copyright © 2015 by stephen a. zajac & gregory m. wierzba ... · microcontroller. the output...

Copyright © 2015 by Stephen A. Zajac & Gregory M. Wierzba. All rights reserved..Spring 2015. 1

ECE 480L: SENIOR DESIGN SCHEDULED LAB

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING

MICHIGAN STATE UNIVERSITY ________________________________________________________________

I. TITLE: Lab I: Digital Color Organ - Power Supply and LED Outputs

II. PURPOSE AND PROCEDURES:

A. Introduction

Over the next several labs we are going to build and test a Digital

Color Organ1. You are also going to try to improve on the

original design.

A color organ is an electronic device that divides sounds into several

frequency bands and modulates colored lights depending on the

frequency content of the sound or music.

Many color organs have been designed since the 1960's using analog

filters to divide incoming sounds into distinct bands2 of frequencies.

Silicon-controlled rectifiers (SCRs) were used to control line-voltage

colored incandescent lamps. This was not only dangerous but very

energy inefficient.

With the advent of microcontrollers, we can accomplish the same

functions with much less hardware and lower voltages. In addition, we

have the ability to reconfigure and tune our design after assembly.

This design does have analog circuitry to provide dc power and to

manipulate a microphone input and a stereo line-input. We also need

to do some overall analog filtering to limit the bandwidth to half the

sampling frequency of 16 kHz as required by the Nyquist criteria3.

The frequency selectivity is done with digital filters using a

microcontroller. The output powers a bank of LEDs.

B. Lab Organization (Please read carefully)

1C. A. Lindley, Psychedelia II: A Digital Color Organ, Nuts and Volts Magazine,

Vol.29, No. 1, January 2008.

2Similar to Lab VIII: Room Equalizer Design in ECE 203.

3See the ECE 202 text: Thomas, Rosa and Toussaint, The Analysis and Design of

Linear Circuits, Chapter 13.


1. In this series of experiments with the Digital Color Organ you will be

working alone. This is being done to help refresh your lab skills and

to prepare you for the capstone design experience. All work must be

done by you and only you. You will be asked to sign a Code of Ethics

Declaration for each Lab Report.

2. You need to stop by the ECE shop (Room 3234) during business hours

and sign out your own lab Storage Box. This Storage Box contains

tools, cables and most of the parts4 needed to build the Digital Color

Organ. This will be your box for the rest of the semester. Please write

your name on the box and take the box home for safe keeping. Bring

the box whenever you come to lab.

If you damage or loose any of the contents of the Storage Box,

you will be required to replace them (See the Bill of Materials for

ordering information or the ECE shop). At the end of this project you

will get to keep the Digital Color Organ and only need to return the

tools indicated in Section V: Parts Required.

3. When inside any of the ECE labs, you must wear eye protection. For

each instance of not wearing eye protection, your lab report

grade will be lowered by 1%.

4. In this lab there are references to the ECE 203 and 303 lab lecture

notes. If you did not take these courses at MSU, you can find videos of

these lab lecture notes at: http://www.egr.msu.edu/~wierzba/ .

C. Bound Lab Notebook and Lab Reports (Please read carefully)

1. In this lab and the upcoming labs, you will be asked many questions

and you will be asked to measure or calculate many things. You must

record your responses and results in your own personal Bound

Lab Notebook. This is done to make sure things are working

correctly and to help you understand how the Digital Color Organ

works. The Bound Lab Notebook is a good place to record design ideas.

2. If the lab asks you to record something in the Lab Report, then you

will find a place for this in the Lab Report Template at the end of each

lab. The emphasis in grading this part of the course is on the final

results and not the steps leading up to it, so weekly lab reports will be

short.

III. BACKGROUND MATERIAL:

See Lab Lecture Notes.

4Some parts were changed from the original article due to availability.


