Propeller-powered IN-12 Nixie Clock

Posted on Feb 6, 2014

After building so many Nixie Tube Clocks from the Internet, I finally decided to design my own. My clock uses IN-12 Nixie Tubes and an 8-core Propeller Microcontroller. The Propeller may a be a bit of overkill for the task, but it`s the microcontroller that I`m most familiar with an is easy to program. A Dallas 1302 RTC chip is used for accurate t

Propeller-powered IN-12 Nixie Clock
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imekeeping. I had many choices of which Nixie Tubes to use, and I chose the IN-12 for several reasons. First of all, they`re very cheap. You can pick them up on ebay for around a buck a piece plus shipping. Second, they use pin sockets. I really hate having to solder tubes direct to the board, like in the IN-14s. Third, they`re a horizontal-facing tube as opposed to the upright tubes. I thought it would be fun to do some horizontal projects. This is the same PSU that I`ve used elsewhere on the web site for other projects (including my dekatron projects). It`s based ont he power supply used in tubehobby`s clock. The TL494 forms a straightforward switching power supply. It`s an easy to build supply, and is very stable and easy to trim for the correct voltage. Next up is the microcontroller: The microcontroller circuit is a very straightforward propeller design, if you`re familiar with the propeller. The 4-pin header is for in-circuit programming. The EEPROM is because the prop stores it`s program in external EEPROM rather than internally. The large header is for expansion. I put 10K pullup resistors on two of the pins on the expansion header in case I want to use them for buttons. Next let`s look at the low-voltage power supply and the DS1302: The power supply uses a pair of linear regulators. The first regulates down to 5V (for the K155D drivers) and the second regulates the 5V down to 3. 3V for the prop, eeprom, and dallas...

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