A Logic Block Enabling Logic Configuration by Non-Experts in

Sensor Networks

Susan Cotterell and Frank Vahid*

Department of Computer Science and Engineering

University of California, Riverside{susanc, vahid}@cs.ucr.edu

http://www.cs.ucr.edu/eblocks* Also with the Center for Embedded Computer Systems at UC Irvine

This work is being supported by the National Science Foundation and a Department of Education GAANN Fellowship

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Introduction

Sensor networks are emerging as an important general computing domain

Small inexpensive battery-powered sense and compute nodes Tens to thousands of nodes Wired or wireless communication Stringent requirements (power, cost, size)

Military Applicationshttp://robotics.eecs.berkeley.edu/~pister/29Palms0103/

Medical Monitoringhttp://www.eecs.harvard.edu/~mdw/proj/codeblue/

Environmental Monitoringhttp://www.greatduckisland.net/http://today.cs.berkeley.edu/retreat-6-03/

Home Automationhttp://www.smarthome.com

Structure/Building Monitoringhttp://www.mrr.dot.state.mn.us/research/MnROAD_Project/MnROADProject.asp

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Potential sensor network application developers may not be computer programmers

Instead, engineers, scientists, office workers, homeowners, etc.

Existing programmable nodes Flexible, but require programming

Existing off-the-shelf end applications

Specialized, so hard to customize Expensive due to small volumes

Our solution – eBlocks Enables non-programming users to

create simple but useful customized sensor network applications

Introduction

Photo: Jason Hillhttp://www.dustnetworks.com/

http://www.smarthome.com

http://www.xbow.com/

Flexib

le,

hard

to p

rogra

m

Easy

to u

se,

inflexib

le

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eBlocks Overview

Function of each block is pre-defined

Block types: Sensors – motion, light, contact,

etc. Output – led, electric relay, beeper,

etc. Compute – logic, prolong, toggle,

etc. Basic configuration required (dials,

switches) Communicate – wireless point-to-

point link Boolean Blocks

Outputs yes/no/error Future implementations - Integer

Users connect blocks to create working customized application

CODES/ISSS’03, SECON’04, DATE’05, SPOTS’05, HCII’05

Light Sensor

yes/no

Magnetic Contact Switch

yes/no

Button yes/no Motion Sensor

yes/no

2-Input Logic

yes/noyes/no

yes/no

Tripper

yes/noyes/no yes/no

Toggleyes/noyes/no

Electric Relay

yes/noLEDyes/no

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2-Input Logic

Configure Logic Block to turn led on when it’s night and when door is open

A’B’

Need a function of light sensor output and contact switch output – use Logic Block

2-Input Logic

Creating an application with eBlocks

Create an application to detect if the garage door is left open at night

Light Sensor

We want to detect night – use light sensor

Light Sensor

Magnetic Contact Switch

We want to know if garage door open – use contact switch

Magnetic Contact Switch

2-Input Logic

A’B’

LED Need something to indicate garage open at night – use led

LED

Plug pieces together and the system is done!

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Building eBlocks Systems

The same basic blocks can be used in a variety of applications

2-Input Logic

A’B’

Light Sensor

Magnetic Contact Switch

LED

Garage Door Open At Night Detector

Motion on Property Detector

Motion Sensor

Motion Sensor

2-Input Logic

A+B

Prolonger

1 2 3 4 5 6 7 8 9

Beeper

Sleepwalker at Night Alarm

Tripper

Motion Sensor

2-Input Logic

A’B

Light Sensor

Button

Beeper

Animal Videoing System

Motion Sensor

2-Input Logic

A+B

Prolonger

1 2 3 4 5 6 7 8 9 eBlock to Camera Interface

Light Sensor

Many of these system utilize a

logic block

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Original logic block was simply a truth table

Select desired output for each input condition, by moving a switch

Informal experiments to test general usability of eBlocks

Users unable to configure the logic block successfully

Need for a better logic block interface

Blocks must be self-explanatory Users prefer exploratory learning

[Gammon, 1999][Sikorski, 1998]

Motivation

A B Output

no yesno nono yesno yesno yesyes nono yesyes yes

Logic Blockconfigurable DIP switch

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Written Experiments – Truth Table

Written experiment given to students

Typical majors include psychology, business, etc.

Randomly distributed 3 different versions of quiz

Each contained same introduced and asked students to configure the logic block

 

motion sensor

light sensor

Logic blockB

A

yes = motion detectedno = no motion detected

yes = light detectedno = no light detected

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Low success rates -- was it the use of variable names?

Used English instead of variables – slightly better, but results still poor.

