Tag: Equipment

More DK421 Hardware

November 8, 2006 » Geek

I think I’ve sorted out how I’m going to make my switches for the drums. I’m still tempted to go the “air-pressure triggered in tubs” route, but I think my current design would be more robust, sturdy and just as long lasting (if not more).

The idea is to get two flat chunks of plywood, as thin as I can go (1/8th” probably?), some nuts, bolts and springs. Cut the plywood to be equal in size, then put together with 4 bolts and the springs in between. That should allow for the give I need to keep the switches apart, plus it should be adjustable if the play is too much for the drummer.

The switch itself will be a bolt that threads up to a contact point (a.k.a. some scrap piece of metal). This will also allow for quick adjustments in the force required to trigger it. The switch will then run off to a standard 1/4″ or 1/8″ mono plug for plugging into the controller. As an added bit there will be silencer padding on the drum, since that’s sorta what we’re going for here… I’m thinking about just searching for a bunch of old mousepads rather than spend $20 on pads.

Here are some explanatory images I painfully crafted in that wonderful prototyping program “Paint”.


DK421 Hardware

November 5, 2006 » Geek

This afternoon I was without anything to do when I remembered my DK421 project, which had been shoved off into a dusty corner of my hard drive. I didn’t feel like programming any, and wouldn’t know what to do or add anyway, so I got into the hardware side of it.


The Sheets

I dug into Stephanies old room and found the keyboard from the green dinosaur, an Acer computer from the early-90’s. Anyway, I found it, took it to my room and cracked it open. Very simple device really. The keypresses are captured by switches composed of two sheets of plastic, very similar to slide-projector transparency sheets, with tracing on them. When you press the key it compresses a rubber bubble in a sheet and smashes the air, and thus the switch, down and completes the circuit. These connections go to a board with some leds and a chip for translating them into whatever goes down that PS2 cable.

I imagine that a newer keyboard might be more complicated, at least if it’s usb. Maybe not though. I only have so many keyboards to rip open.

Following the tearing apart of the keyboard I hooked it up to my old gateway laptop (it’s the computer I care the least about) and fired it up. No lights, no response. I shut it back down and figured out that I hadn’t reconnected a little black ground that had been hooked onto the metal mounting board as well as one of the pins. If you look at the picture of the transparency-stuff circuit you can see that one pin is connected only to a big spot for the ground.


The Pins

I taped it up and got it working right off the bat. Shiny. I then taped it onto the laptop in the lovely testing position illustrated here. I got a piece of thick copper wire, off of an old power supply, and generously stripped the ends (okay, my father did for me), 1.5″ at least, then coiled each end around a long finishing nail (that’s what it said on the box) and taped it up. This made for a nice, easy to control point-to-point connector for me.

With my newly created tool I fired up VIM and started shorting the pins together to see what they wrote. Okay, thats not true. First I tried tracing individual keys on the transparent stuff, but that got old real fast. It is, however, necessary for finding keys like shift. Regardless, I tried out the good old hunt and peck method, and soon had a list with more than enough keys for the drum triggers. I then tried out the shift key with a piece of spare wire, it works great. Thats an important one, because it is needed for the high-hat pedal.


The Shift Key

Well, thats enough for now. Hopefully the pictures shed some light on the matter if it’s still fuzzy. I haven’t made up my mind on what to build the triggers out of. I almost want to go the air pressure route so the switches won’t wear out to fast. I’ll also have to consider how to build and mount all this, I’m thinking PVC at this point. Off to a good start though :)

Additional Photos

DrumKit v0.01

September 30, 2006 » Geek

I finally started work on my DrumKit project today. Essentially this is an attempt to create a electronic drum set from some pads, an old keyboard and a computer. I got down to buisness and wrote up a Java app that plays back the drum sounds on key press events. It filters them and even handles shift for the hi-hat open/close, which I’ll use to make the hi-hat pedal work.

The source is messy, and still has relative path’s for the sound files. Essentially it’s a frame, a keylistener and some clips. Not too rough, though patching this together from the Java API and sparse information on javax.sound.sampled was tougher than I guessed it would be. Anyway, it’s got some bugs and features not implemented, but I can play drums with my keyboard now, which is a good start.

DrumKit v0.01
The Cutting Edge DrumKit GUI

I suppose I should upload the code just in case, and to keep track of my versions. You can get the source and the sounds for Version 0.01 below. As a heads up, all the kit samples are absolute path’d for my machine, so you’ll need to adjust them if you intend to compile it.
» DrumKit001.tar.gz – Everything
» DrumKit.java – Main class
» KeyHandler.java – Event listener
» KitClip.java – Kit sample class

Chu Moy Amplifier

September 24, 2006 » Geek

Today I started working on my Chu Moy pocket amplifier, named after the creator. I’m working from a set of plans I found at tangentsoft.net which are very good and very detailed. A few days ago I bought almost all the parts from Digi-Key for under $20, and I bought the remaining little bits from Radio Shack this afternoon. An important note for anyone who attempts to make one of these, is that some of the parts listed on the tangentsoft pages are obsolete, and you have to do a little searching through Digi-Key for an equivalent piece.

I’ve never done any serious electronics work. In fact, the only thing I have done is put an EL panel in my Linux Zip-It, which I had a marginally tough time with. I was going to do the 5-Wire hack on it, but the points looked just a tiny bit too small, thus I have a serial d-bus and an RS232 IC lying in a box somewhere. Anyway, I’m off topic. I’ve almost no experience with electronics, thats what this paragraph is trying to get at.

My Power Section
The Power Section

Let me be the first to say, this was a mistake. I don’t know what I’m doing here. This picture is the result of about an hour of work. That’s 6 components and 4 jumpers in an hour. Plus, if I had a picture of the underside, it would be even less of an accomplishment. The camera batteries died, so I do not, PTL.

I am decent with a soldering iron, and I can make nice, smooth joints on the board. The problem is, I bought a generic PC board that doesn’t have any traces, so I need a bunch of jumpers. Getting the jumpers in the right place along with the component and soldered all nice just wasn’t happening. I’m still confident it will work, but it sure ain’t pretty.

I’ve finished the power section, got the op-amp on the board, and most of the other components. I still have to put on another 4 resistors and then wire up the potentiometer (thats a fancy word for volume knob) and the input/output jacks. Once I’ve done that and the batteries have recharged I’ll get some more pics up here and we’ll find out if my skillz were sufficient to result in a working amp.

9/24/06 – As promised, here are some more photos. They’re blurry because it’s dark in here and my camera doesn’t focus well. I apologize for all the white space, something’s weird in my layout. Thanks ray326 :)

Part Deux

Underside