Or more precisely – how to build a ring mod and light flasher.

[If you are wondering what a Dalek sounds like, take a look/listen here]

The first step I took was to download the manual for the MoogerFooger and find out what all the knobs do. It looks to me like Nick Briggs uses a “secret Dalek factor” as the carrier and feeds this through a traditional ring modulator constructed from 4 diodes and 2 audio transformers.

Luckily there’s a great website that shows you how to build a passive analog ring mod here:

http://www.asciipr0n…gmod/index.html

Follow the directions on the page and wire up the audio transformers:

Audio Transformers

and the germanium diodes

Germanium Diodes

in the characteristic ring arrangement:

Lovely.

Your voice goes in on the red wires, the secret Dalek factor goes in on the green, and Dalek magic comes out of the yellow. (Actually connecting up in any order will make the RM work)

OK now to add the secret Dalek factor.

I don’t like to re-invent the wheel, so if there’s something out there that can *almost* do the job, I will hack away at that rather than design something from scratch.

The secret Dalek factor (as most of you know) is a 30Hz sine wave. So we need to find an audio oscillator that can provide what we need. Fortunately for us, (and Mr Hewlett, *and* Mr Packard), there’s such a thing as a WIEN-BRIDGE oscillator. Rainbow Kits sells a nice one for $not-very-much-at-all.

However, out of the box this kit does not do what we want. It oscillates at a fixed frequency that is too fast. After a bit of RC [1/2PiRC] math it turns out that we need to replace capacitors C1 and C2 with 0.1uF ceramic caps, and resistors C5 and C6 with approx 53.1KOhm.

Alternatively you can do as I did and get a dual gang pot (200KOhm) and turn this till the output reads close to 30Hz.

Great, so we’ve added the secret Dalek factor on the green wires, now we need to add the voice. For this we’ll need a microphone and a pre-amp. Velleman to the rescue here:

This tiny kit goes straight in unmodded.

All that remains is to add the speakers – for this I hooked up to 12v PC speakers to the red wires. Plug it in and hey presto – instant Dalek.

The sound can be improved greatly by feeding the microphone through an EQ effect pedal, boosting the mid-range and cutting the high and low.

Next stop – the light flashers…

-+-+-+-+-+-+

This was tricky. The standard Schmitt trigger that’s on Dalek City is OK, but the lights can get stuck in the “on” position and you have to cough to toggle them off. Also inside the cockpit there’s no visual feedback to what the dome lights are doing. Also the current requirement to flash 2 x 20W halogen lights on 12V is pretty darned high.

Again, I’m just going to mod some existing cheap kits that are readily available. The first kit is the well-known Velleman MK103 sound to LED light flasher:

This works at a mic level input – great for us – and has high impedance so the signal is not really affected. It only light 4 LEDs though which is no where near what we want to power 40 watts of halogen grooviness.

Here’s a picture showing the basic mod:

I replaced the built in mic with two wires which is connected to the mic socket, and the last LED (4) has been removed. You can simply wire this output into an optoisolator (4n29) through a 1K resistor, then use a big power resistor to switch the lights (TIP142, or a Mosfet)

OR…. you can take the Rolls Royce approach and wire the output directly into this little beauty:

The fantabulous Velleman MK114 12v sound to light kit, rated at up to 50 watts at 12v and a brain tingling 100 watts at 24v!

You just plug it straight in and away you go…

Note – the MK103 really likes to be run at 9v, not 12 – so I added a 9v regulator to run it where it wants to be.

I like this solution, there are two parallel transistors and a nice big fuse. It really *looks* like it can handle the power.

So that’s it, your voice mod, light flashing device is ready to be installed in your favourite MkIII travel machine. The lamps I have plugged in are low power, as my PSU cannot put out enough current to drive the two 20w halogen bulbs I just bought. So I need a bigger PSU…

Of course, this is only half of the story.

To really sound like a Dalek you have to adopt the harsh staccato tone, and do a bit of acting…

Pew! Pew! Pew! Lasers

This is a pretty cool review of Little Boots recent gig at the Highline Ballroom in New York City.

