traffic simple


Posted on Feb 7, 2014

The controller is entirely hardware based, and provides the typical sequencing for a standard 3-light traffic signal. I built this traffic light controller / sequencer when I was firstlearning electronics, and it is what I would consider a crude and ugly device. However, I learned a lot while building it, and it served its intended purpose. making the traffic signal I bought off eBay flash in the standard


traffic simple
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Green - Yellow - Red sequence. In addition, I built the controller with variable speed control, and the ability to "hold" any of the lamps full-on or full-off. The casing for the controller electronics is an old, re-used cookie tin. While not the most eloquent container; the cookie tin served its purpose while provided my circuit a unique and fire-resistant case. If I were to rebuild this traffic light controller, I would suggest the use of a different casing material. The basic sequencing operation of this traffic light controller is simple. The 555 Timer IC generates a voltage "pulse" at a specific timing interval. This interval is set using a capacitor and two resistors, one of which is the potentiometer (basically a variable resistor). The 4017 decade counter IC has 10 output ports, of which only one port is turned on at any given time. Each time the 555 Timer sends out a pulse, the 4017 decade counter turns off the currently-active output port, and turns on the next output port. Output port #10 is connected to the RESET pin of the counter, so that anytime the counter tries to activate output #10 it ends up immediately jumping back to Output port #1 (i. e. it starts over counting from 1). In this way the counter loops continuously from output port #1 through #9. Each of the decade counter`s output ports is assigned to a different color light of the traffic signal. For example, mine is connected so that output ports #1...




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