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wearyhacker

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About wearyhacker

  • Birthday 02/13/1954

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    Slyne-with-Hest, Lancaster, United Kingdom

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  1. I too have a long history in software design. Please note that the following has no relevance to real concertinas only electronic ones. I apologise for the lack of diagrams, pure laziness of my part. My basic idea is for a force based model. So I see the concertina as a pneumatic system. Force is applied to the bellows by the player pushing or pulling. I am guessing that I can ignore pneumatic impedance in the system. When no buttons are pressed that force is balanced by raising the temperature of the air inside the bellows. So the law of conservation of energy is obeyed. As soon as a button is pressed the force is balanced by the production of a sound wave. The magnitude of the sound wave is related to the applied force. If another button is pressed then half the force goes to button one and half to button two. If there was no reed behind button two then the listener would experience a reduction volume of the note from button one, and so on. Back in the real world we are measuring the applied force with some kind of sensor and deriving a number by analogue to digital conversion. This number is a representation of the instantaneous force and unit less. We need to convert this into a value that we can give as a volume parameter to the hardware producing the sound. This parameter is still unit less. So if we call the gadgetry producing the sound of a particular reed a voice. Let V = the volume of the voice. Let B = the number of currently pressed buttons. Let F = the current applied force. V = F * (some sort of calculation) / B Does this make sense? Is my physics correct? Any other comments?
  2. That is a really interesting idea. I think the load cells are actually in parallel, the more the merrier. Maybe the bellows could be made airtight and the servo could incrementally open the valve depending on the number of buttons that are currently pressed. Hmm.
  3. I think we are talking at cross purposes here. I am talking about the abstract mathematical model of a low cost electronic concertina. This concertina in the real does not have reeds in it, does not have valves (pads) in it and does not have any midi interfaces. It is in electronic instrument terms a "rompler". In other words it uses soundfounts that contain looped samples of real concertina reeds to play notes. It has buttons and leaky bellows to go some way towards emulation of the feel of a real concertina. Modelling the pnuematic impedance of a pad and reed is way out if scope. If you can provide me with such a pad/reed model I would be very interested in looking at it.
  4. Richard, I am talking about dividing the force not the "pressure". When the pressure reading inside the bellows is sampled, at that instant you can consider the bellows enclosure as a rigid pressure vessel containing a mass of air (measured in grams) with a number of venturi attached to it. All these venturi will have the same instantaneous pressure differential across them. That is as you rightly say "the same pressure signal". However the units of that measurement are force per unit area. A venturi has a cross sectional area. Provided that all the venturi are the same size then the air mass that exhausts through each one will be same and will move at the same velocity. However the mass will distributed evenly across all venturi. So if there is 100g of air inside the vessel and 5 venturi then each venturi will exhaust 20g of air at the same velocity. So the "force" is shared out evenly between the venturi. My head hurts!
  5. Mea culpa. Sticking load cells on both end caps is stupid. It just will not work! I had not thought it through. Doh, basic physics. The bit about the distribution of the overall force to individual reeds still applies though. Fr = Fb/n where Fr is the force applied to an individual reed, Fb is the force applied to the bellows and n is the number of buttons currently pressed. Fb will relate to the rate of change of the bellows volume. Temperature changes? May be too small to detect. Pantograph? Phase change foam? I need to go away and think!
  6. Tom, Sorry, I thought I had. The current instrument has a hand made set of bellows and the buttons in the end plates operate as both a valve and a switch (edit: this is not true, the bellows are in fact just leaky and the buttons operate tac switches through a specially designed spring loaded push rod). I will be meeting my friend in the pub tonight. I hope to persuade him to make an appearance on this thread and allow me to post some pictures. He has actually been a member of this forum since 2006 but has only ever posted one message, and that was over 10 years ago! The ultimate lurker. Richard, I would be interested in that as well.
  7. Tom, This idea for using a force based model to simulate bellows activity is at a purely conceptual stage at the moment. Back in the real world my friend is building an electronic Anglo concertina that has speakers for audio output. There is no midi output but there is a headphone socket. So this is definitely not a "midi" concertina. The goal on the hardware side is to create an ultra low cost instrument (tens of pounds) that feels like a real concertina. The software part uses Soundfonts and Wavetable Synthesis to emulate expensive real world concertinas. This means taking sample recordings of a real individual concertina and converting them into a soundfont file. The current iteration of the software has a default wavetable built in, this uses samples from a Jones Anglo (worth hundreds of pounds). The microcontroller used has a slot for a sd card so potentially thousands of different concertinas could be loaded in on demand.
  8. When I find out how the quote function works I will use it. @ttonon Regarding the division of pressure. The target machine has a working bellows but no reeds. The idea is to make the "feel" of the instrument as real as possible. In a perfect system the total "work" being put in by two hands must be equal to the total of the "work" being done by all the active "reeds". The presence of a pneumatic reservoir (bellows) means that the work must be distributed evenly. My bedtime now. I will reply to other issues tomorrow.
  9. I too hope that you don't find this disrespectful. However I do think that your post of is somewhat off topic. I am looking for comments on the measurement technique outlined in the second paragraph. I apologise for not making this clear.
  10. For a number of years now a friend on mine has been building an experimental electronic Anglo concertina. He has now arrived at a reasonable working prototype. One of the features of this concertina is volume modulation using a twin port differential pressure sensor. One port of the sensor is connected to the bellows enclosure and the other the outside world. The actual differential pressure variation measured in the bellows during playing proves to be quite small, that is, less than 3 kilo pascals. Finding affordable sensors with that low pressure range has proved difficult. However, using a Chinese manufactured CFSensor XGZP190 3kPa is currently under investigation. The has led me to think about other ways to measure this activity that do not involve pressure sensors. Fundamentally, the energy expended by the player in moving the bellows end plates is transferred to the reeds and converted into sound. The force being exerted on each end plate can be measured using a load cell sensor of some sort placed where the heel of the hand meets the end plate. This force will be divided equally between all the currently pressed buttons. If the additional force applied by fingertips holding buttons down can be ignored, then a simple calculation to provide a numeric value that is applied to all the “voices” currently playing can be made. if the hand grips were hinged at the top with limited movement at the bottom then push and pull could be differentiated as well as measured. Otherwise a differential pressure sensor may still be needed purely to detect pushing or pulling. My friend says that this may have to wait for a future version! Apologies if this has been tried before. But any comments will be appreciated.
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