Sunday, 1 December 2013

The Soundlab Diaries - Part 3 - Build disaster.

Problem 1

Two months into the build I noticed that occasionally VCO1 would "warble" when I touched the coarse tuning pot(entiometer). At first I thought it was a just a dodgy component that had been damaged as I worked, but closer inspection showed that several of them did it.
I put a post on the Electro-Music forum to see if others had the same problem, and they did, it seems that the little green Omeg pots I used are well known for going wrong after a few months.
These pots are sealed so there is no way they can be cleaned or fixed, and as it seemed they were all going to fail eventually I didn't have much choice, if I wanted a reliable instrument they would all have to be changed.

Problem 2

There are no other pots on the market the same size as the ones I have used, so I can't just buy a set of replacements and wire them in.
The panel is already pretty tight for space so anything larger would not fit.
The only affordable, smaller,  ones are clones of the tiny American "Alpha" pot. People on the forum reported good results with them but they require a 7mm fixing hole, much smaller than the 11mm drilled in the panel for the green Omeg ones, so they won't fit in easily either.

Possible Solutions

If time was not an issue I would simply make a new panel with smaller holes, but that would mean a complete strip down and re-wire, which would set me back months, so I have broken one of my personal rules and  ordered a new set of pots without knowing exactly how I am going to fit them.This normally ends up being completely the wrong thing to do and I regret it, but on this occasion I can't see any other way through.
There is nothing on the market to make these fit so I am going to have to make something. I have had similar problems before and in the past have tried these ideas.
  1. Reduce the size of the holes by filling them in with plastic metal and re-drilling, but in this case that would mean a complete strip down and would take ages. 
  2. Stick on a thin skin of aluminum, or plastic laminate, on the front panel and drill new smaller holes in that, but again that would mean a complete strip down.
  3. Rings made from rubber tubing slipped over post shafts to make them a snug fit, but I don't have any the right diameter.
I have just found some nitril o-rings that are 7mm internal diameter and 2mm thick which would give it an external diameter of 11mm... I think this might work and have just ordered some.
Finger crossed.

Update.. arghh.. I have just found some plastic pipe that fits perfectly...

The Soundlab Diaries - Part 2 - First stage build.

Front panel, half way through construction.
The final design was based arund a Music From Outer Space SoundLab PCB. This is designed to be a very simple switched synthesizer for making sound effects,  but it always screamed out to me as being capable of much more.
It is built on 72h (14.4") 3U (Eurorack) format panel, and the lettering was printed on a laser printer, laminated, and glued to the metal before trimming. It is the first time I have tried this method, and it produces a neat easily useable result, but nobody is going to be fooled that it is a professional job.
The sellotape to protect the corners and the Stig sticker are not staying :-)

Modifications from original

Behind the front panel, with main PCB and extension board
Like I said this little beast is capable of more than its original design and I could not resist building in the following modifications.
  • Routing switches changed for 4mm sockets,
  • LFO - Rate in fast mode reduced to 30-0.05 Hz, by increasing C14 to 22nf
  • LFO - LED on triangle output
  • LFO - Inverted triangle output added
  • AR - Threshold level on external input
  • AR - LED
  • AR - Inverted AR output added
  • AR - Attack/On phase output added to provide additional control gate.
  • VCO - VCO1 upgraded to be exactly the same as VCO2
  • VCO - Trigger input via a capacitor so they trigger on any square wave
  • VCO - Triangle output added (Not tested yet)
  • VCF - Control front end modified for logarithmic response (Not tested yet)
  • VCA - Control front end modified for logarithmic response (Not tested yet)
  • Control inputs on VCOs, audio and control on VCF and VCA have one direct socket (input 1) with no attenuator and at least one socket with an attenuator
  • All outputs via 1K resistor to eliminate problems with shorts, and multiple outputs can be directly connected together.
The circuitry for these additions and modifications are on a couple of fiber glass matrix boards, one at each end or the main panel, which are held in place by PCB brackets mounted behind potentiometers


Today, 1st December 2013,  the LFO, AR are completely working, the VCOs are working but not of the modifications have been implemented yet. The VCF and VCA have not been started.
Well that was what I thought...

Sunday, 27 October 2013

The Soundlab Diaries - Part 1 - General Design

I have always wanted to build a modular synthesizer, but components were expensive, racks were the size of a large bookcase and it would have taken years to build even the simplest system, so like many other things, I never got round to it.
I had almost given up on the idea when in 2007 I stumbled across a website showing a range of modules built using the new Eurorack, format. These were much smaller, simpler, and used readily available components if I bought one from completed modules it would me more than I would normally pay for a car, including tax and insurance. But there were also kits, and better still some manufacturers would sell you just the blank PCB.
I spent weeks researching the various options and eventually came up with a clear idea of how I wanted my system.

