Andrew Burks

The Carnegie Mellon Robotics Club has announced $500 in funding for HarmonicaBot!  This is good news, because there was no where else for funding to come from.  The one caveat is that I need to have a proof of concept in order to unlock the final $300 of funding.

During the presentation, some other interesting means of funding were mentioned.  It was recommended that I speak to Clippard directly to try and obtain my 12 solenoid valves for free or at a reduced price.  Also, an engineering professor at CMU who is very involved with harmonicas might be interested in doing something with this project.

Plug

In the hour before the funding presentation, I modeled and rendered a crude first iteration of the plug.  This version routes a 1×10 array of square holes on the harmonica to a 2×5 array of 1/8” NPT fittings on the back.  The harmonica sticks inside a bit, where two pieces of foam or rubber apply pressure to keep the harmonica up against the plug.

The next image is a cross-section of the plug.  The curved parts of the channel may seem to end before reaching the harmonica on the left, but they don’t.  Instead, one of them crosses out of plane towards you, and the other crosses out of plane into the screen.  This complex geometry is why the part needs to be 3D-printed or cast.

Autonomous Harmonica-Playing Robot

I have wanted to add a diatonic harmonica to the RobOrchestra since I joined the group in my freshmen year.  The Carnegie Mellon Robotics Club recently acquired a MakerBot 3D printer, so my dream has become a lot more feasible than before.

Harmonica Interface and Control

The concept for the robot is simple: A 3D printed plug (with complex inner geometry) routes the 10 square holes of a diatonic harmonica to 10 NPT fittings.  The NPT fittings connect to 10 different solenoid valves, each corresponding to one hole on the harmonica.  This allows for individual control of the air going through each hole.

Achieving both “Blow” and “Draw” Notes

The solenoid valves all connect to a single manifold, which is connected to two other solenoid valves.  One of the two valves is connected to positive pressure, and the other is connected to negative pressure (vacuum).  Activating one of the two solenoid valves at a time can simulate a blowing or drawing, while the other 10 valves select any number of holes on the harmonica to play.  Unfortunately, like humans, this robot will not be able to blow in some holes while drawing from others.

Harmonicas of Different Keys

The best part about having one generic plug to route the 10 holes to 10 NPT fittings is the modularity it provides.  Diatonic harmonicas come in all sorts of keys, but they all have the same shape.  Because of this property, harmonicas of different keys can be easily switched in and out of the mechanism.

Funding

The estimated cost of this robot is at $500.  This project is applying for RoboClub project funding, but will not be applying for a SURG.  The largest cost is the 12 solenoid valves at $20 each.  More updates and design will follow if the project gets funding from somewhere.

Also from my update of the RobOrchestra website.  I apologize for the redundancy.

Description

Vibratron is one of the main RobOrchestra projects for the 2010-2011 year. After receiving $1000 in grant money from the Undergraduate Research Office in the form of a SURG and a donated vibraphone from a former member, the team began designing a robotic Vibraphone.

The overall vision for the project involves laying out the 30 vibraphone keys in a circular array and dropping steel ball bearings onto the keys in order to create music. While other more direct methods might have been more effective, the group opted to create a more unique piece of art.

The project is currently in the prototype stage, but the general layout has been designed. The robot will be composed of three main systems. One of the systems will dispense the balls onto the keys, one will collect the used balls and recycle them to be used again on a different note, and the third system will be the structure of the robot that hold the keys and all other systems together.

Mechanisms

The ball dispensing mechanism has been through two complete designs. The initial design used a rotating notched wheel attached to a stepper motor to dispense balls one at a time. The second design used a solenoid as a gate to block and release balls from a queue. Both designs were prototyped, and the solenoid design was chosen because of its greater speed and reliability over the wheel design. Each of the 30 gate mechanisms will cost less than $5.00, and will be capable of dispensing over 14 balls per second. There are renders and photographs of the gate below.

The recirculation mechanism is basically an Archimedes Screw that brings balls from a lower hopper to an upper hopper. Once in the upper hopper, a paintball-style system will be used to spread the ball bearings into the 30 individual tubes, each of which routes to a separate gate.

The structure of the system will not be designed in any detail until the kinks have been worked out of the other two systems. However, a conceptual render of the desired circular layout of the Vibratron is below.

Logic

An Arduino Mega will be used to control the robot. A MIDI shield will allow the Arduino to read standard MIDI signals from any controller, and software will decode the MIDI commands into notes.

Each of the 30 gates will have a small custom printed circuit board (PCB) with a MOSFET and LED. This circuit board receives a digital signal from the Arduino and uses that signal to turn on the solenoid for a certain amount of time.

Images

Side view of the gate mechanism

Render of the gate mechanism

Final gate prototype

Conceptual render of the basic Vibratron layout

Another post I made for the RobOrchestra Website:

Description

Flutophone is one of the oldest members of the RobOrchestra. It’s seven fingers cover and reveal the seven holes on top of the recorder in order to specify particular notes.

Currently Flutophone is in a semi-functioning state. The instrument itself has gone out of tune over time, but it cannot be replaced by any recorder except one with the exact same hole spacing because the fingers are not adjustable.

Mechanisms

Flutophone’s fingers were originally made of cheap hardboard. After considerable use, the keyway on the hardwood gave out and fingers began to slip. Recently, the fingers have been replaced with laser-cut acrylic and reattached to the original sprockets. The sprockets are turned by servos mounted within the casing.

The air flow is controlled by a solenoid valve. The input of the valve is connected to a compressor running at approximately 30psi. The output is connected to the mouthpiece of the recorder, with a latex balloon serving as a buffer to stifle the initial surge in pressure when the airflow is first activated.

Logic

The entire robot is controlled by a single Arduino Duemilanove. It takes in serial commands from a master controller and interprets them as notes with a duration. It then sends a PWM signal to each of the 7 servos to position each of the 7 fingers properly. After a short delay to allow for the fingers to reach their position, it activates the solenoid valve. When the robot is not playing a note, its resting state is with all holes covered.

Images

Note the Arduino in the top right and the Solenoid Valve in the bottom left

The balloon seals perfectly over the mouthpiece