TRAFFIC SIGNALS

Description

• This is a very basic traffic light circuit that is built around the TTL family 74145.

• The circuit is stepped by a 555 astable oscillator. The rate at which the timer IC changes is determined by the value of resistance.

• The Oscillators output is divided by a 74LS90 divider that produces a (BCD) output.

• There are four counts for RED, two counts for ORANGE and four counts for GREEN.

START

Is the Signal Green?

EW Signal isgreen for 10s NS Signal is

green for 10s

EW Signal isorange for 2s NS Signal is

orange for 2s

EW Signal is redfor 10s

NS Signal isred for 10s

FLOW DIAGRAM

REQUIRED TOOLS

       Voltage supply (+5V)        100uF Capacitor        0.01uF Capacitor        Green LED’s (3 required)        Yellow LED’s (3 required)        Red LED’s (3 required)        4-8 ohm resistance (2 required)        555 IC        74LS90 Decade Counter       74145 BCD Decoder

 

IC IMPEMENTATION DIAGRAM

CIRCUIT DIAGRAM