Team B: Jaws

Project Goal

Our primary goal for a can recycler was to create a machine that would be able to obtain a large compression ratio while also being fast. To be fast, we would have to work with multiple cans in no specific orientation. By avoiding the tedious time it would take to orient and process each individual can, we would be able to achieve our quick processing goal. After a little research, we decided that shredding the cans would be the most effective method to accomplish this. This method also allows us to shred cans of different shapes ans sizes

System Overview

Being that our system would be rather dangerous when complete, we focused on the user safety of the machine. We incorporated as many safety mechanisms that we could to prevent any possible injuries. One of the overarching ideas was to automate as much of the process as possible. The automation would reduce the amount of user input and allow the machine to handle itself. Once complete the entire shredding process was automatic. The user only loaded the cans and unloaded the shreds after the process was complete. When the lid was closed and the "Go" button pressed, the lid would lock shut, the teeth would activate and start moving, the safety door that would block the teeth would open, and the cans would shred. The system would detect when there were no cans left to be shred and close the safety door, stop the teeth and unlock the lid, ready for more.


Lid Lock
The lid locking mechanism is activated first to ensure that the user does not interact with the cans that are in the process of being shredded. To know that the lid was closed we employed a photo gate such that when closed, the lid would interrupt a beam, sending a signal to the system and allowing the process to begin.

Safety Baffle
To ensure that the user does not interact with the operational end of the device, the automated safety baffle separates the loading area and the shredding blades. When the process is started, the door opens once the blades are moving and allows the cans to fall into the teeth to be shredded.

Drive Train
The system was driven by an AC motor that had 1/3rd of a horse power. This was more than enough power to shred our thin cans and on more than one occasion forces us to make a few changes to our structural design. This mechanism would not always start the first time so we placed and encoder to watch and make sure that the shafts were turning when they should be.

User Interface
Since most of the machine is automated, the controls are very simple. There is a single "GO" button which starts the machine and in the event of an accident, and emergency stop button. When running, there are warning lights to signal the states of the machine.

Capacity Sensor
We added a small IR sensor to detect the presence of cans in the machine. When the sensor doesn't detect any more cans, it beings the shut-down process to allow the user to interact with the shreds and add more cans to the system.

Our system obtains its power from a borrowed computer power supply unit. It's brains come in the form of an Antel Xmega processor board. These electronics power the entire system aside from the drive train.

Shredding Teeth
The teeth themselves are laser cut from a sheet of 1/2" acrylic that was designed to stop hockey pucks at an ice rink. Design and spacing of the teeth was determined through trial and error to allow for maximum shredding without breaking the teeth or stopping the motor. This same material was used as the wall material to keep cans from leaving or the user interacting with them.


The final operation was fairly good in terms of the speed and various size. The compression ratio was however a disappointment as we were unable to attain the specified 3:1 ratio. This issue is primarily due to the strength of our acrylic teeth. If we were able to use a stronger material, we would have been able to shred them more efficiently without the danger of having teeth crack and break.

Flowchart of States

Video of System

Team Members
Ben Matzke:
   Shredder design and Fabrication
David Alberts:
   Structural design and Assembly
Kevin Kassing:
   Electronics Programming and Integration
Nam-Phuong Cong-Huyen:
   Electronics Assembly and Integration

Team F: MissingNo

Read more about us at our website!

Getting a robot to perform even a simple task is a monumental achievement because so many little things have to all work flawlessly. We emphasize simplicity and robustness in our design, a Connect Four playing robot with few moving parts and closed loop control. The resulting machine was consistent and precise, giving it a winning edge over the competition. The robot can be broken down into three main subsystems: a hopper and magazine, a rack and pinion, and a chip dispenser.

CAD Render of the Entire System

Before the game begins, twenty one Connect Four game pieces are poured into the hopper. A metal rotor inside the hopper agitates the chips until they align with a hole in its base. The aligned chips fall through this hole and stack on top of each other in a vertical tube that serves as the robot’s magazine. The rotor periodically changes direction to prevent jamming. When the magazine is full, the chips block the light from an IR LED. After an infrared sensor in the magazine detects this the robot stops the rotor and signals that it is ready to play.

The Hopper Subsystem

The robot’s chip dispenser is mounted on a set of parallel case hardened steel rods that allow it to move left and right. This motion is controlled using a stepper motor that drives a gear rack and pinion. When it isn’t the robot’s turn, the robot moves its chip dispenser out of the neutral zone surrounding the game board. When it is the robot’s turn, the robot uses the rack and pinion to align the chip dispenser with the column on the game board it chooses to play in. Satisfactory position control may be achieved by counting the stepper motor’s steps, but we close the loop by using an OMRON IR gate sensor. The IR gate is usually blocked by a piece of black acrylic, but narrow slits have been cut out to mark key positions such as the center of game board columns and the base of the hopper. A limit switch at the far left of the gear rack is used as an additional safeguard; it trips to prevent damage if the stepper motor tries to drive past the gear rack’s mechanical limit.

