Project: Nixie Clock – Beginnings

The last two months have consisted mainly of the stress of exams. Meanwhile I have been working on my next project… A Nixie Clock!

A Nixie Clock is a clock which uses Nixie Tubes as the display (mine were made in 1984 in the USSR). Mike’s Electric Stuff, has a good page on Nixie Clocks, if you want to read more. In fact, I am basing my design on Mike’s design, with some modifications, e.g. making it a 24 hour clock.

The circuit counts mains cycles (50Hz in the UK) and uses that to keep time. While this may not sound like the most accurate method, it is. The grid frequency is controlled such that, over the course of a day, the average frequency is exactly 50Hz to a very high accuracy.

The tubes are powered from a rectified mains signal and are switched with transistors.

Having tested the logic circuit on a breadboard, I am now working on building the full logic and power circuit on strip board. The Nixie Tube control circuits will be on separate PCBs.

Because the circuit is build using mainly mains voltages, it is imperative that I take caution when powering and testing the device. To ensure safety I have:

  • Installed a 3A fuse in the plug (the smallest I had)
  • Installed a 1W fusible resistor in series with the circuit
  • Mounted the board on a block of wood with the traces facing downwards. (This ensures that the board doesn’t slip and short/electrocute me)
  • Been very careful to ensure that the power is off when touching the board.

Hopefully, I will survive this project.

Project: Analogue Tape Delay – Slowly Building the Circuit

So now that I am back from uni for Easter, I have a fair bit more time on my hands. I have begun the process of building the entire circuit on a breadboard. This process has been rather slow because at each point I have experimented with different designs to (hopefully) ensure that I am choosing the best component and structure for my purpose.


This is the current state of the breadboard layout. I have attempted to make it as neat as possible. (However, I refuse to trim resistor leads).

While I am using dual op-amp chips, in order to make my life easier I am spreading the circuit out by only using one op-amp from each chip for now. The overall circuit will be clearer if I draw it out:


I have attempted to break the circuit up into sections so it is easier to see how each part functions.

The circuit so far takes an input from the tape head, amplifies it and mixes it with the guitar signal. It also drives the cassette player motor.

I did have a problem with noise from the motor being transmitted along the power lines. This was sorted out by adding 10uF decoupling capacitors across the 10k resistors.

In other news I have modified the tape so that I can fit two tape heads in – one to write and one to read.


I just cut out a little plastic.

Project: PCB Mill CNC – 3D Model

It’s been a little while since I last posted. I’ve been pretty busy with work-work and uni-work. But I’ve also been working pretty hard on the design for the Mill as well as gathering parts.

I decided to base the design off 3×1″ aluminium U-channel and will be using Nema 17 stepper motors.

3D model of the Mill made in Creo Parametric

3D model of the Mill made in Creo Parametric


Here is the back view

I’m pretty pleased with the design.The grey stuff is metal, the brown stuff is wood and the green things are sliders.

You can see the three stepper motors – one for each dimension; the vertical assembly which will have the drill strapped to it; and the horizontal piece of wood which is the actual platform on which the material will rest. The drill I chose was pretty cheap on eBay: 10000-30000RPM and 135 Watts should be perfect, and it doesn’t wobble much at all.

Hopefully the U-channel will come by the weekend and I will be able to get going with building it.