Traffic light circuit with 556 timer?

[phennessey]

Unpopular opinion: That’s a bad idea. Giving people an exact preview of when the light will turn green is only allowing the possibly for abuse and increases the chance for a collision.

[james_s]

Unpopular opinion: That’s a bad idea. Giving people an exact preview of when the light will turn green is only allowing the possibly for abuse and increases the chance for a collision.

How so? You can already get this exact preview if you look at the lights on the cross street. Only an idiot steps on the gas before visually confirming the intersection clear, and the point of the amber light before red is to ensure the intersection is clear before the other direction gets a green. The fact that there are always a few idiots incapable of following the rules is a constant either way.

[phennessey]

Idiots exist, ergo, why give them more ways to be idiots? Sometimes people run red lights. Why give people an incentive to gun it just when the light turns green? It’s certainly not safer to give people advance notice of a green light.

[SmokeyTheElectrician]

There's lots of information out there about traffic light controllers, at least the stuff used in the US. Eagle, Econolite and Crouse-Hinds were some of the big makers here. Early systems used motor driven timing wheels and solenoids, then in the early 80s microprocessor based controllers started taking over.

https://northstarhighways.wordpress.com/2016/09/10/how-traffic-signal-controllers-work-part-1-an-overview-of-controllers/

Back in the early 70s, I worked for a summer for the city’s traffic light department, in maintenance.

There were a couple of systems, that I remember:
-Relay ladder logic as you described.
-A camshaft driven by a 1RPM geared synchronous motor.

Thanks for the insights and link to the interesting reading / vidoes.

[james_s]

Idiots exist, ergo, why give them more ways to be idiots? Sometimes people run red lights. Why give people an incentive to gun it just when the light turns green? It’s certainly not safer to give people advance notice of a green light.

Because it gives people a heads up so they are prepared to go, it's nice to have a chance to put the car in gear before the guy behind starts having a cow. I'm just not seeing this incentive to gun it created by a warning, can you find me some data showing it happens in any of the places where this is commonplace? Someone who is going to gun it at a green light is going to do so whether they have a yellow light or not.

[Ed.Kloonk]

In my part of the ant hill, many peeps run red lights -because- often most drivers aren't ready to go anyway.

[phennessey]

If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light and try to time your entry into the intersection precisely when the light changes. Meanwhile, a car may be trying to get through the light before it turns red. Bad combination.

I don’t have data, sorry! It just seems like a bad idea to give people advance notice when a light will turn green, which is why the US doesn’t employ that system. I can’t believe it would be safer with that feature, but I welcome any data that proves me wrong.

[Ed.Kloonk]

If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light and try to time your entry into the intersection precisely when the light changes. Meanwhile, a car may be trying to get through the light before it turns red. Bad combination.

I don’t have data, sorry! It just seems like a bad idea to give people advance notice when a light will turn green, which is why the US doesn’t employ that system. I can’t believe it would be safer with that feature, but I welcome any data that proves me wrong.

Sometime in our near future, you're forgetting, all traffic light sets will have cameras. It used to be that bad intersections received a camera. Now, at the least, the road triggering infrastructure is being built into the roads with every new set. If the red light runners are indeed as bad as you say, my information suggests that revenue from tickets will pay for a camera installation at every turn.

[james_s]

I would support red light cameras if they were about improving safety but unfortunately they end up being purely for revenue. Multiple municipalities have been caught turning down the amber light intervals and data has shown rear end accidents to increase at camera equipped intersections. In a city near me there was an attempt to put forward a citizen initiative banning red light cameras and it got shot down early in the process with an official quoting that they need the revenue.

[james_s]

If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light and try to time your entry into the intersection precisely when the light changes. Meanwhile, a car may be trying to get through the light before it turns red. Bad combination.

I don’t have data, sorry! It just seems like a bad idea to give people advance notice when a light will turn green, which is why the US doesn’t employ that system. I can’t believe it would be safer with that feature, but I welcome any data that proves me wrong.

Sorry but if you don't have data then it is just baseless speculation and of no value, it makes me suspect you have never driven anywhere that has this feature. All it does it illuminate the amber light for a brief period just before it turns green, it gives you just enough of a warning to have time to put the car in gear, it's very convenient and doesn't cause the problems you believe it does. You still look both ways to verify that traffic has stopped on the cross street before proceeding, just like you (hopefully) do anywhere else.

[Ed.Kloonk]

I would support red light cameras if they were about improving safety but unfortunately they end up being purely for revenue. Multiple municipalities have been caught turning down the amber light intervals and data has shown rear end accidents to increase at camera equipped intersections. In a city near me there was an attempt to put forward a citizen initiative banning red light cameras and it got shot down early in the process with an official quoting that they need the revenue.

   Yeah.

It's good that it is being admitted to. You can now get down to brass tacks on how much they receive and how much they waste.

[james_s]

I don't think they meant to admit it, it was more one of those "Whoops, said that out loud" moments that ended up getting quoted in the article.

