An electrical project known as Simple Traffic Signal Lights Circuit using IC 555 uses an easily accessible component known as the 555 IC to simulate a simple traffic signal sequence with the help of LEDs.
Circuit Working:
Parts List:
| Category | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 470Ω, 100k, 47k | 1 each | 1/4 watt |
| 220Ω | 2 | 1/4 watt | |
| Capacitors | Electrolytic 100μF 25V | 2 | |
| Semiconductors | IC 555 | 2 | |
| LEDs | Red 5mm 20mA | 1 | |
| Orange 5mm 20mA | 1 | ||
| Green 5mm 20mA | 1 |
Introduction about the traffic signal circuits:
The post discusses a clever circuit that builds a set of tiny traffic lights for a layout out of two particular electronic components called IC 555 .
An animation that mimics the precise sequence in which the lights turn on and off in real life is available, it may be based on Australian standards.
The duration of the red lights on and off states is equal, the IC2 555 permits power to pass to the IC1 555 when the red light is off.
The green LED turns on as a result, subsequently the IC1 switches states, temporarily activating the orange LED and shutting out the green light.
At last, the IC2, ending the IC1 and reactivating the red light to complete the cycle.
A power supply between 9V and 12V is essential since the IC1 gets somewhat less voltage than the primary power source.
This design also shows how to directly link LEDs to the 555 IC in both high and low configurations, as well as how to regulate the power supply to a specific pin 8 to control the timers ON/OFF state.
Notably, pin 3 another common pin in this circuit, would not function if the LEDs were connected directly to it.
Pin 7 is skillfully used by the designer for this particular application since it is electrically coupled to pin 3.
Circuit description on how the circuit works:
When switched on, the two 555 ICs exhibit continuous oscillation since they are set in astable mode. Nevertheless, the output of the IC2 555 provides a regulated power supply to the IC1 555.
The IC2 555s C1 capacitor discharges at first power up driving pin 3 high and maintaining the red LED off.
The output of the IC2 555 simultaneously energizes the IC1 555 turning on the green LED.
The C1 capacitor of the IC1 555 charges towards 2/3 Vdd causing a state transition that illuminates the orange LED and turns out the green LED.
While the C2 capacitor charges via the R2 resistor, the C2 capacitor starts to discharge.
The IC2 555s output drops when the orange LEDs specified timer turns out because of the IC1 555s R5 resistor.
This turns off the IC1 555 and flashes the red LED.
The cycle is then restarted when the initial C1 capacitor discharges through the R2 resistor ultimately causing a state change.
The timing sequence is based on the larger cycle time of the IC2 555 which is defined by the R2 resistor, and the shorter cycle of the IC1 555, which is determined by the R5 resistor.
The reason for the first power up oddity is that the timing sequence of the two C1 and C2 capacitors is different from the following cycles because they need time to charge from 0V.
Formulas:
The IC 555 in astable mode may be used to construct a basic traffic signal lights circuit by generating a timing sequence that alternates between the three LEDs that symbolize traffic signals: red, yellow/amber, and green.
The circuits and the necessary formula is mentioned as follows:
Formula for Frequency (f):
In the astable mode of the IC 555, the values of the resistor R and capacitor C define the oscillation frequency f:
f = 1.44 / (R1 + 2R2) *C
where,
- The resistors attached to the IC 555 are R1 and R2.
- There is a timing capacitor C.
Duty Cycle:
The output waveforms duty cycle D is determined by the following formula, which expresses the ratio of the outputs high ON to low OFF times.
D = R2 / R1 + 2R2
To get the appropriate traffic signal light sequence and timing for your particular application adjust these parameters as needed.
How to Build:
To build a Simple Traffic Signal Lights Circuit using IC 555 follow the below mentioned connections steps:
- Assemble all the components shown in above diagram.
- Connect pin 1 of IC1 555 to ground.
- Connect pin 2 to pin 6 of IC1 555 through capacitor C2 to ground.
- Connect pin 3 of IC1 to ground through resistor R3 and LED2 green.
- Connect pin 4 of IC1 555 to positive supply of 12V.
- Connect pin 6 to pin 3 of IC1 555 through resistor R5.
- Connect pin 7 of IC1 555 to positive supply of 12V through resistor R4 and LED3 orange.
- Connect pin 8 of IC1 555 to pin 3 of IC2 555.
- Connect pin 1 of IC2 555 to ground.
- Connect pin 2 to pin 6 of IC2 555 through capacitor C1 to ground.
- Connect pin 3 of IC2 555 to positive supply of 12V through resistor R1 and LED1 red.
- Connect pin 4 of IC2 555 to positive supply of 12V .
- Connect pin 6 of IC2 555 between pin 3 of IC2 555 and pin 8 of IC1 555
- Connect pin 8 of IC2 555 to positive supply of 12V.
Conclusion:
In this circuit, even though both ICs are in astable mode the 555 IC circuit successfully regulates a traffic light sequence.
To produce the proper timing for each light, the trick is to manipulate the power to the second 555s and use resistors that have been carefully chosen.
Due to capacitor charging, there is a variance in the circuits power up period at first but after that it operates consistently.
Always remember to put safety first by utilizing the right components and handling procedures.