Every Digital Electronics' Lead The Way (see sidebar) student has had to build a traffic light controller for a lab assignment. Usually, they are required to build a digital circuit using discrete digital components. The student is then required to use the digital circuit to illuminate Light Emitting Diodes (LEDs) which typically draw 20 milliamps. Some digital circuits can provide this small current directly without the use of drive transistors or relays. More sophisticated students might make use of an Arduino board to design an even better circuit. The advantage of using an Arduino board is that the design allows the use of proximity sensors to detect the presence of a vehicle in a turn lane, and have the Arduino program change the timing of the lights accordingly. The Arduino has input lines to change the timing of all the light outputs. Those who use an Arduino board for this purpose can find many methods of programming it on the Web.
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