3.2 Pedestrian Crossing Button

Overview

When pedestrians cross the street, they just need to touch the button on the lamppost of the roadside signal lamp, and the green light above the traffic lane will turn into red then pedestrians can pass safely. Thus, the hard situation of citizens crossing the street is comprehensively resolved. At the same time, when there is no pedestrian to press, the light above the lane that is set for vehicles to pass will always be green, thus greatly improving the use efficiency of the road and traffic capacity.

Components Required

_images/Part_three_2.png

Fritzing Circuit

In this example, 74hc595, 7-Segment, LED, touch sensor are to be connected according to the chart.

_images/Part_three_2_Fritzing_Circuit.png 3.2 Pedestrian Crossing Button_bb

Schematic Diagram

_images/image270.png

Example Explanation

The workflow of the project is as shown in the flow chart. The function of number display of 7-Segment is realized by writing 8 bit data into 74HC595. When there is a need of displaying「0」, the pins abcdef of the segment display will be connected to the high level. The pins, g and dp need to be connected to low level to write「0x3f」(B00111111) in the codes. The complete codes for number display of 7-Segment are as follows.

_images/Part_three_2_Example_Explanation.png

Numbers

Common Cathode

(DP)GFEDCBA

Hex Code

0

00111111

0x3f

1

00000110

0x06

2

01011011

0x5b

3

01001111

0x4f

4

01100110

0x66

5

01101101

0x6d

6

01111101

0x7d

7

00000111

0x07

8

01111111

0x7f

9

01101111

0x6f

Phenomenon Picture

3.02