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Friday, November 22, 2024

Traffic Lights

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10 years 3 months ago - 10 years 3 months ago #17449 by stonysmith
Traffic Lights was created by stonysmith
The subject has come up a few times of adding Traffic Lights to the streets your layout.
I was messing around with the idea.. there are many small (micro) computers that can do the job, but I also wanted the minimum number of wires possible.

I came up with this:

With just four wires (and twelve LEDs) you can have a four-way stop intersection that is fully automated. With this, you could have a number of intersections all on the same pattern of lights, and depending upon how many pins you have on your microcontroller, you could have several different zones of lights that are timed differently.
I'm still looking for how to get some SMD and a micro-circuit board for each hanging signal, but at least I now have a working arrangement that only requires four wires.
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10 years 3 months ago #17450 by markm
Replied by markm on topic Traffic Lights
Stony,
Dialight produces 1.6mm x 0.8mm color LEDs and they're available in small quantities from Mouser.

Mark

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10 years 3 months ago #17451 by stonysmith
Replied by stonysmith on topic Traffic Lights
This is a bit funny:

Dialight has been pioneering some of the most innovative applications in LED technology since it was developed in the early 1970s. Our LED products for the electronics industry have given engineers better ways to indicate status on all kinds of equipment. Dialight LED traffic signals have saved municipalities millions of dollars in energy costs and maintenance. We put our expertise to work for you by designing the most reliable and cost-effective LED products available. As a vertically integrated supplier, Dialight has the resources to design and produce everything in-house.


If they can do "everything in house", I wonder if they'd be interested in talking to the Model Train market. <grin>

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10 years 3 months ago #17452 by markm
Replied by markm on topic Traffic Lights
Stony,
I have a little more time now than for my earlier post. If you're willing to buy about 500K signal heads, I'm sure Dialight would consider it :)

I've played with the idea of Z scale traffic signals for some time and can give you some thoughts.

Your logic table is essentially correct for a mechanical traffic signal priorr to about 1970. After that those big controller boxes contained an 8008 microcontroller system. At that time a RED-RED state before then next GREEN-RED became common for the signals. You can still do this state by applying complementary pulse streams to lines 1 & 2 and matching pulses on 0 & 3 to keep the greens off.
For building the signal heads, I was planning to use a backlight shield from a single layer of FR4 PCB material with a single layer of copper. This is commonly known as flex PCB. I'd suggest using white LEDs and use color filters: the LEDs are cheaper by the dozens and you won't have to flight the forward voltage differences between the colors.

I built a controller using a 556 timer chip and a 22V10 GAL. It included a train crossing trigger to change the light and signals for the crossing lights. Also could be daisy-chained to stagger the timing for multiple traffic signals.


Hopes this helps,

Mark
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10 years 3 months ago #17454 by Kelley
Replied by Kelley on topic Traffic Lights
Rolf has some, but the controllers are for German sequence, R-Y-G-Y-R. Last time I talked to him, he was working on getting some that were American or at least programmable. You can get them and get your own controller. Here is his website, send him an Email. Or shoot me an email and I will help you order them from him. I can handle everything but the money part. www.rolfs-laedchen.de/
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10 years 3 months ago #17460 by markm
Replied by markm on topic Traffic Lights
Here's the truth table I used for my U.S. modern era traffic lights. The circuit was based on an August 1989 "symposium on Electronics" piece in Model Railroader. If you're modeling prior to the 1970s, stages 0 & 8 can be removed. I've included the binary code which helps in understanding the logic. I'd be happy to discuss details here or privately.

Mark

State North West
decimal binary route route
0 0000 red red
1 0001 green red
2 0010 green red
3 0011 green red
4 0100 green red
5 0101 green red
6 0110 yellow red
7 0111 yellow red
8 1000 red red
9 1001 red green
10 1010 red green
11 1011 red green
12 1100 red green
13 1101 red green
14 1110 red yellow
15 1111 red yellow

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