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Traffic lights


Task

Traffic lights for driver training, school and autodrome. Idle mode selectable by switch.

Technical solution

Arduino Duemilanove with Atmega168 microcontroller onboard is used as controlling device.

The device is supplied from AC power grid via switching power supply, or from 12 V SLA or NiMH accumulator.

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Schematic


Duty cycle polls switch state. If switch input pulled low, device shows idle mode by yellow light blinking. Otherwise, the device goes through traffic light program via delays between lights switching. Lights are switched by 943-1C-9DS relays, driven by any small power NPN transistors, such as S8050.

If SLA cell or other 12 V source is used as power supply, 943-1C-12DS relays should be used insted of 943-1C-9DS. Total current sank from relays should be less than 7 A. 7809 regulator is preferred before Arduino power input to reduce 7805 heating on it.

If AC/DC power supply is used, it should be capable to supply up to 400 mA at 9 V.

Algorithm and Arduino sketch

RED/YELLOW/GREEN outputs is used for main direction and RED2/YELLOW/GREEN2 for perpendicular direction. There no second YELLOW relay since yellow lights on both directions are turned on or off simultaneously.

Arduino sketch
Download Arduino sketch - svetofor.ino

 

проектирование, изготовление, монтаж

PCB