Build a Light Intensity Logger LV DAQ

8/17/2019 Build a Light Intensity Logger LV DAQ

1/33

Build a Light Intensity Logger

October 2008 © 2008 Emant Pte Ltd www.emant.com 1


2/33

able o! "ontentsIm#ortant $ote......................................................................................................................................2

Learning Ob%ecti&es..............................................................................................................................'

Introduction.......................................................................................................................................... (

E)ercise 1 * +sing a "om#uter based Light Intensity ,ata logger......................................................-E)ercise 2 * Build a I and ,ata /cuisition....................................................................................10E)ercise ' * Loo# e)am#le and chart.................................................................................................1'

"reate a sub I................................................................................................................................... 1

E)ercise ( * ulti#lot "hart and /larm............................................................................................ 1-

E)ercise * 3tatistics and Log to !ile................................................................................................ 20

E)ercise 4 * Build your Light Intensity Logger 5o#tional e)ercise6...................................................2'

E)ercise - * 3/7s outbrea...............................................................................................................2E)ercise 8 * Pedestrian "rossing........................................................................................................29

E)ercise 9 * Im#ro&ed /irconditioning "ontrol 5challenge e)ercise6............................................... ''

Important Note

he P" must be correctly setu# in order !or you to com#lete the e)ercises in this instructional guide.

I! you ha&e not setu# the raining :it; #lease do so using the installation guide and run the

diagnostic be!ore #roceeding.

his instructional guide had been re&ised !or LabIE< &er 8 and later.



3/33

Learning Objectives

=ollowing our ste# by ste# Instruction >uide; the user will create a Light Intensity Logger; a 3/73

detector and Pedestrian "rossing 5ra!!ic Lights6. /!ter com#letion o! these e)ercises; the user

would ha&e learnt the !ollowing

Sensor / Actuator

• Photodiode

• 3witch

• LE,

• hermistor

Data Acquisition (DAQ)

• /nalog In#ut

• /nalog Out#ut 5"urrent6

• ,igital In#ut

• ,igital Out#ut

LabVIEW

• Build I; sub I

•


4/33

Introduction

?In #roblem@based learning; the starting #oint !or learning should be a #roblem; a uery or a #uAAle

that the learner wishes to sol&eBoud. ,; 199; #.1'. Enhancing Learning through 3el! /ssessment

Types of problems tat are sol!e" by measurin# li#t intensity

• In #hotogra#hy or !ilm #roduction; creati&e mani#ulation o! light can create stunning images

!rom a low cost consumer camcorder; while #oor lighting will cri##le the most e)#ensi&e; state@o!@the@art broadcast camera.

• Light intensity is an im#ortant management !actor !or breeder ty#e #oultry. here is e&idence

suggesting a minimum threshold intensity is needed to obtain o#timal re#roduction #er!ormance.

• he amount o! light recei&ed by a #lant is an im#ortant !actor; because #lantsC growth may su!!eri! they do not recei&e su!!icient light. hey may lose their characteristic sha#e and grow thin;

leggy stems. $ew lea&es may also be smaller and turn yellow. 3ome #lants may lose their color

or turn dar green. Plants e)#osed to e)cessi&e light; on the other hand; may not !lower #ro#erly

or may turn #ale green. ,i!!erent s#ecies o! #lants reuire di!!erent amounts o! light.

Light intensity decreases dramatically with distance !rom the light source. /n ob%ect located 1 cm

!rom two (0@watt !luorescent lam#s recei&e about 9'00 lu); but only (00 lu) i! they are '0 cm

!rom the lam#s.

he human eye is a &ery #oor DinstrumentD !or measuring light intensity; because the #u#il ad%ustsconstantly in res#onse to the amount o! light it recei&es. o accurately measure the light intensity in

a gi&en s#ot; it is best to use a light meter.