The Rack and Pinion Subsystem

Once the robot is aligned with the column it wishes to play in, the chip dispenser drops a chip into the board. The key to the chip dispenser is a large circular cam at the base of the magazine. This cam is driven by a ¼ scale servo motor, can rotate 180 degrees, and has cutouts on opposite sides that allow it to grasp the bottom chip in the magazine and pull it out. Once the cam has pulled the bottom chip out of the magazine, it deposits the chip in a chute that reorients it and drops it into the game board. The chip dispenser has several sets of IR sensors that follow the chip’s progress. If the cam has failed to remove a game piece from the magazine the IR sensors will detect this and the robot will attempt to retrieve a chip from the magazine again. If the chip becomes stuck in the chute or hung up on the rim of the game board, the robot will shake the chip dispenser with the rack and pinion until the chip is jarred loose.

The Chip Dispenser Subsystem

Our robot is framed with MK T-slotted aluminum. In addition to being stiff and sturdy, T-slotted aluminum is modular. This modularity allows us to easily change the robot’s alignment, or quickly disassemble it for repairs. The non-structural pieces of the robot are made from acrylic because it can be laser cut, allowing us to quickly and easily create complex parts with tight tolerances. Acrylic is brittle and can shatter if too much force is applied, so we manufactured spares of all acrylic components so we could make repairs on short notice.

The Completed Robot

This robot has two processors. The sensors are read and the motors are driven by an Arduino, and a Gumsitx module handles game state and move selection. This configuration allows us to look eight moves ahead during the early game and up to ten moves ahead during the mid and late game. The farther our robot looks ahead, the better our chances of outfoxing our opponent and scoring a win!

Additionally, our robot is Bluetooth capable. Anyone with an Android cell phone and our mobile application can play as or play against our robot.
Our Mobile Phone App

Here's a video of our finished system in action:

Team Members and Roles:
Volkan Erin, ECE ’11:Electrical design, programming, Bluetooth communication, Andriod application
Kaiwen Gu, ECE ‘11: Electrical design, programming, motor control, error correction and detection
Ethan Minogue, ECE ‘11: Mechanical design, fabrication of frame and rack and pinion, website and video
Gary Verma, MechE ’11: Mechanical design, fabrication of chip dispenser and hopper

Team C

Overall Project

The main design goal of this project as specified by the course instructors was to create a machine to automatically crush 10 cans. The cans would be loaded in an unorganized manner into the mechanism, and would exit the mechanism at 1/3 of the original can volume. Additionally, we were given the design objective to crush all of the cans in less than two minutes, and a volume constraint of a 2ft x 2ft x 2ft bounding box. Some of our added “coolness factor” design objectives were to be able to sense, count, and display the number of cans that have been crushed. We also wanted our machine to be safe for human users. Throughout the design process, we focused on the machine’s efficiency by limiting the amount of actuators needed to accomplish the task, which led to innovative designs.

  General System Description

Figure 2.2: Overall System Diagram
For our mechatronics project, we built a robotic can crushing mechanism. The mechanism consists of a large hopper and a pneumatically actuated crusher. Cans are agitated in the hopper by the exhaust from the pneumatic crusher and an agitation wheel. The cans are crushed in a crushing chamber by a pneumatic cylinder, and exit the machine by gravity. The electronics in the system allow the user to run different crushing modes, while displaying useful system information such as the number of cans crushed and the time elapsed. The overall system can be broken down into three main subsystems (see Figure B); the hopper, the crusher, and the electronics; which will be explained in detail in the following section of the report.


     System Block Diagrams

Figure 3.1: System Block Diagram
The diagram above shows how the three main subsystems (the hopper, crusher, and electronics) interact with one another in terms of energy, signal, and material inputs and outputs.  The following sections will describe in detail the design, manufacturing, and functionality of the three subsystems.

2.2.          Hopper

The hopper was designed to move cans and orient them into the crusher chamber with limited agitation. The design consists of laser-cut hardboard, which we bolted together (see Figure 3.2).

