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Introduction
History: how light learned to count people
Lesson 0. Gates from transistors: for those who start from scratch
0.1. The idea: a transistor is a switch
0.2. Building
0.3. Check
Lesson 0 paste (Cmd+I)
Lesson 1. The beam and CD4011
1.1. Idea: how a shop counts people
1.2. Idea: the CMOS 4000 series
1.3. Idea: NAND for everything
1.4. Build
1.5. Check
Lesson 1 paste (Cmd+I)
Lesson 2. The F/F flip-flop
2.1. Idea: a counter is flip-flops that flip
2.2. Idea: flipping through exclusive OR
2.3. Idea: a NAND with three inputs
2.4. Build
2.5. Check
Lesson 2 paste (Cmd+I)
Lesson 3. The CD4029B counter
3.1. Idea: which bit to flip
3.2. Idea: controlling the counter
3.3. Idea: the bubbles on the TI drawing
3.4. Build
3.5. Check
Lesson 3 paste (Cmd+I)
Lesson 4. The CD4511B decoder
4.1. Idea: seven strokes
4.2. Idea: latch, blanking, lamp test
4.3. Idea: a switch on two transistors
4.4. Build
4.5. Check
Lesson 4 paste (Cmd+I)
Lesson 5. Direction
5.1. Idea: two beams one after another
5.2. Idea: remember the first
5.3. Idea: the clock is when both are blocked
5.4. Build
5.5. Check
Lesson 5 paste (Cmd+I)
Lesson 6. The visitor counter
6.1. Idea: two displays on the same beams
6.2. Idea: two digits — two counters
6.3. Idea: Reset holds
6.4. Build
6.5. Check
Lesson 6 paste (Cmd+I)
Summary
All the parts
Instructions in pictures
Lesson 3 in pictures
← Back to the lesson: Lesson 3. The CD4029B counter
3
The CD4029 counter
up and down, binary and decade
kh
HT-04
CD4029
Q4
Q3
Q2
Q1
IN
16×
OUT
7×
P
7×
N
7×
NOT
27×
0
NAND
2×
0
FF4029
4×
2
NAND3
2×
2
AND
9×
0
NOR
7×
0
OR
2×
0
0
8×
Hz
1×
6×
∞
Ctrl
+
G
NOR3
NOR4
CD4029
© 2026 Daniil Khanin · khanin.info · HT-04
22
CANVAS
1
Delete
0
PE
0
J
0
TE
1Hz
CL
FF4029
PE
PE
J
J
TE
TE
CL
CL
Q
Q
QN
QN
CL
Q
QN
© 2026 Daniil Khanin · khanin.info · HT-04
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NOR3
2
IN
3×
OUT
1×
P
3×
9×
A
B
C
Y
VCC
p1
G
P
A
p1
p2
G
P
B
p2
Y
G
P
C
3
N
3×
9×
Y
GND
G
N
A
Y
GND
G
N
B
Y
GND
G
N
C
4
Ctrl
+
G
Library
…
Chip N
2×
Library
…
NOR3
Enter
NOR3
A
B
C
Y
© 2026 Daniil Khanin · khanin.info · HT-04
24
NOR4
5
IN
4×
OUT
1×
P
3×
9×
A
B
C
D
Y
VCC
p1
G
P
A
p1
p2
G
P
B
p2
p3
G
P
C
6
P
1×
N
2×
9×
p3
Y
G
P
D
Y
GND
G
N
A
Y
GND
G
N
B
© 2026 Daniil Khanin · khanin.info · HT-04
25
NOR4 …
CANVAS
7
N
2×
6×
Y
GND
G
N
C
Y
GND
G
N
D
8
Ctrl
+
G
Library
…
Chip N
2×
Library
…
NOR4
Enter
NOR4
A
B
C
D
Y
9
pin names as in the TI datasheet; a bar over a name in the picture = active 0, in the simulator without the bar
© 2026 Daniil Khanin · khanin.info · HT-04
26
CD4029
10
IN
9×
OUT
5×
PE
J4
J1
CI
BD
UD
J2
J3
CLOCK
Q4
Q1
CO
Q2
Q3
11
NOT
3×
0
6×
NOT
I0
BD
O0
