Arduino powered Nixie Clock – the Schematics
Shrike Engineering's Nixie Clock Schematic
We’ve already posted pictures of the Prototype Nixie board, but now it’s time to go back to the original idea and concept behind the board itself:
The board was originally thought up because I fell in love with all the images of Nixies that I found on the Internet. The Nixie is a cold-cathode vacuum tube containing individual cathodes in the shape of numbers along with argon gas in order to allow the cathodes to glow under high voltages. Wrapping these all up into tubes, designers can create devices that use these cathodes to display information to a user of a device. To this end, Nixies are absolutely perfect for things like, clocks, for example.
I chose the Arduino platform (powere by an Atmel atmega168) to create this clock because I was just getting started in programming with microcontrollers and just getting started with circuits more complex than blinking lights. The design goals were not to make the cheapest clock that I could, but to make a working, functioning device even if it meant that the part count was higher and that the board was a little larger. Because of that, this clock is not multiplexed and does not use mains frequency and/or a watch crystal by the microcontroller, but instead uses a discrete RTC chip with it’s own 32.768Khz crystal along with shift registers coupled to IN74141 Nixie tube driver IC’s.
In addition to the Microcontroller, RTC, shift registers and 74141 chips, the Nixie clock also needs to be able to provide a 180VDC power source. This was accomplished in this design by using a boost converter made from a simple 555-timer circuit to boot 12VDC up to 180VDC. Adjustments can be made to the power output level to allow me to output anywhere from around 140VDC to around 200VDC. The tubes chosen for the project are IN-8′s, which are 11 pin Russian tubes that have a great size and look nice to boot.
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