ACCESSIBLE LOCK OPENERRIT CE Senior DesignJeremy EspenshadeJason Fay

Agenda

• Domain Introduction• Project Overview• User Interface• Normal Operation• Mechanical Design• Electrical Design• Software Design• Power Distribution• Operating Conditions• Integration and Testing• Project Feasibility

Domain Introduction

• Combination locks are everywhere– Gyms, schools, general purpose lockers, etc

• The standard Master® lock-style interface is currently difficult or impossible for some people to use– Blind or Visually Impaired– Limited Fine Motor Control

• Elderly• Physically Handicapped• Gloved Hands

• Outside assistance is therefore required, largely defeating the purpose of a private combination.

Project Overview

• A device must be created that allows combination locks to be accessible without outside assistance.

• The user will be able to input the combination and the device will dial appropriately.

• Requirements for normal operation:– No sight required – Reduced need for fine motor control– Time required comparable to unimpeded manual

dialing– Portable

User Interaction

Handheld, Automated Dialing Device User Story:

Pick up the device and turn it on Type in the desired combination on a telephone-

style keypad Orient the lock with zero centered at top of lock Position the device on the lock Press the “dial” button and wait for the device to

spin the lock appropriately Remove the device and pull on the lock to open

it

User Interface

Display is 2x16 characters in size

Keypad is 2’’ by 2.5’’

Keys take up 1.5’’ by 2’’

Keypad

Display

On/Off switch

User Interface

The display has two type of messages Normal messages Error messages

Normal messages just state what numbers of the combination have been entered. Ex: 09-22-19

Error messages tell the user what they did to cause an error Ex: Invalid number

Normal Operation

The user will enter in his or her combination on the keypad

The numbers that the user has pressed will be displayed on the LCD screen

Each time the user has pressed a button a sound is played There a sound for a valid number being entered And another for an invalid number being entered

Normal Operation (cont)

The user has to enter two digits for each number of the combination. So 9 has to be entered as 09

After the user has entered the complete combination they then press the # key to tell the device to physically manipulate the lock.

If the user makes a mistake at anytime they can press the * key to reset the device.

Block Diagram

Stepper motor

Microcontroller board

Driv

e sh

aft

Support circuitry

Batteries

Dial interface

Speaker

Casing

The device casing will be designed so that it is easy to hold.

It will be made out of lightweight durable material Aluminum or plastic

It will be roughly 7’’ x 6’’ x 2.5’’ in size.

The Dial Connector

Dial Connector Construction

Solid aluminum machined with appropriately sized holes

Rubber “grip” inserted in large end to hold lock dial

Connected to motor shaft with set screw

Electrical Design

The Keypad

The keypad has an output pin for each key that is on the board.

There is also a common input line. When a key is pressed, it connects the

corresponding output pin to the common input.

By polling the pins from the keypad, the microcontroller can determine what key(s) are pressed.

The Speaker

The Speaker is just a computer speaker It is controlled by the first PWM line of the

microcontroller. By changing the frequency scaling factor of

the PWM, different tones can be made. There are two different tones:

Error tone. This will be a higher pitched sound. Normal tone. This will be a lower pitched sound.

The LCD display

It has 4 control pins and 8 data pins. The display consists of two 16 character rows It is used to display the combination and any

error that might have occurred. Examples:

C O M B I N A T I O N :

1 2 - 0 9 - 2 0

I N V A L I D N U M B E R

1 2 - 0 9 - 5 0

Stepper Motor Driver

• Microcontroller supplies clock and direction lines

• Output current limited by Rb • Clamp diode suppresses back-EMF

Software Design

• Freescale Codewarrior IDE • HCS12 C-language development• Timer Interrupt

– Poll the keypad– Send data to the LCD – Generate stepper motor driver control signals

• 3 operating states

Software Design – Operating States

• Waiting for Combination– Initial State– Keypad polled for changed input– New key press causes LCD update, tone generation,

and error evaluation– May enter invalid combination or turning states

• Invalid Combination– Error Conditions

• Formatting: 02-05-23 input as 2523• Out of Range: element greater than 39 entered

– Error recovery: *-key combination reset and power reset

Software Design – Operating States

• Turning Motor– Motor resolution = 1.8° and lock resolution = 9°

• 5 clocks/lock position• Clockwise, counterclockwise, and clockwise movements

– Clock generated with period twice the timer interrupt period

– Clock counts are generated at the beginning and the direction control signal changes before and after counterclockwise movement.

– *-key allows manual override to stop the motor from turning

– Mechanical problems undetectable

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Power Distribution

• The requirement of portability implies the need for battery power.

• An RC car battery pack will be used.– 8.4 – 12 volts– 2300 – 4500 mAh

• Power Requirements:– Microcontroller: 5 volts, 65 mA max

• 5 volt Voltage Regulator

– Stepper Motor: 7.6 – 16.5 volts, 150-300 mA• Battery Life: 4500/(300+65) = 12.4 hours• Feedback limiting diode and voltage

regulator provide power supply isolation.

Operating Conditions Usable Outdoors

Water resistant No exposed wires

0 – 50° C Low-temperature components extremely expensive

Portable/Battery Powered Easy access to battery charging

Locks supported Standard Master® Lock Similar shaped locks with 40 positions

Integration and Testing

The microcontroller software and interface electronics are being developed concurrently with the mechanical elements

Electronic portion independently testable Dialing speed determination and accuracy

verification can only occur after the dial interface and shaft are completed

Battery power to be verified after functionality established

Final usability testing to be completed after casing developed

Project Feasibility

Lock dial interface and motor shaft Several approaches proved unsuccessful Machined aluminum with rubber hold expected

to be far superior (Thanks Josh!!) Unforeseen mechanical problems

Secure mounting of motor Ease of lock alignment and steady hold

Power Variability Dips and spikes could cause microcontroller

reset problems Capacitors and clamping diodes may be used

Questions?