Light intensity may be measured in lu) 5metric system6 or !oot@candles 5Im#erial system6. $ote that

1 !oot@candle 10.-4 lu)

o #ro&ide some #oints o! re!erenceF

• =ull sunlight 11000 lu)

• orning sunlight 4000 lu)

• / bright o!!ice has about (00 lu)

• oonlight re#resents about 1 lu)

October 2008 © 2008 Emant Pte Ltd www.emant.com (


5/33

/ com#uter based light intensity logger is made u# o! the !ollowing com#onents

• 3ensor @ a #hotodiode 5BP


6/33

=or an 2(@bit /," o#erating o&er a 2. range; the accuracy you obtain cannot be better than

2.J14---214 or 0.1 u. Gowe&er due to noise; this is only achie&able through care!ul wiring.In a ty#ical a##lication; a noise !loor o! about 18 bits or 9 u is usually achie&able.

he ,/ module used 5the E/$'00 or E/$'806 has u# to 4 di!!erential /," channels;one 8 bit current ,/" channel; 8 digital IJOs and either a 14 bit P


7/33

Exercise 1 – Using a Computer based Light Intensity Dataogger

$b%ecti!e

o learn how to use a com#uter based measurement system

O&er the ne)t !ew e)ercises; you will learn how to use

LabIEo to the

Learn DAQ and LabVIEW !older and choose Light System Demo.vi. his will o#en

the Light 3ystem ,emo I =ront Panel.

October 2008 © 2008 Emant Pte Ltd www.emant.com -

Bluetooth

,/ module


8/33

+sin# te Li#t Intensity Lo##er

In LabIE


9/33

8. =or data loggers; it is &ery common to include alarms whene&er limits allowed are e)ceeded. +se

the O#erating tool to change the Gigh Limit. ou can use the increment or decrement arrows

on the control; or drag the #ointer to the desired &alues.

9. I! you are using a torchlight to increase the light intensity; set the Gigh Limit abo&e the ambient

&alue. I! you are blocing the ambient light; set the Gigh Limit lower. Obser&e the Limit LE,. Itchanges color when the Gigh Limit is e)ceeded.

10.ou may be logging data !rom #eriods as short as minutes to as long as days. "hanging the

u#date #eriod 5how o!ten the light intensity is measured6 is a &ery common !eature. +se the

O#erating tool to change the +#date Period and obser&e the change. he ,/ card you are

using has a ma)imum acuisition rate o! 100 sam#lesJsec so this will limit the lower end o! the+#date Period.

11.Press to sto# the I. I! you are using the +3B ,/; tae note o! the &omm 0ort assi#ne".It is gi&en here.

12.I! this data logger were used in a greenhouse; it may be use!ul to now the ma)imum and

minimum light intensities measured during the measurement #eriod. 3tatistic !unctions in

LabIE< allow the user to read o!! these &alues. In this e)am#le; the results are dis#layed only

when the #rogram ends.

1'."lose the I and do not sa&e changes.

En" of Eercise 1



10/33

Exercise ! – "uid a #I and Data $c%uisition

$b%ecti!e

• =amiliariAe with the LabIE< de&elo#ment en&ironment

• Build a I

• Learn /nalog In#ut and con&ersion

"om#lete the !ollowing ste#s to create a I that read the &oltage across the #hotodiode and con&ertit to a light intensity &alue in Lu).

1. 3tart LabIE


11/33

Be!ore continuing; lets acuaint oursel&es with the tools #alette; controls #alette and the !unctions

#alette. ou will ha&e to use these #alettes o!ten.

,ront 0anel

he !ront #anel is the user inter!ace. It should loo lie the !ollowing



12/33

.loc- Dia#ram

$ow we will create the !ollowing bloc diagram that reads in the &oltage using the ,/ card and

con&erts the &oltage to light intensity in Lu) 5see #age !or euation6.

o learn how to create the =ront Panel and Bloc ,iagram; &iew E 7 &ideo. >oto the &ideo

!older; o#en inde).html and clic on the E) 2 &ideo lin.

he !ollowing I are used.