Also checked to see if writing out the equation helps -- still yielded poor

results.

Written Experiments – Truth Table

Question Truth table with variables (11 students)

Truth table with English(9 students)

Boolean equations (9 students)

Motion at night 36% 22% 11%

Motion 0% 56% 0%

Motion at night or no motion in day

0% 22% 0%

Motion or night 0% 11% 0%

Detect motion at night?AAA’A’

BB’BB’

Detect motion at night?motionmotionno motionno motion

lightno lightlightno light

What would be the corresponding equation needed to detect motion at night (i.e. F=ab+a’b)?

F =

Gave same truth table quiz

(w/variables) to six students in digital

design course

90%Motion or night

90%Motion at night or no motion in day

90%Motion

100%Motion at night

Truth table with variables (6 students)

Question

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eBlock Simulator

Developed eBlock simulator to aid in testing

Enables wider participation

Allows students to test resulting behavior of configured system

Self-contained instructions, to prevent variations due to administrator

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Logic sentence outperforms table based

blocks

Color seems to help truth table based blocks

Simulator Experiments

Defined new “improved” versions of the logic block

Simulator instantiated blocks, users simply needed to configure logic block

Students were non-engineering majors

Comprised mostly of business, history, dance, etc.

Allotted 15 minutes for quizQuestion Phrased truth

table (33 students)

Phrased truth table embedded in sentence(30 students)

Colored truth table embedded in sentence(32 students)

Logic sentence (32 students)

Daytime Doorbell (AB)

15% 20% 22% 38%

Garage open at night (A’B’)

16% 13% 25% 19%

A B

Combine

A is yes, B is yesA is yes, B is noA is no, B is yesA is no, B is no

The output should

be yes when:

yes no:

Phrased truth table

yes no

the output should be

A B

When the input is

outCombine

A is yes, B is yesA is yes, B is noA is no, B is yesA is no, B is no

Phrased truth table embedded in sentence

yes no

The output should be

When the input is

out

A B

A BA BA BA B

CombineColored truth table embedded in sentence

Combine

AND OR

yes no

When A is yes no

B is

then the output is yes

Logic Sentence

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When consider close to correct responses (1 switch wrong), logic sentence shows better success rate

Logic sentence is slightly better Motion on property, a more difficult

problem, shows a better success rate

Simulator Experiments

yes no

The output should be

When the input is

out

A B

A BA BA BA B

CombineColored truth table embedded in sentence

Combine

AND OR

yes no

When A is yes no

B is

then the output is yes

Logic Sentence

Tested top two designs on students in an introduction to programming course Simulator instantiated blocks, users

simply needed to configure logic block

Allotted 15 minutes for quiz

Question Colored truth table embedded in a sentence(15 students)

Logic Sentence(17 students)

Daytime doorbell (AB)

47% (47%) 47% (71%)

Nighttime doorbell (AB’)

33% (52%) 41% (76%)

Motion on property (A+B)

33% (33%) 65% (71%)

92% (100%)42% (67%)Daytime doorbell (AB)

Logic Sentence(13 students)

Colored truth table embedded in a sentence(12 students)

Question

Had students in second course in programming try out the two blocks interfaces

Logic sentence success rate even more pronounced

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Simulator Experiments

63% (63%)Motion on property (A+B)

50% (38%)Nighttime doorbell (AB’)

69% (77%)63% (69%)Daytime doorbell (AB)

Intermediate Students(13 students)

Non-expert students(16 students)

Question

Success rates for separate AND/OR/NOT blocks

65% (71%)Motion on property (A+B)

41% (76%)Nighttime doorbell (AB’)

92% (100%)47% (71%)Daytime doorbell (AB)

Intermediate Students(13 students)

Non-expert students(12 students)

Question

Success rates for logic sentence block

Also considered the use of separate AND/OR/NOT blocks versus a single logic block

Users had to instantiate these blocks within simulator

Comparable to best table based logic blocks

Logic sentence block preferable for physical implementation -- only 1 block needed

Separate AND/OR/NOT blocks

out

A

B

AND out

A

B

OR

outA

NOT

Combine

AND OR

yes no

When A is yes no

B is

then the output is yes

Logic Sentence

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Conclusions and Future Work

Presented a variety of logic block interfaces Logic sentence best performing Incorporating color in truth table

improved table success rates; table has advantage of generality

Present/Future Work Continue usability testing Extend eBlocks to integer domain Gain experience with use of

eBlocks in real applications with variety of users Pro-active healthcare (w/ Intel) Agricultural monitoring (w/ Isca) Environment monitoring (w/

UCR/UCLA)

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Thank you for your attention.