I'm planning to build an accurate simulation of a traffic light controlled intersection near my house. North and south have red/amber/green lights (x3 each direction) + red/white pedestrian lights (x2 each direction). East and west have red/amber/green lights (x2 each direction) + red/white pedestrian lights (x2 each direction). Each corner has a pedestrian button (x1). I'm not sure if the button works for crossing both directions (depending on when it's pressed). Usually, there are two buttons on a pole — one for crossing in each direction. I'll double check but I assume the button works for crossing in both directions, depending on when you press it. [image] [image] LED specs: Forward Voltage: R/Y 2.0-2.2V; B/G/W 3.0-3.2V. Max. Current: 20mA. What spec power supply should I buy for the LEDs and is this MOSFET a good choice? [image]

[image] zerovolts: Is there a better way to write it? Yes there is but you’re not ready yet though you’ve been given links to that way of coding you have to see it working and know the code to understand, it’s NOT something you read once and have it down. It is the lesson of the day every day here since before I got here and it starts with using time to make things happen together. When you use delay(), you COMPLETELY WASTE 16000 cpu cycles per millisecond that could be doing something else like running sensors while many leds get turned on and off. When my code does not BLOCK EXECUTION long enough to matter (100 microseconds might be, analog read takes > 100) then it’s possible to write a function that blinks a status led and add that to loop() and then that led will blink on time within reason no matter what anything else does. I make the whole job run as pieces that interleave 1 small step for every function every time loop() cycles and the CONTROL is at that level, cooperative tasking that keeps it’s own timing rather than having delays FORCE stops. My void loops tend to run at over 50,000 / second with the loop counter function showing that every second, faster when I take that out. That’s loop() running in 320 cycles or less, how many loops don’t run when a delay(1) blows off 16000 cycles?

[image] GoForSmoke: When you use delay(), you COMPLETELY WASTE 16000 cpu cycles per millisecond that could be doing something else like running sensors while many leds get turned on and off. I know! I’m only using it here so I have a starting point that I can build upon. This is version 1. [image] GoForSmoke: …it’s possible to write a function that blinks a status led and add that to loop() and then that led will blink on time within reason no matter what anything else does. The problem with “…no matter what anything else does” is I want the R/Y/G LEDs to not only not block the input from the four pedestrian buttons, but also not rigidly follow the same R/Y/G pattern continuously. Input from the pedestrian buttons should be able to alter the R/Y/G sequence, as will EVP (emergency vehicle preemption) mode — which will essentially be triggered by a 5th button.

[image] zerovolts: a starting point Shorten the delays and you may have a wiring test sketch. Park it somewhere safe. That code might motivate you, but it is not a good starting point! Every second you can spend learning how to code before you go much further will pay off minutes, just in this project. When I am not moving I'll look to be sure everything you need to hear now has been said at least once… a7

[image] zerovolts: Input from the pedestrian buttons should be able to alter the R/Y/G sequence, as will EVP (emergency vehicle preemption) mode Your objections seem to stem from some beliefs you have that aren’t well founded. To always be watching Inputs (buttons in this case) while switching Outputs (leds) requires some form of tasking and cooperative tasking is the fastest you can get. If you make it all work as traffic flow including pedestrian and emergency response, the timing and lights can match the traffic condition.

[image] GoForSmoke: cooperative tasking Interesting. Sounds like non-blocking logic is the name of the game. I read this summary of cooperative multitasking: Cooperative multitasking on Arduino is a software design approach that allows multiple functions to appear to run simultaneously on the single-core microcontroller. Unlike preemptive multitasking (where the operating system controls task switching), in a cooperative system, each task must voluntarily and periodically yield control of the CPU back to a central scheduler. The core principle involves avoiding blocking functions like delay() and busy while() loops. Instead, code uses non-blocking logic, typically by tracking time with the millis() function and employing finite state machines.

Here [image] Yet another Finite State Machine introduction Tutorials Hello everyone, On this gray day, considering the number of questions that boil down to programming a finite automaton (or a state machine), I thought I would translate my small tutorial I also have in French to explain how to approach this type of code in a structured manner. Of course, there are libraries that do this more or less for you, but understanding how it works can often allow you to do without libraries that might weigh down your code. The general idea is to write a program that co… and [How NES Games Use State Machines For Everything] and blink without delay IDE example and google arduino two things at once arduino finite state machine and play with the IDE examlpe blink without delay until you get a good grip on it. There is a competent article https://docs.arduino.cc/built-in-examples/digital/BlinkWithoutDelay/ the code is a available in the IDE examples menu. a7

[image] zerovolts: The core principle involves and learning to do it, to use techniques to achieve that end takes PRACTICE, not reading about it. Until your fingers do all the typing, you haven’t developed a connection or reflex at all, we Grow Long Term Memory, we don’t Matrix Download beyond Short Term Memory.

[image] zerovolts: a software design approach that allows multiple functions to appear to run simultaneously When I blink a led it only takes a little code run as often as I want the blinks to be exactly on time (since perfect doesn’t @#$%ing exist!) and be sure about this…. the whole time, the led Is Blinking even when the code isn’t changing the light. And when I run 2 or 200 leds, they ALL blink at the same time. When I watch a button as well, same thing! Yeah, they APPEAR TO because THEY ARE depending on how you define TASK. The leds blink and the switch gets reacted to, because THEY DO. Ditheads who can’t separate code from action “appear” to be ignorant of all but the code. Interrupt-driven multi-task systems (like RTOS) have to save and restore task conditions when switching. The overhead is enough that tasks don’t get switched every milli (for efficiency, one overhead for many many steps) more like every 10 while non-blocking can run several tasks 50x per milli which is fast enough to drive multiple motors smoothly. RTOS can’t do that as the appearan… errrr what it does is not be able to run ONE motor that needs pulses 1 or 2 millis apart, smoothly.

[image] zerovolts: Is there a better way to write it? as already mentioned, check the example "Blink Without Delay" and consider the function delay() as not existing. Maybe you also want to read about functions, arrays and structures.

[image] alto777: Then, now knowing you mean a small scale implementation, I recommend neopixels or so-called smart LEDs. Very easy to use, one pin only for as many as this will ever need here and very good control over colour and intensity. They are available in single packages, I use these with various filters. With tissue and neutral density gel you can make some very nice display units. Could I use LEDs from one smart strip in separate projects? For example: would it be possible to cut a 200 LED strip into 10 groups of 20 LEDs and use them in 10 different projects (with 10 different controllers)?

Traffic light intersection simulation project

Projects General Guidance

alto777 February 20, 2026, 2:43am 82

Here

and

blink without delay IDE example

and google

arduino two things at once

arduino finite state machine

and play with the IDE examlpe blink without delay until you get a good grip on it. There is a competent article

https://docs.arduino.cc/built-in-examples/digital/BlinkWithoutDelay/

the code is a available in the IDE examples menu.

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Traffic light intersection simulation project

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