nBD
NOT
I0
nBD
O0
A
NOT
I0
PE
O0
E
12
NOT
3×
0
6×
NOT
I0
CI
O0
nCI
NOT
I0
UD
O0
nUD
NOT
I0
nUD
O0
U
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
13
NOT
2×
0
NAND
1×
0
7×
NOT
I0
CLOCK
O0
nCLK
NAND
I0
E
I1
nCLK
O0
ncl
NOT
I0
ncl
O0
CL
14
NOT
3×
0
6×
NOT
I0
J1
O0
j1
NOT
I0
J2
O0
j2
NOT
I0
J3
O0
j3
15
NOT
1×
0
2×
NOT
I0
J4
O0
j4
16
FF4029
2×
2
12×
FF4029
PE
E
J
j1
TE
CI
CL
CL
Q
q1
QN
q1n
FF4029
PE
E
J
j2
TE
te2
CL
CL
Q
D
QN
J
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
17
FF4029
2×
2
12×
FF4029
PE
E
J
j3
TE
G
CL
CL
Q
B
QN
I
FF4029
PE
E
J
j4
TE
te4
CL
CL
Q
C
QN
q4n
18
NAND3
2×
2
NOT
1×
0
10×
NAND3
A
nCI
B
nUD
C
q1n
Y
nf
NOT
I0
nf
O0
F
NAND3
A
q1
B
nCI
C
U
Y
nl
19
NOT
1×
0
2×
NOT
I0
nl
O0
L
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
20
NOR4
1×
NOT
1×
0
7×
NOR4
A
A
B
B
C
C
D
D
Y
bout
NOT
I0
bout
O0
nbout
21
AND
2×
0
NAND
1×
0
9×
AND
I0
nbout
I1
F
O0
ta
NAND
I0
nBD
I1
C
O0
md
AND
I0
L
I1
md
O0
tb
22
NOR
1×
0
3×
NOR
I0
ta
I1
tb
O0
te2
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
23
NOR
1×
0
AND
2×
0
9×
NOR
I0
bout
I1
D
O0
te_
AND
I0
F
I1
te_
O0
tg
AND
I0
D
I1
L
O0
tf
24
NOR
1×
0
3×
NOR
I0
tg
I1
tf
O0
G
25
NOR
1×
0
NOT
1×
0
OR
1×
0
8×
NOR
I0
J
I1
I
O0
th
NOT
I0
md
O0
nmd
OR
I0
th
I1
nmd
O0
H
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
26
NOR
1×
0
AND
2×
0
9×
NOR
I0
D
I1
B
O0
tp
AND
I0
F
I1
tp
O0
tq
AND
I0
H
I1
L
O0
tr
27
NOR
1×
0
3×
NOR
I0
tq
I1
tr
O0
te4
28
NOR3
1×
AND
1×
0
NOT
1×
0
9×
NOR3
A
B
B
D
C
C
Y
tv
AND
I0
F
I1
tv
O0
tw
NOT
I0
A
O0
an
© 2026 Daniil Khanin · khanin.info · HT-04
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CD4029 …
29
OR
1×
0
AND
2×
0
9×
OR
I0
an
I1
th
O0
tt
AND
I0
C
I1
tt
O0
tu
AND
I0
L
I1
tu
O0
tx
30
NOR
1×
0
NOT
2×
0
7×
NOR
I0
tw
I1
tx
O0
co0
NOT
I0
co0
O0
co1
NOT
I0
co1
O0
CO
31
NOT
3×
0
6×
NOT
I0
q1
O0
o1
NOT
I0
o1
O0
Q1
NOT
I0
D
O0
o2
32
NOT
3×
0
6×
NOT
I0
o2
O0
Q2
NOT
I0
B
O0
o3
NOT
I0
o3
O0
Q3
© 2026 Daniil Khanin · khanin.info · HT-04
33
CD4029 …
CANVAS
33
NOT
2×
0
4×
NOT
I0
C
O0
o4
NOT
I0
o4
O0
Q4
34
Ctrl
+
G
Library
…
Chip N
2×
Library
…
CD4029
Enter
CD4029
PE
J4
J1
CI
BD
UD
J2
J3
CLOCK
Q4
Q1
CO
Q2
Q3
35
1
1Hz
2Hz
10Hz
60Hz
4kHz
…
MAX
36
0
5×
5×
0
PE
0
J1
0
J2
0
J3
0
J4
37
0
3×
Hz
1×
4×
0
CI
0
BD
0
UD
1Hz
CLOCK
© 2026 Daniil Khanin · khanin.info · HT-04
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CANVAS …
38
CD4029
1×
14×
CD4029
PE
PE
J4
J4
J1
J1
CI
CI
BD
BD
UD
UD
J2
J2
J3
J3
CLOCK
CLOCK
Q4
Q4
Q1
Q1
CO
CO
Q2
Q2
Q3
Q3
39
5×
5×
CLOCK
Q4
Q3
Q2
Q1
40
1×
1×
CO
0
BD
1
UD
Q4
Q3
Q2
Q1
BD = 0, UD = 1: 0 → 9 → 0
© 2026 Daniil Khanin · khanin.info · HT-04
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← Back to the lesson
Lesson 3. The CD4029B counter