IV. EQUIPMENT REQUIRED:

1 Your own personal Bound Lab Notebook

1 Agilent Infiniium DSO-9064A Digital Storage Oscilloscope

1 Agilent 34401A Digital Multimeter

1 Agilent E3611A Power Supply

1 Extech LCR Meter

4 Agilent N2873A 10:1 Miniature Passive Probes V. PARTS REQUIRED: ECE 480L Storage Box (Tolerances 10% or better)

3 Solderless Breadboard strips

1 Bundle of coated hook up wire

10 Female-Male 6" jumper wires

1 3 ft. Stereo 3.5 mm/1/8” Male-Male audio cable

1 USB cable

W1 Wall Wart (9 V, 300 mA)

C1,C4,C5,C6,C8 4.7 μF capacitor Polarized

C2,C13,C15 0.1 μF capacitor

C3 240 pf capacitor

C7,C10 0.022 μF capacitor

C9 0.01 μF capacitor

C11 0.047 μF capacitor

C12,C14,C16 47 μF capacitor Polarized

R1 4.7K resistor 1/4W

R2,R6-R8,R13,R14 1K resistor 1/4W

R3,R4,R9,R10 20K resistor 1/4W

R5 1 meg trimmer (thumb wheel)

R11,R12 1.6K resistor 1/4W

R15 330 ohm resistor 1/4W

R16,R18,R20,R22 470 ohm resistor 1/4W

R17, R23 22 ohm resistor 1W

R19, R21 18 ohm resistor 1W

D1 1N5819 diode

D2,D27-D34 Orange LED

D3-D10 Red LED

D11-D18 Yellow LED

D19-D26 Green LED

J1 Stereo 1/8” jack male connector

J2 Wall Wart barrel type connector

M1 Electret condenser microphone

Q1-Q4 TIP31A switching/power transistor

SW1 Breadboard SPDT Mic/line switch

SW2 Breadboard SPDT Power off/on switch

U1 LM324 Quad op-amp

U2 LM2940CT 5 V, 1 A voltage regulator

U3 LM3940IT 3.3 V, 1 A voltage regulator

U4 MSP430 LaunchPad with MSP430G255


Tools included that are to be returned at the end of the semester:

1 Needle-nose pliers

1 Wire stripper

1 Flat-head screw driver

1 Side cutters

1 BNC-to-Banana adapter

8 Banana-to-grabber wires

VI. LABORATORY PROCEDURE:

A) Agilent (HP) 34401A Digital Multimeter

1. Check the contents of your Storage Box against the Parts Required in

Section V. The color code for resistors and the code for capacitors can

be found in the ECE 203 Lab I and Lab III lecture notes, respectively.

(One simple way to remember the resistor color code is by constructing

a short sentence with the first letters of each color. For example, “Big

Brown Rabbits Often Yield Great Big Vocal Groans When Gingerly

Slapped,” which might be an easy way to remember Black 0, Brown 1,

Red 2, Orange 3, Yellow 4, Green 5, Blue 6, Violet 7, Gray 8, White 9,

Gold 5%, and Silver 10%.)

The MSP430 LaunchPad has a CMOS microcontroller on it and can be

damaged by handling. Only touch the LauchPad by picking it up by

the outside edges of the printed circuit board. Keep the LauchPad in

the anti-static bag when not in use.

If any of the contents of your Storage Box is missing, see the technical

staff in the ECE shop (Room 3234) for replacement. They will only

replace missing parts the first week of lab.

2. The Agilent 34401A shown in Fig. 1 is a 6½ digit, six function,

autoranging precision multimeter and is usually referred to as a DMM

(Digital MultiMeter). The measurement functions are DC and AC

Voltage, 2-Wire and 4-Wire Resistance, Frequency and DC and AC

current.

You will need two pairs of red and black banana-to-grabber wires. One

such wire is shown in Fig. 2 and these can be found in your Storage

Box. Connect a red banana-to-grabber wire to the HI Input and a black

banana-to-grabber wire to the LO Input terminals on the right side. (It

is common in electronics to use red wires for positive and black wires

for negative.)

Press the POWER push button located in the lower left corner. Press

the Ω 2W (2-wire resistance) button.


Figure 1. Agilent 34401A Digital Multimeter

Figure 2. Banana-to-grabber wire

3. Measure all the resistors in your Storage Box greater than 50 Ω by

connecting the grabber clip to each end of the resistor. The last digits

may drift due to the “aging” of the resistor. If your values are very

unstable it may be due to a high contact resistance between the

grabbers and the wire of the resistor. This is caused by oxidation of

the metal grabbers. One quick way to clean the contact is to hold the

resistor firm and rotate each grabber clip. Try not to bend the wire.

