Freeze the Dizz | Jameco Part No. 2161431
This project is based on a children‟s arcade game. Twenty LEDs are placed on a ring
and each takes turn to light up forming a rotating light spot. If a push-button switch is
pressed, the light spot freezes. If the light spot happens to land on the winning position,
a buzzer is triggered. The rotating speed is adjustable by a speed dial.
See a video demonstration here:
http://www.youtube.com/watch?v=3dcK2xYX3t4
You can learn basic building blocks of electronics circuit such as flip-flop (CD4013),
counter (CD 4017), one-shot and 555 oscillator with this project. You can see how they
are put together to achieve the circuit operations desired. You will test each individual parts
of the circuit to understand the roles of each IC and major components.
Experience Level: Intermediate | Time Required: 12-24 Hours
Kit Overview
Circuit Schematics
Circuit Operation
The circuit consists of the following major blocks: buzzer oscillator (U2B), clock
oscillator (U2A), two count-by-ten counters (U4, U5), alternating LED bank switches
(Q1, Q2, U3B), one-shot circuit (U3A) and LED drivers U6, U7, U8).
U2A (LM556 dual timers) is a 555 equivalent timer configured in the astable mode. The
frequency is adjusted by VR1.The output clock signal at U3 pin 5 is fed to pin 14 of U4
and U5 to run the CD4017 Decade Counters. Each counter‟s output bus Q0 through Q9
drives a bank of ten LEDs making them light up in sequence. The two counters U4 and
U5 operate in parallel. To form a single light spot with LED0 – LED19, one of the two
banks of LEDs will be suppressed. This is done by Q1 and Q2 each controlling a bank
and only one is allowed to turn on. Q1 and Q2 are controlled by U3B (CD4013 Dual
Flip-Flop). The Q-bar (pin 12) of U3B is connected to the Data input (pin 9) forming a
toggle flip-flop. When counter U4 completes one cycle of counting, a positive edge at
Cout (U4 pin 12) causes U3B outputs (pin 12 and 13) to toggle, switching the two LED
banks alternatively.
The outputs of counters U4 and U5 are delivered to U6, U7, and U8 (ULN2003
Darlington Array) to drive the 20 LEDs. The positioning of the LEDs is important. LED9
of U4 Q9 should be next to LED10 of U5 Q0 so that the light spot will run in sequence.
Each bank of LED takes one half of the ring driven by Q0 through Q9 of the counters. In
this configuration, you will notice that (for example) LED11 corresponding to U4 Q1 will
be directly opposite to LED1 of U5 Q1.
Even though the two counters are running in parallel, they may not count in sync as the
initial count during power up is uncontrollable. This is solved by sending the Cout pulse
of U5 at pin 12, through C6 and R16 (to shorten the pulse width) to reset U4 pin 15 so
that they will count in sync after the first reset pulse has arrived.
U3A is configured as a one-shot circuit. When SW1 is pressed, the Q output of U3A
flips to the high state. Through the delay action of R2 and C3, the flip-flop is cleared by
pin 4 after about 2 seconds. The one-shot pulse triggered by SW1 is delivered to U2A
pin 4 to stop the clock oscillator and the counting action of U4 and U5. The pulse also
lights up LED20 through U6 pin 7. Counting resumes when the pulse ends.
U2B is another 555 equivalent oscillator driving a piezo buzzer. Q3 acts as a logic
decision gate. To trigger a winning buzz, three criteria need to be established through
R8, R9 and R11. R8 signals that the one-shot circuit is triggered (SW1 pressed), R9
signals that the winning bank of LED is activated and R11 signals that the winning LED
is lit. Any other state will turn on Q3 and send a low signal to U3B pin 10 to suppress
the buzzer. The buzzer sound pitch is adjustable by trimmer resistor VR2.
The power is supplied by a wall power adapter that can provide 8 - 12V DC or AC.