1. EA!"#$$ %ead Analog.VI !rom the I library EA!"#$$.llb !ound in the

Driver & Example VI older. his I reads the &oltage across the 10:ohm

resistor.5see #age !or schematic6

2. EA!"#$$ Initialisation.VI maes the connection to the ,/ module

'. EA!"#$$ 'lose.VI closes the connection to the ,/ module

(. numeric constant !rom ,unctions230ro#rammin#23'umeric #alette

. ulti#ly !rom ,unctions230ro#rammin#23'umeric #alette

4. "lic the 7un button to run the I. ust lie in e)ercise 1; mae sure that the com #ort

setting is correct and clic O:. 7un the I se&eral times and shine a torch light to the #hotodiode

to create di!!erent light intensity and obser&e the result

-. 3elect ,ile23Sa!e 3a&e the I in the Working VI !older because you will use this I in

subseuent e)ercises. $ame the !ile Data A()*isition Ex +.vi "lose the I.

,id you see this insteadQ It is a Broen 7un button. It indicates that the I cannot run due toerrors.


13/33

Exercise & – Loop exampe and chart

$b%ecti!e

• Learn how to mae re#etiti&e measurements

• Learn about charts

• Learn how to #rogram timed measurements

• "reate a sub I

In the last e)ercise; you ha&e to re#etiti&ely run the #rogram to mae di!!erent measurements. In thise)ercise; you will mae use o! the


14/33

.loc- Dia#ram

"om#lete the diagram as shown

o learn how to create the =ront Panel and Bloc ,iagram; &iew E &ideo.

he !ollowing I are used.

1. Wile Loop !rom ,unctions230ro#rammin#23Structures #alette.

=rom LabIE< Gel#

While Loop repeats the subdiagram inside it until the conditional terminal receives a

particular Boolean value. The Boolean value depends on the continuation behavior of the

While Loop.

o enclose the Is in a


15/33

(. 'umeric &onstant !rom ,unctions230ro#rammin#23'umeric #alette.


16/33

1. he Is that reads the analog &oltage and con&erts the &oltage to Lu) has shrun into a subI.

he bene!it is that in the !uture i! you need to read the light intensity; you %ust need to insert this

subI into your diagram.

2. 3a&e the I. 3elect ,ile23Sa!e. he !ollowing dialog bo) will #o# u# reminding you that you did

not sa&e your subI.

'. "lic O:. >o to the Working VI !older. $ame the subI L*x.vi

(. "lose the I.

$oteF In this e)ercise; you ha&e created two Is.

• o# le&el I called Loop Example Ex #.vi

• 3ubI called L*x.vi

En" of Eercise



17/33

Exercise ' – (utipot Chart and $arm

$b%ecti!e

• Learn how to #lot multi#le &alues

• Learn about Boolean "om#arison

• Learn about "lusters

In the last e)ercise; you learnt how to create a trend chart with user de!ined delays. any times; you

would lie the #rogram to warn the user i! certain threshold are reached. In our e)am#le; #lantse)#osed to e)cessi&e light may not !lower #ro#erly or may turn #ale green.

ou may also want to com#are the measured intensity with the threshold &alue o&er time. In such

instances; a multi #lot chart is use!ul. In this e)ercise; you will build on the #re&ious e)ercise to add

the alarm and multi#le #lots to the chart.

,ront 0anel

1. O#en an e)isting I. Loo !or Loop Example Ex #.vi you sa&ed #re&iously. odi!y it to

the !ollowing !ront #anel.

2. Insert Square LED !rom &ontrol23o"ern23.oolean #alette. $ame it Alarm

'. Insert 'umeric 8nob !rom &ontrol23o"ern23'umeric #alette. $ame it Limit.

"hange the range to 1000. "lic on 10 and enter 1000

October 2008 © 2008 Emant Pte Ltd www.emant.com 1-


18/33

(. E)tend the Plot Legend to show two #lots and change the second #lot label to Limit.

o&e the cursor o&er middle and bottom o! the Plot Legend.


