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Nixie tube clocks

B7179 Smartsocket driver:

Introduction

What does it do? Movies!

Download the PDF manual

 

IN-18 nixie clock

The ball clock

Floating tube clock

The infinity clock

A slim clock

A slim couple of clocks

Pyramid clock

Panel meter clock

Two tube Charlienixie clock

A small two tube clock

 

Panaplex clocks

The pinball clock

 

LED clocks

The Holoclock

 

Charlieplexed LED clocks

Charlieplexed clocks intro

Circular clock 1

Circular clock 2

Circular clock 3

Circular clock 4

Circular clock 5

Circular clock 6

7 segment dotty clock

 

VFD clocks

Approximate clock

Russian IV-18 clock

 

Charlieplexed LED clocks intro

Charlieplexing is an electronics technique developed by Charlie Allen at Maxim in which relatively few I/O pins on a microcontroller can be used to drive a large number of devices, in my case LEDs.

With Charlieplexing, N output pins can be used to drive N x (N-1) LEDs. This is a huge advantage over a traditional multiplexed display.

For 72 LEDs we can use just 9 pins to address 72 pins, 9 x 8 = 72. A conventional matrix would need a 9 x 8 configuration or 17 pins to achieve the same result.

So I started to design my first charlie clocks on this basis and they worked just fine.

An etched board and an assembled clock. This one is for a dual LED clock and uses all combinations of an 11 x 12 charlieplex to drive 132 LEDs.

After a few experiments and changes of layout, I discovered that my 72 LED clock face lends itself better to twelve sets of six LEDs. So if I used twelve outputs I found I could simplify any hand wiring, especially useful as I etch single-sided boards. Eventually I have settled on a system where the LEDs are divided into two sets of six cathode groups, with the six unused anodes on one side providing the cathodes for the other side. I can best explain this by means of a diagram:

The 12 colours represent the wiring from the 12 pins from the microcontroller.

Below is my latest circuit layout, which includes the cathode resistors for each group of 6 LEDs, switches, crystal and caps, the PIC microcontroller, a 5v voltage regulator and its associated caps. The whole board measures 4" or 100mm square.