4. The Resistance Accuracy specifications for the DMM that are given in

the ECE 203 Lab I lecture notes are for the Fluke 8840A DMM used in

the ECE 203 lab. Your Agilent DMM is more accurate. It is 6½ digit

with an accuracy of ± [0.0020% of the reading + 5 digits]. Re-doing the

example from ECE 203, suppose that you read a resistance of R = 1 3 . 3 4 1 3 0 kΩ

Then

(0.000020)(13.34130 k) = 0.000266826 k

+ 5 digits = 00.00005 k

______________________________________________

Accuracy = ±0.000316826 k


Thus your actual value of resistance is between

13.34130 k - 0.000316826 k = 13.34098317 kΩ

and

13.34130 k + 0.000316826 k = 13.34161683 kΩ

What this means is that you can trust the first four digits of the DMM.

5. Connect the second pair of banana-to-grabber wires to the HI and LO

Ω 4W Sense (4-wire) terminals to measure any resistors less than 50

Ω. (Put all measurements in your personal Bound Lab Notebook.)

Connect the resistor as shown in the ECE 203 Lab I lecture notes on

page 6. Measure the resistance in the Ω 2W mode. Invoke the Ω 4W

mode by using the blue shift button. Measure the resistance. From

this data, you can calculate the resistance of the wires and grabber

clips. This should be less than 100 mΩ. If not follow the procedure in

Section VI-A-2 for reducing contact resistance.

B) Extech LCR Meter

1. The Extech LCR meter shown in Fig. 3 is a device that measures AC

Impedance at two frequencies, 120 Hz and 1 kHz. Turn ON the LCR

meter by pressing the power switch button (ɸ) found in the upper left

corner. If necessary, press the L/C/R button until a Capacitance screen

is displayed. (The turn on screen is the last one used.)

2. The LCR meter has a spring clip fixture that allows the insertion of

component leads. The frequency is displayed in the upper right corner

and is changed by pressing the FREQ button. Set to 120 Hz.

Figure 3. Extech LCR meter

3. The accuracy of the LCR meter is ± [0.7% of the reading + 3 digits].


Pick one capacitor and measure it. Using the explanation in Section

VI-A-3, can you predict the number of trustworthy digits? (Put all

calculations in your personal Bound Lab Notebook.)

4. Measure the remaining capacitors in your Storage Box. Note the

polarity markings on the LCR meter for measuring polarized

capacitors. Check that all of your capacitors are within tolerance.

Replace any capacitors that are out-of-tolerance from either the Parts’

Cabinet or the ECE shop.

5. Turn OFF the meter when finished.

C) Agilent E3611A Power Supply

1. We will be using a wall wart to power the Digital Color Organ, but

before we do this we are going to use the Agilent E3611A power

supply shown in Fig. 4. This power supply has an adjustable voltage

and an adjustable current. We are going to set the maximum current

low enough so that if we make a wiring error or if we have a

component failure, we don’t melt our Solderless Breadboard.

Figure 4. Agilent E3611A Power Supply

With no external connections to the three terminals in the lower right,

turn ON the power supply by depressing the button in the lower left

corner. If necessary, set the Range button to the 1.5 A position. There

are two knobs on each supply. The right knob marked Current controls

the maximum magnitude of current available. On this range you can

have a maximum current of 1.5A and a maximum voltage of 20 V. (On

the .85 A range, the maximum voltage is 35 V. For either setting there

is about 30 Watts max). The left knob marked Voltage allows the user

to set a desired voltage magnitude. Turn this knob and observe. Set

the magnitude of the supply to approximately 9 V.

2. Since 1.5 A of current is large enough to melt our Solderless

Breadboard, let's set the maximum current limit much smaller. To set

the maximum current limit, press and hold the CC Set. Rotate the

current control to .05 A.


Note: If your circuit ever tries to draw more than 50 mA of current

then the voltage will collapse, that is, it will drop to a much

lower value in voltage than what is set by the voltage control.

Do not try to increase the current control setting, unless

instructed to do so, because something is seriously wrong.

Increasing the current control may melt the Solderless

Breadboard. Find your error and fix.

3. This is a floating power supply. To make the supply a positive voltage

with respect to ground, we need to connect a wire from the - terminal

to the terminal labeled with a ground (⊥) symbol. To do this, unscrew

the - and ground (⊥) terminals. Strip a piece of wire on both ends and

insert from the top. Screw both terminals being careful not to tighten

down on the insulation. You should be tightening only the bare wire.

4. Turn OFF the power supply.

D) Digital Color Organ Power Supplies

The Power Supply Section of the Digital Color Organ is shown in Fig.

