Nixie Pipe – Modern Day LED Nixie Tube

Nixie Pipe is my interpretation of a modern day Nixie Tube – the cold-cathode vacuum gas-filled tubes from the 1960s.

The project came about when I decided to make a clock for my kitchen, with specific requirement for an egg timer function! I’ve always wanted to make a Nixie Tube clock but having completed a Nixie Tube project recently and one pipe failing after around 6,000 hours, I wanted to come up this something better. Something that didn’t require high voltages, special driving circuitry, could be easily interfaced and was modular, but which maintained the unique visual depth of a Nixie Tube. Continue reading Nixie Pipe – Modern Day LED Nixie Tube

Nixie Tube Energy Meter

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Having recently bought a house, project time has been a bit thin on the ground. As a standard terrace house, the consumer unit and electricity meter were in the entrance hallway, exposed and looking a bit naff. I liked the look of the meter so I quickly created a box that allowed the meter to poke through and leave access to the fuses.

The box covering did the job but felt a bit cumbersome with all that spare space; it needed something else to give it more purpose. An energy meter was the obvious thing but I didn’t want a garish LCD or 7 segment display, it need to match the blown glass electricity meter… …nixie tubes!

The Nixie Module runs off 5V and SPI
The Nixie Module runs off 5V and SPI making the project quick to get off the ground

Continue reading Nixie Tube Energy Meter

Raspberry Pi DAC – MCP4725 with wiringPi

The Raspberry Pi lacks a DAC but using the I2C bus, one can easily add a device like the 12bit MCP4725. The GPIO library wiringPi provides support for I2C devices, however, getting the MCP4725 working with it isn’t a simple as one might hope. The device is 12bit but the I2C protocol works on bytes (8bits). To send 12bit data, the Microchip designed the message transfer like this:

The MC4725 expects the 12bit data to be broken into two bytes and sent directly after each other.
The MC4725 expects the 12bit data to be broken into two bytes and sent directly after each other.

Continue reading Raspberry Pi DAC – MCP4725 with wiringPi

Noise Crayon – Noise Amplitude to Light Spectrum Converter

Continuing on from my Ambient Noise Level Indicator, I wanted to create an enclosure and make it stand-alone – not requiring a computer to do the processing. I ended up with a little device that converts noise amplitude to the light spectrum: Noise Crayon.

The Ambient Noise Level Indicator used the MCU serial host Processing to perform a FFT and various averaging routines to create an indicator for ambient noise. The idea being that it would change colour when background levels rise above a threshold. Moving to an ATMEGA328, performing this processing – especially the FFT – is asking a little too much of it. There are libraries but I’ve heard of limited successes.

Continue reading Noise Crayon – Noise Amplitude to Light Spectrum Converter

Developing Simulink Device Drivers for ARM Cortex

Simulink Embedded Coder offers an ARM Cortex-M support toolbox, which includes code optimisation for the MCU and QEMU emulation but lacks any S-Block drivers for the device. The lack of drivers limits the Simulink development to merely number crunching. You can create cevel blocks that execute external C functions but this requires separate source files with a shared header and pre-defined initialisation, leaving the model without full control of the hardware. In this post, I go over the process of creating hardware driver S-Blocks.

Continue reading Developing Simulink Device Drivers for ARM Cortex

Wooden Bits – Binary Clock

Wooden Bits Gif

I’ve been meaning to make a binary wall clock for a while and to also try out kerf bending with the laser cutter. What put me off creating kerf bends before I found OpenSCAD, was the manual creation of all the lines in the right places. It’s the kind of repetitive, uniform task computers were made to do.

Continue reading Wooden Bits – Binary Clock

SoundBar VU Meter Laminated Wooden Speaker

I felt that the battery powered Bluetooth speaker I made could be improved with more colour! Taking a leaf from the VU meters on amplifiers of the 80s, I decided it would be neat to sandwich clear acrylic between the plywood layers, each with an integrated LED that would form a full body amplitude meter.

Having a look around, I found a IC made by Texas instruments that did the VU meter job for me: the LM3915. Below is a photo series showing the construction and completed unit. I designed this version as a soundbar to sit below my monitors at work, so it doesn’t have a battery or Bluetooth, making the wiring easier inside and a slimmer unit. For this one I also used an Oak stain rather than a clear stain on the ply and filled the text with black acrylic, which looks much better I think.

Ambient Noise Level Indicator

As part of my work at MACH Acoustics – understanding how internal ambient noise levels affect different environments – I was inspired to create an indicator that shows when noise becomes higher than the base level. Some solutions already exist but they are pricey (because they used calibrated sound level meters), and not very engaging. I wanted something that could sit in a classroom and be a friendly indicator for the teachers and students, bringing the noise back down and perhaps learning something in the process!

The solution is a simple RGB led connected to the PWM outputs of an Arduino and uses Processing with the Minim Library to perform a FFT on the mic input – similar to a couple of other projects.

The operation is best described by the video below and commented code. I’ve added a handy GUI that allows the user to do a number of things:

  • View the mic reading, background sample, instantaneous sample, current colour and sample difference.
  • Change the threshold between colours and benchmark colour.
  • Set continuous sampling, direct LED/mic feedback
  • Resample the background
  • Set the frequency band that is used for the amplitude average – this is useful to demonstrate that it is working and also to ignore low frequency to only show speech for example; screechy children in a classroom!
The control panel when the Java applet is running.
The control panel when the Java applet is running.

Its only a prototype concept at the moment. I’d like to design an enclosure that would suit the particular environment, such as a glowing star or dragon for a classroom.

Continue reading Ambient Noise Level Indicator