Diode D1 protects the system against wrong power polarity and also serves as a
rectifier for AC power input. DC battery power of the same rating is also acceptable. The
LM78L05 voltage regulator provides +5V power supply to drive the electronics and
LEDs. The current consumption is very low with each LED consuming ~5mA and
~10mA for the buzzer. The total current consumption should not exceed 30mA at any
given time.
Required tools or supplies not included
Enclosure box
Low voltage signal wires
Wall power adapter, DC or AC 8 – 12V, 100mA (ex. Jameco part number 2100152)
Adhesive and fastener to secure components and circuit board
Soldering equipment
Digital Multimeter
Drill and hardware for enclosure box carpentry
Oscilloscope preferred.
Est. Time Required to Complete: 12 - 24 hours
Bill of material
Component
Quantity
Jameco
Part
Number
1
PIEZO BUZZER
1
2098523
2
SW1, Switch Push Button OFF (ON)
1
315432
3
Connector Power Male 3 Position
1
151590
4
PROTOTYPE BUILDER,4.5 INCH x3.3 INCH ,PCB
1
105137
5
U1, Standard Regulator 5V, 100mA
1
51182
78L05
6
D1, DIODE, 400V, 1A
1
35991
1N4004
7
VR1, POTENTIOMETER,1M,RV24AF-10-15R1B1M,LINEAR TAPER, 1/2 WATT,.335 INCH
1
255582
8
KNOB,1/4 INCH SHAFT,27.1MM,JK901C,BLACK/ALUMINUM,WITH SET SCREW
1
264955
9
VR2, POTENTIOMETER,100K OHM,3362P104LF,SINGLE TURN,.5 WATT,CERMET
1
254036
10
U2, IC,LM556N,DUAL TIMER,DIP-14
1
24328
LM556CN
11
U3, IC, CD4013, DIP-14
1
12677
CD4013
12
U4, U5, IC, CD4017, DIP-14
2
12749
CD4017
13
U6, U7, U8, Transistor Darlington NPN 50V 0.5A 16-Pin
PDIP
3
34278
ULN2003A
14
U2, U3 SOCKET, IC,14PIN
2
37197
15
U4 - U8 SOCKET, IC,16PIN
5
37402
16
Q1, Q2, TRANSISTOR,2N3906,PNP,GP
2
38375
2N3906
17
Q3, TRANSISTOR,2N3904,NPN,GP
1
38359
2N3904
18
LED0 - LED19, LED, Uni-Color Green
20
693901
19
LED20, LED, Uni-Color Red
1
2006730
20
C1, C2 CAP,RADIAL,100uF,50V,20%,85C
2
29962
21
C3, CAPACITOR,RADIAL,1UF,25V, 20%,85C
1
330431
22
C4, CAP,MONO,.22uF,50V,20%
1
25540
23
C5, C8, CAP,MONO,.1uF,50V,20%
2
25523
24
C6, CAP,MONO,.001uF,50V,20%
1
81517
25
C7, CAPACITOR,CERAMIC,DISC,.0022UF
1
1947386
26
C9, CAP,RADIAL,4.7uF,50V,20%,85C
1
31000
27
R1, R12, R14, R15, RESISTOR,CARBON FILM,47K
OHM,1/4 WATT,5%,
4
691260
28
R2, RESISTOR,CARBON FILM,2M OHM,1/4 WATT,5%
1
691649
29
R3, R4, R13, R16, RESISTOR,CARBON FILM,10K
OHM,1/4 WATT,5%
4
691104
30
R5 - R7,.RESISTOR,CARBON FILM,680 OHM,1/4
WATT,5%
3
690822
31
R8 - R11, RESISTOR,CARBON FILM,470K OHM,1/4
WATT,5%
4
691500
Manufacturer Part
Number
Component pin identification
Component
U1, 78L05,Voltage
Regulator
D1, 1N4004, Diode
U2, LM556, IC, Dual
Timer
U3, CD4013, IC, Dual
„D‟-Type Flip-Flip
Pin Identification
Schematic representation
U4, U5, IC, CD4017,
Decade Counter
U6, U7, U8, IC,
ULN2003, Darlington
Array
Q1, Q2, 2N3906,
PNP Transistor
Q3, 2N3904,NPN
Transistor
LED0 - LED19, Green
LED
LED20, Red LED
C1, C2, C3, C9,
Electrolytic Capacitor
C4 – C8, Capacitor
R1 – R15, Resistor,
0.25W
SW1, Push Button
Switch
Power Jack (center
positive)
VR1,
POTENTIOMETER
VR2, Trimmer
Resistor
PIEZO BUZZER
Resistor color codes (5% error tolerance)
Name
Value
Resistor color code
R1, R12, R14, R15
R2
R3, R4, R13, R16
R5, R6, R7
R8, R9, R10, R11
47K
2M
10K
680
470K
Yellow-Purple-Orange-Gold
Red-Black-Green-Gold
Brown-Black-Orange-Gold
Blue-Grey-Brown-Gold
Yellow-Purple-Yellow-Gold
Project Steps
Step 1: Enclosure box planning and construction