1 - Eurorack panel size format

Ironically Eurorack panel sizes were originally defined in imperial measurements and are all 5.25" (3U) high with widths in multiples of 0.2" This is small enough to be easily made by hand, and smaller modules can even be made from lengths of aluminum strip. Best of all I already had enough parts to make two double height 19" racks.

This skelton rack from 4ms wuld be enough to get started, but you will soon run out of space and need something bigger. The bus here is made on a ribbon cable, but most use a PCB fixed across the back of the rack.

 2 - Eurorack bus

Eurorack bus connector
All eurorack modules use a standard 2x8 connector, as shown above. The pin spacing is 0.1" so it is easy to use on pin board and veroboard.
The only thing I don't like is that it doesn't require a keyed connector so its easy to plug in round the wrong way, potentially destroying your module.
The IDC ribbon connectors do have a key block on one side so I will be using keyed connectors on the other half, just to make sure.
Bus cable being used to connect a module to the back plane. Note the back plane connectors do not have a key so the convention is colored stripe down, but it would be easy to wire a connector up wrong and blow up your module.

3 - Connectors

4mm Banana plugs. Note this type has a hole so that plugs can be stacked up so you don't need "multiple" modules.

Between modules in the same case I am going to use 4mm Banana plugs. This may seem like and odd choice as most Eurorack modules use 3.5mm jacks, but I might want to use this live and my experiences of these have not be good.
4mm bananas are almost bullet proof and if the worse came to the worse you can always strip some bell wire and stuff it in the sockets.
Between cases I will be using standard 1/4" jacks, they have their own earth, so are shielded, and are robust enough not to worry about. I use these for audio connections so already have a good supply.

4 - Build standard

I might want to use this live, so it has to be reliable and be able to take a few knocks. I used to work in the Avionics industry where even prototypes were built with an eye to military specification, and anything less now seems like sloppy work.
For my music gear this means
  • All standard PCB components are soldered through the board and secured on the other side with solder, so any strain is pulling the track towards the board and not lifting it. (Except SMD)
  • If I am adding a component and there is no spare hole than I will fit a vero pin and solder to that. This might mean lifting out an existing component from a hole, fitting a pin, then both components are wrapped round it.
  • Flying leads on a PCB will be as short as possible and either soldered to a pin, or if under the board soldered onto a pad with a component lead, so again any movement of vibration can't lift it.
  • No components in flying leads. Any vibration or movement in the wire could cause the component lead to repeatedly bend where it enters the body, leading to stress and potential failure.
  • Panel wiring will be neatly laid out and fixed down. Laying things out neatly makes it easier to check your progress and find any faults that might occur later. Fixing the wires down, reduces movement at the solder joints and thus stress, making it far more reliable.

Tuesday, 22 October 2013

Tested : Ctrl + Shift + T

From Tested "Our Favorite Keyboard Shortcuts by Norman Chan By far our favorite keyboard shortcut ever. Used in any modern web browser, Ctrl + Shift + T (in either Windows or OS X) lets you restore your last browser tab that you closed. Yes, you can turn back internet time! In Chrome, this lets you restore up to 10 tabs. We love this shortcut so much, we even made a video about it."
OK so its not actually a video, just a series of photographs, but several of these were pretty obscure so check them out :-)

Wednesday, 2 October 2013

A Power Supply & Self Powered USB Hub for Raspberry Pi

This is another of those, "this is so simple and so clever, why didn't i think of it" moments.
Like many of us Bharath Bhushan was slightly miffed at the fact that you need separate supplies for a raspberry Pi and its peripherals.
His solution was both simple and elegant. He simply chopped open his USB hub, and tapped off a power feed to go directly to his Pi.
I like the clever way he cut his existing USB cable, the yellow one in the photo, using one end for the power supply and the other to extended the hub so it could more easily reach the Pi.
For an detailed explanation and full construction details go to
[Via Make]

Unfortunately the USB hub I was using did not seem to have a separate supply regulator and so the raw 9V goes straight into a large blob on the PCB.
Its going to be a bit of a gamble if your hub is suitable, and I don't think you can easily check before buying as I can't see the people in PCB World being terribly understanding if you start taking their kit apart in the middle of the shop.
My hub was glued together, you can't just unscrew it, so I had to carefully cut round the seam with a craft knife and then gently lever it apart. Its very easy in this situation to (a) cut yourself (b) cut into the circuitry inside.
If possible hold the Hub in place with a clamp so it doesn't shift, which makes it much easier to work on accurately, and wear gloves.
Once you start to cut through it is normally possibly to gently prize it apart, slowly, without extra cutting, although you might have to work on the case to get it back together again.