Figure 3.2: CAD Model of Hopper
The hopper proved to be the most difficult subsystem to design. This was because figuring out optimal geometry to keep the hopper mostly gravity-driven was difficult to model and test. Various stages of prototyping for our hopper are explained in section 4.1.
The final design creatively used the exhaust from the pneumatic cylinder to blow the cans forward down the chute, while the agitation wheel knocked cans over, ensuring the correct orientation when cans exit the chute into the crushing chamber. (See Figure 3.3).

Figure 3.3: Top View of Final Hopper Design
For this subsystem, cans are loaded into the hopper on the sloped shelf, where they move via gravity and collect in the chute. The chute is also sloped downward toward the crushing chamber. Cans are agitated forward by the exhaust agitation from the pneumatic cylinder, and the orientation is corrected by the agitation wheel before loading.

2.3.          Crusher

The crusher is arguably the most important subsystem of our crushing device as it is the part of the mechanism that actually crushes the cans.  The crusher consists of a pneumatic ram mounted within an aluminum frame.  When actuated, the pneumatic ram moves forward crushing cans with over 160lbs of force.  The aluminum frame is shown below in Figure 3.5.

Figure 3.5: CAD Model of Crusher Frame
The aluminum frame is constructed in such a way that once crushed, a can will simply fall out of the bottom of the crushing chamber.  However, in no orientation could an uncrushed can fall out of the crushing chamber.  The final construction of the crusher frame is shown below in Figure 3.6.

Figure 3.6: Completed Crusher Frame with Pneumatic Cylinder
A pneumatic ram has a crushing head attached to it to allow for can crushing.  The calculation for selection of the proper pneumatic ram is included in section 4.2.  Also included in section 4.2 is a mechanical analysis of the crusher to ensure that it will not fail during operation.
In addition to the frame, the crusher includes a shroud which surrounds the crushing area.  This shroud, shown in Figure 3.7 prevents cans from exiting the crushing chamber during crushing causing injury to people around the device.  The shroud also helps align cans for crushing when they are loaded into the crushing chamber.  Also included in the shroud design are an aluminum backstop which prevents cans that become impinged upon the crushing head to be pulled out of the crushing chamber.  This shroud also has a hinged lid to allow for easy access should a jam occur within the crushing chamber.  This hinge is shown in Figure 3.8.

Figure 3.7: Crushing Chamber Shroud

Figure 3.8: Crushing Chamber with Hinged Lid
 After a can exits the hopper it loads into the crushing chamber.  Once in the chamber the pneumatic ram actuates forward crushing the can.  Once crushed, the can falls out of the crushing chamber.

2.4.          Electronics and Controls

The electronics were all controlled using an Arduino ATXmega a 600W desktop PC power supply.  We used such a strong power supply as our original design called for an electric motor rather than a pneumatic ram.  The power supply had its 5V rail connected solely to the Arduino in order to power it directly as well as to allow the Arduino to distribute power to the rest of the electronics.  The 12V rail was connected solely to the power input of the motor driver board.  The Arduino connected directly to the motor driver board, the safety and can counting sensors, the control pad, and a small breakout board to extend the Arduino's 5V power rails to the various devices that required a very steady power supply in order to do differential voltage sensing.  A high level diagram is shown in Figure 3.10.

Figure 3.10: Electronics Block Diagram
                The motor driver board in turn controlled the solenoid for the pneumatic ram and the agitation wheel, as those both required 12V rather than 5V.  It was powered directly from the 12V rail from the power supply, and connected to the Arduino for control.  Depending on the input from the Arduino, it would extend/retract the pneumatic ram using one output terminal to control the solenoid, or supply power to the hopper agitation wheel using the other output terminal. 
                The safety sensor was constructed as a voltage divider using a photoresistor as a switch in series with a 1k ohm resistor.  It had two terminals connected to 5V and ground on the breakout board and a middle terminal connected to an analog input pin on the Arduino.  It was mounted on the underside of the output from the crushing chamber, directly across from an LED, as shown in Figure 3.11.  If the photoresistor had enough light shining upon it, the middle terminal was raised close to 5V and the Arduino would determine that nothing was being pushed into the crushing chamber from the bottom, therefore it was safe to actuate the pneumatic ram.  Otherwise, something was clearly blocking the LED and therefore it wasn't safe to actuate the ram.  The LED was also supplied with power from the breakout board, and was added so that the signal from the safety sensor would be consistent across environments, allowing us to be very stringent about when it was safe to actuate the ram without needing to fine-tune the code for every location.