It would bother me a bit less if they just were forward about it being about revenue, I'm fine with a tax on people who can't follow the rules and running red lights is a particularly annoying not to mention dangerous habit that has been increasing. Shortening amber light intervals is BS though, they have to know that will increase accident rates, they should have generous amber intervals so that people have time to stop safely without slamming on their brakes and getting rear ended by the guy behind them who thought they were going to gun it through the yellow, that is, if the goal was actually improving safety. I'm also not fond of the fact that our red light cameras are normally run by a private out of state company that skims a substantial profit, and they are not normal traffic tickets so they are much harder to contest in court than a ticket from a police officer.

[Ed.Kloonk]

What is a crime is that you got to 10k posts before I got to 1k. 

[Ed.Kloonk]

But there's still time..


 

[SmokeyTheElectrician]

I would support red light cameras if they were about improving safety but unfortunately they end up being purely for revenue. Multiple municipalities have been caught turning down the amber light intervals and data has shown rear end accidents to increase at camera equipped intersections. In a city near me there was an attempt to put forward a citizen initiative banning red light cameras and it got shot down early in the process with an official quoting that they need the revenue.

Wow,
the official was not fired
plus no injunction against the city?

Around my neck of the woods,
at least they have delayed the green,
as they know everyone is racing it to
get through those amber signals.

With all the "AI" going on these days,
you'd think they would use those traffic light cameras
to intelligently delay ( or not ) the green
depending on whether or not the cross traffic
has stopped ( or is not even present ).

I've never heard it discussed,
but the concept of an amber go zone
    ( if this zone is ahead of you when the light turns amber,
       do not even think about gunning it, get on the brakes )
should be integrated into driver's education
as well as marked out with striping across
the roadway and signage to the side, plus
maybe even a sign strung above the roadway.

It does not take a genius (no offense to any traffic engineers)
to figure out how far such indications should be
from the intersection (including a decent safety margin -- there are
online esitmaters that include reaction time and etc...)
  (there could also be an earlier {further before the intersection}
    indication for wet conditions or whatever is found to increase safety )

 I guess no governing body would actually do this
  as the lawyers would get their greedy fingers in
  there as someone is gonna figure out how to
   to create a wreck no matter what.

Well, then there are those traffic circulations
popping up more and more that seem to
be working out pretty well in most cases....

[james_s]

Wow,
the official was not fired
plus no injunction against the city?

Nope, in at least one case they tried to fine the guy $500 for calling himself an engineer without being a certified professional engineer.

https://interestingengineering.com/calling-himself-engineer-got-this-man-fined-500

[themadhippy]

If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light

dont go to Thailand then,not only do you have the pretty lights but also a countdown timer showing how long each aspect has to last

[Zero999]

Around my neck of the woods,
at least they have delayed the green,
as they know everyone is racing it to
get through those amber signals.

We also have delayed green. The problem is it encourages people to jump the lights when they realise it's still red on the other side and go anyway. Turning red a little early and green a bit late are good safety features, but they shouldn't be too long, otherwise it makes it more dangerous and frustrates drivers.

[schmitt trigger]

It seems that different countries have different ideas to discourage bad driving behaviors.

That is the reason a microcontroller based system is so powerful. Different rules may be easily implemented.

We have drifted far, far away from the OP’s topic.

[phennessey]

If it's just sequentially lighting the LEDs one after the other, just use a ring oscillator. Here's an example which can be built with the 74HC14.
(Attachment Link)

I don't understand a lot of these symbols, can you help me identify the arrows and the "I1" and "O1" tags? Are those supposed to be probe points? And I don't understand the arrow symbols. Are those all ground? I thought a schmitt trigger had one input and one output. But this circuit is showing all the triggers with arrows pointing out of them, which is deeply confusing to me. The 74HC14 only has volts in and out, plus six triggers, all of which only have one input and one output. But you drew this diagram with ground terminals on every trigger. Can you explain this a bit?

I tried to redraw your circuit...did I goof?

[hermitengineer]

A ring oscillator doesn't do the traffic light though.  Around the ring you'll find that each LED is a toggle of the one before it.  Since it's a ring with an odd number of inverters, there will be a toggler running down the ring toggling each LED as it goes.  So effectively, you always have about 2 LEDs lit, as seen in the waveforms that were simulated.  You need a ring one-shot instead.  Maybe something like this:

[phennessey]

Not true at all. I'm literally staring at a completed circuit that is lighting up exactly the way I want (I just had to change some resistance values to introduce an instability in the cycle.)

[hermitengineer]

Not true at all. I'm literally staring at a completed circuit that is lighting up exactly the way I want (I just had to change some resistance values to introduce an instability in the cycle.)

I was wondering if the odd LED hookups were done to eliminate the extra LED in the ring.  Apparently so.  If the LEDs were hooked up in a conventional way (each output to a resistor and LED to ground), then you'd see the typical ring oscillator pattern.