Traffic Lights

The Kits

Breadboard Only

Components

1x Breadboard
5x Green LED
5x Red LED
3x Yellow LED
2x 8bit Shift Registers
2x Tactile Buttons
13x 220 Ohm Resistors
Jumper Wires

Digispark

Components

Same as Breadboard Only plus...
Digispark Controller
Custom PCB
Female Header Connectors

Pro Micro

Components

Same as Breadboard Only plus...
Arduino Pro Micro Controller
Custom PCB
Female Header Connectors

£10

£25

£30

Digispark PCB Only

Components

Custom PCB for Digispark Controller
Female Header Connectors

Pro Micro PCB Only

Components

Custom PCB for Arduino Pro Micro Controller
Female Header Connectors

£15

Choosing a kit

Picking which kit is right for you depends on your skill level and what components you already have:

Breadboard Only

You're getting started with electronics and aren't ready to do soldering yet. To use this kit you will need to have your own controller already. This allows you to use whatever you have, e.g. Raspberry Pi, Arduino, Onion Omega, ESP8266. This is perfect for people that have already bought an Arduino start kit and what to try out their skills with another project kit.

Digispark / Pro Micro Kit

These kits come with everything you need to prototype on a breadboard and then build the circuit my custom designed PCB. The controller and shift registers are designed to be mounted in header connectors on the PCB, allowing you to use them again for other projects.

Digispark / Pro Micro PCB Only

These kits contain just my custom designed PCB and female header connectors. You will need to supply the rest of the components in order to build the circuit. With this option, you could also use jumper wires to connect any other controller you my have.

Getting Started

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Example Code Solution

To help you get the kit running, I've provided an example projects for Arduino IDE and PlatformIO. The guide below outlines some of the concepts and libraries used.

Concepts

Non-Blocking Delay

Using the delay() method to control the timing of code stops other code from running until the delay is finished. It is possible to program the traffic lights using just delay()'s but using non-blocking delays is a better solution. In this kit, we need to be able to switch LEDs on and off at different rates. For more information on this subject, check out this guide from Adafruit.

Interrupts

Interrupts allow the code to be able to react when a button has been pressed without having to repeatedly check for it in the loop(). Checking for button presses in the loop() could result in it being missed if the button is pressed and released before that part of the loop runs. Using interrupts means we don't have to worry about our button press being missed. Adafruit has a tutorial on interrupts. The Arduino site also has some more information in their reference library on the nitty-gritty of interrupts

Shift Registers

The circuit contains far more inputs and outputs than the controllers have IO pins for. This kit contains two 75HC595N shift registers. These enable the code to be able to switch up to 16 LEDs whilst using only three IO pins on the controller. These are the same as the one that comes in the Arduino StarterKit. Information on these can be found on Arduino Learning site and Adafruit also has a tutorial on them.

Libraries

Thread, ThreadController

This library provides a simple interface for creating code that implements a non-clocking delay design but without having to write any timing code. The example code uses three thread timers: tickThread, pedThread, lightsThread. The lightsThread is used to ensure that the LEDs are always updated in a timely manner but not necessarily on every cycle of the loop.

Shifty

A simple library that makes using shift registers as simple as writing to the Serial output.

CarLights, PedestrianLights

I've simplified the main code by moving the management of the three sets of car lights and two sets of pedestrian lights into their own libraries. This means they can manage their own state without having lots of spaghetti code.

ResetThread

The Thread class doesn't support reseting the timer on a thread, so I've implemented my own sub-class that adds this functionality. This is used for the tickThread and pedThread, when switching between car right of way and pedestrian right of way.

Software & Services

Fritzing

Fritzing is an open-source software package that makes circuit design simple. It provides an easy to understand interface for working with breadboard, schematic and PCB designs.

http://fritzing.org/home/

Aisler

Aisler is the PCB manufacturer that is behind the Fritzing Fab PCB production service. They provide a simple web interface for managing project and ordering boards. Their straightforward pricing model makes

https://go.aisler.net/fritzing

PlatformIO

PlatformIO provides an advanced editor for micro-controller programming. It can work with Arduino IDE projects as well as it's own project project structures. Being based on the cross-platform Atom editor, means you're not limited to just micro-controller projects.

http://platformio.org/

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