rbe2001 lab report

7/26/2019 RBE2001 Lab Report

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WORCESTERPOLYTECHNICINSTITUTE

ROBOTICSENGINEERINGPROGRAM

Introduction to Electronics

Date Submitted : 09/16/15

Date Completed : 09/12/15

Course Instructor : Prof

Putnam

!ab Section : "02

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Task 1: Voltage Division

Introduction

The purpose for this section of the lab is to explain how Ohms Law works via the experimental circuit

from the prelab. Our experiment consisted of two parts. The first part verified the correctness of the

voltage division rule in different values of voltage. The second part verified the rule for the same voltage

in three different configurations.

#et$odolo%&

Part 1

In this part, we built a circuit according to the design proposed: in series with three known resistors whilechanging voltage to three different values and measure current and voltage on each resistor see !ppendix

! for circuit diagrams".

Resistor 1 = 1 k-ohms, Resistor 2 = 2.2 k-ohms, Resistor 3 = 1.2 k-ohms

Figure 1: Configuration of circuit with resistors (chose randomly) with three scale of voltage (5,10,15 V)

Part 2

#or the second part, we built three different configurations $%resistors, &%resistors, and '%resistors in

series. !fter finishing the circuit see figures below", we measured the voltage in each resistor as well as

its current. This process could be done efficientl( b( planning out the structure beforehand see appendix

! for circuit diagrams".

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Resistor 1 = 5.6 k-ohms, Resistor 2 = 1.0 k-ohms, Resistor 3 = 0.910 k-ohms,

Resistor 4 = 2.2 k-ohms, Resistor 5 = 1.2 k-ohms

Figure 2: Configuration of circuit with 2 resistors in series

Figure : Configuration of circuit with resistors in series

Figure !: Configuration of circuit with 5 resistors in series

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'esult

Part 1

Applied

Voltage (V

Voltage o!

resistor 1(V

Voltage o!

resistor 2(V

Voltage o!

resistor 3(V

"otal

#eas$redVoltage (V

#eas$red

%$rre!t(mA

&o'er

issipated ()* e!tire +ir+$it

'.) *.*+ $.'' *.& '.)- *.*+ ).))'

*).) $.$' '.)& $.* . $.$ ).)$$

*'.) &.& .'+ +.) *+./ &.+* ).)'*$

Table 1. Experimental data from part 1

AppliedVoltage (V

&o'erissipated ()* Resistor 1



&o'erissipated ()*e!tire +ir+$it

#eas$red%$rre!t (mA

'.) ).))*&) ).))$* ).))*'- ).))' *.*+

*).) )))'** ).)**+ ).))-*' ).)$$ $.$

*'.) ).)**- ).)$' ).)*& ).)'*$ &.+*

Table 2. Power dissipated computation

P=I V

Power dissipated (total for5.0V)=0.00130+0.00291+0.00156=0.00577W

Part 2

ig Resistor 1V

(&o'erdissipated)

Resistor 2V

(&o'erdissipated)

Resistor 3V

(&o'erdissipated)

Resistor 4V

(&o'erdissipated)

Resistor 5V

(&o'erdissipated)

#eas$red%$rre!t

(A

AppliedVoltage

(V

&o'erissipated

() *e!tire+ir+$it

$ +.$/

).)))&&)

"

).-)

).)))'/-"

% % % ).)))* '.) ).)))*-

& &.

).))$'-"

).-)

).)))+'+"

).-))

).)))+)"

% % ).)))-/ '.) ).))&+$*

+ $.'/

).))*$)"

).+')

).)))$*)"

).+*)

).)))**"

*.)$

).)))+-

"

).''

).)))$'"

).)))+- '.) ).))*$'+

Table 3. Experimental data from part 2

P=I V

Power dissipated (total for Figure2 )=0.000330+0.000586=0.000916W

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Discussion

!s seen from the data obtained above, the value of power dissipated was consistent in resistors in series.

This could be verified b( the fact that 0total power dissipated1 was the same for the sum of power

dissipated in each resistor. !dditionall(, sum of all voltages in each resistor was e2ual to the total output

voltage. These two examples verified the validit( of voltage division rule.

