Grain-of-wheat light-pipe displays

[Mike Mitchell]

A few years ago I came across some dual 7-segment displays that I thought might be numitrons.  After taking one apart I found they contained fourteen grain-of-wheat light bulbs, one for each segment.

They sat in my junk box for a couple of years until I thought of something to do with them.

I decided on a test-instrument looking clock, something you might find on a lab bench in the 80's.  I'm showing both GMT time and local time, with the offset from GMT selected via a 12-position rotary switch and a three-position lever switch.

I used 24-channel 12-bit PWM constant-current driver chips from TI, the TLC5947, set for 20ma.  I cheated and used a break-out module from Adafruit, although I threw away their library and wrote my own.

I know the displays aren't neon, VFD, numitron, or even nimo, but they do have glass and a partial vacuum.

Mike Mitchell 

[Nicholas Stock]

I approve....:-) Nicely done Mike!

Sent from my iPhone

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[blkadder]

  Mike,

  I love the look of this clock.  Where did you find a case like this?

 

  Ron

[Mike Mitchell]

I buy most of my components from Digikey and Adafruit.

I searched Digikey's online catalog for a long time, ending up with this case:

   https://www.digikey.com/product-detail/en/hammond-manufacturing/1401AAA/HM287-ND/248016

I painted the front white so the water-slide decals would show up better.

Mike