Objective: Enclosure box with components installed
A cookie gift box made from cellulose or plastic material is ideal for this project. It should
be about the size of a 12" pizza box. Plan the locations of the LED ring (LED0 –
LED19), SW1, LED20, VR1, power jack and the buzzer. Drill holes and attach
components. The winning location shown on the circuit schematic is LED13 connected
to U6 pin 7. With the LED ring installed, solder the anode (longer leads) of LED0 –
LED9 together forming the first bank to be connected to R6. Do the same for the second
bank LED10 – LED19 to be connected to R7. You might want to spray-paint the box
before installing the components. The circuit board can be screwed into two strips of
soft wood that are glued to the box interior.
Step 2: Component placement on circuit board
Objective: Place circuit board components
This is a component planning step without soldering. Insert all components on the circuit
board without soldering. Pay attentions to the signal flow of the circuit. The
recommended placement is to arrange the ICs in 3 rows. U6, U7, U8 are on the top row,
with their outputs (pin 10 - 16) close to the top edge of the board where some 20 wires
will go to the LED ring. Place U4, U5 (CD4017) on the center row with pin 1 facing U6,
U7, U8 (ULN2003). U2 (LM556) and U3 (CD4013) are placed at the bottom row with
transistors, resistor and capacitors near them. Run wires from the circuit board to the
power jack, VR1, SW1, buzzer, LED0 – LED19. Try to arrange the components so that
these external wires access the circuit board near the sides.
Some components may have a different size than the placement plan given below and
therefore may not be possible to have identical placement. It is important to place all
components before soldering to avoid time-consuming rework after soldering. Use
Scotch Tape to secure IC sockets and components to the circuit board if necessary.
Step 3: Circuit board wiring
Objective: Solder circuit board components and wires
Solder the components on the circuit board according to the wiring diagram below. It is
recommended to start with the top side signal wiring, then bottom side signals followed
by top side power ground and bottom side power ground wires. Pin 9 of U6, U7 and U8
are unconnected.
Pay attention to the pin configuration and polarity of Q1, Q2, Q3, U1, D1, C1, C2, C3,
and C9. Note that the components are mirrored left/right when viewed from the bottom
side.
Use the wiring plan as the reference. Do not use the prototype photos.
The kit might contain slightly different components.
Step 4: External component wiring
Objective: Solder all components and wires
This step completes all internal and external wiring of the circuit. The wiring diagram is
shown below. It is a good practice to label the external wires because you may need to
unconnected and re-connect some wires to locate problems. Wrong wiring may cause
damages to electronic components. Use the continuity test of DMM to check wiring.
Step 5: Project completion and testing
Objective: Final circuit testing and IC installation
There are many components and wirings in this project. Wiring errors may cause the
circuit behave in unexpected ways. Severe errors like shorting an IC pin to power or
ground may cause permanent damage to the component.
