Introduction

This is a kit of the "How Things Work" series. You put the car into reverse — and it starts beeping: the closer the wall, the more often. The screen shows a bar at each sensor and digits — how many centimetres to the obstacle. In the bumper there are four ultrasonic sensors, and behind them a few chips. In this kit you build such a parking sensor completely: from the chips after the datasheet to the bars, the digits and the buzzer.

  • lesson 1 — the CD4013 D flip-flop and the divider: the whole device steps on it;
  • lesson 2 — the CD4017 counter: the sweep of the sensors in a ring, ten steps;
  • lesson 3 — ultrasound and the CD4072: four sensors beep in turn, one echo for all;
  • lesson 4 — centimetres on the CD4029: an 8 kHz clock while the echo is on, and a synchronizer;
  • lesson 5 — zones and bars: the CD4585 comparator and latches;
  • lesson 6 — the nearest and the digits: a minimum register, the CD4511 and calibration;
  • lesson 7 — the buzzer: the closer, the more often.
4 sensorsustxsweepCD4013 · CD4017echoCD4072centimetres2 × CD4029zones2 × CD4585 · CD4013nearestCD4585 · CD4029bars12 LEDbuzzerSpeakerdigits2 × CD4511TRIGECHOwrite steps8 kHz clock = 1 cm · a sweep step 1/30 s · a round of 10 steps
The whole parking sensor in blocks: the sweep wakes the sensors in turn, their echoes merge into one, the counter measures it in centimetres; then each sensor's zone drives the bars and the buzzer, and the nearest of the round drives the digits.

What you need

The kit is standalone. The gates NOT, NAND, NOR, AND, OR, XOR — from any kit of the series or from lesson 0. The CD4011, CD4029 and CD4511 are already there if you built "The Visitor Counter" — those steps can be skipped (the CD4511 only needs four resistors added, lesson 6).

How big it is

CD4013 — 80 transistors, CD4017 — 290, CD4072 — 44, CD4585 — 168, CD4029 — 454, CD4511 — 204, CD4011 — 16. The parking sensor: 29 packages — 4,006 transistors.

A model of real chips

The CD4013, CD4017, CD4072 and CD4585 are made by Texas Instruments, and each has a datasheet with a logic diagram. We build them after these diagrams with the same pin names; the power pins VDD and VSS are not needed — power in the simulator is shared. Where we departed from the drawing, we say so plainly: weak feedback in the latches (a resistor, lesson 1), two inverters before Q in the CD4013 instead of three (as the TI function table requires), the right part of the CD4585 from simple gates with the same logic. If you build with wires rather than with labels, every new chip has its circuit as one drawing.

Mode

The centimetre counter needs every clock of the 8 kHz generator. Build and check in Fast mode: in Real the editor cannot keep up with 16,000 calculations a second and skips clocks.