Bill Fredette just sent me this link to his successful laser harp build…

Laser Harps are notoriously difficult to film – so top marks to Bill for completing the build and getting some good quality footage.

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.

Oooh feel the burn...

Nowhere near the 16,000 RPM+ that this guy gets, but my own personal blister-inducing record.

There are a few circuit simulation packages out there – and most of them are rather expensive. A colleague at work recently gave me a link to this cool Java based simulator written by Paul Falstad:

http://www.falstad.com/circuit/

(Obviously you will need the Java plugin to run it)

What really sets this one apart is that it visually models the electrical flow along the connecting wires – so it really makes it obvious how the circuit will behave.

If you are new to electronics this is an absolutely brilliant way to learn what transistors, diodes, gates and op-amps do.

*And*

Here’s another great prototyping product:

http://fritzing.org/

Great stuff!

I took the Dalek along to a local cub scouts meeting.

They were having a Robot night, and my buddy Lloyd asked me if I’d be able to get the Dalek transported.

I just wish I’d had another operator – or at least someone to run the camera while I controlled the Dalek.

Pushing a Dalek through a blizzard is not the easiest of tasks – but we did it.