The Circuit Testing procedure outlined below is designed to detect errors and avoid
costly mistakes. Be sure to follow the test procedures in the order described.
Circuit Testing
All electrical construction and wiring should be completed before conducting circuit
testing. Completion of mechanical construction is not necessary.
Make sure that you follow the test procedures below in the order described. This is
essential to ensure that you have wired the components properly. It also minimizes the
risk of permanently destroying any IC due to improper construction or soldering. When
installing ICs to their sockets, pay attention to the polarity. Wrong installation may cause
permanent damage to the ICs.
Follow the test procedures in the order described
Test 1A: GND network continuity
The purpose of Tests 1A, 1B and 1C is to make sure that the soldering work of the
power supply network is good. This is done without installing any ICs on the sockets. Do
not insert U2 through U8. Do not apply any power to the circuit. Set your Digital
Multimeter (DMM) to beeping continuity test or resistance measurement. Pick a ground
signal, for example the negative pin of C1. Measure the continuity to every test-point
listed below to ensure that the resistance is less than a few Ohms. Refer to Figure 1 for
ICs and pin locations.
Test 1A: Test-points for GND network
continuity test. No power should be applied.
U1 GND pin
U2 pin 7
U3 pins 3, 5, 7, 8, 10
U4 pins 8, 13
U5 pins 8, 13,15
U6 pin 8
U7 pin 8
U8 pin 8
R1, C1, C2, C3, C4, C5, C7, C8
Power Jack
Piezo Buzzer
Figure 1. ICs and pin locations for Tests 1A, 1B, 1C and 1D.
Test 1B: +5V network continuity
This is the same as Test 1A but repeated for the +5V network. The following test points
should be connected:
Test 1B: Test-points for +5V network
continuity test. No power should be applied.
U1 VO pin
U2 pin 14
U3 pin 14
U4 pin 16
U5 pin 16
Q1, Q2 pin E
R5, R10, R12, R13, R15
SW1
Test 1C: IC output short-circuit
This is an important test ensure that no output pin of any IC is shorted to the power or
the ground network. This condition often causes large current to flow through the ICs
leading to permanent damages. Do not insert U2 through U8. Do not apply any power to
the circuit during this test. Set your DMM to beeping continuity test or resistance
measurement. Measure the resistance of an output pin at an IC socket to the ground.
The resistance should not be near zero. Otherwise you have a short circuit at the pin.
Repeat the same test from the IC outputs to the +5V power network.
Test 1C: Test-points for IC output pins. No
power should be applied. No pin should be
shorted to power (+5V) or ground.
U2 pins 5, 9
U3 pins 1, 2, 12, 13
U4, U5 pins 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12
U6, U7, U8 pins 10, 11, 12, 13, 14, 15, 16
Test 1D: IC sockets power supply
In this test, we want to make sure that power is properly reaching all IC sockets and
there is no short-circuit of the power supply network. Do not start this test if Tests 1A,
1B or 1C have not passed.
Disconnect power from the power jack. Do not install any ICs U2 through U8. Use a
DMM to measure the resistance between pin 14 and pin 7 of U2. It should be about 4K
Ohms. This is from the internal resistance of U1 (78L05). If this resistance is only
several Ohms, you have a power-ground short. Check your soldering work to locate the
problem. Do not power up the circuit when there is a power-ground short.
If all power network tests have passed, apply battery power 8 – 12VDC to the power
jack. Measure the voltage across the following pairs of power supply pins of the IC
sockets. The voltage should be 5.0V +/- 5%. Figure 2 shows the test setup. U6, U7 and
U8 do not have +5V power supply.
Measure the current consumption. It should be less than 5mA.
Do not install any IC into socket until Tests 1A, 1B, 1C and 1D all
passed. Doing so may cause IC damages. Check your soldering work.