19/33

8. "lic the 7un button to run the I. +se the O#erating tool to change the Limit. ou can

drag the nob to the desired &alue. 3hine a torch light to the L,7 to create di!!erent light

intensity and obser&e the result

9. Press to sto# the I.

10.3a&e the I. 3elect ,ile23Sa!e. "all the !ile *ltiplot 'hart and Alarm Ex ,.vi

"lose the I.

En" of Eercise ;



20/33

Exercise ) – *tatistics and Log to +ie

$b%ecti!e

• Learn about arrays

• Learn how to use the statistical Is

• Learn how to sa&e the data to a !ile

It is o!ten use!ul to now the ma)imum; minimum and a&erage light intensity that has been logged.

ou will also ha&e noticed that once you sto# the I; the data is lost when you run the I again.


21/33

.loc- Dia#ram

1. 3elect Win"o423So4 Dia#ram to dis#lay the bloc diagram. "om#lete the diagram as shown


22/33

resol&e this; clic on the terminal shown below and select Enable Inde)ing. his will cause the

single &alues to accumulate to !orm an array when the loo# e)its.

-. o bac to the =ront Panel. "lic the 7un button to run the I. "o&er the #hotodiode tochange the light intensity and obser&e the result

9. Press to sto# the I. / dialog bo) will a##ear. Enter the name o! the !ile to sa&e the

s#readsheet.

10.ou may now use $ote#ad to o#en the s#readsheet !ile sa&ed. his is in the "3 !ormat that can

be read by te)t editors and s#readsheet #rograms lie E)cel.

11.>o to the Learn DAQ and LabVIEW older and o#en the I called %ead LV -ile

Ex a.vi 7un the #rogram !irst and then loo at the diagram to see what is reuired to read

bac and dis#lay logged data.

12."lose the I. ,o not sa&e.

En" of Eercise =



23/33

Exercise , – "uid your Light Intensity Logger -optionaexercise.

$b%ecti!e

• Learn ,ecoration controls

ou will now use your nowledge o! LabIE< and ,ata /cuisition learnt !rom the #re&ious

e)ercises to build the data logger that you ran in E)ercise 1.

,ront 0anel

1. O#en a new I. Build the !ollowing !ront #anel.

GintF o beauti!y the !ront #anel use the "ontrol@Rodern@R,ecorations #alette and the coloring

ool !rom the ool Palette

.loc- Dia#ram

2. Build the diagram on your own. I! you run into di!!iculties; re!er to the #re&ious e)ercises or the

LabIE< Gel#. /s a last resort; you can re!er to the Light System Demo.vi

'.


24/33

(. "lic the 7un button to run the I and obser&e the results.

. Press to sto# the I.

4. "lose the I.

En" of Eercise >

October 2008 © 2008 Emant Pte Ltd www.emant.com 2(


25/33

Exercise / – *$0s outbrea

$b%ecti!e

• Learn =ormula $ode

• Learn /nalog Out#ut 5"urrent6

• Learn how the hermistor measures tem#erature

0roblem

3e&ere acute res#iratory syndrome 53/736 is a res#iratory or airways in!ection that broe out in

/sia in early 200'. It is highly in!ectious and death !rom the disease is not uncommon. =e&er is one

o! the !irst signs o! 3/73. On une 1; 200'; in aiwan; a $ational em#erature onitoring"am#aign was launched. In the cam#aign; !e&er was de!ined as !orehead or a)illary tem#erature

R'-S". ou ha&e been tased to create a !e&er detector.

SolutionWarning" This is intended as proof of concept exercise and not intended for real life use.