5. It has three voltages used to power different parts of the Digital

Color Organ. A wall wart will be connected to J2 to supply power.

A wall wart consists of a step-down transformer with full-wave

rectification and a smoothing filter capacitor. We built this type of

circuit in Lab IV of ECE 303 and added a load resistor. As we saw in

ECE 303, the average value of the output voltage decreased as the

load resistance decreased (or the load current increased). The wall

wart for this project is listed as 9 V @ 300 mA. This means that the

output voltage of the wall wart is approximately an average of 9 V

when there is a load current of 300 mA. This would be the effect of

connecting a load resistance of 9/.3 = 30 Ω. What is not known is the

peak-to-peak ripple voltage, vr ,which will cause the minimum output

voltage to be 9 - vr /2 volts. This minimum output voltage needs to be

big enough to run the linear voltage regulator, U2.

Figure 5. Power Supply Section


We will use the Agilent E3611A power supply in place of the wall wart

for now so that we can protect our Solderless Breadboards and

circuitry. The Agilent power supply is very well regulated and will not

have any noticeable ripple.

1. The Solderless Breadboard strips used for this project are the same

ones that formed the larger Proto-Board we used in ECE 203 and 303.

See the ECE 203 Lab II lecture notes, if you need to review the layout

of the holes. Each strip has 63 rows of holes. We want to fit the circuit

for this lab on about 1/2 of one Solderless Breadboard strip.

2. Obtain the data sheets of linear regulator ICs U2 and U3 by searching

the Texas Instruments web site: www.ti.com and find the front

view pin out of the TO-220 package. Note that the metal tab is

connected to the center pin. Make sure that this doesn’t touch any

other metal surface.

3. Build the circuit in Fig. 5 with J2 ONLY to the extreme left as shown

in Fig. 6 and try to use roughly 30 rows or less of the Solderless

Breadboard strips. Do not wire J2 at this time. To help you, here

are some tips:

a. We want to use the SPDT switch SW2 as just an on/off switch. It has

three terminals, using the ohmmeter figure out which 2 of the 3

terminals you need to use. The switch should fit directly into the

breadboard. Position the switch in the block of rows just below the

channel where J2 is connected. Leave enough room for your finger.

Figure 6. Breadboard with J2

b. If you need to connect holes that are close, strip the coating off the


coated wire with the wire strippers and the pair of pliers. Use this

bare wire to connect these nearby holes. Check to see that these

jumpers are not touching any other metal objects.

c. As shown in Fig. 7, mounting resistors or diodes vertically instead of

horizontally can save a lot of space.

Figure 7. Mounting a resistor vertically

d. LEDs have the n-side shorter than the p-side. Also the lens usually

has a flat or notched side indicating the n-side of the LED.

4. Please check over all of your connections again before doing the next

step. If power is applied incorrectly, component damage can occur.

5. Using the grabbers, connect the E3611A power supply to the left-side

of SW2 in Fig. 5 in place of the wall wart. Turn ON the power supply.

If necessary turn ON switch SW2 and the orange LED should be on.

If your power supply voltage drops from its initial setting, there

is something seriously wrong. Turn OFF the power supply. Look for

a wiring error and fix.

E) Agilent Infiniium DSO-9064A Digital Storage Oscilloscope

The Agilent Infiniium DSO-9064A Digital Storage Oscilloscope, shown

in Fig. 8, is the next generation of Infiniium oscilloscopes from the one

we used in ECE 203 and 303. In addition, this scope has four analog

scope channels and a touchscreen display.

Figure 8. Agilent Infiniium DSO-9064A Digital Storage Oscilloscope


1. Turn ON the Infiniium by pressing the button in the lower-left corner.

Use the KVM Switch located behind your left computer monitor to

switch the keyboard and mouse to the Infiniium. Use your EGR login.

2. The Infiniium should have four Agilent N2873A 10:1 passive probes

connected to it. If not, carefully reconnect them by rotating the collar

clockwise and gently pushing. Press the Default Setup button to

clear the settings of the last user.

For this lab and all of the following labs we will always use the probes.

The probes are somewhat fragile, so do not remove these probes from

the scope when you are finished with the lab.

Please take a few minutes and familiarize yourself with this scope. A

good place to start is to see if the probes are compensated properly.

3. Connect one probe up to the calibration hook at the bottom left of the

scope face and connect the probe ground clip to the ground tab. Do

not use auto scale! Start out by pressing the Default Setup button.

