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• Project Log #11: More design tweaks and assembling the first six.

  XenonJohn • 11/24/2019 at 15:19 • 0 comments

  I am assembling six DG's for some brave early adopters out there. 

  A few design changes: 

  i) On startup the software measures the voltage on the analog pin from the buzz-sensitivity potentiometer 200 times and calculates the standard deviation. If low, a crank module is present and if large it is not. This means I can use same software for both variants of the design. I have added a gaming button to the crank module now instead of a small switch, so you can play it by tuning the crank, or by pressing this button with right hand. If you want to remove the crank module at some point in the future, you can unbolt it, remove the glowing glass dome and remount the switch from the crank module into the hole where the glass dome was (it will fit exactly). Screw on an end blanking plate, which will be supplied and the machine will then work again just fine in crankless mode with no software changes required.

  ii) In demonstration mode there are now 22 songs.

  iii) Some changes to the code have been made allowing the crank buzz to operate a little more like the real thing.

  iv) Acetone polishing of the 3D printed keys: I want the stems to remain unchanged as they fit the slots in the wooden laser cut panels perfectly, but I do want the key ends to be smooth and shiny, i.e. I want to acetone vapour polish the ends of the keys only. The solution is to wrap the stems in aluminium foil before placing them into my vapour chanber.

  Despite using laser cut panels to reduce the amount of 3D printing, as you can see I have been on a 3D printing-fest for the past 3 weeks to produce all the parts required.

  Have experimented with various pushbuttons, the gaming ones work best.

  Just some of the acetone polished keys.

  Some of the laser cut panels.

  End structures and crank housings, printed and acetone polished.

  Six sets of microswitches mounted and wired up to Teensy boards along with the OLED screens.

  Key-Henge. My acetone polishing rig. The felt is soaked with acetone and held to inside of glass bell with magnets.

  Some nice potentiometers with gold anodized knobs.

  Alloy extrusions all cut to length.

  Fishing reel handles from China.

  Better photo of the acetone polishing rig.

  Self contained crank module wiring now has multi-pin plug to connect it to main body of the DG.

  Bags and bags of 3D printed upper and lower keys, all of which are in the acetone polishing queue!

• Project Log #10: New Build Videos 21/10/19

  XenonJohn • 10/21/2019 at 22:51 • 2 comments

  Here are some new build videos (in 2 parts as YouTube only allow a max video length of 15min. This is the new hybrid version made from laser cut 3mm ply, aluminium extrusions and 3D printed parts. The version shown here is the basic one without the crank module.

• Log #9: Redesign using laser cut ply to reduce 3D printing

  XenonJohn • 10/20/2019 at 21:50 • 0 comments

  October 2019: REDESIGN IS COMPLETE using laser cut ply for the front and rear panels to reduce the amount of 3D printing required somewhat, to reduce overall build time and also to reduce the time spent filing and fettling the keys, keyslots and so on to make everything fit and work smoothly.

  The set of files I have just uploaded all refer to this easier to build crankless version. All the information is there for you to build one. This has an arcade FIRE button on the front right hand surface. Just hold the right hand end in your right hand, press this button with your middle 2 fingers; the drones and open melody string will sound as if you had started to turn the crank, then you start playing.

  - A small amount of filing of the keys may be required but the laser cut ply parts require none at all.

  - The keys can easily be renewed if you break one.

  - Rear ends of the keys project from rear of keybox in a way more similar to a real HG.

  - Keys shaped to hit front deck just before the maximum microswitch travel is reached. This should better protect the microswitches if played too hard.

  I am working on a version of this with the previously described crank module. The build for that version will be 95% the same as this i.e. the extra wiring for the bolt-on crank module and slightly different code.

  The play button does not have to be lime green, they come in many other colours!

  Next project log will feature the crank version of this new design.

• Log #8: Different tunings enabled & feature in "Prog" magazine

  XenonJohn • 09/13/2019 at 14:13 • 0 comments

  Short update:

  I have improved the software so now you can select either of the two commonest tunings for the keyboard i.e. G/C or D/G. You can select the one you want on startup and also change the tuning while the device is in operation by pressing the upper rightmost three keys simultaneously. It is a bit like a Tesla car, load in a software upgrade and your (unchanged) hardware suddenly performs better.

  I have uploaded this version of the code (Version 37).

  Also the original red plastic DigiGurdy has to my surprise been featured in the current edition of Prog magazine - as in Prog Rock. Aug/September 2019.

  I intend to go through all the 3D print files one more time then will also post them up here.

• Log #7 How to connect to phone and use Fluidsynth to create music

  XenonJohn • 08/23/2019 at 23:30 • 3 comments

  This video update shows how you use a phone to play the MIDI data coming out of the DigiGurdy.

  The soundfont file (.sf2 format) has to have been uploaded onto the phone in advance. I will make this file available soon. All the sounds to be played are stored in this file.

  The MIDI player I am using is called FluidSynth and is available free from the Google Play store for Android phones. An Apple version also exists but I have not tried it with the DigiGurdy.