/ thermistor will be used to measure the !orehead tem#erature. hermistors are widely used in

industrial a##lications because o! their sensiti&ity; small siAe; ruggedness and low cost. hermistors

ha&e an electrical resistance that &aries non@linearly with tem#erature. he 7@ characteristics o!

most thermistors can be described by the 3teinhart@Gart euationF

1J / T BH5Ln 76 T "H5Ln 76'

is the absolute tem#erature 5in :el&in6 and /; B; and " are constants which can be determined bymeasuring three sets o! resistance and tem#erature &alues during calibration.

ost thermistors ha&e a negati&e tem#erature coe!!icient 5$"6; their resistance decreases withincreasing tem#erature. hermistors are s#eci!ied according to its nominal resistance at 2 o" and

commonly a&ailable thermistors range !rom 20 ohms to 100 ohms

he thermistor that we are using has the !ollowing characteristics

• $ominal resistance U 2 o"F 10 ohms

• negati&e tem#erature coe!!icient 5$"6

• 3teinhart@Gart euation #arametersF• / 0.0011291(8

• B 0.0002'(12

• " 8.-4-(1E@8

/s the ,/ module /nalog In#ut measures only &oltage; we will need to #ro&ide a current sourceto con&ert the resistance to &oltage. he E/$'00 has an 8 bit current ,/" 5digital to analog

con&erter6. /s the ,/" has 8 bits resolution; we can dri&e the resistance !rom 0 to 1m/ in 2

ste#s with increments o! about '9u/.



26/33

• "onnect the thermistor to the Light /##lication /da#tor screw terminals labeled I,/" and

/>$,

• "onnect a wire !rom I,/" to /I$'

• "onnect a wire !rom />$, to /I$2

,ront 0anel

O#en a new I. Build the !ollowing !ront #anel.

1. Insert Stop .utton !rom &ontrol23o"ern23.oolean #alette

2. Insert 'umeric In"icator !rom &ontrol23o"ern23'umeric #alette. $ame it hermistor

7esistance

'. Insert Termometer &ontrol !rom &ontrol23o"ern23'umeric #alette. 7ight mouse

clic on the thermometer and select Visible Items23Di#ital Display to enable the numeric

indicator associated with the thermometer.



27/33

.loc- Dia#ram

3elect Win"o423So4 ,iagram to dis#lay the bloc diagram. "om#lete the diagram as shown

(. =rom the I library EA!"#$$.llb !ound in the Driver & Example VI older.;

insert the EA!"#$$ Write IDA'.VI his I sets the current o! the 8 bit current

,/"

. Insert ,ormula 'o"e !rom ,unctions230ro#rammin#23Structures #alette.

/ ,ormula 'o"e e&aluates mathematical !ormulae and e)#ressions similar to " on the blocdiagram. his is use!ul i! the mathematics is uite in&ol&ed and is clearer when im#lemented in

te)t !orm rather than in a gra#hical manner.

o create an in#ut; use the #osition tool; right clic on the le!t border o! the =ormula node. 3elect

/dd in#ut !rom the #o#u# menu. $ame it o. $e)t right clic on the right border o! the =ormula

node. 3elect /dd out#ut !rom the #o#u# menu. $ame it . /dd all the other nodes shown in the

diagram. =inally select the e)t tool and clic on the =ormula $ode to enter the !ollowing!ormula

%t / Vo01i2$.$$345" / 30 1a 6 ln1%t421b 6 (21ln1%t422+4445' / " 7 +8#.35

he !irst line calculates the hermistor resistance. he ne)t line con&erts !rom resistance to

tem#erature in :el&in and !inally con&erts the tem#erature !rom :el&in to "entigrade.

8. Insert 'umeric &onstant !rom ,unctions230ro#rammin#23'umeric #alette. ,o the same

!or the remaining 'umeric &onstants

October 2008 © 2008 Emant Pte Ltd www.emant.com 2-


28/33

9. >o bac to the ,ront 0anel

10."lic the 7un button to run the I. +se the O#erating tool to change the Gigh and Low

hreshold.

• Obser&e the ambient tem#erature

• +se your !inger to touch the thermistor. he tem#erature should change to re!lect the

higher tem#erature o! your body.

1(.Press to sto# the I.

1.3a&e the I. 3elect ,ile23Sa!e. "all the !ile SA%s and "hermistor.vi "lose the I.

En" of Eercise ?

A""itional Eercises

1. In the +3; =ahrenheit is a more common unit o! tem#erature measurement. odi!y the I to

allow the user to select the reading in o= or o".