Figure 3.11: Safety Sensor
                The can counting sensor was another voltage divider powered by the breakout board, however rather than a photoresistor it used a manual switch in series with a 1k ohm resistor.  When depressed, the middle terminal  would rise to 5V from ground and signal the Arduino that something had fallen out of the crushing chamber.  It was mounted underneath the crushing chamber, slightly above the safety sensor so as not to interfere with it. 
                The control pad consisted of three three-position switches and a pair of dual-digit seven segment displays, as shown in Figure 3.12.  The two-position switches were constructed as matched voltage dividers, all powered by the breakout board.  When a switch was pushed "up," one signal would be almost 5V and the other pulled to ground, when pushed "down," the opposite would happen.  When a switch was in the "middle" position, both signals were pulled to ground.  The first switch controlled whether the system was operating in automatic ("up" position) or manual ("down" position) mode.  The second switch had different functions depending on whether the system was in automatic or manual mode.  In automatic mode, it controlled the number of cans to crush, in manual mode it would directly actuate the pneumatic ram.  The "up" position would extend the ram while the "down" position would retract it.  The third switch was the start/stop switch.  In automatic mode the start, or "up" position would tell the system to begin crushing cans, and the stop, or "down" position would tell it to cease crushing and retract the pneumatic ram.  In manual mode the start switch, when pressed, would allow the user to use the second switch to actuate the ram until the stop switch was pressed or the system was taken out of manual mode.  This was done both as a safety factor, in that no single inadvertent touch of a switch could actuate the system in manual mode, our testing mode, as well as to allow users to play a game.  In manual mode, when the start switch was pressed, a clock would begin ticking, only stopping when the stop switch was pressed.  The clock would be displayed on one of the seven segment displays and the best time so far on the other seven segment display.  In automatic mode, those displays would show the number of cans the machine would attempt to crush before stopping on one display while the other would show the total number of cans already crushed since it was turned on.  The seven segment displays were connected and powered by the digital output pins of the Arduino using ribbon cable.  Depending on the number to be displayed, the Arduino would set certain pins high to light up the correct segments.  It should also be noted that only the switch for auto/manual mode would stay in the up or down position, all the other switches would spring back to the center once released. 

Figure 3.12: Control Pad
                The breakout board was mainly constructed as a convenience factor to distribute power, as initially the Arduino was powered through a serial connection to a laptop before we added the power supply.  After we added the power supply, we kept it connected to the Arduino as our thresholds for analog sensing were determined using the Arduino's 5V rail rather than the power supply's 5V rail.  It had already been determined that the Arduino could supply enough current for accurate analog sensing, so we kept the breakout board powered by the Arduino rather than connecting it directly to the power supply.  In total, the breakout board supplied stable 5V and ground signals to the safety sensor's photoresistor circuit and LED, the can counting sensor, and the three three-position switches on the control pad.  

Team Members

Wil Hamilton-Mechanical Engineering
     Pneumatics Fabrication

Kyle Gee-Mechanical Engineering
     Hopper Fabrication

Henry Kung-Mechanical Engineering
     Pneumatics and Hopper Design

Steve Williams-Electrical and Computer Engineering


Team H - Gambit

This project was developed at Carnegie Mellon University as part of the Mechatronic Design (18578/24778) course.
                                                              Gambit - The name of our device

Main Design Concept
Connect Four is a two player game, in which each player chooses chips of different colours, and takes turns to then drop the chips from the top into a 6 row, 7 column grid. The chips fall straight down, occupying the next available space in the grid. The objective of the game is to arrange 4 chips of the same colour in a line - either horizontally, vertically or diagonally on the grid. Each player gets 21 chips.

Variations of the game
Pop Out starts the same as traditional gameplay, with an empty board and players alternating turns placing their own colored discs into the board. During each turn, a player can either add another chip from the top or — if one has any chips of his or her own color on the bottom row — remove (or "pop out") a chip of one's own color from the bottom. Popping a chip out from the bottom drops every disc above it down one space, changing their alignment with the rest of the board changing the possibilities for a connection. The first player to connect four of their chips horizontally, vertically, or diagonally wins the game.
We fabricated a mechatronic device to play the game against another device/human. The device is capable of thinking on its own using the game algorithm that is implemented in it, and intelligently drop chips into the desired column with the help of mechanical systems.
The device is also capable of playing the pop-out variant of the game. More of this game playing ability can be seen under System Overview and Subsystems >> Pop-out Mechanism.
Simple CAD model

System Overview

The design consists of five subsystems:
1. The chip sorter
2. The chip feeder
3. The chip dropper
4. The linear carriage
5. The Pop-out Mechanism
The complete system

The chips are initially dumped into a hopper, from where they get stacked into the vertical tube as shown. The disc then rotates and drops a single chip into the chip dropper. The explanation of its working can be found under subsystems >> chip feeder.
Once a single chip is present in the chip dropper, the linear carriage to which it is attached, moves with the help of a belt - pulley system.  Once the desired position along the game board is reached, the chip is dropped from top, and into the column.
The device is also capable of playing the Pop-out variant of the game. A slider-crank mechanism attached to the bottom of the carriage 'pops' chips out of the last row when the pop-out variant of the game is being played. The slider, of the slider-crank mechanism pops the chips out of the last row.

