my own project I'm wondering if it's possible to use a 74LS47 7 segment decoder to drive incandescent bulbs from a lamp supply voltage that's lower than the supply voltage of the IC. I'd like to run this little thing off a LiPo, and it would be great if I could just use a pwm output off the uC to make ~4.5 for the IC and draw the lamp current from the 3.7 LiPo directly, rather than adding a special boost circuit.

I love VFs, but many are going EOL. We had to design a PCB that accepts scanned VF drive, decodes that, and drives an LCD. We won't use VFs in any new designs.

I'm guessing they used incandescents, programmed by a punched paper tape.

Open collector, no voltage problem. But it only sinks 8 mA, not enough for a lamp.

I like the TPIC6595 as a relay/LED/anything driver. It has a separate "G" output enable pin that can be used for PWM.

Used them here:

to drive 271 relays. It works!

THat 'Darth Vader' Nixie is pretty neat. It my not show up in the recomended videos, so just search for it. The video shows how it's made, It seems he produces Nixie tubes.

Cheers

Yes, tons of small incandescent bulbs. I believe they used a paper tape, a plate with "nails" and a mercury bath. This was also used in the original nite-sign helicopter scrolling display. Mercury baths were a lot messier in an airplane!

Jon

What was the mercury bath for?

This might count as the great-grandpa of VFDs:

There is, and a lot older. Here is a single-bit version:

Not for me. I prefer a VFD over LCD any time. LCD have poor contrast and poor visibility in non-ideal light situations. Also better in cars. I can see the smaller VFD odometer numbers in a Jeep dashboard much better than the larger backlit LCD numbers in mine.

Maybe I don't know about VFDs, but the ones I have seen in my purchased products seem to fade over a few years. I have one now that is only barely visible in the dark after my eyes get adapted.

To be fair, I think it is about 9 years running now. But, the device still works if I could just see the display for a clue to setting the functions.

We have an oven with a VF display clock thing that has been on continuously since 1992, and it looks fine. Cars often have VF's that last, but they don't run 24/7 like the oven display.

Could be some defect, like bad filamant emission or outgassing or something. Afrer all, it is a tube.

We used VFs in our NMR gradient drivers, which customers left on for max stability. We used 3400 pieces of one Noritake tube (8 digits/16 segments), and they were very reliable.

That is the downside of VFD. They are tubes and thus not meant to be run non-stop. In a car the odometer only needs to live a few thousand hours of operation. Household goods often run 10-20 years non-stop. Even then they can perform. A prime example is the green VFD clock in our microwave. That is now running about 15 year and still looks as bright as ever. It was the same in the various VCRs we had. The displays survived the rest of the units. So it can be done.

Good VFDs come from companies such as Noritake.

There are ways to milk an old VFD for some more years, for example by increasing the filament current. Eventually you'd see the faint glow of those wires but that might esthetically be ok.

Sliding contact, I would suppose.

Tim

On Sun, 22 May 2016 13:06:18 -0400 (EDT), bitrex Gave us:

Switching circuits