Make: Visualize Your Heartbeat With This Homemade Pulse Sensor

Here is a clever little project from those awfully nice people over at the make website.
It s a front end sensor for measuring your pulse rate with an arduino, raspberry pi or any other board with GPIO access.
The principle is simple, illuminate the inside of your thumb with an LED, and measure how much light comes back. It works because there is an artery in your thumb that reflects back some of the light, but as the blood pulses the diameter of the artery increases so it reflects more light.
The Op-Amp circuit detects these changes in light level, amplifies them and passes then as a clean digital signal onto the processor board.
The whole thing can easily be built on vero-board or some other pre-printed generic PCB, although in practice if you were just making it out of curiosity I can't see any reason why it wouldn't work on a breadboard.
It only uses readily available components, although its not clear why they use a quad op-amp and then don't use half the circuit, perhaps it was just the way their PCB was made. Personally I would try a dual op-amp to save space and few pence.
For full details, and a video,  go to

Friday, 27 September 2013

Rock, Paper, Scissors, Lizard, Spock

This confused the hell out of me at first, but seeing it like this makes it easy to remember.
Arrange the objects in a circle, in the order of the title, Rock, Paper, Scissors, Lizard, Spock.
Each item beats the next one item on the circular list. Is defeated by the one after that, defeats the next and defeated by the last.
I have no idea what the hand movements are for lizard and Spock!

Tuesday, 24 September 2013

Synthopia: Gestural Orchestration With Leap Motion, GECO & Albion I

This is amazing. Hagai Davidoff has developed a unique system for controlling the Virtual orchestra on his computer using his right hand to play the notes and left hand, through a Leap Controller, to select the instruments being played.
In this excellent Video he is using the Leap controller with GECO to control the instrumentation and articulation of Albion 1, an Virtual Orchestra, but I could write about this for hours, just watch it and let me know what you think.
Ok I can't get the youtube video to link properly so for now, go to me this is the next logical step in playing music and I am going to be thinking very seriously how I could use this in my set up.

Original Synthopia article at

Monday, 23 September 2013


Electronic "Drum Machines" started to appear in the late 1960, sometimes as stand alone units but more frequently built into a home organ. These had intriguing preset patterns such as "Bossa Nova" and "Beguine" but rarely "150Kg neanderthal on two pints of Stella" which would have been far more use to the the contemporary musicians.
The market really took off in the mid 1970's largely due to Roland, initially with their CR-78 as made famous by Kate Bush and Phil Collins, and then their monster TR-808 which was used by just about everybody.
The trouble is that as good as they were, they still didn't sound like real drums, until Roger Linn introduced his "Linn Drum 1" with its carefully made 12 bit samples. Even this was not perfect but at that time drums were normally quite heavily treated so Joe Public was fooled for most of the time.
During the next 25 years Drum machines enjoyed various success, as the quality got better and cheap machines, such as the Roland TR-606 found their way into teenagers bedrooms fueling the embryonic Drum'n'bass sound.
Now days most studio musicians use software to create their drum and percussion sounds, and very good they are too, but not exactly as fun or intuitive as a hardware box.
PICs lend themselves so nicely to controlling electronic music instruments and I am sure that many of us have though about using them to them to actually generate the sound, but In this article Catmacey shows he he actually did it.
He has used one of the newer PIC devices to make his own, and damn fine it looks too. He goes through the design process which lead to his choice of device and details how he turned the early prototype into a work end product.  Its a fascinating article which can be found at

On a personal note I would love to build one of these as a project, but not just to get a new drum machine.
For that I use a Raspberry Pi. Yes you would have to make a GPIO connected switch board, but that's not hard. The sound system is already complete, with software drivers readily available, For a display I would probably use a a larger, color, 7" VGA display from amazon, and storage storage could either on the built in SD card or external USB device.
But lets not detract from what Catmacey has done here, its a really nice project.

