LEGO traffic lights (WeMos, Wi-Fi and MQTT)

This project is a work in progress. Please check back later for additional changes.

Two channel traffic lights controller, using a WeMos microcontroller.

Sequence and timing

I've followed the standard set by the Norwegian Public Roads Administration, in handbook 303 and 310.

• Yellow time: 3-4 seconds, depending on speed limit (above or below 50 km/h)
• Red/yellow time: 1 second
• Yellow and red/yellow time for two conflicting flows of traffic must not overlap
• Switching time: $t_{s}=t_{clear}-t_{enter}$
• Yellow flash: 60 times per minute (1 hz), 50% interval

Cold start

• 5 seconds yellow flash
• 5 seconds yellow solid
• 5 seconds red (minimum), all directions
• 1 second red/yellow main direction
• Green main direction

Videos

• First test with single traffic light output and MQTT communication.

• Added second traffic lights and auxiliary output.
• Faster MQTT command response.
• Added cold-start sequence on first boot or when ending yellow flash mode.
• Made two traffic light LED test boards.

I/O

Wemos D1 mini pinout

Outputs

• GPIO 4 : Traffic light 1, green
• GPIO 0 : Traffic light 1, yellow
• GPIO 16 : Traffic light 1, red
• GPIO 14 : Traffic light 2, green
• GPIO 12 : Traffic light 2, yellow
• GPIO 13 : Traffic light 2, red
• GPIO 15 : Auxiliary (e.g. street lights)
• GPIO 2 : Built-in LED, MQTT connection status

Source code

Arduino sketch is available in a git repository:
https://github.com/thomasjsn/WeMos-Traffic-lights-controller-MQTT

Gallery

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Schematic diagram