  The DigiGurdy outputs data on 5 MIDI channels. In FluidSynth we must assign an instrument or sound to each of these 5 channels for it to work correctly. This is best explained with a video and so the video below shows me setting up Fluidsynth on a phone in this way. FluidSynth has a very basic user interface but it also has very low latency (time between pressing a key and hearing the sound) and so works well with the DigiGurdy.

• Log #6: Fully Assembled With Crank Module

  XenonJohn • 08/19/2019 at 20:56 • 0 comments

  Here is the DigiGurdy coming together at last, with the crank simulator module attached. This video clip gives an overview of the functions of the device from the point of view of a user and also shows how you select and play songs in demonstration mode. I will add a more detailed video at some point showing you how to get the soundfont onto your phone and set it up to play the sounds correctly with the current version of the DigiGurdy. In this update video you can see:

  - Crank operated drones and open melody string.

  - Crank operated buzzing sound (sound audio file supplied by Nigel Eaton, many thanks).

  - More realistic key-click sounds

  when the keys are pressed.

  - Use of a control knob to adjust the sensitivity of this buzzing rhythm sound when cranking to suit your own style of playing.

  - Blue orb on front panel which glows when turning the crank.

  - Demonstration of the crank-override switch which allows you to practice the melody without need to turn the crank.

  - Demonstration mode is shown being used with user-selection of songs and playback speed.

  The whole assembly is held together with just 4 long screws at each end. Almost no adhesives are required apart from where the screen is held in position.

• Log #5. Workable crank solution found at last

  XenonJohn • 08/06/2019 at 12:00 • 0 comments

  Project Log #5. DigiGurdy project. 

  I finally have a reasonable crank simulator now i.e. a robot gearmotor in reverse (where the crank spins up a motor acting as a dynamo). To create resistance to turning I originally shorted out the motor connections which long term is probably a bad idea as it can cause arcing at the motor brushes and so on. 

  Here, to create a more controlled load on my dynamo, I experimented with secondary motor + wind resistance vane, inspired by old clock chime mechanisms, before settling on a simple filament torch bulb (remember those?) as the best low cost compact solution.

  To be clear, I could have a large pulley with an adjustable friction band around it, or a wheel with a friction material against its edge. That would cost more, be less compact and also push the assembly and adjustment/fettling time up to get it all working properly. The gearmotor-bulb is low cost, compact and just bolts/glues in place. Also as the bulb flashes nicely with each burst of crank rotation speed which in a hurdygurdy also creates the buzzing rhythm sound, I may be able to make a feature of it.

  I am retaining the chopper wheel which senses the speed of rotation of the crank. Originally I had thought I might measure the voltage output of the motor using one of the Arduino analog input pins. However the chopper wheel does have low latency, is working well and the sensor adds almost no extra cost.

  Most of the cost of a real hurdy gurdy is the labour of the skilled luthier who builds it. Part of this project is to keep the human assembly time down to an acceptable level to make this an affordable compact second instrument for silent practice. This is why, if I can use or adapt a more or less pre-assembled mechanical mechanism, I will do so where possible.

• Crank handle chopper-wheel experiments and progress

  XenonJohn • 07/28/2019 at 19:48 • 0 comments

  I have been experimenting for quite a while now with robot gearmotors as a means of creating something that can be hand cranked, with just the right amount of resistance to turning. I have been encouraged by Nigel Eaton (Hurdy Gurdy maestro) to continue my effort to simulate a crank handle if at all possible and not give up on this aspect of the project. Again, where possible I am trying to keep the component costs down.

  The Teensy microcontroller inside the DigiGurdy needs information on the rate of rotation of the crank. When the crank is turning, the Teensy can then activate the simulated drone strings and open melody string(s) to simulate what would happen when the rosined wheel rubs against or bows these strings in a real hurdygurdy. Furthermore, whenever the rotation suddenly speeds up, it can then also simulate the buzzing sound that this would normally produce, i.e. the rhythm part of a hurdygurdy. 

  I have created a 3D printed chopper wheel which intermittently breaks the infra-red beam of a low cost sensor designed for this purpose. This structure has an unusual shape as it has to be somewhat removed from the area where your hand is cranking the handle to avoid damage, it also has to be shaped to fit onto the shaft of the fishing reel crank I am using, while also allowing access to the grub screws that hold the handle onto the motor and also fit over the end of the motor.

  I used software with interrupts for reading position encoders etc. but had major problems as the program would freeze and crash when connected to the phone but not when using the Serial window of my laptop. I eventually found a frequency counter library designed for the Teensy microcontroller and this works really well.

  I now have all the functions above more or less working OK, i.e. the drones come on when you turn the handle, the trompette buzz sounds when you accelerate your rate of turning and you are able to play the melody on the keys once the handle is turning. I am very pleased with the outcome so far.

  The next step is to redesign the enclosure for this so it is more in keeping with the rest of the DigiGurdy so can be added to the end in a modular manner.

• Experiments to simulate a crank handle

  XenonJohn • 07/08/2019 at 11:09 • 0 comments

  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.

• Setting up Digi-gurdy with drones & rhythm buzz via a mobile phone

  XenonJohn • 07/08/2019 at 11:00 • 0 comments

  Update 08/07/2019

  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.

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