Sunday, 22 September 2013

Polyurethane for protecting one-off PCBs

A trawl through Hack A Day lead me to this article about protecting the copper tracks on DIY PCBs using spray polyurethane varnish.
As normal the products are not available here in the UK but there is something very similar in B&Q. Personally I use Games Workshop's "'Ard Coat" which seems to do the job nicely.
For full details go to
[Via Hackaday]

Monday, 5 August 2013

Small Build, Big Execuition - Good Practices

There is a huge difference between building an electronic circuit that works, and and well built electronic device.
Both will do there job, but the well built one will do it for longer and be easier to work on in the future. Simple things like including a copy of the circuit diagram in the case and making sure that the battery can be easily changed might seem like minor details, but in practice they are often overlooked.
Quite often, for a well built project, actually assembling the circuit boards is one of the easiest jobs, considering and designing in the details takes far longer.
You are probably doing most of this already, but its always good to check that you are on the right track.
Go to CP's projects for full details
[Via Hack A Day]

Hack A day : DIP switch adjusted voltage regulator

This simple adjustable power supply is another simple device that will be useful in any electronics toolkit.
Based around the widely used LM317 linear voltage regulator the output voltage is easily selected using the DIP switches below.
Go to Hack A day for full details.

Hack a Day : ProtoSynth, the prototyping synthesizer

This is more than just a keyboard and some prototype boards. Some of the tracks a re pre-wired to power supplies and cross connected to each other.
Go to Hack A day for full details.

Hack A Day : Replace your project power supplies with recycled Li-Ion cells and a switching regulator

Dr. Iguana has started powering his projects with recycled LiOn cells and Buck regulators, casting aside the more familiar disposable batteries and 7805 type regulators.
This has made his projects lighter, cheaper to run and smaller, which has to be worth considering.
Go to Hack A Day for full details.

Poor man's MSOP soldering

MSOP stands for Mini Small  Outline Package, where the spacing between leads is about a quarter that of standard breadboard, making a right pain to use.
This article shows how you gave use a pair of pin headers and lump of veroboard to make your own header bringing these tiny devices into the realm of the average hobbyist. 
Highly recommended.
Go to Coding Laboratory for the full article.

Zaarduino MIDI Organ Pedals

Armed with the pedals from a dead Logan organ, and a Korg Microsampler whose keys were to small for a hobbit these guys came up with an interesting solution to both problems.
Go to for the full article.
[Via Hack A day]

Rejuvenating and Expanding a PAiA 1550 Stringz’n'Thingz Synthesizer

Back in the 70's most us could only dream of owning a polyphonic synthesizer that brought such wondrous sounds from the fingers of our keyboard heroes.
Prices were way out of our league and the only option we had was to build one ourselves, often from a kit or magazine article.
One such kit manufacturer is PAiA, who are still going strong, but to be honest their products were at best a compromise for most people.
Years later these old devices are popping up at bargain prices on e-bay, and this article, which I found via Hack A Day details how StefanV bought one at a bargain price and refurbished it into the 21st century.
Go to for full details of the project.
[Via Hackaday]


[Via George Takai]

Sunday, 23 June 2013

Nature : Tetraquark - a 4 quark particle?

An article in the recent edition of Nature recalls the discovery of an extremely rare 4 quark particle, amusingly named the "Tetraqaurk"
Unlike our well known cuddly 2 quark Mesons and 3 quark Baryons these new boys on the block probably only existed at the time of the bang bang itself.
The picture here shows the arrangement is similar, but different to a Two meson "molecule". I wonder if this is officially a Hadron?
For full details of this fascinating article go to

Wednesday, 19 June 2013

Tested: Getting Started with Arduino

I love working with Microcontrollers,but somehow I completely missed the whole Arduino thing, which is a shame as they have so much to offer,  especially in the range of hardware extras that are easily available.
 Will and Norm, from Tested, have just published a video where they sit down to chat about Arduino microcontrollers and give an overview about how they work, what you can do with them, and how the varying models differ from each other
Worth a look if you are still undecided and as they say no scary programming involved!.
Which is a shame. I like scary programming :-)

Make: Farm Drones Take Flight

Drones, or autonomous unmanned aircraft have been around with us for years, normally by the military who don't want to risk a human pilot in a dangerous situation.
But Chris Anderson, CEO of 3D Robotics and founder of DIY Drones, introduced a new idea about how they can be used for more peaceful purposes, in agriculture.
Growing the volume of crops we require is intensive and expensive for the farmers, just spraying a field with chemicals can cost hundreds if not thousands of pounds, which is a bit of a waste when there is actually nothing wrong with some of them in the first place, but how do you tell?
Chris's solution is to fit phonographic sensors to a drone which can over fly crops and use infra red cameras to spot anomalies in the way crops are growing, and then target just those areas with insecticide, or maybe if the problem is found early enough avoid the issue all together.
For full details and a video go to the make blog at

