# Important 4 me

1. Jun 16, 2006

### mohdfasieh

Hello Genius guys,
I am beginner in the field of electronics engineering.Well i am planning to make LED TRAFFIC SIGNAL /i know the wroking of 555 timer ic iknow the working of Multiplexer,Demultiplexer,encoder ,decoder. well can u tell me the circuit diagram of LED TRAFFIC signal 4 way traffic signal .

2. Jun 16, 2006

### Danger

I'm not into electronics yet, but I suspect that you'll have to provide more information. There are a lot of variations. For instance, most large-city units are computer controlled from a central location. Also, a busy street intersecting a quiet one will usually have a longer green on its side. Then there's the matter of advance/delay turn arrows and their attendant trigger sensors, whether or not the turn lane stays green along with the main ones or turns red, etc..

3. Jun 16, 2006

### Staff: Mentor

You can either build the traffic light project with discrete logic or with a microcontroller. Both approaches are valuable educational exercises. I still remember building one from discrete logic way back in school....

But I digress. To build the discrete logic one, you will need to write up a state diagram or at least a list of states that shows step-by-step how the lights all sequence. The list should include the amount of time between steps. Once you have that list, you build logic that takes the clock, divides it down to your human time scale (like 5 seconds per yellow light), and steps through the state diagram in sequence. If you haven't had state diagrams and logic design in your classes yet, just google it and you will get some good examples. I googled state diagram logic design tutorial, and got this useful list:

The more modern way to do this exercise is to program a small microcontroller (uC) to do it, and drive the LEDs directly from the uC. You could get a Basic Stamp, for example, and program it in Basic (hence the name) or some other language.

http://www.parallax.com/

4. Jun 19, 2006

### mohdfasieh

well i want to make this traffic signal by discrete components.plz can u send me the ckt diagram plz

5. Jun 19, 2006

### wolram

http://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm [Broken]

Has a circuit.

Last edited by a moderator: May 2, 2017