Project idea
A row of junction controllers uses ATmega328P nodes linked over an RS‑485 multi‑drop bus to implement a “green wave,” computing offsets so vehicles at an advisory speed meet green lights consecutively instead of stopping.
Nodes share phase state and timing via a simple framed UART protocol over MAX485, while outputs are driven through ULN2803A channels to indicator LEDs or low‑voltage lamps for a safe lab/demo build.
 
Project description
Each junction has a Nano‑based controller that runs its local signal timing plan and listens to corridor timing frames from a designated master, adjusting offsets to maintain progression bands at the target speed.
Basic speed detection for demonstration uses two IR sensor pairs per approach to estimate travel speed and, when within the progression band, advance to the green window to maintain flow.
Status, offsets, and bus health are shown on a 16×2 LCD via a PCF8574 backpack, and power is provided by a compact 12 V/2 A SMPS feeding local 5 V regulators as needed
 
Total components list
4 × Arduino Nano (ATmega328P, CH340)
4 × MAX485 TTL‑to‑RS‑485 modules
4 × ULN2803A driver ICs
1 × 16×2 LCD with I2C (PCF8574)
8 × IR obstacle/speed sensor modules (two per approach for 4 approaches demo)
1 × 12 V 2 A SMPS power supply
1 × CAT6 10 m patch cable for RS‑485 trunk (pre‑terminated)
1 × Beginner starter kit (breadboard, jumpers, LEDs, resistors, small parts) 
1 × 3 mm acrylic sheet 30×30 cm base for mounting
 
Features
RS‑485 multi‑drop bus with differential signaling for robust inter‑junction communication and long cable runs.
High‑current open‑collector outputs via ULN2803A to drive LED stacks or small relays for lamp simulation.
16×2 I2C LCD diagnostics for offsets, phases, and bus status using PCF8574 backpack.
 
Applications
Teaching synchronized “green wave” progression and corridor timing in transportation labs and classrooms.
Demonstrating serial bus networking, framed UART protocols, and distributed control with low‑cost modules.
 
Project Includes:
Fully assembled and tested circuit
Circuit diagram
Source code 
(For DIY KITs - only the components will be provided)
 
Project Types:
DIY KIT(Do IT YourSelf KIT) - We are providing only components in this kit for this project
DIY KIT with Code & Circuit Connections - Along with the components, you will get the Code and the Circuit Connections file to help you build the project easily.
Readymade Breadboard - We are providing fully assembled, tested and ready-made project using plug-n-play jumper wires and breadboard with all the other components, code & circuit diagram.
Readymade Soldered - We are providing fully assembled, tested and ready-made project soldered on a PCB with all the other components, code & circuit diagram.
 
Dimensions (cm)
Approx. assembled demo on 3 mm acrylic base: 30 × 30 × 8 cm, using a 30×30 cm plate as the mounting platform.
 
Shipping dimensions (cm)
Suggested packaging: 35 × 35 × 12 cm with protective padding around the 30×30 cm mounted assembly.
 
Weight
SMPS unit weight is about 67 g; with controller boards, wiring, sensors, and acrylic base, the assembled demo is approximately 0.9 kg.
 
Estimated project weight
Packed shipping weight (with box and padding) approximately 3 kg.
 
otes: All the products are made by LearnElectronics India and not for re-sale.