Picture of The Tnychron Clock
Have you ever seen a pocket calculator from the 1970s? If you have, you know that many used a series of tiny, red, LED seven-segment displays. These displays used little "bars" of light-emitting material which were placed behind little magnifying bubbles to make them more readily visible. They were very crisp and readable, and used a lot less power than vacuum fluorescent displays (VFD), which were also in use at that time.

I recall the little LED bubble displays were at one time in all sorts of handheld electronics and, in a slightly different form, watches. By the time LCDs became cheap in the late 1970's, the more power-hungry LED display was on its way out.

I was pleasantly surprised back in 2011 to find on ebay a seller with numerous rails of HP 5082-7433 LED displays. These are three-digit displays in a 12-pin standard DIP format. I bought a few rails since the price was good. I've a tendency to get "stuff" and then never get around to using it so I decided this time there would be a project to make use of all the displays.

The "Tnychron" clock was born!
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Step 1: Design

Picture of Design
Design requirements:
- 1970s-looking retro case
- Arduino IDE environment project
- use the HP displays effectively
- make it play music
- make it easy to use

Step 2: The Case

Picture of The Case
I settled on a Serpac A20. It looked retro enough and initial layout tests in Eagle indicated there would be enough space inside for the PCB.

The only downside to this case (and probably most cases) is the choice of pre-made front windows - clear or black/IR transparent. I wanted red, so I found an online supplier of 1/16" acrylic sheet and ordered some. I used a small table saw with a fine pitch blade to cut the plastic.

Measurements were obtained from the Serpac spec sheet and the PCB size was confirmed by exporting an image of the .brd file, punching the mounting holes out and making sure the holes matched the mounting posts and everything fit they way it should.
I love clocks!
uhclem (author) 1 year ago
I really wanted to find right-angle switches with long buttons and have the button part poke through holes on the rear plastic. I couldn't find them at the time.
Spannerz1 year ago
Just my two cents, but (if you had the room) I would use fixed push-momentary switches on the back and solder them to the board via wiring that way, saves gaping holes (but I don't know if you could have shrunk the board any more?)
This is a great clock, I love the displays and the angles on the enclosure, has a very "futuristic in the 1970s" feel about it. Thank you for sharing it with us.
topcat52 years ago
Very Nice.

And nice job on the retro look. Have a look at the Heathkit GC-1092 electronic clock kit that was sold in the 1970s. Very similar looking. It was the fancy version of the GC-1005.
uhclem (author)  topcat52 years ago
Thank you. I do recall the 'regular' version of the Heathkit clock. I have a set of the panaplex displays and sockets as used in the clock. One of these days I ought to build one.
rocketguy2 years ago
Niiiiice! I still have my dad's HP calculator with the red bubble display. Seeing this makes me feel all warm and fuzzy inside. Great work!
Aleator7772 years ago
I really love the style of this. I'm a big fan of retro display technology. Good work!
uhclem (author)  Aleator7772 years ago
Thank you!
thegrendel2 years ago
Wunderbar! The LED clocks of a previous generation
had a look and feel that can't be duplicated by the modern
hi-tech alarm gadgets. And, recall that the very first run of
digital clocks, around 1972, retailed for thousands of dollars.

Thanks for a great project.
amotoalain2 years ago
Very nice clock,
uhclem (author) 2 years ago
For those wishing to build this you can also buy the board directly from BatchPCB via this link:

As for the displays, if you can't find the originals, there is an eBay seller who currently has a unified 9-digit, 7-segment bubble display which is common-cathode and could definitely be made to fit in the Serapac A20 case.
If you had this as a kit I'd buy it.
uhclem (author)  mettaurlover2 years ago
Hi there. I only have it available as a built clock or just the PCB. If you can find the displays, everything else is easy to source from the larger parts suppliers.
ajoyraman2 years ago
Great work ! A combination of vintage, current, & imagination makes an excellent project.
uhclem (author)  ajoyraman2 years ago
Thank you for your comments.