MohawkCollege of Applied Arts and Technology
Electro-Technology Department
TR Formal Report
PLOTTER
Prepared by: Robert Krndija
Student ID: 256214
For: Pat Lundy
Date: April 25, 2006
25 Titan Dr.
Stoney Creek, Ontraio
L8E 5Z9
April 25, 2006
Mr. Pat Lundy
MohawkCollege of Applied Arts & Technology
Hamilton, Ontario
L8N 3T2
Dear Mr. Lundy:
I have prepared this report titled “Plotter”, as my 5th semester formal report. Objective of this report is to introduce the reader with how my project will be produced and how the product will function once completed.
Plotter was selected as my project because I was always interested how 2-D CNC machine operates.
This report was written entirely by me and has not received any previous academic credit at this or any other institution.
Sincerely
Robert Krndija
ID 256214
Table of Contents
Page
1.0 Project Summary………………….………………………………….……….……5
2.0 Plotter Description….……………………………………………………………...6
3.0 Project Information.………………………….….……………….………....………8
4.0 Project Design and Components…………………………….…………………..…10
4.1 68HC11EVBU9 as the Motor Driver.....…………………………………..……..10
4.2 Microcontroller Source Code Description...………………………...... ….11
4.3 PC application Source Code Description……………………………...…………11
4.4 Microcontroller I/O Diagram………...………………….……….………...…….11
4.5 Stepper Motor and Drive IC………………….….………………………...... 12
4.6Additional Components…….………….…………………………………..….....12
4.7 Mechanical Parts Design..……………….………………………………..……..13
5.0 Conclusion……………….………………………………………………………….13
List of Figures
Figure Page
1. Example of laser plotter (cutter)…………………………………….………6
2. Etch-a-sketch mechanism…………………..……………………………….7
3. 200 X 200 square matrix……………………..……………………………...8
4. Microcontroller program flowchart…………………………………..…….9
5. 68HC11EVBU9 Layout.………………………………………….………...10
6. Micro controller I/O diagram………………………………………………..11
7. Oriental 2-Phase Stepping Motor PK series….…………………………...... 12
8. Bipolar driver IC…..……………...…………………………………………12
9. Mechanical design…………………………………………………………...13
1.0Project Summary
Plotter is a vector graphics printing device. Plotters are used in technical drawing and CAD applications. Another Use for plotter is as a cutter, by replacing the pen with a cutter plotter can cut out shapes. As a cutter device plotters can be found in many sign shops and garment shops. The actual design of plotter devices didn’t change considerably over time.
Plotter was selected for this project because I was always interested how it works. Building the plotter from scratch will be challenging but the knowledge obtained over last five semesters will be helpful.
The main objective of this project will be application of embedded systems (micro controller), stepper motors, circuit design, sensors, mechanical engineering and some computer programming.
2.0Plotter Description
Plotter design has not changed considerably since the initial concept just prior 1960’s. Roller of paper would move back and forth on X-axis, while the pen holder would move left and right on Y-axis. Some of the disadvantages of plotter are that it is slow and they require the space size equal to paper.
Figure 1 – Example of laser plotter (cutter)
Figure one shows a laser plotter that works on X, Y-axis principle. The size of the plotter is equal to the size of the object being produced on the plotter.
The easiest way to describe plotter is to analyze the etch-a-sketch mechanism.
Figure 2 – Etch-a-sketch mechanism
As shown in Figure 2 (obtained from stylus is mounted on a pair of orthogonal rails. By turning the knobs the rails move and draw out the picture.
By replacing the knobs with stepper motors I will be able to control the motion of the stylus by micro controller.
3.0Project Information
In order to build a plotter a concept similar to Figure 2 needs to be implemented. Two motors are needed to move the pen in the desired direction.
The process is started with the user entering (drawing) the desired picture on a PC. The application design and implementation is also part of the project. The application will be a picture matrix of 200 X 200 dots, as shown in Figure 3. That resolution was selected as the stepper motors have a step of 1.8◦ (360 / 1.8 = 200).
Figure 3 – 200 X 200 square matrix
The resolution can be increased as desired but the railing system has to be changed. Application will be designed with Visual Basic due to ease of use. Once the picture is drawn program will have to interpret the position of the dots to X,Y co-ordinate and send it to micro controller over RS-232 (serial port). The program flowchart for micro controller is shown in Figure 4.
Figure 4 – Micro controller program flowchart
4.0Project Design and Components
4.168HC11EVBU9 as the Motor Driver
As mentioned above micro controller is need to drive stepper motors. Decision to use 68HC11EVBU9 was made as that is the device we have used for past five semesters. It is easy to program and it has all of the required interface inputs and outputs available. Figure 5 below shows the outline of the micro controller used (obtained from Axiom manufacturing website
Figure 5 –68HC11EVBU9 Layout
The micro controller will be interfaced with PC thorough serial port (RS-232) and information will be sent by application from PC directly.
4.2Micro Controller source code description
For the micro controller to work,a program will have to be written. The program will be written in C programming language. It will be designed is separate task (function) for each operation. First program will move the motors to (0, 0) position, start position, than it should await the co-ordinates from PC transferred through RS-232. After each co-ordinate is obtained motors should position the pen and start drawing the picture.
4.3PC application source code description
The application should look similar to the windows paint program. Program will be writhe in Visual Basic. User will be able to draw picture on 200 X 200 dot drawing. Once the drawing is completed the program should interpolate the dots into X,Y co-ordinates and send them to micro controller.
4.4 Micro Controller I/O diagram
All of the devices used in this project will be connected to micro controller either as input or an output. The motors will be connected to an output through an IC H-bridge which will be operated by micro controller. PC will be connected to the micro controller through a serial port. Figure 6 shows the actual diagram.
Figure 6 – Microcontroller I/O diagram
4.5 Stepper Motor and Drive IC
Stepper motor was chosen due to ease of control. By using two of them pen will be able to move on X, Y axis. Motor is shown in Figure 7.
Figure 7 – Oriental 2-Phase Stepping Motor PK Series
In order to control the stepping motors micro controller will have to be connected to the motor through a bipolar driver IC shown in Figure 8.
Figure 8 – Bipolar driver IC
The bipolar driver IC was chosen because the user only needs to apply clock signal and inputs for a Full/Half step and direction control. This will offload CPU loading and will shorten the code and memory requirements. Two of IC’s will be used one for each stepping motor.
4.6 Additional Components
Railing system is need for motors to run on them. There will be a solenoid installed so the pen can be lifted while it is being positioned. Also the pen has to be lifted where there are no lines or in between the lines. To power the motors additional power supply will have to be acquired as each motor requires 6V @ 0.8A.
4.7Mechanical Parts Design
The final project will be made out of wood. Railings and motor holder will be made out of steel. The final dimensions are still uncertain but for the report purposes design will be similar to the Figure 9.
Figure 9 – Mechanical design
5.0 Conclusion
From the initial design to final completion project should be done by December of 2006. Majority of the project will be completed this summer in order to have more time to test and troubleshoot if the need arises.
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