Make: Bringing a Classic Marklin Z-Scale Model Railroad to Life With Arduino

I have always loved model railways, which apart from a love of Physics is probably the only other thing I have in common with Sheldon Cooper.
Years ago I enjoyed building my own models and constructing a layout in my bedroom, but that gave way to SciFi models, and then electronics, followed by music, which then gave way to girls, which is pretty much where I still am some thirty years later.
I couldn't help but be impressed by this layout and it made me think about maybe its time to think about building another.
Except mine will be on mars. With lots of girls playing synthesizers.
This lovely little model combines two of those, railways and electronics, including the ever present Arduino to make the engine move when come near it.
For full details go to the Make blog

Saturday, 15 June 2013

Hack A day : Giving an RC tank a fire control computer

From Hack A Day: "[Vincent] plays around with remote control tanks, and even though his current model is a WWII-era armor piece, he’d still like modern accoutrements such as a fire control computer and laser sighting for his main gun. His latest project did just that (French, Google translation) with the help of an Arduino, a few modifications to the receiver, and an IR rangefinder.
The stock RC tank includes servos to move the turret and the requisite electronics to fire an Airsoft gun. The precision of the mechanical movements inside the turret weren’t very precise, though, so [Vincent] had to gear down the servos to turn large movements into slight adjustments. After that, he installed an IR rangefinder and laser diode onto the barrel that allowed the gun to sight a target and read its distance.
After some experimentation with the rangefinder and laser, [Vincent] plotted data from firing a few BBs at a whole bunch of distances and targets. The graph came out fairly linear, and after plugging this into a graphing calculator, he was able to find an equation that took into account the distance and angle so the Arduino-powered fire control computer would hit its mark.
The accuracy of the gun is very impressive, all things considered. [Vincent] is able to accurately fire BBs downrange and hit an 8×12 cm target at five meters. You can check out that action below."

[From Hack a Day at]
[Original article at]

Tuesday, 21 May 2013

THE BIT BANG THEORY : Lab tip for power connectors

This is a nice one. Its a very simple idea, that tackles the age old problem of having the right connector on the right power supply for the device you want to use.
Sure there are numerous commercial packs of adapters for phones and the like but they tend to be expensive and don't necessarily work with each other.
To get round this the author of this blog has designed his own standard, based on the cheap and easy to use Phono (RCA) plug and sockets.
It works by you chopping up your existing supply cables and attaching phono plugs to both ends. You can then reconnect them in various configurations using female to female adaptors.
The full story can be found over on the Bit Bang Theory site at

Word of caution

As much as I like this idea, if I were to adopt it then I think I would limit myself to 5V supplies only, it would be too easy to mix them up other wiese and damage something.

Monday, 20 May 2013

ATX Raspi

I knew the Raspberry Pi was going to be a winner as soon as I saw the original specification, but I had no idea it would be this popular or that it would stimulate such a healthy crop of third party add-ons.
The latest one I found was this really clever little power supply controller that allows the Pi to shut itself down and disconnect its own power supply.
The power supply is reconnected to the ATX board, which is in turn connected to the Pi through GPIO pins.
What makes this so special is that the ATX has a PIC processor, which monitors the Pi while it is shutting down and only turns the power off, via its on board relay, when the Pi is completely ready.
Full details can be found at
[Via Hackaday]

The Register : US boffin builds 32-way Raspberry Pi cluster

Beowulf (see ) is way to produce a high power parallel computing system by networking together a number of low cost computers with a free to use operating system, based on Unix.
This was an extremely attractive idea to university departments who wanted a huge amount of computing power on a limited budget. There are many stories of clusters being made from systems rescued from skips, and legend has it that in one London university students would swarm over the building late at night, rebooting every available PC from a floppy disk into the cluster, and then rebooting them back before anybody else arrived next morning. It would be nice to suggest that this was for Astrophysics or sub-atomic particle research, but in fact it was to run a Dungeons and Dragons programme.

