Project Summary:

The motivation behind establishing this project was the desire by both engineering students and faculty to introduce a technical, yet artistic feel to their new home, the Fred M. Keller Engineering Laboratories. This automated sketching machine is an interactive device that will allow students, professors, and visitors to create sketches by simply motioning their hands in front of four optical sensors attached to the apparatus. The design of this project utilizes a Programmable Logic Controller (PLC) to control the mechanical components of the system.
 

Machine Components:

Controls – Heart of the System

The machine consists of a PLC 5 programmable logic controller. The PLC is used to control the system, and this is done in two steps. First, the PLC receives the input signal provided by the machine user. When the user triggers either the sensors by hand movement or the buttons by depression, the PLC analyzes the input data and provides the desired output through the machine. For instance, if the user triggers the sensor that would cause the pen to move to the left the PLC will recognize this and send a signal to the motor which drives the pen to the left.

Mechanics – Body of the System

The mechanical portion of the project consists of a base structure to which a paper feeding device, pen assembly, driving motors, and drive screws are mounted. Figure 1, below, provides a detailed sketch of the apparatus.
 
 

Technical Specifications:

Controls and Software:

        -  PLC 5 - Programmable Logic Controller

The software used to create the program which drives the system was RS Logix 5. This program was downloaded to a PLC 5 programmable logic controller, which the PLC used to control the Motionsketch sketcher. This particular PLC was chosen mainly because of it's ability to accommodate several inputs and outputs.  Both the state diagram for the program and the program file (hold down <shift> and left click to download file) in RS Logix 5 are attached.
 

Driving Motors:

        - 2-Dayton 12 Volt DC Motors
        - 1-Buehler 12 Volt DC Gearhead Motor
        - 1-12 Volt DC Solenoid

Two Dayton 12 Volt DC Motors were used for travel in the x and y directions.  The motors were chosen after calculations were made to determine how much power and torque were required to cause the pen apparatus to translate.  These calculations are attached along with motor specifics.
 

Optical Sensors:

        - 4-optical sensors

Four optical sensors were used as inputs to the PLC to control the four directions of pen travel (up, down, left, and right).  These sensors are triggered by motion such as that of a hand waving in front of them.

Other Components:

        - 6-Limit Switches for x-direction and y-direction motions

Limit switches were necessary in order to prevent excess travel by the pen, which could have led to the machine binding.  One switch was placed at each end of travel in both the x and y travel directions.
 

Operating Instructions/Control Panel:

1.  Turn on power to the machine by turning the power switch to the "on" position.  The machine will initialize, and the pen will travel to the lower left-hand corner of the  plane.  The pen will then travel to the center of the machine, which is the point that the pen will begin drawing from when a sensor is triggered.

2.  Create movement before the sensor which corresponds to the direction you want the pen to move.  The pen will change directions when the sensor for the opposing direction is triggered.  Note that an x-direction and a y-direction sensor can be triggered, and the machine will move in both directions.

3.  When the sketch is complete it can be removed by pressing the feed button.  The paper will feed the drawing out one end of the machine, and it can be torn free.  A clean portion of paper is now in place for the next sketch.

4.  When the machine is no longer sketching, it can be turned off by switching the power switch to the "off" position.