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OT sequential switch to run a traffic light

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  • OT sequential switch to run a traffic light

    Need a circuit that can run a traffic light, red, yellow, green, repeat. About 15 seconds on each color. The plan is to convert the fixture from incandescent bulbs to LEDs, so the current draw should be minor. Also the unit could be run off 120V AC, or battery pack. I have no idea how to do this.
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard

  • #2
    Simple with something like an Arduino. There is probably a circuit and code you can directly copy out there already.

    found it in 10 seconds:

    https://create.arduino.cc/projecthub...mulator-2ec9f7

    If you are using full size higher powered lights you'd need a bit more circuitry to drive them. Also simple.
    Last edited by mickeyf; 04-01-2021, 11:38 AM.
    "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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    • #3
      There are many ways to do this, depending on how much you want to learn in the process and how much you want to spend. There are modules used in industrial automation / industrial wiring that will do this for you but will cost some money and are probably overkill. If you're more into home-brew solutions and want to learn some basic electronics along the way, you could do something with the ubiquitous 555 timer and a shift register to drive some relays. Alternatively, you could pick up a cheap, small microcontroller and learn to program it. In that case, you could easily expand to do different patterns at the push of a button or etc.

      So, how much do you want to learn and how much are you willing to spend? That will help others guide you towards an appropriate solution.

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      • #4
        There used to be a chip that did the count and decimal decode with 10 output lines. Add some diodes and a LED level driver chip.

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        • #5
          HI Dave C,

          Here is one that is like the one I use for the light in my shop to look COOL I typed in traffic light control relay and a lot popped up, including ebay so a quick search will keep you from having to build anything and have it going in no time with just plug and play.

          https://www.amazon.com/Galak-Electro.../dp/B00LM5RM6M

          TX
          Mr fixit for the family
          Chris

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          • #6
            What you want is essentially a "ring counter", which is a shift register composed of flip-flops. A CD4017 or 74HCT4017 decade counter will also do the job. It has 10 outputs which activate sequentially, so you might want to use Q0-Q3 for green, Q4-Q5 for amber, and Q6-Q9 for red. If you drive the clock with a 555 timer set for 4 seconds, you will get 16 seconds green, 8 seconds amber, and 16 seconds red. Use diodes to combine the outputs. You can even get clever and have 12 seconds green, 4 seconds green+amber, 8 seconds amber, 4 seconds amber+red, and 16 seconds red. That uses "wired OR" diode logic.

            https://en.wikipedia.org/wiki/Ring_counter

            https://en.wikipedia.org/wiki/Wired_..._OR_connection

            https://www.build-electronic-circuit...cuits/ic-4017/

            https://circuitdigest.com/electronic...-light-circuit (4 way traffic light)

            https://theorycircuit.com/traffic-li...-using-ic-555/ (only two 555s for traffic light)
            http://pauleschoen.com/pix/PM08_P76_P54.png
            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030

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            • #7
              I could whip out a circuit with a 555 timer and some other ICs, but the Ardunio or some other PIC based device really is the way to go. The circuit is dead easy, you just need some current drivers on the three outputs used for red, yellow, and green.

              Check out the link that Mickeyf gave above. It has the code. And if you need help with the current drivers, I am sure many of us can help. I see a resistor (10K) from the output pin the positive power rail. That output pin also goes to a FET's gate. FET drain to ground and FET source to the LED array with the other end of that array coming from a power supply, probably the positive terminal, through another resistor. You will need to do a little math to find the value for that series resistor. And of course, you do that three times for the three colors.

              EDIT: I am assuming that you are talking about an actual traffic light fixture which will need the current drivers. But a single, low current LED could be driven directly by the Ardunio.
              Last edited by Paul Alciatore; 04-01-2021, 06:00 PM.
              Paul A.
              SE Texas

              And if you look REAL close at an analog signal,
              You will find that it has discrete steps.

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              • #8
                I just looked up 'electronic circuits traffic light control'. A couple of ready-made pc board controllers are available under $5, and there is a simple two chip circuit you can build, using a 555 timer ic and a 4017 counter ic. Anything that will drive an led will also drive an opto-isolator, which can easily drive a power triac- which in turn would let you safely control several hundred watts of ac lights if needed.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #9
                  Thanks to all who replied. Lots of info there, most of which is way above my head. My Air Force electronics training in 1959 is not of much use these days. I do remember the Eccles-Jordan multivibrator flip flop circuit used in the ANFST2 computer. Thanks for the memory of freezing my ass off on mid shift while the air conditioning worked to keep the 8,000 vacuum tubes from exploding. I'll probably opt for a ready made gadget that can do the job. BTW it is a real, red, yellow, green traffic light, that was taken out of service and sold at a city auction.
                  “I know lots of people who are educated far beyond their intelligence”

                  Lewis Grizzard

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                  • #10
                    Just get a simple PLC (programmable logic controller)and be done with it. Dead simple to program and versatile if you want to make changes in timing and such. I use Siemens Logo PLC's and they work perfectly.
                    Location: The Black Forest in Germany

                    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                    • #11
                      BTW it is a real, red, yellow, green traffic light, that was taken out of service and sold at a city auction.
                      Then the first thing you need to know is what are its voltage and current requirements, then proceed from there. (You gonna put this at the end of your driveway, or at the garage door? )
                      "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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                      • #12
                        Originally posted by mickeyf View Post

                        Then the first thing you need to know is what are its voltage and current requirements, then proceed from there. (You gonna put this at the end of your driveway, or at the garage door? )
                        Going to gut it and install led bulbs. I will hang in a corner of the basement game room in my daughter's house. Novelty decoration only. It's traffic direction days are over.
                        “I know lots of people who are educated far beyond their intelligence”

                        Lewis Grizzard

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                        • #13
                          ...taken out of service and sold at a city auction.
                          I've been hoping for a parking meter to come up, to discourage people from taking up the limited parking space in front of our house. Or maybe make a few bucks when they do.
                          "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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                          • #14
                            I once saw in a one of those theme bar/restaurants in California a old camshaft and bunch of micro switches rigged with a small motor to sequentially blink a string of lights. Pretty cool looking but you did say electronic and not electro-mechanical.
                            Tom - Spotsylvania, VA

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                            • #15
                              Originally posted by flathead4 View Post
                              I once saw in a one of those theme bar/restaurants in California a old camshaft and bunch of micro switches rigged with a small motor to sequentially blink a string of lights. Pretty cool looking but you did say electronic and not electro-mechanical.
                              That's a pretty cool idea. I've got an old stoplight, and a walk/don't walk sign I've been wanting to light up for a while, but never get around to. A camshaft to time the lights would be awesome.

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