The Coin-Operated Washer/Dryer Control System
Final Report
May 04-05
CLIENT
George Ensley
FACULTY ADVISORS
Nicola Elia
Ratnesh Kumar
TEAM MEMBERS
Greg Herr
Craig Zamzow
Latrice Baggett
Hisham Chowdhury
DISCLAIMER: This document was developed as a part of the requirements of an electrical and computer engineering course at IowaStateUniversity, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and IowaStateUniversity make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.
May5th, 2004
1
TABLE OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
LIST OF DEFINITIONS
1.0 INTRODUCTORY MATERIALS
1.1 Executive Summary
1.1.1 The Need For The project.
1.1.2 Project Activities
1.1.3 The Final Result.
1.1.4 Recommendations for Future Work.
1.2 Acknowledgements
1.3 Problem Statement
1.3.1 General Problem Statement
1.3.2 General Solution Approach
1.4 Operating Environment
1.5 Intended User(s) and Intended Use(s)
1.6 Assumptions and Limitations
1.6.1 Assumptions
1.6.2 Limitations
1.7 Expected End Product and Other Deliverables
2.0 PROJECT APPROACH AND RESULTS
2.1 Functional Requirements for the End Product
2.2 Design Requirements including Constraints
2.3 Approach Considered and One Selected
2.4 Detailed Design
2.4.1 Component Interface Diagram
2.5 Implementation Process Description
2.6 Testing of the End Product and Its Results
2.7 End Results of the Project
3.0 RESOURCES AND SCHEDULES
3.1 Resource Requirements
3.1.1 Personal Effort
3.1.2 Other Required Resources
3.1.3 Financial Costs
3.2 Schedules
3.2.1 Project Schedules
3.2.2 Deliverable Schedules
4.0 CLOSURE MATERIALS
4.1 Project Evaluation
4.2 Commercialization
4.3 Recommendations for Additional Work
4.4 Lessons Learned
4.5 Risk and Risk Management
4.6 Project Team Information
4.7 Closing Summary
4.8 References
5.0 Appendix A
LIST OF FIGURES
Figure 1: Interface Diagram
Figure 2: Scematic of PIC interface with Components
Figure 3: Gantt chart for Fall Term
Figure 4: Gantt chart for Spring Term
Figure 5: Deliverables for Senior Design Fall and Spring Semesters
LIST OF TABLES
Table 1: The Functional Requirements
Table 2: The Design Constraints
Table 3: Personal Effort Budget
Table 4: Additional resources
Table 5: Financial Budget
Table 6: Milestone Evaluation
LIST OF DEFINITIONS
Owner – the owner or manager of a Laundromat
Customer – a person paying for use of a washer or dryer
PIC – programmable interrupt controller, micro-controller
LCD – small monochrome display unit
12 button keypad – numeric keypad, input device
1
1.0 INTRODUCTORY MATERIALS
The following sections will discuss the Executive Summary, Acknowledgements, Problem Statement, Operating Environment, Intended User(s) and Use(s), Assumption and Limitations, and Expected End Product and Other Deliverables.
1.1 Executive Summary
The Executive Summary will present the need for the project, project activities, the final result, and recommendations for future work.
1.1.1 The Need For The project.
When laundromat owners purchase washers and dryers they must pay for the electronics that make the machines coin-operated. Since the machines wear out much faster than the electronics for coin operation, if the owner could purchase machines without the electronics, it would provide a savings. Machines with the coin-operated electronics included can cost $300-$400 more than typical household machines without them. This project solves that problem by creating an inexpensive device that will allow the coin-operated electronics to be reused. A previous team started this project and it is the goal of this team to complete the work that was left unfinished by the previous team.
1.1.2 Project Activities
During the Fall 2003 semester, the team researched various algorithms and methods of implementation for the coin control box. The team created a design with a simple programmable micro-controller system. During the Spring 2004 semester, the team programmed a PIC 16F877 to interface with an AND491GST LCD screen and a simple keypad. The micro controller was programmed with C which was compiled into an assembly language for the micro controller. After the programming was complete, the team constructed the final prototype.
1.1.3 The Final Result.
The device is wall mountable, or (washer/dryer) machine mountable, and allows for data to be kept for individual machines and for the electronic device itself. This data includes number of machine cycles, hours of operation on the attached machine and hours of operation on the device. By recording the number of cycles a particular machine has run, machines can be rotated to provide equal wear amongst all of the machines.
1.1.4 Recommendations for Future Work.
Ideas for further development include: circuitry to detect unbalancing within washers and networking several coin control boxes to a central server to offer coin less service.
1.2 Acknowledgements
The team would like to acknowledge the work of the Phase 1 and previous Phase 2 groups. The team would also like to thank George Ensley for his help.
