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The Visitor Counter
RU
EN
ES
Contents
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 0 in pictures
← Back to the lesson: Lesson 0. Gates from transistors: for those who start from scratch
0
Gates (optional)
NOT, NAND, NOR, AND, OR, XOR from transistors
kh
HT-04
NOT
NAND
NOR
AND
OR
XOR
IN
11×
OUT
6×
P
11×
N
11×
∞
Ctrl
+
G
NOT
NAND
NOR
AND
OR
XOR
© 2026 Daniil Khanin · khanin.info · HT-04
4
NOT
1
IN
1×
OUT
1×
P
1×
N
1×
6×
I0
O0
VCC
O0
G
P
I0
O0
GND
G
N
I0
2
Ctrl
+
G
Library
…
Chip N
2×
Library
…
NOT
Enter
NOT
I0
O0
© 2026 Daniil Khanin · khanin.info · HT-04
5
NAND
3
IN
2×
OUT
1×
P
2×
N
1×
9×
I0
I1
O0
VCC
O0
G
P
I0
VCC
O0
G
P
I1
O0
mid
G
N
I0
4
N
1×
3×
mid
GND
G
N
I1
5
Ctrl
+
G
Library
…
Chip N
2×
Library
…
NAND
Enter
NAND
I0
I1
O0
© 2026 Daniil Khanin · khanin.info · HT-04
6
NOR
6
IN
2×
OUT
1×
P
2×
N
1×
9×
I0
I1
O0
VCC
mid
G
P
I0
mid
O0
G
P
I1
O0
GND
G
N
I0
7
N
1×
3×
O0
GND
G
N
I1
8
Ctrl
+
G
Library
…
Chip N
2×
Library
…
NOR
Enter
NOR
I0
I1
O0
© 2026 Daniil Khanin · khanin.info · HT-04
7
AND
9
IN
2×
OUT
1×
P
2×
N
1×
9×
I0
I1
O0
VCC
n
G
P
I0
VCC
n
G
P
I1
n
mid
G
N
I0
10
N
2×
P
1×
9×
mid
GND
G
N
I1
VCC
O0
G
P
n
O0
GND
G
N
n
11
Ctrl
+
G
Library
…
Chip N
2×
Library
…
AND
Enter
AND
I0
I1
O0
© 2026 Daniil Khanin · khanin.info · HT-04
8
OR
12
IN
2×
OUT
1×
P
2×
N
1×
9×
I0
I1
O0
VCC
mid
G
P
I0
mid
n
G
P
I1
n
GND
G
N
I0
13
N
2×
P
1×
9×
n
GND
G
N
I1
VCC
O0
G
P
n
O0
GND
G
N
n
14
Ctrl
+
G
Library
…
Chip N
2×
Library
…
OR
Enter
OR
I0
I1
O0
© 2026 Daniil Khanin · khanin.info · HT-04
9
XOR
15
IN
2×
OUT
1×
OR
1×
NAND
1×
AND
1×
9×
I0
I1
O0
OR
I0
I0
I1
I1
O0
o
NAND
I0
I0
I1
I1
O0
n
AND
I0
o
I1
n
O0
O0
16
Ctrl
+
G
Library
…
Chip N
2×
Library
…
XOR
Enter
XOR
I0
I1
O0
© 2026 Daniil Khanin · khanin.info · HT-04
10
← Back to the lesson
Lesson 0. Gates from transistors: for those who start from scratch