Designing a Traffic Light Circuit with 555 Timers

[JoshHolloway]

I am trying to make a circuit that works basically just like a traffic light. I want to use LED's and a 555 timer. So I want the first LED to be lit upon applying a voltage, then I will use some type of switch that activates the next LED to light up and stay lit for a specific amount of time, then the last LED will light up and stay lit. And I only want one LED to be lit at a time. I know I can do this with a decade counter, but the only IC I want to use is a 555 timer, but it doesn't matter how many of them I use. Any ideas?

 

[Number2Pencil]

without counters, 555 timers could work as one shots. But for some reason many people I knew had trouble getting 555 timers to work as one shots. With JUST 555 timers, your design would be somewhat limited. Hook it onto a state machine for more flexibility

 

[ravenprp]

First of all, using a 555 timer to design a traffic light circuit is a great idea! The 555 timer is a versatile and commonly used IC that can be easily integrated into various circuits. In order to achieve your desired functionality, you can use a 555 timer in astable mode to generate a square wave signal with a specific frequency. This signal can then be used to drive the LEDs in a sequential manner.

To start, you can connect the first LED to the output of the 555 timer. This LED will light up as soon as the circuit is powered on. Next, you can use a switch to trigger the second 555 timer, which will be configured in monostable mode. This timer will generate a pulse of a specific duration, which can be used to light up the second LED for a specific amount of time. Similarly, you can use a third 555 timer in monostable mode to light up the third LED.

To ensure that only one LED is lit at a time, you can use the output of the first 555 timer to trigger the second timer, and the output of the second timer to trigger the third timer. This way, the timers will be triggered one after the other, ensuring that only one LED is lit at a time.

You can also use a capacitor and resistor in parallel with the switch to adjust the duration of the pulse generated by the monostable timers, allowing you to control the amount of time each LED stays lit.

Overall, using multiple 555 timers in this circuit can achieve the desired functionality without the need for a decade counter. I hope this helps and good luck with your project!