More coils

Here I have started to wind the solenoid coils using 0.25mm diameter magnet wire. A 25g spool filled up 4 solenoids nicely, I didn't worry about counting the number of turns.

The winding jig was very simple. Just a crank handle made from a couple of 3mm screws and a scrap of 2mm aluminium. The bolt in the vice is being used as a pin, the thread isn't being used. The spool of wire is being held behind a couple of bits of steel, ground parallels in the case, this keeps a bit of tension on the wire. I just used my finger to guide the wire to get an even distribution. The winding took about 2 mins per coil.

After winding I soldered longer wire leads to each of the enamel wire endings. The soldering process removes the enamel, so you don't need to worry about scraping it off. I used some shrink tube to protect the join.

After successfully winding 6 coils, that brought the total to 8 including the prototypes. Enough coils for a single octave and a good chance to test out playing some songs.

Here is a fast version of the "doe a deer" song from The Sound of Music. This was about as fast as I could play with the first prototype coil. It required a 100ms pulse while the later design with more windings only needed a 7ms pulse to get a note to ring. So when all the coils are wound it will play about 14 times faster than this, which, after a little test, is ridiculously fast.

Solenoid spools.

Now that the test solenoids worked well it is time to get stuck in making the rest. Starting off with the spools.

Here is the design.

Turning on the lathe. I had to use a the tail stock and turn between centres as the nylon was deflecting. I think a more machining friendly plastic could have helped. I had more deflection problems with the drill producing a well undersized hole and ended up using a 6.5mm drill.

All finished.

Circuit Progress

So I spent a little time getting the chain of 4 shift registers to behave and now have 32 output pins to play with. The glockenspiel I made has 25 keys so things should work out well.

I also wound a second solenoid coil of a slightly different design to the first. I used 12mm nylon for the spool which allowed for some more windings than the first.

The circuit to actuate the solenoids is similar to one shown on the arduino forum.

I am now using a new Arduino Uno purchased from ebay au store microcontrollers and more.

Here is the result with both solenoids connected.

Some more musical notes.

I found a little time last weekend to finish off the glockenspiel notes I've been making.

To make things a little bit interesting I used 10x40mm aluminium for the natural notes and 12x25mm for the sharps. I was quite happy with the results from a design aspect.

Next is to wind some coils for the solenoids.

Glockenspiel Keys

Here are the first few keys for my glockenspiel. I crept up on the finished lengths of the first two bars, taking 0.1mm increments and measuring frequency. With the remaining six I put my trust the physics and was surprised by how well tuned they turned out.

For those interested in the physics, the ratio of frequencies differing by a semitone is 2^(1/12).

Also the fundamental frequency of a bar is inversely proportional to the square of its length.

Thus the ratio of bar length between semitones is (2^(1/12))^(1/2) = 2^(1/24).

For example if it is known that say a bar tuned to C is 200mm long then a bar tuned to C# is given by:

Length(C#) = Length(C) / 2^(1/24)

Length(C#) = 200 / 2^(1/24) = 194.31

MIDI Glockenspiel

So I have been inspired by a post over at NerdKits where they made a solenoid actuated glockenspiel. Quite impressive, and I figured why not have a go using the roboduino arduino board.

If things work out well, what I hope is to be able to have the glockenspiel play using the MIDI output from my You Rock Guitar MIDI controller. Am looking into getting a dedicated shield to aid this.

A couple of little proof of concept videos, the first is testing out the shift registers required. I opted for 74HC595 8 bit registers which have a latch function.

The next is of a solenoid I made striking a test note which the tuner on my phone tells me is approximately a D#.

Fretboard supplies.

I am beginning preparations for work on the fretboard!

I purchased 4 x 2 ft lengths of medium gauge fret wire from stewmac.com they had very good service to Australia. The folks at Maton Guitars were kind enough to bend it for me. I wasn't too keen to undertake that job myself.

I have also bought a piece of 10mm 5083 aluminium plate for the fretboard itself. Am a bit concerned about internal stresses at the moment, the plate has a fair bend in it to begin with which I might press out before machining. And after machining who knows what will occur. Some more thought I think.

Am also planning on making a small sample piece to test the size of groove that the fret wire will press in to. I have bought a couple of 0.508mm (0.02") end mills which I was planning on doing the job with, the fret wire tang measures .75mm in width so I might need to take a couple of passes. It occurs to me the barbs on the fret wire tang was not designed to be pressed into aluminium, so some experimentation is required, I bought plenty of wire for this reason.

I also must finalize the CAD and CAM. More about that later, along with some info on the VMC I'll be using to do the machining. Also I am still to work out how I will fixture this part to machine it.