[rasteri]

'Fraid I need electrical contact with the wheel - the metal surface acts as a big capacitive touch sensor.

[dstamand]

Quote

how can I make electrical contact with the steel rod (and therefore the scratch wheel) if it's going to be rotating? Carbon brushes? Or just stick it through a bush and hope for the best?

Brass bushing works.

You can try this :
Slip Ring, cost around 75$ USD for 6 conductors.
http://www.polysci.c...s/slipring.html
http://www.polysci.c...AC6373small.jpg

[p13fke]

hi,
in an earlier post you said that the sensor sometimes misses the grooves so you made your pattern smaller. Have you tried to split the pattern in two patterns with half the grooves. I dont know how to explain this exactly ,because my english is not the best.so i made a little picture. Keep in mind that i only draw it for one sensor. you have to do the same for the  B Sensor later on.



As you can see Signal A1 and Signal A2 combined are the same as the original Signal A. So the sensors only need to read half the amount of information.

[dj3nk]

I think it has more to do with the update rate of the pic. optical devices are fast enough.

[cimo]

Quote

I've been designing a more robust version of the device. The scratch wheel will be made out of aluminium or something, attached to a steel rod going down inside the device, then attached to an encoder wheel. It means the optical components can be inside the device.

I'm kinda stuck with one thing though - how can I make electrical contact with the steel rod (and therefore the scratch wheel) if it's going to be rotating? Carbon brushes? Or just stick it through a bush and hope for the best?

I'm obviously going to experiment with various things and post results, but if anyone has any thoughts on this matter I'd really appreciate them. I'm very much out of my area of expertise here.

i would go for capacitive sensor placed under the wheel, 3mm acrylic shouldn t be a problem for the signal

Simone

[dstamand]

Hey hey! Congrats  :o :o


http://www.skratchwo...ents.php?id=991

Quote

The coolest thing you'll see this year
Manufacturers around the world are pumping squillions into R&D labs trying to make the perfect MIDI controller. I'm sure there are shelves full of almost but not quite platters of all shapes and sizes littering the vaults of the big boys and many a frustrated Product Manager still searching for the perfect platter for their next generation of bandwagon hopping product. So imagine my glee when some guy in the UK armed with an open source project, a cardboard box and some gaffer tape serves the manufacturers their arses on a MIDI platter. All hail Rasteri - king of the controllers.

[stryd_one]

Fame :)

[nILS]

"Fame" in this context == credit where credit is due ;D

[rasteri]

Heh, Gizmo from skratchworx has been really cool about it. I'm gunna send him one for testing, see how it holds up to other DJ controllers.

Just a few updates. The non-cardboard version is up and running, using a real piece of 7" vinyl sprayed with conductive nickel paint.

Also, the photodiodes now use the comparators of the 18f4620, so it tracks perfectly no matter what. This opens the possibility of a higher resolution wheel, but means 18f452s can't be used. (who cares)

I'll post pics/vids/code as soon as I can. Probably about time I improved the wiki page too....

Future plans include making the unit completely standalone. I've already got 8bit 22khz sample playback working (kinda sorta), just need to figure out if the PICs are powerful enough to allow scratching (probably not). A couple of dsPICs are on their way, maybe they can be used?

[Sasha]

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...The non-cardboard version is up and running, using a real piece of 7" vinyl sprayed with conductive nickel paint.

I suppose you sprayed the vinyl so it can be used as a touch sensor. But, how did you connected it to the circuit? Wasn`t that problem?
Looking forward to see some new pix and videos.  ;)

[cimo]

25 kits without 0.0005% cut resistor leads for me.

[Sasha]

Wow, I see you found some good local supplier for cut resistor leads! Are you willing to sell some? I pay good!

[cimo]

.. you know i own a favor or two but this stuff is hot, too hot.Need to think about it ok?

EDIT: yep my noise to signal ratio is too high, this stuff is amazing, i was wondering if 1.8" HDD motors can be used.Maybe not cause the chassis is embedded in the HD.
What about my idea of using "touch" sensitive capacitance system for the wheel?

[rasteri]

Quote

I suppose you sprayed the vinyl so it can be used as a touch sensor. But, how did you connected it to the circuit? Wasn`t that problem?
Looking forward to see some new pix and videos.  ;)

This pic explains all :

(http://picasaweb.goo...080813603959586)

That's an older design, from when I was planning to use an aluminium disc as the scratch wheel, but the principle is the same.

The vinyl is held between 2 nuts (with washers) on an "engineering stud", which is a threaded rod with a smooth non-threaded middle section. The non-threaded part makes contact with the brass bush, which is in turn connected to the PIC. I wasn't sure if it would work, but it's perfect :) Whether it'll still work in a few months time is a matter for debate however...

[Sasha]

Rasteri, thanks for posting the diagram, but you probably disabled some layer in photoshop as I don`t see any Kryptonite part. We all know how importance of Kriptonite in scratch controller designs are, but some neeb can be confused.

EDIT: Not sure did you know, but Kryptonite is recently discovered in serbia (where I live)  ;D
http://news.bbc.co.u...ure/6584229.stm

[cimo]

Quote

Rasteri, thanks for posting the diagram, but you probably disabled some layer in photoshop as I don`t see any Kryptonite part. We all know how importance of Kriptonite in scratch controller designs are, but some neeb can be confused.

EDIT: Not sure did you know, but Kryptonite is recently discovered in serbia (where I live)  ;D
http://news.bbc.co.u...ure/6584229.stm

in this case i would trade 0.0005% tolerance cut resistor leads for Kryptonite, or, for what it matters, it could be Kryplateintheevening, i am not in a hurry you know...
I ll PM you with details

[Sasha]

OK man, we have a deal.  ;)

[rasteri]

Have some code.

(Note the encoder now needs to be on pins 4&5, and it requires a PIC with comparators).

Attached File(s)

•  main.c (8.2K)
  Number of downloads: 92

[rasteri]

Some pics :









(http://picasaweb.goo.../Scratchtroller)

Not pretty looking, but pretty damn functional :P

[Sasha]

I see.. you want wear your records no more.  :)
How do you place it... horizontally or vertically. I ask because of fader position.
I`m not an expert, but to me it feels most natural fader position would be something like 45°. What do you think?
Thanks for the pics.