Contents

  1. Introduction
  2. History: how light learned to count people
  3. Lesson 0. Gates from transistors: for those who start from scratch
    1. 0.1. The idea: a transistor is a switch
    2. 0.2. Building
    3. 0.3. Check
    4. Lesson 0 paste (Cmd+I)
  4. Lesson 1. The beam and CD4011
    1. 1.1. Idea: how a shop counts people
    2. 1.2. Idea: the CMOS 4000 series
    3. 1.3. Idea: NAND for everything
    4. 1.4. Build
    5. 1.5. Check
    6. Lesson 1 paste (Cmd+I)
  5. Lesson 2. The F/F flip-flop
    1. 2.1. Idea: a counter is flip-flops that flip
    2. 2.2. Idea: flipping through exclusive OR
    3. 2.3. Idea: a NAND with three inputs
    4. 2.4. Build
    5. 2.5. Check
    6. Lesson 2 paste (Cmd+I)
  6. Lesson 3. The CD4029B counter
    1. 3.1. Idea: which bit to flip
    2. 3.2. Idea: controlling the counter
    3. 3.3. Idea: the bubbles on the TI drawing
    4. 3.4. Build
    5. 3.5. Check
    6. Lesson 3 paste (Cmd+I)
  7. Lesson 4. The CD4511B decoder
    1. 4.1. Idea: seven strokes
    2. 4.2. Idea: latch, blanking, lamp test
    3. 4.3. Idea: a switch on two transistors
    4. 4.4. Build
    5. 4.5. Check
    6. Lesson 4 paste (Cmd+I)
  8. Lesson 5. Direction
    1. 5.1. Idea: two beams one after another
    2. 5.2. Idea: remember the first
    3. 5.3. Idea: the clock is when both are blocked
    4. 5.4. Build
    5. 5.5. Check
    6. Lesson 5 paste (Cmd+I)
  9. Lesson 6. The visitor counter
    1. 6.1. Idea: two displays on the same beams
    2. 6.2. Idea: two digits — two counters
    3. 6.3. Idea: Reset holds
    4. 6.4. Build
    5. 6.5. Check
    6. Lesson 6 paste (Cmd+I)
  10. Summary
  11. All the parts
  12. Instructions in pictures