Category: Mechanical

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.

All the layers ready to be oiled and put together whilst listening on my battery powered one!
The acrylic layer with rectangular LED being glued in place.
Showing the LM3915 chip and connections to LED layers
Speaker layer off for front access.
Ready to bolt together. It’s the minimum depth for the width of the amp.
On a rug – the clear layers look nice even without the VU meter!
On a rug – the clear layers look nice even without the VU meter!
The black acrylic infill.

Laser Cut Battery Powered Bluetooth Speaker

I wanted to create a special birthday present for my girlfriend, whom had no speaker system. I decided a battery powered Bluetooth speaker would be neat, and having just learnt use of the laser cutter I came up with a layered design.

I created a mock up in SketchUp, which I used to visualise the layers together and make sure it would work.
I create a mock up in SketchUp, which I used to visualise the layers together and make sure it would work.

The internals consist of a 2x15W RMS digital amp, 2x15W 80 cones, a Bluetooth module, 1800mAh NiMH battery and a basic fast charger – plus a few voltage regulators to bring everything together. It’s all wired so that you can charge while plugged in and still play, and turn the Bluetooth on and off. Finally it’s all insulated with sheep’s wool I had left from doing my van. I found the insulation helped reduce reverberation (probably due to the thin layers) that muddied the mid-ranges. One thing I like about it is that the front and back can be easily changed: the front grill pattern to change the look and the rear could be tuned to include a bass port for better bass response.

iPhone plugged into jack
The back labeled up with inputs/switches and charging light
Special happy birthday edition!
In the wild!
Can be stood up too
Mk.2 has a latching button for bluetooth and better internals. It’s also made from 3mm ply, rather than 6mm.
For my friends Trevor and Sarah, I created this illustration to engrave on the back.
Mk.3 is much tidier
With an oak stain
Latest revision back panel

I fairly pleased with the result and might start producing them if there is enough interest.

Audi TT Vent iPhone Mount

A render of my first idea that I created in SketchUp
A render of my first idea that I created in SketchUp

I wanted a place to mount my phone, to use for navigation, a bluetooth music player and handsfree in my Audi TT. The sloping windscreen makes it impossible to mount anything and the curved dashboard makes it difficult there too. Plus I wanted something neat, not a naff eBay mount and also an excuse to toy around in SketchUp.

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Long-Range Coastal Autonomous Underwater Vehicle (AUV)

AUV with logo

The second semester of the third year of my Mechanical Engineering degree was a group design project. My group of six was tasked with the design of a coastal autonomous underwater vehicle (AUV). I was assigned design of the gliding sub-system (a long-range AUV it had to optimise energy use) and was also the business manager (as part of the project we were required to develop a business plan).

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Pressure Washer Pump Teardown (ProUser PP150 5.5hp 2200psi)

My ‘cross season has gradually gotten more serious, with two bikes and a pressure washer; both vital at last Sunday’s National Trophy. I’ve always wanted a pressure washer anyway (partly for washing bikes but also because I like mechanical things!) and this £100 GumTree special couldn’t be turned down. It’s been good to me so far but it’s clear the previous owner didn’t look after it. I noticed one of the pump mounting bolts had vibrated loose and after some suspicious drips, then loosing a bit of oil, I decided to take the thing apart to learn about it and give it a service.

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HDD Clock

With a cupboard full of old hard drives and some spare time, I recently set about making a persistence of vision clock. Using the platter of a hard disk, a slot is cut to allow backlighting to be emit. When the disk is spinning at 5400rpm+ and backlight constant, the disk appears opaque, as the slit is ‘refreshing’ each point of the revolution faster than our eyes. The trick is to measure the revolution time then flash or change the backlight colour at a fraction of this revolution time at the same point each revolution, in order to create a light segment. For example, flashing the light at a frequency twelve times the disk frequency in phase with the disk will create 12 light segments:

f_{light}=12.f_{disk}=\frac{12}{p_{disk}}

Expanding on this, one can create a light based clock, which takes some getting one’s head around on first sight!

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