Adjust the horizontal (x-axis) scale until you see a square wave. Next,

adjust the vertical (y-axis) scale for the channel you are using until

the signal is maximized on the screen without clipping.

[One way to fix high-frequency noise is to lower the bandwidth of the

scope. You can find this by clicking on or touching the number of the

channel you have connected your probe to on the top of the scope

screen. A dialog box should appear. Click or touch the HW BW Limit

(20 MHz) box. Close the dialog box.]

You should also pick the triggering for the channel that you are using

in the grouping labeled Trigger and rotate the Level knob to intersect

the trigger with your waveform.

4. To further clean up any noise you can use averaging. To activate

averaging, move the mouse pointer to the menu bar on top and find

Setup. Under this find Acquisition in the pull down menu. Click on this

and find Averaging in the resulting dialog box. Click on the box next to

Enable. Set the # of Averages to 16, by clicking on the up or down

arrow until you find this value. Your waveform should now appear to

be smoother than before. Close the dialog box.

You should now see a square-wave at approximately 810 Hz and 1

Vpeak. These probes need a special tool for adjustment. If there is a

problem only the ECE shop can re-compensate your probes.

5. The probes tend to pull parts out of the breadboard. So strip the ends

off of some coated wire and place one end of each wire in each of the 4


non-grounded nodes in Fig. 5. Connect the 4 scope probe tips to these

wires. Connect the alligator ground clips to the ground strip on the

breadboard likewise using coated wires with stripped ends.

6. Press Default Setup. Do not use auto scale! Adjust the time-base

to display 10 msec/div. Adjust all four volts/div scales to the same

value, and align the reference grounds for the 4 measured voltages to

the same level. All four reference grounds should be visible on

the scope.

7. We next want to measure the average (dc) voltage for each probe. By

holding the mouse cursor over the Toolbar icons on the left-side of the

screen, you can see what the icons measure. Find the V average icon

and select by right-clicking the mouse or by touching the icon on the

screen. Pick the appropriate Channel for that probe and select Entire

Display. Click or touch Ok. Repeat for the remaining probes.

Are the values consistent with what you expect? (Answer all questions

in your personal Bound Lab Notebook.) If not, look for a wiring error

and fix.

Make a hard copy of the screen (select invert waveform colors)

including the average measurements. Since we are printing in black

and white, you will need to mark which node is which on your

printout.

Mark this section letter and number on the plot. Give the plot an

appropriate title. Attach as indicated in the Lab Report.

8. Turn OFF the power supply and connect the two 22 Ω resistors in

parallel from your Storage Box at the output of the 3.3 volt regulator

(node 4). Calculate the total current in the parallel combination. (Put

all calculations in your personal Bound Lab Notebook.)

9. Turn ON the power supply and observe what has happened to the

values of the node voltages from Section VI-E-8. Does this make sense

with what you calculated in Section VI-E-9? (Answer all questions in

your personal Bound Lab Notebook.)

10. What value should you reset your current limit to on the E3611A

power supply? (Answer all questions in your personal Bound Lab

Notebook.) Disconnect the power supply and re-adjust the current to

20% more than you need.

11. Reconnect the power supply and observe what has happened to the

values of the node voltages from Section VI-E-5. Does this make sense

given the data sheets of the voltage regulators? Which plot in the data

sheet helps explain what just happened? (Answer all questions in your

personal Bound Lab Notebook.)


12. Please do not touch the 22 Ω resistors because they may be very hot.

Knowing the average voltage across each resistor, calculate the power

dissipated. Is it less than the 1-Watt rating? (Answer all questions in

your personal Bound Lab Notebook.)

13. Turn OFF SW2 and turn OFF the power supply. Disconnect the

wires from the power supply.

F) Wall Wart

1. Locate the wall wart (a rectangular box with wall outlet prongs) in

your lab Storage Box. Remove the connector J2 from the Solderless

Breadboard. The connector has three terminals. Carefully plug the

wall wart into the wall socket on the lab bench and insert the other

end into the wall wart connector J2.

2. We need to figure out which terminal is positive and which is

negative. We will use the Agilent DMM. Change scales to read dc

voltage by pressing the DC V button. Connect the positive terminal to

one pin of the wall wart connector and the negative terminal to

another pin of the wall wart connector. Do you read a positive voltage

greater than 9 V? If so you have found the + and - terminal of the wall

wart connector. If not, try another combination. Be careful not to short

wires or connections. Make a sketch of this in your personal Bound

Lab Notebook.