Conclusion

The experiment successfull( verified the correctness of voltage division rule. The result of both parts of

this experiment proved that the sum of all voltages in each resistor in series" was e2ual to the output

voltage. !lso, the sum of dissipated power in each resistor in series" was e2ual to the total power

dissipated.

Task 2: Signal GenerationIntroduction

In this section, we used a signal generator to produce waveforms. It showed the peak voltage, peak%to%

peak voltage, fre2uenc(, and period of the waveform. This part demonstrates our understandings of the

use of apparatus and knowledge about signal and wave production.

#et$odolo%&

The output voltage of the function generator was set to '3, and its fre2uenc( was set to $)))45. This

configuration generated a signal waveform for the function

f(x )=5sin(4000t)

!fter that, the signal was shifted and the offset was raised to $.'. This configuration generated a signal

waveform for the function

g (x )=2.5 sin (4000t)

'esult

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Figure 5: "aveform for the function f(#)

Figure $: "aveform for the function g(#)

(/ (/

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pper-&eak (V '.) .'

o'er-&eak (V %'.) %$.'

&eak-to-peak (V *) *)

re$e!+ ( $.))) $.)))

&eriod (s ).)))' ).)))'

Table 3. Measurement for the two functions

Discussion

The measurement from the oscillator gave us more insight about the characteristics of the two functions.

These two functions had the same peak%to%peak value, fre2uenc( and period. 4owever, the function gx"

was shifted upward $.' units.

Conclusion

This lab successfull( showed us the use of a function generator coupled with an oscillator. 6uch devices

are essential in investigating the waveforms of various functions and in inspection of our later circuits.

Task 3: R ir!"it

Introduction

This experiment investigates the effect of a capacitor on a s2uare waveform.

#et$odolo%&

The following circuit was constructed with C=10F , and R=2000 . ! function generator was

connected to the circuit as Vs and generated a $45 waveform with a peak of '3 and a 78 offset of

$.'3. The voltage of the capacitor was measured and captured using an !rduino coupled with Lab3iew.

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Figure %: Circuit for this e#&eriment'

'esults

The measurement of the capacitors voltage (ielded a stable and smooth line of approximatel( $./3

Figure : easured voltage across the ca&acitor'

Discussion

In the result, it could be seen that there was a small bend at the end of the rising edge and another one at

the falling edge of the wave. These two bends characteri5ed the dela(s caused b( the capacitor. 9hen the

signal voltage went up at the rising edge, it took sometimes for the capacitor to charge until the potentialdifference between its two conductors became e2ual to the signal voltage. 9hen the signal voltage went

down at the falling edge, it took sometimes for the capacitor to discharge. To make the statement more

evident, below is the measured voltage for the same segment in the circuit without the capacitor.

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Figure *: easured voltage for the same segment in the circuit +ut without a ca&acitor

Conclusion

The experiment clearl( shows the how the capacitor affected how the voltage change over a period of

time. Its abilit( to charge and discharge created a dela( on the change of the voltage.

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Task 4: &'( Signal (eas"re)ent

Introduction

The purpose of this experiment is to observe how the 9; signal is used to control a motor and a servo.

#et$odolo%&

In this experiment, a 3ex ;otor ;odule was connected to the servo port 6 of an !rduino via a

breadboard. Two wires were plugged into the holes on the breadboard corresponding to the


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Figure 10: -" signal when o&erating the motor and servo using myservo.write(0).

Figure 11: -" signal when o&erating the motor and servo using myservo'write(10)'

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Discussion

The result showed that b( var(ing the dut( c(cle of a 9; signals, one can control the speed and

direction of a motor or the angle of the shaft of a servo. #or a motor, if the dut( c(cle is as low as $.-= or

below, the motor runs at full speed in one direction. If the dut( c(cle is increased to about *$=, the motor

runs at full speed in other direction. #or a servo, one can map the range of dut( c(cle from $.-= to *$="to its rotation range from ) degree to */) degree", and control the shaft rotation angle accordingl(.

Conclusion

#rom the experiment, one learns how 9; signal can be used to control a motor or a servo. #or a motor,

var(ing the dut( c(cle of a 9; signal changes its direction and speed. #or a servo, var(ing the dut(

c(cle of a 9; signal changes the position of its shaft.

