Traveling light displays were popular into the 1960's, especially for theater marquees. Sometimes called chase lights, traveling light displays were a string of lights in which every third or fourth bulb was lit. Every second or so, all the bulbs turned off and the next bulb clockwise (or counterclockwise) would turn on, giving the impression that the lights moved along the string. The string was often arranged around the marquee of a movie theater to attract attention.
We can use MasterFlasher to easily model a traveling light display in which every fourth bulb is lit. Take a look for a moment at the sample waveforms in Figure 1.
Recall that Outputs 1 and 2 are grounding outputs, which either ground the output or leave it disconnected, and Outputs 3 and 4 are driving outputs, which either drive the output or leave it disconnected. The disconnected (high impedance) portions of the waveforms are shown in dotted lines.
Note that for the first portion of the waveform, from 0 to 1 seconds, only Output 3 is driving and Output 2 sinking. For the second portion, from 1 to 2 seconds, only Output 3 is driving and Output 1 sinking. For the third portion, from 2 to 3 seconds, only Output 4 is driving and Output 2 sinking. Finally, for the fourth portion, from 3 to 4 seconds, only Output 4 is driving and Output 1 sinking. The cycle then repeats.
If we connect every fourth bulb across Outputs 3 and 2, the next bulbs clockwise across Outputs 3 and 1, the next bulbs clockwise across Outputs 4 and 2, and the last bulbs across Outputs 4 and 1, we will have our traveling lights display. The way to do this is shown in Figure 2. Output 3 drives 2 bulbs, then skips 2, then two more bulbs, then skips two, and so on. Output 4 drives the bulbs skipped by Output 3. On the other side, Output 2 and Output 1 are connected to every other bulb as shown. For having the lights travel in the other direction, swap Output 3 with Output 4, and Output 2 with Output 1.
We can also make a traveling light display using LEDs. We need to keep in mind that current limiting resistors are required for each LED, and that Outputs 3 and 4 are the positive outputs, so that we get the LED polarity correct. The correct circuit for LEDs is given in Figure 3. For VLED = 5 volts, use resistors = 150 ohms or less. You can also adjust the speed of the display to go faster or slower by adjusting the base rate timer values of the Master Flasher.
A traveling light sign is a prototype feature that adds visual interest to your layout.