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| en:projects:nixie-clock:start [2011/02/19 12:50] – alex | en:projects:nixie-clock:start [2011/06/04 09:11] (current) – [Specifications] alex |
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| ====== Nixie Clock ====== | ====== Nixie Clock ====== |
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| I designed and built this nixie tube clock in my senior year of high school. It's a basic 4 tube design controlled by a Microchip PIC microcontroller. | {{:nixieclock-1.jpg?380|Nixie Clock}} |
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| ===== Introduction ===== | ===== Introduction ===== |
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| In my senior year of high school, the [[http://www.nutsvolts.com/index.php?/magazine/issue/2006/10|October 2006]] issue of [[http://www.nutsvolts.com/|Nuts and Volts]] featured an article about a Nixie tube clock. The [[http://www.nutsvolts.com/index.php?/magazine/issue/2006/09|previous issue]] had discussed a high voltage power supply built around a PIC microcontroller. I had been experimenting with PIC microcontrollers for quite some time before and I was intrigued by the prospect of using a PIC microcontroller to generate a rather high voltage from a logic-level supply. I didn't have much use for it, though. After seeing the Nixie clock article, I now had the perfect application for it. So, I bought several tubes off of ebay, direct from the Ukraine, and got to work. | I designed and built this basic 4 tube nixie clock in my senior year of high school. |
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| The most important part of the clock is the nixie tube. I wanted to make a clock with a low part count and a small physical size, so I settled on a four tube clock. I did some research online to determine the most optimal drive configuration for the least complexity hardware-wise. Many designs biased the anodes directly and then used either ten transistors and a demultiplexer chip or a special high-voltage demux chip per tube. I definitely liked the hv demux chip idea because it means I need one part instead of 21 (demux + 10 transistors + 10 bias resistors). Another site that I looked at added anode-side switching and then used only one driver chip. I really liked this idea, primarily because the driver chips are expensive and, just like the tubes, I had to order them directly from the Ukraine. Replacing three driver chips with eight transistors and eight bias resistors seemed like a fair trade. | |
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| Then I had to figure out how to do the other thing the clock will have to do well – keep track of time. I settled on a Maxim/Dallas part, the [[http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3914|DS1340C]], with an I²C interface and a built-in crystal, further reducing the parts count. | For more a detailed introduction, please read the [[history]] page. |
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| In researching how I would build my clock, I looked at many pictures online of other clocks. Some were completely over-the-top, some were too simple. I wanted a sleek, modern looking clock that isn't too difficult to build. One of the ideas I liked about one of the completely over-the-top clocks is blue lights underneath the tubes. The little hole in the bottom of the spacer on the bottom of the tubes that I bought happens to be just the right size for a 3mm LED. So I bought a bunch of 3mm blue LEDs off of ebay. | ===== Detailed Information ===== |
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| For the case, I decided on a simple design based on acrylic. The top and bottom would be black acrylic and the sides would be made of clear acrylic. | * [[History]] |
| | * [[Power supply]] |
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| I decided to write the firmware for the clock in C in [[http://www.mikroe.com/|mikroElektronika]]'s [[http://www.mikroe.com/en/compilers/mikroc/pro/pic/|mikroC]] development environment; I had bought it along with an EasyPIC4 development board from them some time before. | ===== Specifications ===== |
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| The result of a pile of work spread out over several months is shown above. | * Display |
| | * 4x ИН-16 (IN-16) Nixie tubes |
| | * 208V anode bias |
| | * 1x К155ИД1 (K155ID1) high voltage BCD to decimal decoder/nixie tube driver (74141 equivalent) |
| | * Processor |
| | * Microchip PIC18F2550-I/SO |
| | * 20 MHz clock, 5 MIPS |
| | * 32K Flash |
| | * 2K RAM |
| | * 10x 10-bit ADC |
| | * I²C, SPI, and EUSART peripherals |
| | * Clock |
| | * Maxim/Dallas DS1340C |
| | * I²C Interface |
| | * Built-in crystal |
| | * Backup battery support |
| | * Power Supply |
| | * Input: 12V DC |
| | * Output: 5V DC |
| | * 7805 regulator |
| | * High Voltage Power Supply |
| | * Input: 12V DC |
| | * Output: 12V - 300V DC variable |
| | * Boost topology |
| | * IRF720 400V 3.3A N-channel MOSFET |
| | * HER105 400V 1A fast recovery rectifier |
| | * 4.7µH Inductor |
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