Disconnect the wall wart from the wall wart connector J2. Unplug

the wall wart from the wall outlet socket.

3. Put the wall wart connector J2 back into the breadboard as shown in

Fig. 6.

Using your sketch, wire the connector into the breadboard with the

negative terminal connected to ground and the positive terminal

connected to the left of SW2 in Fig. 5. Does this wiring make sense to

you? If not please ask the ECE 480 lab TA for help.

4. Double check that switch SW2 is OFF and that your Agilent power

supply is OFF and is totally disconnected from your

breadboard.

5. Plug the wall wart back into the outlet on your lab bench and connect

the wall wart to the connector J2. Turn ON switch SW2. The orange

LED should come on and you should see new waveforms on the scope.

6. Are the voltages on the scope consistent with what you expect?

(Answer all questions in your personal Bound Lab Notebook.) If not,

look for an error and fix.


7. Using the Measurement Toolbar, add a measurement to find the

voltage peak-to-peak at node 2 in Fig. 5. This is the ripple seen by our

power supply with a load. If you have troubles getting a stable trace,

try Line for your triggering. Adjust all four volts/div scales to the same

value, and align the reference grounds for the 4 measured voltages to

the same level. All four reference grounds should be visible on

the scope. (Include the 4 average voltage measurements)

Make a hard copy of the screen (select invert waveform colors)

including the Toolbar measurements. Since we are printing in black

and white, you will need to mark which node is which.



8. Look up the data sheet for D1 on the web. Can you explain what the

purpose of D1 is and why did the author choose this type of diode?

(Answer all questions in your personal Bound Lab Notebook.)

9. Turn OFF SW2, unplug the wall wart. Caution: the 22 Ω resistors in

parallel are very hot. Disconnect these resistors from your circuit

using a pair of pliers and let them cool down.

G) LED Bank of Lights

1. The LED bank of lights for the Digital Color Organ is shown in Fig. 9.

2. You will need one full Solderless Breadboard strip of the three that

you have to build this circuit. Only build the Red LED light bank at

this time. To help you here are some tips:

a. If you need to connect holes that are close, strip the coating off the

coated wire and use this bare wire to connect these nearby holes.

Check that these jumpers are not touching any other metal objects.

b. LEDs have the n-side shorter than the p-side. Also the lens usually

has a flat or notched side indicating the n-side of the LED.

c. Obtain the data sheet for the TIP31A on the web and find the front

view pin out of the TO-220 package. Note that the metal tab is

connected to the center pin. Make sure that this doesn’t touch any

other metal surface.

3. Again we want to be cautious and so let’s use the Agilent E3611A

power supply with the current limiter to make sure we protect our

circuit from damage.

Set the voltage to 9 V and the maximum current to 200 mA.


Figure 9. LED Bank of Lights


4. Using banana-to-grabber wires, connect the positive terminal of the

E3611A power supply to the 9 V arrow in Fig. 9. Connect the negative

terminal to ground. Turn ON the power supply.

If your power supply voltage drops from its initial setting, there

is something seriously wrong. Turn OFF the power supply. Look for

a wiring error and fix.

5. To test the Bank of Lights, we will need to connect the function

generator. There are two different models of function generators in the

ECE 480 lab. Steps 6 and 7 will explain some of the differences.

6. Agilent 33250A Function / Arbitrary Waveform Generator

a. If your lab bench has the 33250A generator, proceed to the next step.

If not, go to step 7).

b. The function generator’s setting for amplitude is defaulted to the case

where it is assumed that the function generator is connected to a 50 Ω

load.

We can reset the function generator’s default load of 50 Ω to a high

resistance load by using the Utility button located in the second row of

rectangular buttons. Press it and highlight Output Setup. Then select

High Z and Done. If we don’t do this our displayed voltage will be off

by a factor of two.

This resetting of the high resistance termination option will remain in

effect until we turn off the function generator. So please do not turn

off the function generator until instructed to do so.

7. Agilent (HP) 33120A Function Generator / Arbitrary Waveform

Generator

a. If your lab bench has the 33120A generator, proceed to the next step.

b. The function generator’s setting for amplitude is defaulted to the case

where it is assumed that the function generator is connected to a 50 Ω

load. We can reset the function generator’s default load of 50 Ω to a

high resistance load by entering into the SYStem MENU.