1.3 Problem Statement
The general problem statement, general solution approach, operating environment, intended user(s), intended use(s), assumptions, limitations, and end-product description is outlined in the following sections.
1.3.1 General Problem Statement
The Coin-Operated Washer/Dryer Control System must be relatively inexpensive and the internal logic must be designed to recognize and control various situations which may arise while using a non-commercial washer/dryer. These problems include the recognition of an idle dryer and reclaiming this time; recognize an open door on a washer, recognizing the end of a cycle for a washer and dryer, and detection of coin payment.
1.3.2 General Solution Approach
The Coin-Operated Control Systems design will use timers and an inductive current sensor circuit to recognize idle machines and the end of a cycle. A mechanical relay will be used to detect the coin payment. When a customer inserts coins into the slotted coin device and pushes the handle of the coin mechanism, the relay will send a signal to the microcontroller, recognizing the payment.
1.4 Operating Environment
The Coin-Operated Washer/Dryer Control System will be placed inside a heated and air-conditioned laundry facility. The temperature will not vary greatly, but the machine may be placed near the potentially drafty escape duct of the dryer. The system should be able to operate from forty degrees Fahrenheit to one hundred twenty degrees Fahrenheit. Since the machine is going to be near a washing machine, it should be watertight in case of broken pipes or other accidents that might cause water to build up around the machine. The casing should also be able to withstand a moderate amount of abuse since it will be touched and used on a daily basis.
1.5 Intended User(s) and Intended Use(s)
Primary users of the Coin-Operated Washer/Dryer Control System will be laundry facility customers who will pay for the use of laundry machines, and laundry facility owners/operators. The laundry facility customers will have basic interactions with the device, such as coin payment and starting and stopping the washer/dryer. The laundry facility owners/operators will have administrative privileges such as setting cycle timers, setting cost per load, and reading and resetting the number of cycles per machine. In addition to these settings, the laundry facility owners can set the open door window time, which is the time allowed for a customer to open the machine door and restart the machine before the system resets.
This product is ideal for people who own laundry facilities with multiple machines. This product allows them to monitor a machine’s usage and allow them to strategically move machines according to their usage, which will in turn allow for more uniform wear on all of the machines. Other potentials for this product include: pay-by-hour televisions in a public setting, coin-operated tanning salons and coin-operated computers/internet.
1.6 Assumptions and Limitations
Assumptions and limitations of the coin-operated washer/dryer unit are outlined in the next two sections.
1.6.1 Assumptions
The following assumptions were used in the project.
- The current through the washer or dryer is considerably less when the machine’s door is open compared to normal operation.
- The temperature in the laundry facility will always be between 40º F and 120º Fahrenheit.
- The coin mechanism only takes quarters as the coin payment.
- The current though the washer is considerably less when the machine is done.
- The non-commercial washers will stall under the unbalancing condition.
- Dryers used in the laundry facility will have a start button or knob; they will not automatically start when the door is closed.
- Upon power loss the coin-operated system will be reset when power is reconnected.
- The owner will not enter the coin-operated system box menu during machine operation.
- A notice sign reading “Customers beware of the machine unbalancing during the spin cycle. Please be present to rebalance” will inform customers of the potential loss of money due to unbalancing.
1.6.2 Limitations
- Prototype must cost less than $150.
- The machines require a 240V or 120V outlet.
- The unit has the possibility to be subjected to theft and vandalism.
- The wire connections between the washer/dryer and the coin-operated control system must be able to be easily disconnected by owner only. Otherwise users can bypass coin-operated control system.
- The total time and window time is limited from 0 to 99 minutes.
1.7 Expected End Product and Other Deliverables
The final product will be a fully functional coin-operated control system that will regulate power flow to non-commercial washers and dryers. The end-of-project deliverables include the final prototype, the PIC code (see Appendix A), wiring schematics, the prototype budget, copies of all senior design course documents, and a brief user’s manual.
2.0 PROJECT APPROACH AND RESULTS
The following sections describe the approaches and the results of the project.
2.1 Functional Requirements for the End Product
The functional requirements in Table 1 describe the end product’s functionality.
Table 1: The Functional Requirements
Requirement / Brief DescriptionThe cost per cycle may be varied by the owner of the laundry facility. / Different markets will allow for different prices in laundry machine usage. By using a variable cost the control unit will be applicable to all markets which use U.S. currency.
The unit shall cut power from the washer/dryer when the overall timer expires and indicate to the customer that the cycle has ended. / The control unit will regulate the maximum amount of time the machine may run for each payment. When the control unit detects that the machine has finished its cycle or total allotted time, a light or sound will be transmitted to the laundry customer to indicate the end of the cycle.
