Traffic light project for Multisim

[brett1405]

Hello, I am trying to design a working traffic light for both N/S and E/W sides of traffic (i.e., six lights). I will build it later, for real, using the Elvis II breadboard. I have been looking around at other schematics on the web, I have drawn many of these on Multisim and none of them work. It also needs to be a U.S. traffic light, as the ones in the U.K. are different. I have tried many different combinations, with the 555 timer and the 4017 decade counter, but I don't know how these components actually work. I need help. The simplest circuit would be better, I know, like some kind of RS flip-flop or JK flip-flop (?). I don't know how these components really hook up together or how I am supposed to get the timing right, where the red and green on opposite times will stay on for a required time, like 15 seconds for demo purposes, and then go to yellow on the side the green was on for 3 seconds ( after the green goes out and the red stays on with the yellow) and then it flip-flops to green and red on the other side for 15 seconds. I don't know how to go about this. A good example would be very helpful. Thank you, brett1405

[Vacrow]

Have you thought about using a PIC?

[brett1405 · Accepted solution]

Thank you for your reply, but I have the circuit working finally. I might need your advice in upcoming projects though, as we will be building it with a microcontroller very soon. Thank you, brett1405

[GarretF]

There is also a sample circuit in the Educational version of Multisim that implements a traffic light on a FPGA. Click File > Open Samples... then browse to Edu\PLD Sample Circuits\Traffic Light State Machine.ms11.

[brett1405]

I didnt get help from any one on here. Also, I dont have Multisim 11. Why mark it as solved, I was the one who solved it and i say so in my post.

[Crebble32]

Hi -

 I am trying to build the same type of circuit in Multisim and am unable to get any simulation to run.  The error keeps saying my "timestep is too short", which I have no idea what that means...  Do you have any suggestions? I wasn't able to find the sample circuit in my Multisim version for the traffic light either.

I have what looks like a mess of a circuit and I don't even know where to begin to trouble shoot it... 

[brett1405]

I'll have to take a look at that file and get back to you and see if I can help. I have a design, but it's kind of complicated to do on Multisim, but i'll take a look at yours anyway. I'll send you the design if I can't help you with yours.

[brett1405]

I also built the design on a prototype board using IC chips and LED's and it works really good.

[brett1405]

One more thing, when u run the Multisim circuit error check, like u did and got the "timestep too small" error, that usually means your 555 timer is set up incorrectly (i e, you didnt use the right combination of capacitors and resistors, or you got some wiring messed up somewhere).

[Crebble32]

Thanks so much! I'll adjust resistor/cap values to see if perhaps its a lack of voltage flow getting to my LEDs.. Initially when I built just the simple 555 circuit I was able to get it to work and light an LED ok, however I couldn't get my frequency where I wanted it... it was either too fast or too slow.

I appreciate you checking it out for me! Thanks again!