MIDI saxophone update

After another BuildBrighton meeting last night, a bit more work has been done on MIDI-fying our saxophone. This is now the third attempt and looks the most likely to get a working result! The first time, the wires were ran from the bell to the neck, leaving little or no room for the microcontrotroller circuit. The second time, the wires were run to the bell, so there was a large area we could fill with a circuit board, but the copper-tape-making-contact-with-the-body idea failed on number of pads.

This time, we're sure we've got it right. Only because, we couldn't have come up with a more difficult-to-implement solution! We're (slowly) removing each pad - yes, complete with linkages and springs - and fitting a pushbutton under each one.

In doing this, we're finding out quite a bit about the saxophone.
Namely that it's been badly dropped at some point during it's life, and would be unplayable as an acoustic instrument! There are four or five pads misaligned - and rings on the leather showing where the pad used to sit, and a shallower indent showing it's new resting position after the (presumed) accident.

So despite filling the body with hot glue and generally making a mess of things, at least we can be satisfied in knowing we're not ruining a perfectly good sax for this project - it was only destined for a junk shop somewhere, or an expensive repair job!

 (Saxophone fitted with five pushbuttons, mounted into acrylic disks. The push buttons are the slightly clicky tactile ones and the guard has been removed to allow the pads to open more fully). 

When operating the pads, it's interesting to feel the tactile clicky button through the button on the body of the sax. This gives a really nice, responsive feel.
However, some pads are "normally closed" and open when you press a key (or combination of keys) rather than the simpler push-to-close type. We found that sometimes, if you release a key gently, the spring on the pad isn't always strong enough to force the pad fully closed again. Here's an example of one such pad. An extra spring was added between the pad cover and the guard, to help push the pad into it's normally-closed state, and force the pushbutton to "click closed")

MIDI sax

It's late and it's Thursday, which can only mean it's BuildBrighton night again.
We've been busy working on our MIDI saxophone, trying to get it ready for next Saturday's MIDI workshop. Sadly, despite a promising start, it looks like we're going to miss the deadline. Here's why:

The original idea was to use copper tape on the insides of each pad and run a wire to a microcontroller. By detecting which pads were open and closed (copper tape touching the grounded body of the sax where the pad was closed would pull an input pin low, whereas an input pin linked to an open pad would be pulled high by a pull-up resistor) we could work out which note was being fingered, and play the appropriate note.

Sometimes it was necessary to add a little extra tape to the back of the pads, to stop the weight of the wire pulling the copper tape free. The copper tape is very sticky, but despite this, sometimes would start to peel away from the end where the wire met the centre of the pad.

With the first few pads, everything worked according to plan (with the exception that we had to file a little bit of lacquer away from the very rims of the sound holes, so that the copper tape could touch something metallic/conductive to make the circuit)

After completing the first few pads, we stopped and thought about where these inputs were going to. So far, we'd wired the entire instrument from the pads to the top of the instrument neck. This was a very small opening into which we needed to fit our microcontroller.

It was only when someone pointed out that we'd also have to use very small batteries that we realised our mistake! Instead of taking the wires to the top of the neck of the instrument, we'd have a lot more room (and could make accessing the battery compartment much easier) if we put the microcontroller onto a board and used it to "plug" or cover the opening of the larger bell part of the sax. D'oh.

It took just three minutes to undo about three days wiring work. But less than an hour to wire the first few pads up "properly".

As each wire went in, we closed the pad it was connected to, and tested for continuity between the end of the wire and the body of the instrument. This proved that the pad opening and closing could be used on an input pin of our microcontroller. All went well for the first six pads......

The seventh pad (on the left, below) was a bit more problematic.

This particular pad was not pressed directly by the player pressing a button, but was closed by a linkage from one of the other pads. As a result, it didn't quite have the same pressure upon it.
This was compounded by the face that this particular pad had a slight leak - it didn't sit exactly flush over the opening. When played as an acoustic instrument, this leak would cause the instrument to sound out-of-tune.

A more immediate problem for us is that because of where the tape sits inside the pad (sometimes fitting the copper tape to the underside of the pad is a tight squeeze and we can't always put it where we'd like) when this pad is pulled closed by the linkage, we're not getting the input signal going low.

It seems that, although relatively easy to implement, our copper tape idea needs a bit of a rethink......

MIDI saxophone

This rather tongue-in-cheek article (http://www.mindworkshop.com/saxophone.html) explains how I feel about learning saxophone. I bought one a few years ago, even took a few lessons, learned a few songs, but then put it back in it's case, where it's stayed ever since.

Why? I guess I'm just too considerate!
I didn't like the idea of my neighbours having to listen to the squeaks and farts that came out of the shiny bendy bit day and night, and the cost of going to someone else's house to learn and practice become prohibitive quite quickly. So I figured that one day I'd build a practice sax, that would let me learn the fingerings and notes without having to blow the thing too loudly.

That was four or five years ago.
My lovely saxophone was too nice (and too expensive) to hack, so every now and again I'd check eBay for a cheap instrument. Well, this morning, all that waiting finally paid off

Here's my new sax, ready to be fitted with a load of wires to be converted into a midi instrument. My first idea was to run some CAT5 cable through the body, then separate the wires afterwards. This very quickly proved too difficult

So I separated the cable into individual strands and placed a small weight (capacitor) at one end of each wire.

I then pushed the capacitor through an open, erm, valve? pad? hole? and wiggled it round, while feeding the wire into the body of the sax.

Eventually it appeared at the neck end of the instrument (I started feeding the wire into the larger holes in the curved bit at the bottom of the bell and worked up the instrument)

Sometimes - especially once a few wires were in place - the cap got caught up with other wires or fell into the hole of another note. If it couldn't be shaken free, a bent bit of solid-core wire was easily pushed down the next to hook it free and retrieve the other end of the wire.

After about an hour of wire-wiggling, I managed to get twelve wires from the lower 12 holes, through the instrument body and secured out of the top of the neck. Once all 24 are in place (the body has 23 holes and a 24th on the crook of the mouthpiece) then can be soldered to a PCB and hooked up to a PIC microcontroller for the MIDI fun to begin!