Hello Engineers. Hope all are good. Here in this article, we are going to discuss how to make your own adjustable time Traffic light controller circuit without the use of any microcontroller. A traffic light controller basically controls the operation and timing of the traffic signal lights according to a set time.
Here we are discussing a smart traffic light controller circuit whose time can be adjusted by a potentiometer and is also very customizable just by changing the value of some components.
Usually, the maximum time is 2.5 (or, you can customize easily according to your need) in all and the maximum time between each light change can be from 30 secs to 1 minute &30 secs. Although everything can be adjusted within the time range of selected components by just adjusting the potentiometer.
You can also make your own customized time circuit, by just selecting the R1, R2, and C2 by yourself and calculating the time by a formula. We’ll talk about that later. Let’s first start with the circuit, components, and working of our traffic light controller circuit.
Automatic traffic light controller circuit
- IC 555
- R1 10K
- R2 100K Potentiometer
- C1 10nF
- C2 220uF
- IC CD4017
- D1,D2,D3 – LEDs (Red, Yellow, Green)
- D4-D7 1N4007
We know about the IC 555 delay timers & clock circuits. In case, if you are new you can sum-up from here (IC555 Calculator Online Tool IC555 Astable oscillator Calculator) and ( IC 555 Delay Timer).
You can read about the IC 555 in astable multivibrator and how to calculate the IC 555 clock pulse generators components according to the desired time, frequency, duty cycle , etc.
We have IC 555 here as the clock pulse generator, whose pulse high and low duration can be calculated and set by the formula below:
Frequency(Hz) =1.44 ⁄ ((R1+2R2)*C)
=> T=1/F=0.694(R1+2R2)C , where T is Total time period
=> T1=0.694(R1+R2)*C , where T1 is Time for the Pulse to be high
=> T0=0.694*R2*C , where T0 is for Time low
The Time Period is the sum of Time High(T1) and Time Low(T0). Both are measured in milliseconds (ms). In case you are not familiar and comfortable with calculations, you can check this detailed article and online ic 555 calculator tool here, IC555 Calculator Online Tool IC555 Astable oscillator Calculator.
Output from IC 555 pin3 is input for the IC4017 Decade counter. Which then increments the counter by one, according to the Time period of the clock input.
We have used PIN 3,2,4,7,10,1 ( outputs: Q0,Q1,Q2,Q3,Q4,Q5) of IC 4017 to derive the output to control the LEDs.
Outputs are appropriately combined with diodes to on/off the particular LEDs. The yellow LED will always glow for half of the time, the other red and green LEDs are glowing.
When you first turn on the circuit with power, the time duration of Red LED and Yellow LED is the same during the first process(or iteration). But, after that, the time duration for RED and GREEN LEDs will remain the same and Yellow LED will always glow half of the time as compared to the other two LEDs.
You can use this circuit and can also make one according to your needs using the formula and online calculator mentioned above.
To use it with bigger lights, suppose higher power LEDs or 12V LEDs strips or 220v AC Lightings, you can use a transistor at each output and a relay.
So, I hope you guys liked it. If you want to suggest or ask anything, you can comment below.