I'm building a robot that scratches

**mushrooshi** · 07-13-2015, 05:40 AM

Hi guys~

I've been DJing for about 3 years, which is cool I guess

, but I've been interested in robotics since I was 3, and I uh have decided to combine the two? I feel bad that I might be helping to make these kinds of scenarios a reality. oh well, I like robots XD

my crossfader-gating and vinyl-manipulating thing prototypes are working as of an hour ago. They're crappy cardboard XD,

however, I'm designing the parts in Solidworks. I've had the crossfader thing designed for a couple weeks now, but I'll be designing the vinyl thing (based off my silly cardboard prototype)

My materials science professor at my uni (Texas A&M) and his grad student are opening an "Open 3D Printing Studio", and I took a midterm early and we started talking about 3D printing, and they thought my idea was dope so they're helping me out with that. The first parts I've already designed were printed over the weekend; I accounted for plastic expansion after printing so I hope they fit and it works

It is powered by an Arduino Mega and it uses the MIDI Clock and a few Traktor midi outs based on things like beatphase and such for the timing to sync up accurately. I chose a Mega so I could fit maybe 64 instant-grat scratching patterns on it, it has a lot of memory!

I think tomorrow, I'll work on building more scratches. when I get more building blocks put together, a beat or two's worth of a scratch takes only one line which notes the timings and angles of a scratch. I might even make a GUI to build routines later.

I need to upgrade the servo motors, they are pretty cheap and I already broke one.

I bought the scratch record (45 is kind of awkward small and fast though, I have a 33 DJ Rectangle record on the way soon) and my first turntable when I started this. to be honest... its easier for me to build and program this robot to scratch than it is for me to learn it myself XD but I still plan to learn how to manually scratch anyway.

I'd like to be able to control this with a Launchpad or a MIDI-Fighter, but it seems the Arduino only wants to talk to one MIDI signal at a time (which would be Traktor right now). I'm not sure if I want to try to mix the MIDI-In into the Arduino, or if I would rather get some arcade buttons to directly interface (which would be a lot easier and more reliable, though less flexible)~

a bit more code XD

**Patch** · 07-13-2015, 05:58 AM

There is already a robot that scratches.

It's cuts are so precise, the human eye and ear cannot identify ANY deviation from the prescribed BPM.

It's called a "Q-Bert".

**Stewe** · 07-13-2015, 08:34 AM

Robots are cool - I used to hide them in my mappings

**fadex** · 07-13-2015, 01:30 PM

Haha, awesome!

**mushrooshi** · 07-13-2015, 02:59 PM

Originally Posted by Stewe

Robots are cool - I used to hide them in my mappings

I could've written a pure software solution sending MIDI signals buuuuut something about getting it to work physically feels magical XD

so I recieved my 3D printed parts. I hope they fit, I accounted for tolerances

**calgarc** · 07-13-2015, 07:32 PM

Dis gon be fun!

**Deejaesnafu** · 07-13-2015, 08:08 PM

haha i want to see more of this thing!

**mushrooshi** · 07-13-2015, 11:24 PM

Okay, so I put together the new 3D-Printed crossfader mechanism, and it is far more solid than the cardboard prototype (which... should be obvious :P). I did a gate test (It's not scratching for the test, its just playing pink noise on loop); it's upper limit on gating 4 times a beat seems to be about 135 BPM (you can hear it skip a few mutes in the last test)

As far as the fit of the 3D printed parts went, the bearings fit inside snugly, but the shafts that go inside the bearings were a bit too small, so they are wrapped with a bit of tape.. The servo horn also did not fit in at all, so I had to shave one of mine down to fit inside. Both changes have been made in the CAD models and I'll get it re-printed again.

Old mechanism:

New mechanism

**Kwal** · 07-14-2015, 12:02 AM

Those are very nice brony stickers.

**mushrooshi** · 07-14-2015, 05:35 AM

I got some more progress done, mostly in coding the routines and getting it a bit smoother, as well as optimizing the fader mechanism a bit more.

https://vine.co/v/evLZ3YtUjpH

Originally Posted by Kwal

Those are very nice brony stickers.

I'm not really into MLP so much, but I can't bring myself to remove the sticker, its too cute :P