traffic controller with down counter

[digitaldesign]

I am trying to make the digital circuit for a 4-way traffic intersection and I am following the circuit below:

**broken link removed**

However, as per my understanding, this circuit will change the traffic lighting for any particular road after every second/clock pulse (i.e. green-yellow-red-green). However, I want to modify the circuit in the link to keep green on for, say, 9 secs, yellow for 3 secs, and red for 8 secs. Can someone suggest how I should modify the circuit to do this? Also, how would I add a down counter for the traffic light from green to red? Would I use 2 decade counters connected to the 555 timer in the circuit to do this?

Please attach circuitry needed if possible. Thanks again.

 

[Dragon Tamer]

To start, your link is bad.

Secondly, you don't need a cound down timer, you can just use a 555 and a 4017 in conjunction.

Finnaly, I really hope that you don't think that this is a legidiment way to control trafic on a busy street.

 

[digitaldesign]

@Dragon Tamer,
Sorry about the link, it is actually: https://www.electro-tech-online.com/custompdfs/2010/05/traffic.pdf

Can you tell me how I can modify the circuit shown in the link according to the above specifications? thanks again.

 

[Dragon Tamer]

He seems like he is really detailed in that he has included everything from cross walks to the truth table that he came up with.

Some of the easier ways to make a traffic light have been talked about in this forum before, just search for: traffic controller, traffic light, traffic signal, etc. until you get a result.

If you still don't find what you want, I'm sure I can help you work something out.

 

[colin55]

Here is a very simple circuit to do what you want. It produces traffic lights for a "4-way" intersection. The enormously complex circuit from "Electronics For You" can be simplified to this:
**broken link removed**

 

[mneary]

Although the original message is far from clear, I think the OP wants a display showing how many seconds until the next time the light will change. This is becoming quite common on newer "walk" lights.

 

[MrDEB]

A PIC plus an LCD and your almost done.
Include for crosswalks, where to have the dog go pee when to run instead of walk, etc.
Just program for desired ON times.
Even add a beeper when to walk across cross walk for the blind.
Pretty sure an easy code, just turn ports off and on and display time out

 

[digitaldesign]

mneary is right also, I want to make the circuit so that I can show the countdown timer for each side (N,E,S, and W) and also keep the green, yellow and red lights on for some time (not just 1 sec each).

colin55, if i understand correctly, the circuit you show will keep green on for 4 secs, yellow for 1 sec and red for 4 secs? I am a little confused of the output sequence, could you show a simple truth table for the lighting sequence?

Also, if I want to make the sequence from green N/S to green E/W say 20 secs (instead of 10 secs as shown), would I simply attach two 4017 IC's in parrallel?

 

[MrDEB]

In collins schematic, all the RED and GREEN LEDs stay on the same amount of time while the YELLOW stay on 1/4 the time.
Collins schematic could be altered to perform as needed.

 

[digitaldesign]

Thanks again. Just to clarify, in colin's diagram:
Red N/S Is ON (Q1-Q4)
Green N/S Is ON(Q1-Q4)
Yellow N/S Is ON(Q0)
--
Red E/W Is ON(Q6-Q9)
Green E/W Is ON(Q6-Q9)
Yellow E/W Is ON(Q5)
- But how come green and red (E/W) are both on for Q6-Q9?

Also If I wanted to also display the countdown to the next light on a 7-segment what IC would I use and where to connect it? Thanks again.

 

[digitaldesign]

I also found another circuit diagram which mostly seems to perform the function I need. Here is the link: **broken link removed**. However I dont understand where the input for the 74LS145 is coming from and the need for the 74LS145 IC in the circuit? Can't the 74LS145 IC be replaced with a 555 timer connected to the input of two 4017 IC's instead?

 

[colin55]

Here is the output pattern:
**broken link removed**

 

[pjl83]

(i.e. green-yellow-red-green). However, I want to modify the circuit in the link to keep green on for, say, 9 secs, yellow for 3 secs, and red for 8 secs. Can someone suggest how I should modify the circuit to do this? Also, how would I add a down counter for the traffic light from green to red?

Be careful with your sequencing. A traffic light will never go from green to red. The sequence quoted above is incorrect. Traffic lights go red-amber-green-amber-red-amber-green-amber.......

HTH
Paul

 

[digitaldesign]

I am trying to implement the circuit in this link: https://www.electro-tech-online.com/custompdfs/2010/06/traffic.pdf. However, I just wanted to clarify some confusion:

1. for adding the various LED outputs, would I first add a 470 ohm resister at the output of the OR gate, then add the LED after the resistor and connect the other LED terminal to the ground?

Can you please guide in this, as I want to complete this design soon.

 

[colin55]

Link is broken

 

[digitaldesign]

Sorry, this is the link: https://www.electro-tech-online.com/custompdfs/2010/06/traffic-1.pdf