thinking about a project - cdj plate as 2500 jog wheel

so ive picked up my arduino board.. a usb host shield and im currently going through the steps of making a usb device to midi contraption.. learning about arduino as i go.. the hardware side of things is easy but finding templates to adopt for the coding is a bit tough..but anyway

but now im thinking about a different project that i thought id put out there to see if anyone has any input on if it would feasibly work..

i dont know much about the internal workings of CDJ's but CDJ plate/wheels feel awesome and seem to be built to take a pounding. are they just a large rotary encoder?. and if so it should be feasible to attempt to rout them to an arduino to send a pulse in one direction as a midi note and a pulse in the other direction as a midi note - and therefor using JJOS midi note to button to make an awesome wheel controller to sit alongside the MPC for pleasurable scrolling when in sample editing.

spare parts for CDJ's don't seem to be ridiculously expensive
http://www.instrumentalparts.com/picdmkicdj80.html

im on the hunt locally for a dead CDJ that maybe i can pull to bits and try it out. but if anyone can offer feedback on the idea before i find one that would be awesome.

dam Nym

just found this.

was just thinkin the same thing but i see youve already been there
viewtopic.php?f=25&t=146130

I think it would be super easy to interface with an arduino. Even easier than interfacing with a regular rotary encoder, which this isn't.

But it might not be cheap, because there's a lot of parts required to assemble the encoder. I'd first look around online for a cheap used cdj, even a broken one you could get for cheap. As long as the encoder works.


The part that would be relevant to the arduino is this:



If I'm correct, what that is is two long circular resistive wires on that plastic sheet. Each little circle I would guess connects both resistive wires. So the further the circle is along the circle, the higher the resistance between the two connections on the connector ribbon in the center.
Hook it up correctly with a resistor to an Arduino analog port, and it's as easy as reading the analog input.


The software might be a bit more tricky getting it to keep track of the position.

cracking the problem of the rotary encoders in the 1k/25k has not been solved yet.
for someone to design an arduino replacement would be badass and i hope it happens.

awesome info there sciguy.. yeah it will be interesting to see one of these cdj parts in real life once i can find an old dead one..ive got a few adds up on my local classifieds.

i should be able to make a decent housing for it as ive got access to an awesome metal lathe and someone who can use it well.. ill make 2 if you wanna help me get the coding to sing!

problem could arise from not having physical detent action.. but the way i see it is as a sidekick unit only for heavy scrolling during sample editing which may be ok not having detents - provided it stops spinning once you take your hand off it.

i notice a bunch of cdj's send midi - most seem to be by usb tho.. but even so perhaps an alternative, obviously far more expensive, option is to make a usb midi to actual midi conversion with an arduino.. on the plus side one would have an actual cdj and all the fx it brings to the party. I doubt any of them would sendmidi note info from the encoder wheel by default..

BTW Nym - how far did you end up getting with using a HD platter?

as im thinking if it had some kind of brake pad built up against it so it doesnt free spin but spins easy enough it could function pretty well

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 1251656637

BTW Nym - how far did you end up getting with using a HD platter?

not very far, but the research i did was promising.
you could conceivably use your DAW's integrated MOBO sound card as an input for a 8th inch jack soldered to the terminals of HD platter. spinning the disk results in a tone which is read by soft5ware by this guy nix808 ... read this kvr thread...

something like this would be simpler/more lofi than an arduino based system, but cool if you're using a computer.

http://www.kvraudio.com/forum/viewtopic ... 1bb3597102

I would try it, but I'd have no way to test it. I'm too cheap for any of the paid jjos's, so no MIDI button mapping stuff for me.


Though if you've got jjos2xl, it would be really easy to code. Just have the arduino remember the last position of the "encoder". When it receives a new input, have it check whether it is clockwise or counterclockwise from the last position. Then send the appropriate MIDI message to trigger a DATA+ or DATA- action.

right on.. well until i find a dead cdj i think im gonna start exploring this HD platter thing.. much easier to find thats for sure

Wouldn't have to neccessarily be a cdj... I would guess that a lot of dj controllers use a similar "encoder" setup.

If not, then the hardware they do use should certainly be interface-able with the arduino somehow.


So just keep an eye out for anything with that kind of jog wheel.

or.. cd roms are easy to find.

http://www.youtube.com/watch?NR=1&featu ... QPQVmoT3zA

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 1219763383

Nym wrote:you could conceivably use your DAW's integrated MOBO sound card as an input for a 8th inch jack soldered to the terminals of HD platter. spinning the disk results in a tone which is read by soft5ware by this guy nix808

Sounds like rotary encoder serato