Rockdude discusses precision rectifiers and positional sens

[rockdude]

mackanov, can you record some audio or video using the positional sensing feature? I know that you've got inconsistent results in the higher velocities, but maybe you could do a demo when playing lower velocities?

[mackanov]

My rolls are lame (I'm a guitar player ) but here you go. Remember my snare is using a foam "cylinder" not very cylindrical and the foam is way too soft. It tends to get confused on rolls, but detects very well when playing slower.

[Ken Forgettable]

For those people who get two distinct positions this is what is happening:

OscEdgeReflection.GIF

You whack the head and the wave travels to the sensor.
The same wave bounces off the edge (rim) too.
Hitting closer towards the edge will eventually cause the two waves to converge into one fat ripple.

The effect of this is an apparent sudden decrease in frequency as seen by the sensor.

If you play with the stereo balance of this audio file you will see this problem is not unsurmountable

ps_scopeMIX.mp3

NB. Be clear - this is frequency to pitch not a velocity to pitch mapping - this is a 3D drum...

[rockdude]

For those people who get two distinct positions this is what is happening:

OscEdgeReflection.GIF

You whack the head and the wave travels to the sensor.
The same wave bounces off the edge (rim) too.
Hitting closer towards the edge will eventually cause the two waves to converge into one fat ripple.

The effect of this is an apparent sudden decrease in frequency as seen by the sensor.

If you play with the stereo balance of this audio file you will see this problem is not unsurmountable

ps_scopeMIX.mp3

NB. Be clear - this is frequency to pitch not a velocity to pitch mapping - this is a 3D drum...

Good explanation! I'm trying to surf those waves.

[dmitri]

It tends to get confused on rolls

I know why it is happening and have ideas how to correct it in upcoming firmware versions.

[Ken Forgettable]

It tends to get confused on rolls

I know why it is happening and have ideas how to correct it in upcoming firmware versions.

Rolls 'ave a tendency to tension the -head and !pre-stresses the brain ^don't !they.
(Hey I suddenly lapsed into phonic programming. Very disturbing).

Try this (snigger):

OnARoll.mp3

[mackanov]

It tends to get confused on rolls

I know why it is happening and have ideas how to correct it in upcoming firmware versions.

I don't know when I'll be able to get the new processor with the secure bootloader, so for now I'll have to live with this.

[rockdude]

Ok, reviving my old positional sensing and precision rectifying-thread now that I'm ready again to attempt building one.



I've spent some time trying to track down the components I need for the build.
Here's links to the components I plan to buy (please correct me if I'm wrong, I really don't know much about this stuff):

OPAMP:
LMC6034 Op AMP *2
http://uk.farnell.com/national-semicond ... tt=LMC6034

Can any other OPAMP in this link be used instead so that I can order everything from one place?
http://www.electrokit.com/operationsforstarkare.c1385/1
Or maybe you can send me some of your spare ones ignotus?

RESISTORS:
Resistor 100K *1
http://www.electrokit.com/motstand-100k.41389

Resistor 15K *2
http://www.electrokit.com/motstand-15k.41379

Resistor 10K *1
http://www.electrokit.com/motstand-10k.41377

Resistor 12K *1
http://www.electrokit.com/motstand-12k.41378

Resistor 330ohm *1
http://www.electrokit.com/motstand-330r.41359

CAPASITORS:
Capasitor 1uF *1
http://www.electrokit.com/keramisk-mlcc ... -5mm.51696

Capasitor 100nF *1
http://www.electrokit.com/keramisk-100n ... iell.45633

Capasitor 1nF *2
http://www.electrokit.com/keramisk-1nf- ... 54mm.41768

DIODE:
Diode 1N4148 *1
http://www.electrokit.com/1n4148.41532

I guess that's all I need (except for the jack inputs? I won't order the parts before anyone has confirmed that I have found the right components. I noticed the schematic says +5v at some places and I don't really know what that means or if I need something more there? I also don't know what the red numbers around the OPAMPS means?

I found an old board that I've practiced my soldering skills on earlier that would work just fine to build the precision rectifier on? I just need to desolder the components from it. Or do I need a bigger one?

[ignotus]

On Monday I'll have a look and make a drawing for you so you can see how to connect everything. That board will more than enough.

[rockdude]

On Monday I'll have a look and make a drawing for you so you can see how to connect everything. That board will more than enough.

Thanks! Looking forward to your drawing. Until then I'll try to read up on reading electronic schematics

I have a few questions about dimitris schematic:


Are all the nets/lines with this symbol supposed to be connected together and go to ground somewhere?


And all the nets with this symbol are supposed to connect together and go to power somewhere? To power on my synthex board or somewhere else?


Is this some kind of isolated part of the schematic? It's not connected to the rest as far as I can see...more than the 5v power and ground.


This is the opamps pins if I'm not wrong. Found the pdf for it. Are the numbers pointing out from the opamp on dmitris schematic the corresponding pin on the ompamp like I've highlighted to the left?

Im curios to see how this board is connected to my Synthex 3.1 board. Or maybe it's a separate unit that connects only to the jack input I'm planning to use positional sensing on. I'll wait curiously until monday