Test 1D: Power supply of IC sockets
+5v
GND
U2 pin 14
U3 pin 14
U4 pin 16
U5 pin 16
U2 pin 7
U3 pin 7
U4 pin 8
U5 pin 8
Figure 2. Measuring power supply of IC sockets in Test 1D.
Test 2A: Buzzer oscillator
With Tests 1A, 1B, 1C and 1D, you have verified that the proper power supply has been
delivered to the IC sockets and there are no severe abnormal conditions of the power
supply. You are ready to energize the ICs. Tests 2A and 2B verify the two oscillators of
LM556.
Disconnect the power supply and insert U2 (LM556). Do not insert U3 through U8. Use
a “bypass lead” to connect between pin 7 (GND) and pin 12 (Q-bar) of U3 socket. A
scrap pin lead from a resistor or capacitor is ideal for this purpose. Use another bypass
lead to connect between pin 8 and pin 13 of U8 socket. This will turn on the buzzer
oscillator. The setup is shown in Figure 3.
Figure 3. Use two “bypass leads” to turn on the buzzer oscillator in Test 2A.
Now apply battery power to the power jack, you should be able to hear the buzz tone.
Adjust VR2 to change the buzz tone and sound volume to the desired level. A piezo
buzzer has resonance frequency ranges depending on its physical construction. You
will notice that certain frequencies near resonance produce louder sound output.
If the oscillator is not working, check VR2, R13, R14, C7, C8 and Q3. Also check the
voltage at pin 10 of U2. It should be near 5.0V for the buzzer oscillator to work. If it is
less than 3.0V, check the bypass leads, Q3, R8, R9, R10, R11 and R12.
Test 2B: Counter oscillator
In this test, we want to verify that the oscillator of U2A (LM556) is working. Disconnect
the power and install a bypass lead between pin 2 and pin 14 of U3 socket. Do not
install U3 through U8. The test setup is shown in Figure 4.
Check the waveform at pin 14 of the U4 socket with an oscilloscope. You should see a
square wave with 5Vp-p. Adjust VR1 to make sure that the oscillator frequency can
change between 3 to 150Hz. Check VR1, R15, C4 and C5 if the oscillator is not
working. Also check the voltage at U2 pin 4. It should be near 5.0V for the oscillator to
work. If it is less than 3.0V, check the bypass lead on U3 socket.
Check pin 14 of U5 socket. You should get identical signal since the two pins are
connected together.
Figure 4. Oscilloscope waveform of counter clock in Test 2B.
Test 2B without oscilloscope
Without an oscilloscope, you can measure the DC level of the clock signal. This can
give you some indication of the oscillator output although it is not as reliable as an
oscilloscope.
Disconnect the power and install a bypass lead between pin 2 and pin 14 of U3 socket.
Do not install U3 through U8. Use the test setup shown in Figure 4.
Dial VR1 to about half turn position and apply power. Measure the voltage at pin 14 of
U4 socket. It should be about 2.5V. If you reduce the resistance of VR1, the oscillator
should run at a higher frequency and higher duty cycle. This will increase the voltage
reading. If the voltage reading is constantly at a certain voltage and does not change
with VR1, the oscillator is not working.
Check VR1, R15, C4 and C5 if the oscillator is not working. Also check the voltage at
U2 pin 4. It should be near 5.0V for the oscillator to work. If it is less than 3.0V, check
the bypass lead. You should get identical reading at pin 14 of U5 socket since the two
pins are connected together.
Test 3: CD4017 counters
In this test, we want to verify the operations of the CD4017 counters U4 and U5.
Disconnect power supply and insert U4 and U5. Do not install U3, U6, U7 and U8.
Install a bypass lead between pin 2 and pin 14 of U3 socket.
