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Traffic Signals

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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.

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Traffic Signals

  1. 1. TRAFFIC SIGNALS
  2. 2. 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.
  3. 3. START Is the Signal Green? EW Signal is green for 10s NS Signal is green for 10s EW Signal is orange for 2s NS Signal is orange for 2s EW Signal is red for 10s NS Signal is red for 10s FLOW DIAGRAM
  4. 4. 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
  5. 5. IC IMPEMENTATION DIAGRAM
  6. 6. CIRCUIT DIAGRAM

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