Project: Nixie Clock (upgrade) – Accuracy

Throughout this project, I have been saying that the oscillator I am using, the DS32kHz, is accurate to 7.5 parts per million, or 4 minutes per year. Having run the clock continuously for about 3 weeks now I would expect the clock to have drifted by approximately 14 seconds. However, measuring the clock against the clock on my phone I have found that it has drifted by approximately only two seconds.

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Mini Project: Guitar Amplifier (old!)

Playing guitar and electronics have been two of my favourite things for a long time now. When I was about 14, I combined these two for the first time and built a pretty simply 32W amplifier. While the design is super simple, it actually has a really nice clean tone and does not distort the sound at all. It’s capable of diving an 8 ohm or 4 ohm load. Today I decided to give it a bit of a clean and check if it still worked.

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Project: Nixie Clock (upgrade) – Final Code

The clock is controlled by an ATTiny87 which has three main jobs:

  1. Counting the pulses from the Maxim DS32kHz
  2. Controlling the display via the shift registers (read more)
  3. Interacting with the user via the reed switches to produce a user interface

Each of these jobs will be discussed separately below as well as the main code to bring it all together in a power efficient way. Full code can be found at my GitHub.

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Project: Nixie Clock (upgrade) – SPI Bus Chip Select/GPIO Contention

As discussed in the previous article, the display is controlled by a number of shift registers. Shift registers can be controlled directly by a SPI bus, which is useful as most microcontrollers (including our ATtiny87) have a built in SPI bus peripheral. This means that writing a byte to the shift register is almost as easy as just writing a byte to a register.

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Project: Nixie Clock (upgrade) – Using 74HC595 Shift Registers

My Nixie tubes have 11 active pins each: a common anode and one cathode per digit (ten in total). The anode is connected to +180V via a 47k current-limiting resistor and each cathode is connected to the collector of a high voltage bipolar transistor (MPSA42) so that current can be controlled through each of them via the base of the transistor. This gives a total of 29 transistors that need to be individually controlled (24 hour clock requires 3 possible numbers for the first digit, 10 for the second, 6 for the third and 10 for the fourth). I chose to do this by using four 8-bit shift registers, connected in series to make one, 32-bit shift register.

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An Intuitive Derivation/Proof of the Sum of an Infinite Geometric Series based on Zeno’s Paradox

A geometric series is a series of numbers where each number in the series is equal to the previous number multiplied by a constant multiplication factor. For example: 2, 4, 6, 8, 16… is a geometric series with a constant multiplication factor of 2.

The sum to infinity of such a sequence, then, can be represented as:

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