The unit shall power on when the customer enters in the correct amount of currency. / The control unit will remain in a standby/ready state until a form of payment is detected. At that time the control unit will allow power to the machine and monitor the machine.
The unit shall accept quarters as payment. / The coin mechanism will accept up to 8 quarters as a form of payment.
The unit shall display the total remaining time during the washing/drying process on the LCD display. / This time will be displayed in units of minutes and seconds in a mm:ss display.
The unit shall contain a 120V and a 240V plug-in socket for the washer/dryer. / Most washers use a 120V outlet and most dryers use a 240V outlet. Either machine may be connected via either socket.
The unit shall keep records of the washer’s/dryer’s cycles and the total cycles of the mechanism. / The control unit will count cycles. The owner will have the access to view cycle counts and reset cycle counts. The owner will interface with the control unit by a 12-button keypad.
The unit shall enter a standby mode when machine is not in use. / In this standby mode the LCD will display the cost of a cycle. In the standby mode, the micro-controller will be idle until a form of payment is detected.
The unit shall allow a variable amount of time for customers to open and close the washer/dryer doors, after which the unit will reset. / Laundry customers may need to add or remove articles of clothing from machines during a cycle. This window of time will be displayed on the LCD in terms of minutes and seconds. At the end of this window the unit will reset; this allows us to reclaim time when a user is done using the machine. For example: if 20 minutes were used on a dryer who was allotted a total of 60 minutes.
The unit shall control only one laundry machine at any time. / Even though the team has two sockets within the control unit, the design will only monitor and control one laundry machine.
2.2 Design Requirements including Constraints
The design constraints consist of cost, safety, and parts availability. The design constraints that are considered throughout the design and implementation process are listed in Table 2.
Table 2: The Design Constraints
Constraints / Brief DescriptionCost constraints: / A prototype unit with a maximum cost of $150. This will allow laundry facility owners a low investment cost and higher return on investment. This will also allow George Ensley to produce a product with a cost-competitive advantage.
Safety constraints: / A secured plug-in mechanism. The plug-in cord will be securely fastened to the control unit’s chassis so it cannot be removed by laundry facility customers.
Part availability constraints: / The PIC, LCD, power supply, relay, and coin mechanism should be readily available parts with a minimal chance of being discontinued by their manufacturers/suppliers.
2.3 Approach Considered and One Selected
The technologies that the team considered are listed in Table 3.
Table 3: The Technology Considerations
ProjectComponent / Technologies
Considered / Advantage / Disadvantage / Selected
Current sensing circuit / Inductor / Inexpensive / Less accurate than AC voltage circuit. / X
Solid state AC voltage circuit / More accurate / More expensive than inductor.
Coin Payment / Variable coin receptor – a device that allows for multiple units of currency. / Variable cost per load. Some laundry facility owners prefer this.
Not very durable. / Need for coin return.
Slotted coin mechanism – a device that accepts quarters. / Set cost per load. Some laundry members like to round the cost per load up to the next quarter.
More durable. Mechanically sound. / Slightly more expensive than the variable coin receptor. / X
Circuit Components / PIC microcontroller- Programmable Interrupt Controller / Less expensive / No programming experience. No simulation program. Programming limited to Senior Design Lab / X
FPGA-Field Programmable Gate Arrays / Lots of experience. Simulation program. Portable simulation software. / More Expensive
2.4 Detailed Design
The component interface is described in detail in the following section.
2.4.1 Component Interface Diagram
A component interface diagram shows an overall picture of how the many components of the team’s unit will interface with each other. For a more detailed description on each component please see Table 4 the Table of Components. Figure 1 shows the interface diagram.
Table 4: Table of Components
Component / Brief DescriptionLCD Display / A liquid crystal display that can display all numbers and letters of the alphabet.The selected model is AND491.
Coin Mechanism / This mechanical device accepts up to 8 US or Canadian quarters. To deposit the quarters the user will push a bar into the device. This will be used in both washer and dryer units.
12-Button Keypad / This keypad includes numbers 0-9, ‘*’, and ‘#’.
Inductor / This is a simple wire wrapped in a coil. The power cords to the laundry machine are routed through the coil; current through the power cords will induce an alternating current in the current transformer.
Micro-controller / The micro-controller is a PIC16F877. The controller has inputs and outputs and can be programmed with the C programming language. The micro-controller can be interrupted by one external source and several internal sources.
Low voltage power supply / This power supply powers all the low-voltage devices such as the micro-controller, LCD and keypad.
120V socket / This is the 3 prong electrical socket commonly found in most houses.
240V socket / This is a 3-prong or 4-prong electrical socket most commonly found in a utility room. 240 volts is achieved by offsetting two 120v sources.
120V/240V relay / This relay allows power to flow to the laundry machine.