To set the calibration of the function generator’s amplitude to the high

resistance option, press the Blue Shift button, followed by pressing the

Enter button just above the Shift button. A: MOD MENU should

appear on the display. Pressing the > button once should cause B:

SWP MENU to appear. Pressing the > button again should cause C:

EDIT MENU to appear. Pressing the > button again should cause D:

SYS MENU to appear. We can go down into this menu by pressing the

V button which will cause 1: OUT TERM to appear. Pressing the V


button again will cause 50 OHM to appear. Pressing > will finally

cause HIGH Z to appear. To pick this option all we need to do is to

press the Enter button again. If we don’t do this our displayed voltage

will be off by a factor of two.

This resetting of the high resistance termination option will remain in

effect until we turn off the function generator. So please do not turn

off the function generator until instructed to do so.

8. Setup the function generator to output a 5 Vp-p, 100 Hz square-wave

with a dc offset of 2.5 V. Remember to set High Z. Use the scope to

verify that this is indeed the signal coming out of the function

generator.

9. Connect the positive terminal of the function generator to R16 and the

negative terminal to ground of Fig. 9. The Red LEDs should be on. The

E3611A power supply is displaying the average current supplied to

the Red LEDs for a 50% duty cycle.

On 2 channels of the scope display the two node voltages of the leads

of R17. Calculate the maximum difference and divide by the nominal

resistance value of R17. This is the peak current. How does this

compare to the average current for a 50% duty cycle read on the

E3611A?

10. Make a hard copy of the screen (select invert waveform colors)

including the peak-to-peak measurements. Since we are printing in

black and white, you will need to mark which waveform is which.



11. Lower the frequency to 1 Hz. How has the appearance of the Red

LEDs changed? Explain why.

Change the frequency back to 100 Hz.

12. Build the remaining three LED light banks (Yellow, Green, and

Orange), and test them as you did in step 9 to verify proper operation.

13. Disconnect the function generator from the Digital Color Organ.

14. Using your previous calculations, calculate the total average current

drawn by the LED Bank of Lights for a 50% duty cycle. What is the

total peak current?

15. Move the 9 V connection from the LED Bank of Lights to the left side

of SW2 in the Power Supply Section. Connect the LED Bank of Lights

to node 2 of your power supply. Turn switch SW2 ON, if necessary.


The E3611A power supply is now displaying the average current

supplied to the Power Supply Section and to the Analog Section of the

Digital Color Organ. This is our total current consumption for the

parts we have built.

H) Demonstration

1. Once you have finished the lab, call the lab TA over to grade your lab

report before you leave. There are also a few demonstrations that will

be required to show the functionality of your circuit; make sure that

you have these working before you call the TA.

2. Using the digital multimeter, measure the voltage at node 2, 3 and 4

of figure 5, that is, the voltage of the 9 V supply, the 5 V supply, and

the 3.3 V supply. Take this measurement with the two 22 Ω resistors

in parallel attached to simulate a full load.

3. Use the function generator to drive all four LED outputs at the same

time with a 1 Hz square wave. Measure the voltage across the power

resistor of one of the LED light banks using the oscilloscope.

I) Clean up

Do not remove the scope probes from the scope. Turn off all

equipment. Put all of your things back into your Storage Box and take

it home with you.

VII. ASSIGNMENT FOR NEXT LAB PERIOD

1. Listen to the next recorded lab lecture and read the Lab Procedure

portion of that experiment. There will be a quiz on this material at the

beginning of the next lab.


Lab Report

Lab I - Digital Color Organ - Power Supply and LED Outputs

Name: ..................................................................................................................

Date: ....................................................................................................................

Code of Ethics Declaration

All of the attached work was performed by me. I did not obtain any

information or data from any other student. I will not post any of my work on

the World Wide Web.

Signature .............................................................................................................


VI-E-7

Mark VI-E-7 on the top right side of your plot and attach as the next

page. Give the plot an appropriate title.

VI-F-7

Mark VI-F-7 on the top right side of your plot and attach after VI-E-7.

Give the plot an appropriate title.

VI-G-10

Mark VI-G-10 on the top right side of your plot and attach after VI-F-

7. Give the plot an appropriate title.

VI-H-2

Measured 9 V Supply: ____________________

Measured 5 V Supply: ____________________

Measured 3.3 V Supply: ____________________

Instructor Signoff: ____________________

VI-H-3

Instructor Signoff: ____________________

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