Trouble with Roland FD7

[kupooglop]

FD-7 works with a kind of rubber hammer that press a FSR sensor. Try to put some foam on the hammer, it will become to press on the FSR earlier (and then become to decrease the resistance earlier).

sounds like roland use fsr to tell how hard pedal pressed, not how far pedal traveled. maybe you could use linear fsr & put a stylus on pedal? that way as pedal moves up & down the stylus moves along fsr? not sure. i'd have to play with one to figure it out.http://www.robotshop.com/interlink-24-long-fsr.html

I would prefer have 1,5cm or 2cm, best would be to have the possibility to set the course lenght.

hall effect sensor measures change in magnetic flux field density in ~1cm range when operated in head-on mode. it is rock solid reliable & never drifts or changes. since it is magnetic effect, light doesn't bother it .you set course length (i assume pedal travel?) using custom curve in megadrum.

Unfortunatly I can't since I not use my FD-7 with megadrum

sounds like you need to plug pedal into megadrum & see what it does first. megadrum is surprisingly flexible. pedal just might work the way you want as-is just by choosing different curves.

[Sylv1co]

sounds like roland use fsr to tell how hard pedal pressed, not how far pedal traveled

The rubber hammer is shaped to let the resistance decrease with some travel of the pedal, but you're partially right and it's one reason I don't really like it. You need to press a bit to much strong to get the fully closed level, unlike a real HH.

maybe you could use linear fsr & put a stylus on pedal? that way as pedal moves up & down the stylus moves along fsr? not sure. i'd have to play with one to figure it out.http://www.robotshop.com/interlink-24-long-fsr.html

The FSR you point in your link don't decrease its resistance depending on where you press it. It depends on how hard you press it, regardless of where you do. You may want to refer to a Softpot : http://www.spectrasymbol.com/softpot

hall effect sensor measures change in magnetic flux field density in ~1cm range when operated in head-on mode. it is rock solid reliable & never drifts or changes. since it is magnetic effect, light doesn't bother it .you set course length (i assume pedal travel?) using custom curve in megadrum.

If your hall effect sensor (associate to his magnet) begins to decrease its resistance in about 1cm range, then physically, you can't increase its range over 1cm, even with all the megadrum settings. The only thing you can do is decrease it (but 1cm is already short) or change its curve. If you can have more than 1cm range, it means that your Hall effect sensor have a bigger range.
However, using a stronger magnet should raise this range.

[kupooglop]

However, using a stronger magnet should raise this range.

Precisely. i use an old hard drive magnet. it is strong enough to give you a good pinch if you get between it and whatever it is attracted to.

If your hall effect sensor (associate to his magnet) begins to decrease its resistance

Hall effect sensor takes megadrum 5v and varies it based on how far away it is from the magnet. It acts like voltage source as opposed to acting like voltage divider. Circuitry inside chip makes output voltage stable as opposed to other devices. as long as megadrum voltage doesn't fluctuate, hall effect sensor output doesn't fluctuate. The voltage is low when magnet is far. the voltage increases linearly as magnetic field approaches. That is why you have to use ratio-metric linear hall effect sensor as opposed to other types of hall effect sensors.

then physically, you can't increase its range over 1cm

True, but look at a diagram of the magnetic field lines surrounding a magnet. Even though the field lines are weak at distances greater than 1cm, they still exist. Moving the magnet at these distances will perturb the hall effect sensor output up to a point. It just doesn't cause the hall effect sensor to behave in the linear fashion that the manufacturer's data sheets describe. That is why I used custom curve to build a curve that is linear in one region then becomes exponential in another region then goes back to linear. Looks like hysteresis curve. that way as soon as i move my pedal, megadrum responds like a real hi hat. Then I use open, semi-open, half-open & closed to determine which drum samples fire off. That way I get chick sound, open hi hat & closed depending on pedal position.

it means that your Hall effect sensor have a bigger range

With the magnet I am using, the observable behavior indicates that this is true. The 1cm range is the range that the manufacturer provides data for. It took a while to find the "sweet spot". You have to have the pole of the magnet positioned properly in relation to the hall element.