An article in The Register tells how Boise University PhD candidate Joshua Kiepert  built a 32-way Beowulf cluster from Raspberry Pis.
The RPis were stacked in groups of eight with enough room between them for a reasonable amount of air flow and component clearance he writes. “This configuration suited our needs for power distribution very well since it allowed for a power line to be passed vertically along each stack."
Joshua is extremely happy with the results of his cluster and has written his work up as a PDF file, and if you have any interest in doing something similar then I can recommend reading it in detail.  The cost of this? around £1500, or the cost of a decent high powered 4 core system.
[Full story from The Register]

Saturday, 18 May 2013

The Bit Bang Theory : High torque encoded DC motors for robots from car window motors

Second hand car windscreen wiper motors are still the first choice for many robot builders. They are easy to use, easy to control and you can normally pick them up for around £15 each from scrap yards.
They are normally pretty manky when you get them and need so cleaning up.
My process is
  • Strip them down to bits, taking photos at each step.
  • De-grease the entire thing with petrol and a on old toothbrush. (Goggles, gloves, outdoor space and obviously no smoking people!)
  • Make sure that each electrical carbon brush is isolated from the case, and replace each feed wire with 5A flexible cable. Add a third earthing wire to the case, as close as possible to the brushes. 
  • Fit 100nf capacitors between the brushes, and each brush to the earth point, so that's 3 capacitors. If you don't do this the moor can generate high frequency noise interference which will attract the attention of all around you, including the authorities,
  • Grease all moving parts with SILICON grease, not mineral grease, that can damage the nylon parts apparently.
  • Re-Assemble
  • Clamp the wires to the case with two cable ties and test with a 12V source.
OK this might not seem easy, but I actually enjoy watching something new and useful being born out of scrap, however there is a problem. For most projects you need several motors, often in closely matched pairs for drive systems, but scrap motors come in all shapes and sizes, and getting two the same can be a challenge.

Window Motors

I looked at using window winder motors, because they come in pairs and will be perfectly matched, but here the axle is fixed to the chassis and the rubber drive wheel moves round it, which isn't quite what we need.
However I came across a really interesting article on "The Bit Bang Theory" blog which solves this problem by stripping them down and re-assembling them with a fixed axle. I f I can make this work then that will solve another problem, especially for smaller projects.
Check out the article at
and let me know what you think
[Via Hackaday]

Thursday, 16 May 2013

Instructables: Making PCBs

This appears to be one of the simplest, cleanest, easiest ways I have ever come across for making PCBs.
  • Print your PCB mask on white paper with a laser printer
  • Use an iron to transfer the design to a sheet of copper clad board
  • Soak off the paper backing
  • Etch
  • Drill
  • Clean
  • Solder.
If this works you could easily make a working PCB in under an hour, possibly even less.
I am about to make a MIDI to CV convertor for my synthesizer, and will definitely be trying this method. I will post the results here.

Tuesday, 30 April 2013

Tested : Hacking a $20 Toy Helicopter into an Autonomous Drone

Tuesday, 23 April 2013

Hack A day: Pulse Oximeter from LM324, LED, and Photodiode

From Hackady: "This pulse oximeter is so simple and cheap to build it’s almost criminal. The most obvious way to monitor the output of the sensor is to use an oscilloscope. The poor-man’s stand-in for that is a sound card, which is what [Scott Harden] demonstrates in his write-up.
It uses a concept we’ve seen a few times before. The light from an LED shines through your finger and is measured on the other side by a phototransistor. It’s that light grey plastic thing you see on a patient’s finger when they’re in the hospital. [Scott] went with a common wooden clothes pin as a way to mount and align the sensor with your finger. It is monitored by the simplest of circuits which uses just one chip: an LM324 op-amp. There are three basic stages which he explains well in the video after the jump. The incoming signal is decoupled before being fed to the first amplifier stage. From there it is fed to an adjustable low-pass filter to help eliminate 60Hz noise from AC power in the room. The last stage amplifies the signal again while using another low-pass filter in parallel."
[From Hack A Day]

Make: BeagleBone Black Has Arrived

A new version of the BeagleBone is available, and from the name, Black, you might be forgiven for thinking that its got carbon fibre components, low profile wheels and it's weight has been reduced by getting rid of all unnecessary luxuries (Car joke BTW).
But no, all this has lost is the ability to reflect colored light, and replaced them with some stunning new features
  • The CPU runs at1GHz, up from the original’s 720MHz.
  • RAM doubled to 512MB.
  • Connection to an HDMI monitor through the on-board MicroHDMI port.
  • 2GB of on-board flash memory, which will be loaded with the Ångström Linux. You can overwrite this, and still get the micro-sd option.
  • The OS has been upgraded to Linux Kernel 3.8 and included upgrades to Java and the disk software.
This is all very good, I have been keeping the best until last, which is the price has dropped to $45 bringing it into direct competition with the Raspberry PI. And with that on-board OS Flash I think it might have just crept into the lead.