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Task 5: D (otor &ara)eters

Introduction

The main purpose of this section of the lab is to stud( the behavior of 78 motor. 7ata of parameters such

as voltage and current are monitored at all time. This provided some insights and understanding about 78

motor. The experiment consisted of two parts. The first part investigated the amount of current drawn b( a

78 motor in two states: stall and no load. The second part showed a linear relation between applied

voltage and motor speed.

#et$odolo%&

Part 1

! *$%3 78 motor was connected to the power suppl(. The motor was then run at + different input voltagevalues ranging from -3 to *$3. #or each motor voltage, record the current of two states: motor running at

no load and running when stalled using hand".

Part 2

! 3ex 6haft >ncoder was attached to the motor via a shaft. The motor was then applied *) different input

voltage values ranging from $3 to *$3. To measure the speed of the motor, the encoder was connected to

an !rduino which was uploaded with the code in !ppendix !. !fter rotating the shaft ' complete rounds

for better accurac(", the !rduino would calculate and print the speed of the motor on the screen. >ach

value pair of voltage and motor speed was recorded to an >xcel file.

'esult

Part 1

Voltage 7!p$t (V %$rre!t (8o oad(A

Resista!+e (8ooad (

%$rre!t (:tall(A

Resista!+e(:tall (

-.) ).)$ &)) ).- /.-

/.) ).)$ +)) )./' .+*

*).) ).)$ ')) *.) .&'

*$.) ).)$ -)) *.$) *)Table 4. Measurement of current for different status of the DC motor and their correspondin resistance.

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Part 2

Voltage 12 11 10 9 8 7 6 5 4 3 2

RPM

19

6

17

7

15

9

14

7

12

5

11

2 94 79 63 47 29Table !. "oltae #alues applied to the DC motor and their correspondin speed.

) $ + - / *) *$ *+)

')

*))

*')

$))

$')

fx" ? *-.)&x@A ? *

3oltage 3"

6peed @;"

Figure 12: /ra&h of motor s&eed versus motor voltage and a linear leastsuares fit on the data &oints

Discussion

The result from part * showed that without load, the motor drawn the same amount of current regardless

of the applied voltage. On the other hand, when the motor was stalled, a larger amount of current was

drawn and this amount also increased linearl( proportional with the motor voltage. This linear

relationship could be observed b( seeing how the terminal resistance did not var( much with different

voltage values.

art $ demonstrated a positive linear relationship between motor voltage and speed. The data points fit

ver( well to the linear approximation, which was proved b( how close the value @$to *.).

Conclusion

The lab demonstrated three characteristics of a 78 motor. #irstl(, if there is no load applied, the motor

will draw a constant amount of current. 6econdl(, if there is load, it draws larger amount of current, which

is also linearl( proportional to the motor voltage. #inall(, there is a linear relationship between the motor

voltage and motor speed.

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A**en+i, B

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int Slot % 0;

&loat 'ound % 0;&loat time % 0&loat ptime % 0;int encoder % ;&loat '*+;

void setup() { pin+ode (encoder,-*!/*!!*);Serial.1e2in(9300);

}

void loop() {

he method &or &indin2 the speed o& the motor is countin2 the total slot inside the ve4 encoder that pass the led divide 1y total time. 5alculation is per&ormed a&ter $ rounds

&or 1etter accuracy.

while('ound < $) { oop until the wheel rotates throu2h 90 slotswhile (Slot < 90) {int sensor6alue % di2ital'ead(encoder);while (sensor6alue %% 0) {

sensor6alue % di2ital'ead(encoder); i& (sensor6alue %% ") { Slot77; 1rea8; }

}}

Slot % 0;'ound77;

} time % millis(); -um1er o& milliseconds since last reset time % time ptime; :et num1er o& milliseconds &or this loop time % time"00030; 5onvert to minute'*+ % 'oundtime;

Serial.print('*+ ); Serial.print('*+=5); Serial.print(?n);

ptime % millis(); Save the cumulative milliseconds to 1e su1tracted on ne4t loop 'ound % 0; Slot % 0;

rbe2001 lab report

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