U.S. Traffic Light

brett1405 · Apr 25, 2011

Hello, I am new to your forum. I am trying to build a traffic light for both N/S and E/W directions ( 6 lights, U.S. version). I am new to electronics, as I am in my second quarter for a two year degree in Industrial Control Systems Tech. program. We have already designed and built the same traffic light using analog timers and relays. Now we have to do it with IC chips. I have looked over and tried to build alot of circuits posted on the web, but none have worked out. I am designing it on Multisim 10.1.1. I have learned a lot so far about the analog timers and relays, but this IC stuff is way more complicated. I am thus far thinking about designing it using a 555, a 4017 decade counter and some sort of J-K flip-flop arrangement.(?) If there is a simpler way that anybody knows of, any help would be appreciated, especially if it is a Multisim design. I don't know if we can use microcontrollers to run it, as we are supposed to keep cost to a minimum when building this. We are going to be building it for real using the Elvis II breadboard. Thank you, brett1405

carbonzit · Apr 25, 2011

Sounds like an interesting project. I've often wondered about the inner workings of traffic signals, which I ASS-U-me are nowadays controlled by microelectronics. Could you post some links to circuits you've found so far?

I'm wondering whether the "real thing" here uses discrete logic, as you're thinking of doing, or a microprocessor. Keeping in mind that such circuits must be extremely robust and fail-safe, I'd lean towards the discrete logic choice, but I really have no idea.

DerStrom8 · Apr 25, 2011

A microcontroller would definitely be the easiest, but as you mentioned, the chip and the programmer costs money (about $50 U.S.) I suggest you still look into it, though, just in case.
Der Strom

colin55 · Apr 25, 2011

Here is a simple 4-way set of traffic lights:
**broken link removed**

carbonzit · Apr 25, 2011

Heh; is that really the way 'Strine traffic light sequences work? Here in the U.S. they go green-yellow-red, not red-yellow-green.

Other than that, looks good.

killivolt · Apr 25, 2011

carbonzit said:
Heh; is that really the way 'Strine traffic light sequences work? Here in the U.S. they go green-yellow-red, not red-yellow-green.

Other than that, looks good.

The first electronic traffic light I think, here is some history. "Regardless of it being wiki"

I'm glad this was brought up; I didn't know a police officer from Utah started the electronic version "Red & Green" in 1912. Interesting.

KeepItSimpleStupid · Apr 25, 2011

I remember in one town (Scranton PA area) in the US, they didn't have yellow. Went from red to green.

colin55 · Apr 25, 2011

Here is the modified circuit:
**broken link removed**

carbonzit · Apr 26, 2011

Colin, you never answered my question. Do your traffic signals really go from red to yellow? That's completely contrary to how they work here (and in Mexico, and I assume in Canada). I thought this was pretty much a global convention.

Just thinking out loud here, for enhancements to your simple circuit: what's needed are several different delay timers.

Delay 1 (green): long (allows traffic to pass in one direction).
Delay 2 (yellow): short
Delay 3: delays change to green after opposite direction goes red; very short

I'll bet all this stuff is in a basic textbook on traffic management, which I've never seen. I've been curious about this stuff, though.

Oh, almost forgot: there's a mode where all signals flash red, when there's a power outage or other fault condition. Not sure exactly when or how this is triggered.

Some lights are more complex, and may be programmed to do different things at different times of day. For instance, late at night some signals will change to blinking yellow in all directions (proceed with caution) or even blinking red (treat like a stop sign).

4pyros · Apr 26, 2011

brett1405 said:
Hello, I am new to your forum. I am trying to build a traffic light for both N/S and E/W directions ( 6 lights, U.S. version). I am new to electronics, as I am in my second quarter for a two year degree in Industrial Control Systems Tech. program. We have already designed and built the same traffic light using analog timers and relays. Now we have to do it with IC chips. I have looked over and tried to build alot of circuits posted on the web, but none have worked out. I am designing it on Multisim 10.1.1. I have learned a lot so far about the analog timers and relays, but this IC stuff is way more complicated. I am thus far thinking about designing it using a 555, a 4017 decade counter and some sort of J-K flip-flop arrangement.(?) If there is a simpler way that anybody knows of, any help would be appreciated, especially if it is a Multisim design. I don't know if we can use microcontrollers to run it, as we are supposed to keep cost to a minimum when building this. We are going to be building it for real using the Elvis II breadboard. Thank you, brett1405

Brett; Is this just going to be a simulater or dose it need sensors to triger the lights to change? Andy

4pyros · Apr 26, 2011

Delay 1 (green): long (allows traffic to pass in one direction).
Delay 2 (yellow): short
Delay 3: delays change to green after opposite direction goes red; very short

The delays can be set by the number of outputs from the 4017 that are used for each color and tied together with the diodes. Andy

KeepItSimpleStupid · Apr 26, 2011

For fun reading: https://www.electro-tech-online.com/custompdfs/2011/04/ch3.pdf

MrDEB · Apr 26, 2011

Where do you get the idea that it goes red yellow green?
LOOK at the schematic and pattern layout--Green, Yellow, Red

killivolt · Apr 26, 2011

MrDEB said:
Where do you get the idea that it goes red yellow green?
LOOK at the schematic and pattern layout--Green, Yellow, Red

That's what Carbonzit was talking about.

DerStrom8 · Apr 26, 2011

killivolt said:
That's what Carbonzit was talking about.

KV, I think you misunderstood. MrDEB was asking carbonzit what made him think that the circuit goes Red-Yellow-Green. This question was directed at carbonzit.

carbonzit · Apr 26, 2011

DerStrom8 said:
KV, I think you misunderstood. MrDEB was asking carbonzit what made him think that the circuit goes Red-Yellow-Green. This question was directed at carbonzit.

Well, yes. And after examining the circuit, it looks to me as if it does go red-yellow-green

I'm really not trying to be a nuisance here. I checked the circuit out, and I also looked at the 4017 datasheet, including the timing diagram. Bear with me a minute if you will:

The 4017 advances one output each clock in sequence. So on each pulse, Q0, Q1, Q2 ... Q9 are set high, in that order.

So the output sequence is exactly what's indicated at the bottom of the schematic. For N/S, it's

yellow
green
green
green
green
red
red
red
red
red

and the same, in a shifted sequence, for E/W.

Checking the schematic for the sequence of which lights get lit when, I believe this is the sequence here.

I'm willing to admit that this is a brain fart on my part. Am I wrong here? I'm certainly willing to be corrected.

killivolt · Apr 26, 2011

DerStrom8 said:
KV, I think you misunderstood. MrDEB was asking carbonzit what made him think that the circuit goes Red-Yellow-Green. This question was directed at carbonzit.

Ok, DerStrom8. I did.

Edit: I'm glad we are all on the same page.

kv

carbonzit · Apr 26, 2011

I see you ignored my post.

So am I wrong about the sequence? No big deal, I'd just like to know if I'm understanding correctly how this thing works.

4pyros · Apr 27, 2011

I see you ignored my post.

So am I wrong about the sequence? No big deal, I'd just like to know if I'm understanding correctly how this thing works.

Ya you missed somthing.

How do you get yellow first when green is connected to Q0?

Andy

kpatz · Apr 27, 2011

4pyros said:
Ya you missed somthing.

How do you get yellow first when green is connected to Q0?

Andy

X2. For N/S, green is lit through Q0 - Q3. Q4 - yellow is lit. Q5 - Q9, red is lit. Then it wraps back to Q0 so the light goes back to green.

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