Make: 200,000 Piece Lego Sci-Fi Jaw Dropper

From Make "New York-based graphic designer and artist Mike Doyle caught our attention a couple of years ago with his beautifully rendered eerie Lego Victorian houses. His latest piece, titled Contact 1, employs over 200,000 Lego bricks, took him over 600 hours to build, and stands 5 feet tall and 6 feet wide. Contact 1 is the first in a series Doyle is working on, and he writes, “The Contact Series of Lego-built creations was designed to promote the beauty of all intelligent life forms as extensions of our family – children under the same creative force.”
The images seem unreal, leaving the viewer wondering if they are of an actual sculpture or a rendering. Doyle responds, “The project is built and then photographed. 90% of the saucers are connected to the model with black Lego hoses. These mostly disappeared against a black screen. Those hoses that remained, I darkened to disappear. For some of the saucers appearing in front of the buildings, they were attached and then the attachments photoshopped out for a cleaner presentation.”
For full article go to]

Sunday, 14 April 2013

WOMinator MIDI bass pedals

I have wanted a set of bass pedals since I read that Mike Rutherford used them on early Genesis albums.
His original set came as a kit from a company called "Dewtron" and were designed for use by organists whose instruments came without them.
By the mid-70's people, such as Geddy Lee from Rush, were using the original Moog Taurus Pedals which had their very own unique, really powerful, gut wrenching sound, but they were expensive. REALLY expensive, like half a years salary expensive and they had a reputation for melting most amplification systems.
With the advent of MIDI it was an easy job to make a foot controller, like that in the photo, and link it up to a synthesizer, but not many people seemed to bother, they just carried on using a set of Taurus pedals.
Now Lee O'Donnel, has used an old set of organ pedals and an Arduino to make a very handy looking instrument.
If you don't happen to have a set of pedals lieing around then new ones are available from Doepfer, but they will currently set you back 150 of the nasty Euro thingies. By the time you have added a box, and arduino, or a Raspberry Pi, and all the gubbins, don't expect to see much change from £200. Mind you it will probably be worth it :-)
See for Lee's original article.

Monday, 1 April 2013

The Molecule Synth

A fascinating idea where individual physical synthesizer modules can be plugged together, like Lego blocks, to make unique musical instruments.
Go to for full details.

BigDog doesn't want to play fetch.

"BigDog handles heavy objects. The goal is to use the strength of the legs and torso to help power motions of the arm. This sort of dynamic, whole-body approach to manipulation is used routinely by human athletes and will enhance the performance of advanced robots. Boston Dynamics is developing the control and actuation techniques needed for dynamic manipulation. The cinderblock weighs about 35 lbs and the best throw is a bit more than 17 ft. The research is funded by the Army Research Laboratory's RCTA program."
BigDog is a military grade all terrain robot that cay carry several hundred kilos of kit over rough terrain, amd easily keep up with a human. They are hoping that it will be used in places like Afghanistan to carry addition kit, water and munitions to soldiers freeing them up to concentrate on fighting and staying alive. 
There have been all manners of rumours surrounding the project, such as it can be modified to carry a human, either like a horse or a casualty on a stretcher, or even be fitted with weapons that it can fire on command or autonomously. This fits in the the idea that one could be set of by itself to re-supply soldier several miles away without the need for a human operator. This could either be done by a remote pilot, like a predator drone, or even using AI.  
It was already scary but the thought of an autonomous mobile missile platform, with machine guns wandering around the place is getting a bit too close to SkyNet. At least the T800 didn't start throwing masonry at you!

How-To: Phone Plug Tilt Switch

This is such a simple, yet Genius idea from Makezine.
If the plug is tip down the ball shorts out the tag to the tip and the main body, but tip it back and the ball rolls backwards breaking the circuit. Brilliant :-)
For full details go to
[Via Make]

Making MIDI hi-hat controller from unused bass drum pedal

A tidy little project from HWMayer that converted a standard Bass drum pedal into a controller for the Alesis interface.
Most of the mechanical bits came from pedal itself, while the electronics is nothing more than a variable resistor, some wire and a connector.
For regular live use you could enclose the whole thing in a die-cast box, held in place by the aluminum plate used here, and use a standard 1/4" Jack.
Go to the original article for full details.

