FSR sensor compatible with Megadrum?

[hyeatman]

I am new to the forum. I would like to know if the megadrum controller can work with FSR sensors instead of piezo sensors. I would like to build a drum controller that works with pressure instead of vibration. My goal is to make a zendrum like device using FSR sensors instead of Piezo sensors. Any advice would be appreciated.

Best,
Hoyt

[dmitri]

I am new to the forum. I would like to know if the megadrum controller can work with FSR sensors instead of piezo sensors. I would like to build a drum controller that works with pressure instead of vibration. My goal is to make a zendrum like device using FSR sensors instead of Piezo sensors. Any advice would be appreciated.

Best,
Hoyt

I don't have FSR sensors so I cannot tell.

[hyeatman]

Thank you for the reply. I have listed below some examples that show FSR (Force Sensor Resistor) in use with drum machines. I guess the difference from Piezo sensors is that with FSR sensors the reference voltage to the FSR changes with pressure as opposed to a Piezo sensor that generates a small voltage when vibrated like a microphone. I am trying to make a very sensitive finger drum much like a Zendrum which I believe is Piezo technology. With FSR sensor there is no cross talk between pads. I would like to use the MegaDrum controller to produce the Midi output. Since the Megadrum is sampling voltage ( A to D conversion) do you think the FSR sensor idea might work. Again thank you for your time.

Hoyt




http://www.alternatemode.com/trapkat.shtml
http://www.inmotion.pt/store/product_in ... ucts_id=74

[dmitri]

Since the Megadrum is sampling voltage ( A to D conversion) do you think the FSR sensor idea might work. Again thank you for your time.

From DIY point of view FSR sensors are expensive. There is no technical limitation for MegaDrum not to work with FSRs but I don't think it is wise to spend time developing support for a feature with very weak prospect among DIYers.

[hyeatman]

Thank you for your input. I understand your position on the cost of FSR sensors but if I did build a system that used FSR sensors in place of Piezo could I expect the MegaDrum Controller to work properly with these input sensors without additional changes to either your hardware or software design. For what I intend to build I would like to use these sensor and I am just checking to see if there is any obvious problem you might be aware of that would prevent me from consideration the use of the MegaDrum controller. I thank you again for your input.

Best,
Hoyt

[dmitri]

Thank you for your input. I understand your position on the cost of FSR sensors but if I did build a system that used FSR sensors in place of Piezo could I expect the MegaDrum Controller to work properly with these input sensors without additional changes to either your hardware or software design. For what I intend to build I would like to use these sensor and I am just checking to see if there is any obvious problem you might be aware of that would prevent me from consideration the use of the MegaDrum controller. I thank you again for your input.

It won't work since FSRs work differently from piezos and it is not supported in MegaDrum firmware.

[jmcdougall]

dimitri could you explain your response in a little more detail ? There are a lot of DrumKat units out there that have old versions of the operating system and for most people, would be too expensive to have Alternate Mode upgrade as these require an expensive main board replacement. There might me a little more market out there than you suspect.

[Rubis]

I saw an instructable on how to build your own FSR. It really is not that difficult. You just use some conductive foam between a couple of sheets of copper. Conductive foam comes with most static sensitive components, like the atmegas, to keep them from getting damaged in transit. I know they wouldn't work for triggers, but would they work as a hihat controller?

[jmcdougall]

For a variable resistance high hat controller, it should work. I've thought more about the problem and here are the challenges. A piezo trigger is a very simple device as you indicate. When deformed (pad hit), it produces a voltage spike. The pad itself acts as a distribution media so that where you hit the pad has minimal impact on the level produced. The intensity of the impact controls the level within a limited range and the velocity curves serve to expand that dynamic range. However, to implement good FSR support, a lot more code and a much faster processor would be required. In essence, the drum brain (Megadrum) now has to act like a very faster midi keyboard controller. If you think about the model for a conventional synthesizer, a waveform has four dynamic components, Attack, Decay, Sustain, Release. A piezo can only provide Attack and Decay because the start is 0V and escalates to max and then Decays at the piezo's decay rate. We rely on the sound definition in our Drum synthesizers for the acoustic decay.
However the dynamics of an FSR are completely different. First unlike the piezo, they are very positional so the strike area is very narrow or like you see in the FSR for the DrumKat, the material zigzags back and forth across the whole pad area. Coupled with that is the waveform. An FSR can produce true ADSR because I can hit and hold the stick to the pad and in fact create true aftertouch by changing this pressure and then, there is also a true release when I lift pressure off the pad. Modern keyboards handle this and have a lot more code in their program to do this. That being said, I have yet to see a keyboard player execute a high speed roll on a keyboard. The processor on the keyboard doesn't have to sample that fast so it can handle the extra code.
In Megadrum, this would be much more of a challenge and would definitely require a very fast processor.
That being said, I would still like to see at least some of that capability for FSR's in Megadrum. CPU's keep getting faster and cheaper so the real issue is the additional code to configure and support them.

[Ken Forgettable]

A piezo can only provide Attack and Decay because the start is 0V and escalates to max and then Decays at the piezo's decay rate.

Close but not touching - ADSR ramps are not sampled from the input signals.
The piezos only supply velocity information as do most keyboards.
Keyborards often just use two switch bars one below the other, the first is for the note on event and the second (lower bar) is used to calculate the velocity of the hit.
A low speed 8 bit controller should manage a two manual full sized keyboard...

For a variable resistance high hat controller, it should work.

I think it will too. Try it.