Looking for a clock project from the 1970s

[Mitch]

Around 1973 I build a clock from what I think was a magazine article. I've been looking for that article for years. I've searched archives with no luck. Here is the description:

The clock was point to point wired on two stacked pieces of breadboard, around five inches square each. It included two incandescent seven segment displays on the top board, and was built with 7400 series ICs. It flashed hours, minutes, and seconds.

Does anyone remember this project? I may have asked this question years ago. Thanks in advance. Mitch

[Instrument Resources of America]

Just a wild guess on my part, due to the topic, and the year, but could it have been a Pop Tronics (Popular Electronics) article?

Ira

--
You received this message because you are subscribed to the Google Groups "neonixie-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/ba633cd5-7f1e-4877-83a3-541112213122n%40googlegroups.com.

[Peter Csaszar]

Well, maybe you'll just have to design it from scratch yourself. :-) The jury is still out though whether the Numitorns can be driven from a regular TTL (or LSTTL) output. One opinion is that they can, as long as there is a diode in series with the Common, to lower the voltage on the filaments a bit. Another concern is the inrush current when a cold filament is lit up, jeopardizing the output driver of the IC - but based on some accounts, it is not a real problem.

[Mitch]

I believe that I searched those archives. Thanks for the suggestion. I'll try again.

[Mark Moulding]

For me anyway, the jury is *not* out on driving Numitrons (or Russian equivalents) directly from TTL.  In my case, I've made many clocks directly driving the filaments from 74HCT595s, with precisely zero failures of either the tubes or the drivers.  On my newer devices I use PWM to control the brightness, andalso keep the filaments warmed to just below visibility when off, but I didn't do that at first, and a couple of those 15-year-old units are still working just fine.

This is true with a variety of tubes, too; I've used a lot of the Russian IV-9s and IV-16s, some DTF104Bs, and some of the Aurora/Apollo flatpack devices.  I fully realize that the '595s are operating a bit out of spec, but they stay cool during operation, even in less than ideal conditions (110 degree heat at BurningMan, for example).

~~
Mark

[Peter Csaszar]

Hey Mark, thanks for this info - a useful data point! I have a couple of these incandescent displays, but was always a bit wary of driving them directly. With all that said, keeping the filaments warm is definitely a good idea.

-Peter

[Mark Moulding]

Although I used a PWM signal to keep the filaments warm, if one is not too concerned about power usage then just resistors from each filament to ground (assuming NPN open-collector drivers) can be used.  Somewhere around 680 ohms would be a good starting point.

~ Mark

[Joe Croft]

Hi Mitch,

There is a great archive of old magazines, You can find it here: https://www.worldradiohistory.com/index.htm .

It's a great resource for finding old electronics  information.

-joe

[Mitch]

I did look through the archives, still no luck, and I clearly remember building it. Guess it will remain a mystery.