2. odi!y the I to re!lect a tem#erature limit has been e)ceeded.

'. It has been !ound that some #eo#le ha&e a normally higher body tem#erature and there!ore a rise

in body tem#erature is a more a##ro#riate indication o! !e&er. Im#lement this in your #rogram.



29/33

Exercise 2 – 3edestrian Crossing

$b%ecti!e• Learn digital in#ut

• Learn digital out#ut

• Learn shi!t registers

0roblem

he #rinci#al decided to #rototy#e a #edestrian crossing outside the school that is controlled by a

com#uter. Ge en&ision a system where e&entually the lights can be acti&ated !rom the o!!ice; &ia

internet or 33. /s a !irst #art o! the #ro%ect; you ha&e been tased to de&elo# a basic crossingsolution.

he lights will stay green until the button is #ressed.


30/33

he Light /##lication /da#tor has a 7ed; ellow; >reen LE, and switch connected as shown

4. =rom the EA!"#$$.llb I library !ound in the Driver & Example VI older9

insert the EA!"#$$ 'onig DI:.VI his I sets the con!iguration o! the ,IO. 8

bits 51 byte6 determines the direction o! the digital IO. 3#eci!ying the corres#onding bit as 1

con!igures that bit as in#ut and 0 as out#ut. 3ince ,0 * ,2 5see abo&e schematic6 are out#uts and,' is an in#ut we set the con!iguration byte to binary 0000 1000

-. =rom the same I library; insert the EA!"#$$ Write Digital ;it.VI 3et the bit

address and the bit state to dri&e the out#ut accordling. here!ore; i! we are interested to light u#the 7ed LE, then we set bit address2 and bit state=.


31/33

=rom LabIE< Gel#

#se shift registers on $or Loops and While Loops to transfer values

from one loop iteration to the next . %ou can create multiple shiftregister terminals on the left side of a loop to remember more than one previous value.

he 3hi!t register is uniue to LabIE< because it is a gra#hical #rogramming language

and data!low determines the seuence o! the #rogram. Witout te sift re#ister@ it 4oul"

be impossible for pre!ious !alues in a loop to be store" an" use" in subsequent

iterations5

In our solution; the shi!t register is used to store the state o! the lighted LE,. In normal

o#eration; the switch is not closed and the >reen LE, is turned on. his means that

,0 ; ,' and the right shi!t register is .

iteration n-2 n-1 n n+1 n+2 n+3 n+4

right shift register T T $ T T T T

&' T T T $ T T T

&( T T T T $ T T

&) $ $ $ T T $ $

&* T T $ + + T T

3u##ose at iteration n; the switch is closed. he 2 subseuent iterations see the = state

cascaded to the le!t shi!t registers and ,1; ,2. ,0; the >reen light will be lighted u# only

when both the 7ed and ellow LE,s are o!! as the result o! the $/$, o#eration.

1'.Insert 'an" !rom ,unctions230ro#rammin#23.oolean #alette

1(.Insert $r !rom ,unctions230ro#rammin#23.oolean #alette

1.Insert Time Delay !rom ,unctions230ro#rammin#23Timin# #alette. 3et thedelay to 0.s

14.Insert numeric constants !rom ,unctions 23 0ro#rammin#23'umeric #alette.

/!ter inserting the constant; right mouse clic on it.


32/33

In the =ormat and Precision ab; choose Binary. "lic O:.

1-.Insert the remainder o! the icons; which you ha&e used in the #re&ious e)ercises.

18.+se the o bac to the ,ront 0anel

20."lic the 7un button to run the I. he lights will stay green until the button is #ressed.


33/33

Exercise 4 – Improved $irconditioning Contro -chaengeexercise.

$b%ecti!e7ein!orce understanding o!

• analog in#ut

• analog out#ut

• sub I

• digital out#ut

0roblem

Build a Light Intensity Logger LV DAQ

Documents

Transcript of Build a Light Intensity Logger LV DAQ