“There’s not much you can say against the laser harp. At the Highline Ballroom on Tuesday night a beam of green light shot up from the floor, then fanned out into eight individual rays. The tiny synth-pop singer Little Boots, wearing a gold lamé gown and face mask, played the melody of her song “Earthquake” by moving her hand among the streams of light; each time she blocked one, it triggered a synthesizer pitch, and she could alter its tone by lowering or raising her hand on each beam…”

Read More at NYT…

It’s been great to finally put the laser harp into the hands of a creative artist. Victoria’s going to take her band to the Ultra festival this month, and then on to Coachella next month. We’ve been working on something very special for that gig…

9700 Visualizer in action

The PAIA 9700s is a compact analog modular music synthesizer, available as a kit. It took me about 3 weeks to get everything constructed and installed in the case.

After building the next task is to set the scale trimmers on both voltage controlled oscillators so that they stay in tune over the largest range of musical octaves. This process involves going “back and forth” between the scale pot and front tuning knob until you get both oscillators tuned. It’s a difficult task as it’s not always obvious how the oscillator tracking is moving around when you alter the scale.

I found that the best way to set the scale is to tune the root note to ‘C’ then play one octave above and note how much shift there is in the upper C. If the shift is positive (sharp) then actually set the scale to make it sharper (counter intuitive I know) then drop back down to the lower C and use the front panel pitch control to move the whole range down.

On my PAIA 9700s page I mentioned a neat tuning utility that could help with the process. I contacted the author; Andrew Steer, as I was hoping to incorporate his source code into something I was creating to help tune my PAIA 9700s synthesizer. He sent me the routine that detects pitch – it was in Borland C++, but it turned out not to be too difficult to replicate the code in C#. I added MIDI support and a graphing function to assist in the tuning.

Now all you need to do is connect the first oscillator output to your mic in, click “Start” to see the signal in the oscilloscope window, and adjust the mic input level to get a clean signal.

Then you click start test, and it will send MIDI data out of the default MIDI port (which you should connect to the input of the 9700) and read the frequency output. Once it has completed a pass of oscillator one, it will prompt you to connect up oscillator two, and repeats the test. Finally it plots a graph of the two oscillator responses against an ideal curve. (Log plot is also available).

In this way you can see the changes as you make them.

Download the exe here.

MIDI Relay - sends serial port data straight to the default MIDI port

When it comes to creating MIDI controllers the Arduino is tough to beat. There’s a great development community out there and creating MIDI data is a breeze.

What’s not so cool is that it’s very very difficult to send MIDI data over the standard USB serial port that is used to communicate with the Arduino.

Wouldn’t it be nice if there was something you could do to test your creations, without:

(a) having to solder a 5 pin DIN connector onto the serial port TX pin
(b) hunting around the house for that old USB/MIDI interface that you *know* is in one-of-those-boxes-over-there(tm).

?????

Well now you can – I put together this really simple application that lets you choose a serial port, click start and then it retransmits all the incoming data over to the default MIDI port you configured in Windows control panel.

Click here to download – it was built using Visual Studio 2008 – so will need the .Net framework 3.5 installed to run.

If you use MidiYoke you can route the data straight back into a VST softsynth.

You will need to transmit from the Arduino at 38400 speed.

Job done!
…and not a 220 Ohm resistor in sight.

P.S. – At the moment it only supports note on / note off and controller data.

I recently revisited some of my early laser harp work and thought it worth making a posting of the original beam detection circuit. This is an active low comparator circuit and the output line can be hooked directly into an Arduino.

Shine the laser/light onto the Light Dependent Resistor and turn the 100K potentiometer until the LED just comes on. Then shading the LDR should turn the LED off. All the parts are easily available from Radio Shack (Note: the power and gnd connections for the LM324 are not shown).

The circuit is in 5 parts. See attached picture.

Part 1 is the power hookup – you need to connect the 5 volts output from the Arduino (or another source) and gnd to the two lines that run along the longest edge of the breadboard.

