07/08/2019 at 11:09 •
Having finally worked out how to play the buzzing rhythm sound from the soundfont file on the attached mobile phone MIDI player, at present by pressing a button on the handle, this means I can now replace this button in theory at least with some form of crank handle.
The crank handle is low cost and intended for a fishing reel. I have attached it to a motor which has a reduction gearbox. I had to buy 3 motors with different reduction ratios before I found one with the right amount of mechanical resistance to turning. In this video update I show each motor and also show how I can make an attached pager motor buzz by turning the crank. As the handle on the current Digi-gurdy can slide fully out and is attached electronically to the main body via a headphone plug, this means it could possibly be replaced by a crank module with no modification of the main body of the device, for those who wish to try it. More work required here but clearly this has potential. I will see how I get on and show the results in the next update.
07/08/2019 at 11:00 •
Setting up the Digi-Gurdy to play via a mobile phone.
I have now worked out how to play the melody via Channel 1 of a MIDI player running on a phone, the High D trompette via Channel 2, a Low G drone via Channel 3 and the crank-activated buzzing rhythm sound via Channel 4.
The MIDI player is free and called FluidSynth. The soundfont file (a library of sound effectively) that it uses is from the open source MIDI-gurdy project https://github.com/midigurdy/midigurdy to which I have added an extra buzzing sound.
By pressing the upper green button on the handle, the device behaves as if you are turning the crank handle, i.e. you get the drone sounds you have set up plus the open melody string (G4). You then play the melody via the keys while the drones continue to sound.
In this version, the lower yellow button on the handle activates the buzzing trompette sound which is the rhythm section of a hurdygurdy, normally produced by momentary increases in rotation speed of the crank handle.
This means, in my next update, I can look at ways to simulate the crank handle by generation of a suitable voltage signal to the Arduino Teensy via a geared motor to which a crank handle has been attached.
I have also included in the video two quick bursts of the device running in demonstration mode just for fun.
05/24/2019 at 15:05 •
Here is a video outlining the main features of a hurdy gurdy, the instrument we are aiming to partially emulate with an electronic practice version.
The Digi-Gurdy presents two challenges. The first is the physical design and the second will be the internal electronics. It must be compact, have keys with the same layout as a real hurdy gurdy and while looking good, must be potentially capable of manufacture at reasonable cost. Current experiments combine 3D printed parts which could ultimately be made of plastic in combination with a frame which includes aluminium extrusions.
- There are ongoing experiments in an attempt to simulate a crank handle but for now a rigid handle is provided for the right hand, which helps you stabilize the device on your lap while playing the keys with your left hand. This may end up being the best compromise.
- This handle is a commercially available plastic pistol-grip handle for cameras.
- It has been fitted to an alloy bar which slides telescopically out of the body of the Digi-Gurdy.
- This keeps the device compact and portable.
- The OLED screen has been relocated into the main body of the device to improve ruggedness.
- The keys are no longer held in place by a small bolt through their tail ends but now reversibly snap into place. This will reduce assembly time and allow easy replacement if ever damaged.
- The micro switches for each key also now push-fit into their sockets without requiring glue to hold them in place. I am now also using roller switches as they give a great feel to the key action.
- I could use resistance wire, contacted by the keys, or a ribbon potentiometer. This would reduce the quantity of wiring, however microswitches will probably be more reliable after heavy use, are designed to operate many thousands of times, give a good feel on each keypress and also return the keys well to their start positions after being pressed.
The video below outlines the main aspects of the physical design. The electronics will be the subject of future updates.
Here are the main parts laid out on the bench.