Monday, 4 March 2013

Curiosity put into 'safe mode' after computer glitch

From the BBC:
"Nasa's Curiosity Mars rover has been put into "safe mode" after a computer glitch caused by corrupted files.
The robot, which is analysing rock samples on the Red Planet, is now running from a back-up computer.
Nasa engineers are looking into possible causes for the files on the robot's flash memory being damaged.
The fault means the rover's work has been put on temporary hold while the back-up computer is reconfigured so it can take full control.
"We're still early on in the process," said project manager Richard Cook, in an interview with
"We have probably several days, maybe a week, of activities to get everything back and reconfigured."
The rover has been running on the back-up computer since Thursday"
For full story go to
[Via BBC]

Sunday, 3 March 2013

Richard Nakka's Experimental Rocketry Web Site

Several years ago I bought a copy of the book "K450 PVC Rocket Engine Design and Construction", which had to be imported from the US. It shows you, in extremely easy steps, how to build a K450 (very powerful) rocket motor which can lift reasonable sized payloads far higher than commercial "model" rocket motors, however there were several problems that stopped me from making one.
Firstly you can't easily buy the chemicals needed to make this in the UK. You can try to extract it from weedkiller, but in the UK this is mixed with a chemical that stops it exploding so it can't be used to make bombs, but that also stops it being used for rockets.
The second problem is that there is nowhere here, in South East England, that I could safely let one off and expect to get it back. It would be dangerous on public access land and farmers do get a tad feisty when attacked by rockets which are twice the size of a shoulder mounted anti-tank missile. I suppose I could launch it out to Sea but then I have the pain of trying to recover it so I would need either a fast boat or a search a rescue drone first.
But the final hilarious issue was that HM Customs and Excise were notified by the US Government that I had bought this book and I had to sign an import form for it, so somewhere I am on a list and if one turns up embedded in somebody's roof then the Rozzers might well be round here first!
I had forgotten all about this but today I noticed this article on Hack A Day, which leads to "Richard Nakka's Experimental Rocketry Web Site". Richard has developed the use of Sorbitol as an alternative rocket propellant may overcome the problem with getting the right chemicals in the UK.
What I didn't expect was that his website is an absolute treasure house of articles about making experimental rockets, most of which he has written himself.  It must have taken years to amass this information so hats off to you Richard, I am looking forward to getting a cup of coffee and a doughnut then spending an afternoon going through your work.
[Via HackADay]

Update: The Sorbitol replaces the sugar, not the weedkiller, so its not really going to help. Shame.

Tuesday, 26 February 2013

Sixty Symbols

The University of Nottingham have produced an excellent collection of videos covering a huge variety of Physics topics, such as "Do electrons stop moving at absolute zero?" and "What happens when two black holes collide?"
I have watched several of them now and can highly recommend the lot!
Go to for full details and the videos.

Sixty Symbols: Periodic Table of Videos

"Tables charting the chemical elements have been around since the 19th century - but this modern version has a short video about each one. 
We've done all 118 - but our job's not finished. Now we're updating all the videos with new stories, better samples and bigger experiments.
Plus we're making films about other areas of chemistry, latest news and occasional adventures away from the lab.
We've also started a new series - The Molecular Videos - featuring our favourite molecules and compounds.
All these videos are created by video journalist Brady Haran, featuring real working chemists from the University of Nottingham."

Monday, 25 February 2013

Raspberry Pi and Breadboard (Raspberry Leaf)

If you have ever tried connecting jumper wires to a Raspberry Pi then you will have noticed that unlike other systems, the pin names are not printed on the PCB.
While not a showstopper it is a bit of an irritation, especially as my two older Pis have different pinouts to current ones, which is why I was so interested by this idea from Dr. Monk's DIY Electronics Blog
They are simply printed paper templates that push over the GPIO pins making it so much easier to see what you are doing, and I can tell you after this weekend that they really help.
You can grab copies of these templates from
[Via Make]

Saturday, 23 February 2013

HackADay: Self-waking computer for DIY cloud storage

This one will require more than a bit of normal controller coding, you will need to hack the code on a network router.
The builder [Dominic] wanted to use Owncloud, which as the name suggests allows him to provide his own cloud storage, using his own computer, but to save his electricity bills he didn't want to leave the computer on all day.
His plan was to leave the server normally turned off, and hack the router to turn it back on when somebody wanted to access it.
Its quite a clever solution, have a look for yourself over at
[Via Hackaday]

Thursday, 21 February 2013

Embedded Projects: Small web server displays sensor data

This Ethernet controllercan be easily connected to any embedded controller system and yet costs around £5 from e-bay. Bargain.
The device is based on the ENC28J60 Ethernet controller for which has extensive libraries for both the arduinino and  Microchip PIC, building a project with one should be relatively straightforward.
Over on Embedded Projects Jer has combined one with an ardunio and a sensor shield to make a self contained webserver, all for a around £30. (That's my estimate)
Atthe moment I can't think what I would want one for, I wish I had know about these last year when I started building mine, it would have saved me hours.
The original article can be found at
[Via Embedded Projects]