Part 2 is the first of 2 potential divider circuits. These divide the input voltage up from part one into different levels. This first one is adjustable with the potentiometer (100K). If you connect the resistor and the potentiometer as shown, then measure the output of the divider ( the middle tab of the potentiometer) you should see a voltage change as you turn the control knob of the potentiometer.

Part 3 is the second potential divider circuit. This uses a light dependent resistor in place of the potentiometer alter the voltage. Same as before though, if you wire this up and measure the output (the line that is connected to pin 3 later in the circuit) you should see the voltage change as more or less light shines on the circuit.

Part 4 uses the op-amp integrated circuit to compare the 2 voltages from parts 2 and 3. When the voltage output of part 3 is above that from part 2 the pin 1 from the IC will go “high” and cause the LED in part 4 to light up. In addition to wiring in pins 1,2 and 3 you will need to connect the power and gnd pins to the power and gnd lines we created
in part 1.

Part 5 is the output stage – this uses a simple LED and current limiting resistor to light up when the pin goes high. You want to have this LED light up when the laser pointer is pointing at the photocell, and go off when it is not. Note the polarity of the LED, it should only go in one way round.

I used 8 of these circuits in the very first static laser harp I built:

The view from the front...

I’ve been working away for the last month or so on developing a laser harp controller that could hook into an existing stage lighting rig.

This project was for Victoria Hesketh or “Little Boots” as she is known in the UK.

If you already own an ILDA compatible projector and are looking to add MIDI based interactive laser instruments into your line-up then this will just about do the job…

I can custom build these units, and if there’s enough interest I might start offering them for sale.

…and I missed it.

Maker Faire 2008

I just stumbled across this last night, I remember giving the interview, but forgot to watch it…

I’m sandwiched between the robotic giraffe and the cupcake bicycle at about 1:49

http://www.dailymotion.com/video/x7mcd1_attack-of-the-show-maker-faire_videogames

Oooh I’m all sweaty.

I recently was asked if it were possible to output continuous controller data from the WiiMote Theremin device I created here

This should be pretty simple as the Toub.Sound.Midi library supports CC data just like the Note On/Off.

If you open up the source code in Visual Studio Express C# – you should be able to find the line in the Form.cs file that plays the notes…

This can be easily changed to support CC data as follows:

// Removed, since we are no longer sending MIDI Notes,
// just CC we do not need to send a note off
//if (LastNoteNo != 255)
//    NoteOff();
// ----------------------------------

// Convert the raw val to a MIDI note by dividing by 10
LastNoteNo = temp;

// This is the line that takes the camera X coordinate value and outputs it as a MIDI note
// start to output CC data instead
//Toub.Sound.Midi.NoteOn _n = new NoteOn(0, 0x0, LastNoteNo, 100);
//Toub.Sound.Midi.MidiPlayer.Play(_n);

// Set this to 0-15 for the 16 MIDI channels
byte MIDIOutChannel = 0;
// Set this to your desired controller number
byte ccNumber = 33;

Toub.Sound.Midi.Controller _cc = new Controller(0, MIDIOutChannel, ccNumber, LastNoteNo);
Toub.Sound.Midi.MidiPlayer.Play(_cc);

I’ve had the parts to build one of these on my shelf for over a year – I thought it was about time I dusted them off and actually put the thing together.

I first tried it with some small ceramic magnets attached to a hard-drive platter. But this only put out about 7-10mV – which did not seem to be enough to get the switching function going.

Replacing it with a low friction bearing from a VCR, a plastic CD spacer and some “rare earth” magnets seemed to do the trick.

The iron coil attracts the magnet, but then when it draws level it generates a trigger pulse that switches on the coil – this reverse magnetises the core and pushes the magnet away. The cycle then repeats with the next magnet.

Basically this is a super-efficient motor.

But it’s rumoured to be the basis of a zero point energy device as well…

[Cue Twilight Zone Music]

I’ve had the parts to build a Bedini mono-pole motor for a while. I just hooked up everything this morning, but so far I can’t get it to spin…

Bedini motor hookup

Close up on the coil and rotor