The device consists of the following subsystems:
1. The chip sorter
2. The chip feeder
3. The chip dropper
4. The linear carriage
5. The Pop-out Mechanism

Working of the Chip Sorter

At the beginning of the game, the chips are dumped into the hopper.
Chip Sorter    

The hopper is a cylindrical, acrylic tube as shown above in the figure. A hole in the acrylic plate below (see figure), deposits the chips into the vertical tube. A blade, driven by a motor, tosses the chips about, which eventually fall into the vertical tube.

Working of the Chip Feeder
Once the chips are stacked in the vertical tube, the chip feeder helps in depositing the chips into the chip dropper.
The Chip Feeder

The chip feeder consists of a circular, acrylic plate and a rectangular, acrylic plate (see figure). The circular plate is rotated by a servo motor. This plate has a hole (HOLE 1 in the figure above) whose diameter is slightly bigger than the diameter of the chip. The rectangular plate also has a hole (HOLE 2 in the figure above) cut in it - diametrically opposite the tube. As the circular plate rotates, one chip falls from the tube and into the hole cut in it. The gap between the tube and the circular plate is approximately one half of the chip thickness. This vertical positioning of the tube prevents the other stacked chips from rotating along with first chip. Hence only one chip falls into the hole at a time. Once the plate rotates by 180 degrees, the hole in the circular plate is above the hole in the rectangular plate and the chip falls into the chip dropper.
The sequence of this operation can be seen in the figures below.

    (a) Chip falling from tube into HOLE 1 
(b) Chip being carried

(c) Chip falling in HOLE 2, and finally into the Chip Dropper

 Working of the Chip Dropper

The chip dropper is a box-like structure made of acrylic. The two main functions of the chip dropper are to act as a buffer for the chip, and finally drop the chip into the required column as the carriage moves along the game board.
Chip Dropper

The black acrylic plate has a rectangular cutout, through which the chips fall from the chip feeder. The chip dropper has an aluminum sheet that helps in orienting the chips in the vertical position. A stopper, operated by a servo motor prevents the chips from falling down and rotates by 90 degrees when the chip has to be dropped into the required column. The figure above shows the stopper preventing the chip from falling through.

Movement of the Linear Carriage

A stepper motor is used to drive the carriage. The motion of the stepper motor is transmitted to the linear carriage with the help of a belt and pulley mechanism. The belt is attached to the acrylic mounts (see Figure 2), which are in turn attached to the carriage with the help of screws. The acrylic mounts have two circular holes. Steel guide bars pass through these holes, and help in keeping the carriage in an upright position. 

Figure 1. The Belt-Pulley Mechanism 

Figure 2. Acrylic mounts and linear bearings

We have inserted linear bearings (see Figure 2) in between the mounts and the guide bars. This reduces the friction by a large amount, and hence increases the speed of the carriage, ensuring that a move is completed well within 20 seconds. The steel guide bars are lubricated to further reduce the friction.
The stepper is calibrated to ensure that the the carriage stops at the desired column while the game is being played.

The Pop-Out Mechanism

The Pop-Out mechanism was incorporated into our device as our coolness factor. The coolness factor is what  helps in distinguishing one team from the other.
The Pop-Out variant of Connect Four enables a player to pop chips of his/her/(its) own colour only, from the last row of the grid. This causes the chips above to fall down one position, changing the alignment with the rest of the board and hence changing the possibilities of a connection.

The Pop-Out Mechanism

The Pop-Out mechanism is a simple slider-crank mechanism. It is attached to the underside of the carriage and is level with the last row of the game board. A servo motor screwed onto the carriage drives a crank. The crank drives a connecting rod, which finally causes the slider to move in a straight line. The slider pops the chips out of the last row. 

Team Members

  Jihang Shin - Senior in Electrical & Computer Engineering
  Responsibility: Electrical Systems

  Nikhil Korwar - Graduate Student in Mechanical Engineering
  Responsibility:  Mechanical design and Fabrication

   Pushkar Rege - Graduate Student in Mechanical Engineering
   Responsibility:  Mechanical fabrication and Game Algorithm

  Yan Yan - Graduate Student in Mechanical Engineering
  Responsibility:  Mechanical design and Fabrication