hardware/eagle- PCB design and schematicshardware/docs- various PDF datasheets for components usedsoftware- clock program
Main components
- IN-8-2 Nixie tubes
- MH74141 BCD decoder
- SN74LS77 4-bit D latch
- 74MH238 BCD 3-line to 8-line demux
- Raspberry Pi 1, 2 or 3 (Models A, B, B+)
The BCD decoder IC and Nixie tubes is hard to obtain, so far they're only available on ebay and most of them are NOS(new old stock)
Check the schematics for the rest of the passives
Every digit of the display is composed by a Nixie tube (IN-8-2) driven by a decimal decoder designed for directly drive this kind of gas-filled cold-cathode indicators (MH74141) which input is supplied by a 4-bit D Latch (SN74LS77).
Each latch is multiplexed, with one 3-line to 8-line demux (74MH238), in order to share the 4 bit bus with all the drivers.
In this way it's only needed 7 bits to control the clock's display.
.___.
+3V3---$1-|O O|--$2--+5V
(SDA) GPIO2---$3-|O O|--$4--+5V
(SCL1) GPIO3---$5-|O O|--$6--_
(GPIO_GLCK) GPIO4---$7-|O O|--$8-----GPIO14 (TXD0)
_--$9-|O.O|-$10-----GPIO15 (RXD0)
(GPIO_GEN0) GPIO17--$11-|O O|-$12-----GPIO18 (GPIO_GEN1)
(GPIO_GEN2) GPIO27--$13-|O O|-$14--_
(GPIO_GEN3) GPIO22--$15-|O O|-$16-----GPIO23 (GPIO_GEN4)
+3V3--$17-|O O|-$18-----GPIO24 (GPIO_GEN5)
(SPI_MOSI) GPIO10--$19-|O.O|-$20--_
(SPI_MOSO) GPIO9 --$21-|O O|-$22-----GPIO25 (GPIO_GEN6)
(SPI_SCLK) GPIO11--$23-|O O|-$24-----GPIO8 (SPI_C0_N)
_-$25-|O O|-$26-----GPIO7 (SPI_C1_N)
'---'
MH74141 74MH238
,--------------, ,---------,
A B C D A B C
| | | | | | |
| $22 $18 $16 $15 $13 $12 $11 |
'-----------------------------------'