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rasteri

Scratch wheel

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Hi, I've been working on and off on a MIDIBox-based portable scratching solution. I have a scratch-capable crossfader hooked up to midibox and working fine (http://www.youtube.com/watch?v=h8e2hHiw1fk) and the next step is some sort of scratch wheel. Right now I'm using timecode vinyl and real turntables, which are a bit unwieldy for gigging.

This needs to be more than just a simple jog wheel - it needs to be very responsive to slight movements. I figure I'm going to need 256 (or more) steps per rotation. SmashTV sells encoders with 24 steps per rotation and detents, so I guess they're no good. My questions are :

1) Where can I get a higher-resolution rotary encoder in the UK? I can only find industrial suppliers.

2) Would using some kind of gearing mechanism and a lower-resolution encoder be a better solution?

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That MIDI cutting seams fast enough. I really thought MIDI is not really usable for scratching. But seams I was wrong. What exactly crossfader you are using and where did you get it from?

1) Where can I get a higher-resolution rotary encoder in the UK? I can only find industrial suppliers.

I doubt you can find high resolution encoder anywhere for some reasonable price, but you could make one for decent price. Check the small 80 steps I made last week on the page below. If it is size of a record you could comfortable fit much more than 256 steps you are expecting.  ;) If I remember resolution of those code vinyls are much higher than 256 anyway.

http://www.midibox.org/forum/index.php/topic,10662.msg86906.html#msg86906

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That MIDI cutting seams fast enough. I really thought MIDI is not really usable for scratching. But seams I was wrong.

Warning - while you were reading a new reply has been posted. You may wish to review your post.

Hah, I was just about to politely post the opposite.

The short version of this is that a dedicated midi channel is fast enough for simple scratching but really fast scratches will be lossy.

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but really fast scratches will be lossy

NO !  :) look at my video ;)

Hint : Ignore the latency of the Video, most ppl asking me if its the controller, I must say NO again :) its the conversion youtube do on their own videoformat :( .... so the scratching is perfect without latency and fast enough (my thinking, im not a scratching-pro !!!)

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Keep in mind that my background in mixing is underground hiphop turntablism, so what I call "really fast" is simply faster than midi's baud rate...

Edit: no, I don't mix, but the people around me sure did....those guys are crazy!

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That MIDI cutting seams fast enough. I really thought MIDI is not really usable for scratching. But seams I was wrong. What exactly crossfader you are using and where did you get it from?

It's a Vestax PCV fader. I borrowed it from my Vestax PMC-06 scratch mixer. They're pretty good, but there are better scratch faders out there, like the Pro-X-Fade, Infinium, or (when it comes out) Innofader.

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With all respect Robert, I think that is not really useful for scratching, and belt driving mechanical encoder isn`t really good solution. belt slipping is very possible on your design when moving fast. It is great for winding and nudging but really not for scratching.  :-\

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Well let's do the math. Assuming you're scratching digital media (problematic already, but we'll ignore flaws in the audio engines and the formats ppl use )  then your sound is at 44k1. Thanks to nyquist, in order to be able to scratch that sample-accurate, you need 88k2 hz modifiers. You need two bytes to send a midi CC,so that's 196k4 bBs. That's 1,569.6 baud. MIDI is not that fast ;)

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With all respect Robert, I think that is not really useful for scratching, and belt driving mechanical encoder isn`t really good solution. belt slipping is very possible on your design when moving fast. It is great for winding and nudging but really not for scratching.  :-\

Have you ever tested this for months ???

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It's a Vestax PCV fader. I borrowed it from my Vestax PMC-06 scratch mixer. They're pretty good, but there are better scratch faders out there, like the Pro-X-Fade, Infinium, or (when it comes out) Innofader.

well, I asked you because you don`t usually see the impedance and tapper details on replacement parts shops. They mostly say just the model of mixer it is replacement for.

What impedance is yours? I can see it is linear :)

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Have you ever tested this for months ???

No, but knowing you are mostly in Psy, I expected you are not doing much scratching. Looking at your video (and many times before) I wasn`t convinced it is really good enough for real hip-hop scratching.

EDIT:

I dare you to let some scratch master to test your Traktorizer. I would really like to be proven I`m vrong. Honestly. :)

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Thats right, Im mostly in Psy, but I was on intense testing with all kinds of music while I programmed this scratch-solution...as I said Im not a Scratch-Pro, but spinning the wheel fast and hearing the music is in same format like the spinning telles me all ;)

Edit : :)

I dare you to let some scratch master to test your Traktorizer. I would really like to be proven I`m vrong. Honestly. Smiley

Thats what I need for final confirmation :)

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OK now I'm determined to prove this can be done :P

Where can I get one of those encoder wheel things? I figure I'll harvest the optical sensor from a mouse or something.

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I get some mostly from printers. Most of computer peripherals with moving parts have it. Good luck and keep us informed. ;) As for encoder wheels... you better CNC it!

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Where can I get one of those encoder wheel things?

... old mice are a good source, while a.f.a.I.k from inkjet printers you mostly have only single "light barriers" which would make it pretty hard by using two of those and getting a proper quadrature.

Greets, Roger

Edit:

http://www.alliedelec.com/Images/Products/Datasheets/BM/HONEYWELL_OPTO_PRODUCTS/Honeywell-Opto-Products_Actives-and-Passives_2760060.pdf

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Idea. Get one of those CD capable inkjet printers. Put a suitable acrylic disc in the hole. Print your quadrature patterns on to the disc, then cut it down to the right size.

Rather than a slot type opto, it may be better to print onto something reflective, (like maybe an old CD), and use that as the sensor disc, with reflective opto coupling.

One last thought. Could the HP 'disc tattoo' type CD burner be of use here?

The idea being bigger disc = less critical spacing.

Just a couple of thoughts

Mike

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Idea. Get one of those CD capable inkjet printers. Put a suitable acrylic disc in the hole. Print your quadrature patterns on to the disc, then cut it down to the right size.

How about just printing it on a transparent sheet (overhead projector stylie)? Attached is my first attempt, I'll get this printed at a print shop tomorrow (I have no printer!). This should give 360 steps per rotation, which I'm not convinced will be enough, but we'll see what happens.

encoderwheel.pdf

encoderwheel.pdf

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Maan, some of us have problems even understanding English sometimes. ::)

I was waiting for this project to show in English section when complete but as it didn`t it is like it don`t exist at all. At least for me. I used auto translators one for german/engllish and I find it more confusing than helpful for technical stuff. It`s more like just for knowing what is it about.

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Oh yes , Im also very sad because of this very very interesting project isnt written in english  :'(

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yep, Alogic is also sad about that, he s put so much effort in this project, too bad that a language barrier is avoiding the sharing! I m gonna have a talk with him and see if i can help with the translation of the main part, also his gf (Aleeeeee!!!) is eager to help out, let s see if we can sort something out.

simone

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That's creepy, it looks almost exactly the same as what I was planning...

...guess that means the basic theory must work though :)

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How about just printing it on a transparent sheet (overhead projector stylie)? Attached is my first attempt, I'll get this printed at a print shop tomorrow (I have no printer!). This should give 360 steps per rotation, which I'm not convinced will be enough, but we'll see what happens.

... yes you can do this. JLCooper JogWheels are done like this.

Did you study the datasheet of the optical encoder you're using? The way you write this, makes me suspect, that you just want to print 360 lines on the foil-disc. I hope you are aware of the fact, that you have to "build" the quadrature with your lines and spaces.

Greets, Roger

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Works Great ;D

Bq3QkT22ieU

(crossfader not shown)

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