Apply power and observe the waveforms at pin 14 and pin 1 of U4 with a two-channel
oscilloscope. You should see a 5Vp-p pulse at pin 1 for every ten clock cycles of pin 14,
as shown in Figure 5. Repeat the measurement for the following signals of the counter
pins: 1, 2, 3, 4, 5, 6, 7, 9, 10, and 11. Pin 12 of U4 is the Carry Out pin. It is at logic high
for the first half of the courting cycle and goes to low at the second half. The test setup
and the observed waveform are shown in Figure 5.
If the counter is not working, check if pin 14 is receiving the proper clock signal. Also
check that pin 13 and pin 15 is near 0V to enable the counter.
Repeat the same test for the corresponding signal pins of U5.
Figure 5. Counter outputs and Carry Out signals.
The sync pulse at pin 15 U4 occurs when the Carry Out (pin 12) of U5 goes from low to
high. At that time, C6 and R16 generate a positive pulse of about 1us to reset U4 to
zero count so that U4 and U5 will synchronize their counting. The pulse occurs once
every ten clock cycles. The waveform is shown in Figure 6.The pulse is very narrow
(about 1us) compared to the clock cycle (about 10ms). Use the highest clock frequency
by dialing VR1 to the lowest resistance.
Figure 6. Counter sync pulse at U4 pin 15.
Test 3 without oscilloscope
Disconnect power supply and insert U4 and U5, CD4017. Do not install U3, U6, U7 and
U8. Install a bypass lead between pin 2 and pin 14 U3 socket. The test setup is shown
in Figure 5.
Dial VR1 to the highest resistance for the lowest counting speed. Apply power and
measure the voltage at pin 1 of U4. Since the positive pulse only appears once every
ten clock cycle, the DMM will read near zero voltage when there is no pulse and near
5V when there is a pulse. However, many DMM voltage reading cannot response fast
enough to a short pulse and the voltage reading may not go up to 5V. If you see a
rhythmic rise and fall of the voltage reading with the low voltage near zero, the counter
is probably working. If you dial VR1 to the fastest counting speed, the voltage value
should stabilize at 0.5VDC. If the voltage value is jumping and difficult to read, you can
put a large capacitor (for example, 1uF) across the two DMM probes to try to get a
sable reading.
Repeat the measurement for the following signals of the counter pins: 1, 2, 3, 4, 5, 6, 7,
9, 10, and 11. For pin 12 (Carry Out) of U4, the voltage reading should be about 2.5V.
If the counter is not working, check that U4 pin 14 is not constantly stuck at 0V or 5V.
Also check that pin 13 and pin 15 are near 0V to enable the counter.
Repeat the same test for the corresponding signal pins of U5.
The sync pulse at U4 pin 15 is too short and cannot be checked with a DMM. The DC
voltage level is near zero when measured with a DMM.
Test 4: Counters and LED drivers ULN2003
This test checks that the counting pulses at U4 and U5 are driving LED0 – LED19
properly.
Disconnect power supply and insert U6, U7, and U8 (ULN2003). U3 is the only IC not
installed in this test. Three bypass leads will be needed on the U3 socket between pin
pairs (2, 14), (5, 13) and (8, 12). The bypass (2, 14) turns on the counter oscillator. The
other two bypasses turn on both Q1 and Q2 so that the light spot of both counters are
visible simultaneously. The test setup is shown in Figure 7.
Figure 7. Testing counters and LED drivers in Test 4.
Apply power and you should see two LED light spots running in sequence, one from
each counter. Check the counting sequence of the LEDs to make sure that you have
soldered the wiring properly. Vary VR1 to adjust counting speed.
Test 5: Complete system test
Disconnect power supply and install U3. You should now have all ICs installed. Apply
power and you should see only one LED light spot with each bank of LED taking turns
to turn on. This gives the illusion of only one rotating light spot on LED0 – LED19 even
though the two counters are working simultaneously. If you still see two light spots,
check Q1, Q2, R3 and R4.
