My teacher, Mr. Clark, mentioned making a nixie tube clock once, and I have kept this idea on my scratchpad for a while as something I’d like to do. The plans that I have looked at so far have been a little more than I wanted to do, but I never realized how easy this could be. I am strapped for cash right now, but I will publish my ideas and then update as things come along.
I just finished building a tube guitar amplifier, and watching the tubes glow is almost as fun as…being a geek? The next step is to build something that has the same glow, but is also more useful. In some past blogs I have built digital clocks, so all I need to do now is add some high voltages. Below is the block diagram that gives a pretty good idea of what is needed to complete this project.
Parts list and expected cost:
1 – Box/enclosure (depends on board size and number of nixies)
4 – IN-12a Nixie tubes (lot of 18) Ebay $28.00 with postage
4 – 74141 Nixie driver IC Ebay $13 with postage
4 – 12a tube sockets Ebay $13 with postage
1 – MCP23S17 multiplexer Digikey.com $2 + postage (opt)
1 – PIC16F887 600mil microcontroller Digikey.com $4 + postage or
PICAXE 40X microcontroller Hvwtech.com $12 + postage
1 – 4MHz oscillator (if using Picaxe)
1 – 40 pin 600mil IC socket Digikey.com $3 + postage
1 - Nixie power supply Ebay $15
1 – DS1305 RTC Digikey.com $5 + postage
1 – 16 pin 300mil IC socket Digikey.com $1 + postage
1 – 1F supercap Digikey.com $4 + postage (opt)
1 – 32.768kHz crystal 6pf Digikey.com $1 + postage
2 – 6pF 2pF or 3pF ceramic caps Digikey.com <$1 + postage
3 – NO momentary switches Digikey.com $7 + postage
1 – Barrel Power Connector Digikey.com $1 + postage
1 – 12v 1A wall wart buy locally or salvage $??? + gas
Enclosure, wire, soldering tools, heat shrink…stuff you probably already have.
Step 1: Decide on your design and needs. The parts list above is fairly good for a starting point. You might decide to use different tubes, microcontroller, or clock, but this should give you an idea of what I am using.
Step 2: Measure and cut holes for the nixie sockets. I am installing 4 nixies on the 4″ front panel of my enclosure. The 3 buttons and power connector will be installed on the 4″ back panel. I found that cutting holes for the odd shaped nixie sockets is difficult. I am using J-B Weld to cover up my mistakes and to secure the sockets. Measure holes for the standoffs and drill them. Be sure that they line up with your PCB. I will sand the rough spots on the box and panels and paint them. I am painting the panels metallic silver and the box a textured black. NOTE: Be sure that you orient your nixie sockets correctly. The tiny hole in the socket should go to the bottom. I made this mistake and had to flip my finished clock over to have the numbers display correctly. The nixie tube also has pin 1 marked on the bottom and with a white mark on the inside.
Step 3: Fun time! Print the PCB layout and make a printed circuit board and drill holes. (see bottom for Instructables link) Be sure to drill 4 holes in the corners for standoffs.
Step 4: Solder parts onto PCB. If you are using the PIC16F887 with the program/Hex file that I have here then you can omit the 4MHz resonator. If you use any other 40 pin chip, check the datasheet to see if you need it. The Picaxe 40X requires a 4MHz resonator.
Step 5: Connect power supply to the power connector and the PCB. Be sure that the power connector is installed through the panel before making connections. Connect common grounds and connect the 5v power to buttons. The 5v should go from buttons to the board.
Step 6: Solder 100k resistors to anodes of nixie sockets and connect to the power supply. Then solder wires to each cathode and solder them to the PCB as instructed by the schematic. Then solder the switches to the PCB and install them into the panel.
Step 7: Download C program and compile, or write your own C or Basic program and compile. Then program your chip with the Hex file. If you decide to use a Picaxe chip, be sure to program it before adding it to the PCB I designed. It does not have the programming circuit built it.
Step 8: You should have made all connections for a functional clock. Insert the nixie tubes into their sockets before closing the box, and plug it in to check the functionality of the clock. If it does not work then check the connections, the power supply, and the programming on the chip. A multimeter and/or logic probe may come in handy if things are not as they should be. If the clock does work then you can close it up.
Step 9: Close your box up and enjoy your new nixie tube clock.