If you press SW1, the light spot should stop for about 2 seconds and then resume
running. If counting is not stopped, check SW1, R1, R2 and C3. LED20 should be lit
when the counting is momentarily stopped. If not, check R5 and the signal path from U3
pin 1 to U6 pin 10. If the light spot stopped but resume counting too quickly, you might
have the polarity of C3 reversed or wrong value of R2.
Dial VR1 to the lowest speed. Verify that if the light spot lands on the wining position, it
will trigger the buzzer. Verify that all other positions will not trigger the buzzer.
If you concluded this test, you have completed the electronic construction of the project.
Figure 8. All wiring completed and ICs installed.
Summary of test procedures
Test procedures
1A: Continuity test
of GND network.
No power supply.
Test
setup
Fig. 1
Test points
Passing criteria
U1 GND pin
U2 pin 7
U3 pins 3, 5, 7, 8, 10
U4 pins 8, 13
U5 pins 8, 13,15
U6 pin 8
U7 pin 8
U8 pin 8
R1, C1, C2, C3, C4, C5,
C7, C8
Power Jack
Piezo Buzzer
All test-points should be
connected and have near zero
resistance.
1B: Continuity test
of +5V network. No
power supply.
Fig. 1
U1 VO pin
U2 pin 14
U3 pin 14
U4 pin 16
U5 pin 16
Q1, Q2 pin E
R5, R10, R12, R13, R15
SW1
All test-points should be
connected and have near zero
resistance.
Test 1C: IC output
pins shorted to
power or ground.
No power supply.
Fig. 1
U2 pins 5, 9
U3 pins 1, 2, 12, 13
U4, U5 pins 1, 2, 3, 4, 5,
6, 7, 9, 10, 11, 12
U6, U7, U8 pins 10, 11,
12, 13, 14, 15, 16
All test-points should not have
near zero resistance to GND.
Test 1D: IC socket
power supply.
Fig. 2
U2 (pin 7, pin 14)
U3 (pin 7, pin 14)
U4 (pin 8, pin 16)
U5 (pin 8, pin 16)
No power-ground short circuit.
5.0V for all ICs power supply
pin pairs.
Test 2A: Buzzer
oscillator U2B
LM556.
Fig. 3
N/A
VR2 can adjust buzzer tone.
Test 2B: Clock
oscillator U2A
LM556.
Fig. 4
U4 pin 14
U5 pin 14
5Vp-p square wave at test
points, adjustable by VR1.
All test-points should not have
near zero resistance to +5V.
Test 2B without
oscilloscope.
Fig. 4
U4 pin 14
U5 pin 14
2.5VDC at test points,
increasing voltage with higher
frequency (smaller resistance
at VR1).
No 0V or 5V constant voltage
at test points.
Test 3: CD4017
counters U4, U5.
Test 3 without
oscilloscope.
Test 4: Counters
and LED drivers
ULN2003.
Fig. 5, 6
Fig. 5
Fig. 7
U4 pins 1, 2, 3, 4, 5, 6, 7,
9, 10, 11, 12, 15.
U5 pins 1, 2, 3, 4, 5, 6, 7,
9, 10, 11, 12.
U4 pins 1, 2, 3, 4, 5, 6, 7,
9, 10, 11, 12.
U5 pins 1, 2, 3, 4, 5, 6, 7,
9, 10, 11, 12.
N/A
Positive pulse for every 10
clock cycles at Q0 – Q9 output
pins of U4 and U5.
Logic high for first 5 counts at
Carry Out (pin 12) of U4 and
U5. Logic low for the remaining
counts.
1us pulse at U4 Reset (pin 15).

0.5VDC at each Q0 – Q9
output pins.
2.5V DC at Carry Out pins.
Two LED light spots, one for
LED0 – LED9, another one for
LED10 – LED19.
VR1 can adjust LED light spot
speed.
Test 5: Complete
system test.
N/A
N/A
Only one LED light spot.
SW1 can stop the light spot
and resume.
Winning position can trigger
buzzer.
Non-winning positions cannot
trigger buzzer.